preferences: rewrite in kotlin

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

12 files changed, 452 insertions, 600 deletions

diff --git a/ui/src/main/java/com/wireguard/android/preference/KernelModuleDisablerPreference.java b/ui/src/main/java/com/wireguard/android/preference/KernelModuleDisablerPreference.java
deleted file mode 100644
index 885e48b3..00000000
--- a/ui/src/main/java/com/wireguard/android/preference/KernelModuleDisablerPreference.java
+++ /dev/null
@@ -1,94 +0,0 @@
-/*
- * Copyright © 2020 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.android.preference;
-
-import android.annotation.SuppressLint;
-import android.content.Context;
-import android.content.Intent;
-import android.util.AttributeSet;
-
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-import com.wireguard.android.activity.SettingsActivity;
-import com.wireguard.android.backend.Tunnel;
-import com.wireguard.android.backend.WgQuickBackend;
-import com.wireguard.util.NonNullForAll;
-
-import java.util.ArrayList;
-import java.util.Collection;
-
-import androidx.preference.Preference;
-import java9.util.concurrent.CompletableFuture;
-import java9.util.stream.Collectors;
-import java9.util.stream.StreamSupport;
-
-@NonNullForAll
-public class KernelModuleDisablerPreference extends Preference {
-    private State state;
-
-    public KernelModuleDisablerPreference(final Context context, final AttributeSet attrs) {
-        super(context, attrs);
-        state = Application.getBackend() instanceof WgQuickBackend ? State.ENABLED : State.DISABLED;
-    }
-
-    @Override
-    public CharSequence getSummary() {
-        return getContext().getString(state.summaryResourceId);
-    }
-
-    @Override
-    public CharSequence getTitle() {
-        return getContext().getString(state.titleResourceId);
-    }
-
-    @SuppressLint("ApplySharedPref")
-    @Override
-    protected void onClick() {
-        if (state == State.DISABLED) {
-            setState(State.ENABLING);
-            Application.getSharedPreferences().edit().putBoolean("disable_kernel_module", false).commit();
-        } else if (state == State.ENABLED) {
-            setState(State.DISABLING);
-            Application.getSharedPreferences().edit().putBoolean("disable_kernel_module", true).commit();
-        }
-        Application.getAsyncWorker().runAsync(() -> Application.getTunnelManager().getTunnels().thenApply(observableTunnels -> {
-            final Collection<CompletableFuture<Tunnel.State>> c = StreamSupport.stream(observableTunnels.values()).map(t -> t.setState(Tunnel.State.DOWN).toCompletableFuture()).collect(Collectors.toCollection(ArrayList::new));
-            return CompletableFuture.allOf(c.toArray(new CompletableFuture[0])).thenRun(() -> {
-                final Intent restartIntent = new Intent(getContext(), SettingsActivity.class);
-                restartIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
-                restartIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
-                Application.get().startActivity(restartIntent);
-                System.exit(0);
-            });
-        }).join());
-    }
-
-    private void setState(final State state) {
-        if (this.state == state)
-            return;
-        this.state = state;
-        if (isEnabled() != state.shouldEnableView)
-            setEnabled(state.shouldEnableView);
-        notifyChanged();
-    }
-
-    private enum State {
-        ENABLED(R.string.module_disabler_enabled_title, R.string.module_disabler_enabled_summary, true),
-        DISABLED(R.string.module_disabler_disabled_title, R.string.module_disabler_disabled_summary, true),
-        ENABLING(R.string.module_disabler_disabled_title, R.string.success_application_will_restart, false),
-        DISABLING(R.string.module_disabler_enabled_title, R.string.success_application_will_restart, false);
-
-        private final boolean shouldEnableView;
-        private final int summaryResourceId;
-        private final int titleResourceId;
-
-        State(final int titleResourceId, final int summaryResourceId, final boolean shouldEnableView) {
-            this.summaryResourceId = summaryResourceId;
-            this.titleResourceId = titleResourceId;
-            this.shouldEnableView = shouldEnableView;
-        }
-    }
-}
diff --git a/ui/src/main/java/com/wireguard/android/preference/KernelModuleDisablerPreference.kt b/ui/src/main/java/com/wireguard/android/preference/KernelModuleDisablerPreference.kt
new file mode 100644
index 00000000..0bb728df
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/preference/KernelModuleDisablerPreference.kt
@@ -0,0 +1,63 @@
+/*
+ * Copyright © 2020 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.preference
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.content.Intent
+import android.util.AttributeSet
+import androidx.preference.Preference
+import com.wireguard.android.Application
+import com.wireguard.android.R
+import com.wireguard.android.activity.SettingsActivity
+import com.wireguard.android.backend.Tunnel
+import com.wireguard.android.backend.WgQuickBackend
+import java9.util.concurrent.CompletableFuture
+import kotlin.system.exitProcess
+
+class KernelModuleDisablerPreference(context: Context, attrs: AttributeSet?) : Preference(context, attrs) {
+    private var state = if (Application.getBackend() is WgQuickBackend) State.ENABLED else State.DISABLED
+
+    override fun getSummary() = context.getString(state.summaryResourceId)
+
+    override fun getTitle() = context.getString(state.titleResourceId)
+
+    @SuppressLint("ApplySharedPref")
+    override fun onClick() {
+        if (state == State.DISABLED) {
+            setState(State.ENABLING)
+            Application.getSharedPreferences().edit().putBoolean("disable_kernel_module", false).commit()
+        } else if (state == State.ENABLED) {
+            setState(State.DISABLING)
+            Application.getSharedPreferences().edit().putBoolean("disable_kernel_module", true).commit()
+        }
+        Application.getAsyncWorker().runAsync {
+            Application.getTunnelManager().tunnels.thenApply { observableTunnels ->
+                val downings = observableTunnels.values().map { it.setState(Tunnel.State.DOWN).toCompletableFuture() }.toTypedArray()
+                CompletableFuture.allOf(*downings).thenRun {
+                    val restartIntent = Intent(context, SettingsActivity::class.java)
+                    restartIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
+                    restartIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+                    Application.get().startActivity(restartIntent)
+                    exitProcess(0)
+                }
+            }.join()
+        }
+    }
+
+    private fun setState(state: State) {
+        if (this.state == state) return
+        this.state = state
+        if (isEnabled != state.shouldEnableView) isEnabled = state.shouldEnableView
+        notifyChanged()
+    }
+
+    private enum class State(val titleResourceId: Int, val summaryResourceId: Int, val shouldEnableView: Boolean) {
+        ENABLED(R.string.module_disabler_enabled_title, R.string.module_disabler_enabled_summary, true),
+        DISABLED(R.string.module_disabler_disabled_title, R.string.module_disabler_disabled_summary, true),
+        ENABLING(R.string.module_disabler_disabled_title, R.string.success_application_will_restart, false),
+        DISABLING(R.string.module_disabler_enabled_title, R.string.success_application_will_restart, false);
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.java b/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.java
deleted file mode 100644
index 32b3e33c..00000000
--- a/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.java
+++ /dev/null
@@ -1,113 +0,0 @@
-/*
- * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.android.preference;
-
-import android.Manifest;
-import android.content.Context;
-import android.content.pm.PackageManager;
-import android.util.AttributeSet;
-import android.util.Log;
-
-import com.google.android.material.snackbar.Snackbar;
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-import com.wireguard.android.util.DownloadsFileSaver;
-import com.wireguard.android.util.DownloadsFileSaver.DownloadsFile;
-import com.wireguard.android.util.ErrorMessages;
-import com.wireguard.android.util.FragmentUtils;
-import com.wireguard.util.NonNullForAll;
-
-import java.io.BufferedReader;
-import java.io.InputStreamReader;
-
-import androidx.annotation.Nullable;
-import androidx.preference.Preference;
-
-/**
- * Preference implementing a button that asynchronously exports logs.
- */
-
-@NonNullForAll
-public class LogExporterPreference extends Preference {
-    private static final String TAG = "WireGuard/" + LogExporterPreference.class.getSimpleName();
-
-    @Nullable private String exportedFilePath;
-
-    public LogExporterPreference(final Context context, final AttributeSet attrs) {
-        super(context, attrs);
-    }
-
-    private void exportLog() {
-        Application.getAsyncWorker().supplyAsync(() -> {
-            DownloadsFile outputFile = DownloadsFileSaver.save(getContext(), "wireguard-log.txt", "text/plain", true);
-            try {
-                final Process process = Runtime.getRuntime().exec(new String[]{
-                        "logcat", "-b", "all", "-d", "-v", "threadtime", "*:V"});
-                try (final BufferedReader stdout = new BufferedReader(new InputStreamReader(process.getInputStream()));
-                     final BufferedReader stderr = new BufferedReader(new InputStreamReader(process.getErrorStream()))) {
-                    String line;
-                    while ((line = stdout.readLine()) != null) {
-                        outputFile.getOutputStream().write(line.getBytes());
-                        outputFile.getOutputStream().write('\n');
-                    }
-                    outputFile.getOutputStream().close();
-                    stdout.close();
-                    if (process.waitFor() != 0) {
-                        final StringBuilder errors = new StringBuilder();
-                        errors.append(R.string.logcat_error);
-                        while ((line = stderr.readLine()) != null)
-                            errors.append(line);
-                        throw new Exception(errors.toString());
-                    }
-                }
-            } catch (final Exception e) {
-                outputFile.delete();
-                throw e;
-            }
-            return outputFile.getFileName();
-        }).whenComplete(this::exportLogComplete);
-    }
-
-    private void exportLogComplete(final String filePath, @Nullable final Throwable throwable) {
-        if (throwable != null) {
-            final String error = ErrorMessages.get(throwable);
-            final String message = getContext().getString(R.string.log_export_error, error);
-            Log.e(TAG, message, throwable);
-            Snackbar.make(
-                    FragmentUtils.getPrefActivity(this).findViewById(android.R.id.content),
-                    message, Snackbar.LENGTH_LONG).show();
-            setEnabled(true);
-        } else {
-            exportedFilePath = filePath;
-            notifyChanged();
-        }
-    }
-
-    @Override
-    public CharSequence getSummary() {
-        return exportedFilePath == null ?
-                getContext().getString(R.string.log_export_summary) :
-                getContext().getString(R.string.log_export_success, exportedFilePath);
-    }
-
-    @Override
-    public CharSequence getTitle() {
-        return getContext().getString(R.string.log_export_title);
-    }
-
-    @Override
-    protected void onClick() {
-        FragmentUtils.getPrefActivity(this).ensurePermissions(
-                new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
-                (permissions, granted) -> {
-                    if (granted.length > 0 && granted[0] == PackageManager.PERMISSION_GRANTED) {
-                        setEnabled(false);
-                        exportLog();
-                    }
-                });
-    }
-
-}
diff --git a/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.kt b/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.kt
new file mode 100644
index 00000000..b4671309
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/preference/LogExporterPreference.kt
@@ -0,0 +1,94 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.preference
+
+import android.Manifest
+import android.content.Context
+import android.content.pm.PackageManager
+import android.util.AttributeSet
+import android.util.Log
+import androidx.preference.Preference
+import com.google.android.material.snackbar.Snackbar
+import com.wireguard.android.Application
+import com.wireguard.android.R
+import com.wireguard.android.util.DownloadsFileSaver
+import com.wireguard.android.util.ErrorMessages
+import com.wireguard.android.util.FragmentUtils
+import java.io.BufferedReader
+import java.io.InputStreamReader
+
+/**
+ * Preference implementing a button that asynchronously exports logs.
+ */
+class LogExporterPreference(context: Context, attrs: AttributeSet?) : Preference(context, attrs) {
+    private var exportedFilePath: String? = null
+    private fun exportLog() {
+        Application.getAsyncWorker().supplyAsync {
+            val outputFile = DownloadsFileSaver.save(context, "wireguard-log.txt", "text/plain", true)
+            try {
+                val process = Runtime.getRuntime().exec(arrayOf(
+                        "logcat", "-b", "all", "-d", "-v", "threadtime", "*:V"))
+                BufferedReader(InputStreamReader(process.inputStream)).use { stdout ->
+                    BufferedReader(InputStreamReader(process.errorStream)).use { stderr ->
+                        while (true) {
+                            val line = stdout.readLine() ?: break
+                            outputFile.outputStream.write(line.toByteArray())
+                            outputFile.outputStream.write('\n'.toInt())
+                        }
+                        outputFile.outputStream.close()
+                        if (process.waitFor() != 0) {
+                            val errors = StringBuilder()
+                            errors.append(R.string.logcat_error)
+                            while (true) {
+                                val line = stderr.readLine() ?: break
+                                errors.append(line)
+                            }
+                            throw Exception(errors.toString())
+                        }
+                    }
+                }
+            } catch (e: Exception) {
+                outputFile.delete()
+                throw e
+            }
+            outputFile.fileName
+        }.whenComplete(this::exportLogComplete)
+    }
+
+    private fun exportLogComplete(filePath: String, throwable: Throwable?) {
+        if (throwable != null) {
+            val error = ErrorMessages.get(throwable)
+            val message = context.getString(R.string.log_export_error, error)
+            Log.e(TAG, message, throwable)
+            Snackbar.make(
+                    FragmentUtils.getPrefActivity(this).findViewById(android.R.id.content),
+                    message, Snackbar.LENGTH_LONG).show()
+            isEnabled = true
+        } else {
+            exportedFilePath = filePath
+            notifyChanged()
+        }
+    }
+
+    override fun getSummary() = if (exportedFilePath == null)
+        context.getString(R.string.log_export_summary)
+    else
+        context.getString(R.string.log_export_success, exportedFilePath)
+
+    override fun getTitle() = context.getString(R.string.log_export_title)
+
+    override fun onClick() {
+        FragmentUtils.getPrefActivity(this).ensurePermissions(arrayOf(Manifest.permission.WRITE_EXTERNAL_STORAGE)) { _, granted ->
+            if (granted.isNotEmpty() && granted[0] == PackageManager.PERMISSION_GRANTED) {
+                isEnabled = false
+                exportLog()
+            }
+        }
+    }
+
+    companion object {
+        private val TAG = "WireGuard/" + LogExporterPreference::class.java.simpleName
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/preference/ModuleDownloaderPreference.java b/ui/src/main/java/com/wireguard/android/preference/ModuleDownloaderPreference.java
deleted file mode 100644
index 8bea5f8c..00000000
--- a/ui/src/main/java/com/wireguard/android/preference/ModuleDownloaderPreference.java
+++ /dev/null
@@ -1,93 +0,0 @@
-/*
- * Copyright © 2019 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.android.preference;
-
-import android.annotation.SuppressLint;
-import android.content.Context;
-import android.content.Intent;
-import android.system.OsConstants;
-import android.util.AttributeSet;
-import android.widget.Toast;
-
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-import com.wireguard.android.activity.SettingsActivity;
-import com.wireguard.android.util.ErrorMessages;
-import com.wireguard.util.NonNullForAll;
-
-import androidx.annotation.Nullable;
-import androidx.preference.Preference;
-
-@NonNullForAll
-public class ModuleDownloaderPreference extends Preference {
-    private State state = State.INITIAL;
-
-    public ModuleDownloaderPreference(final Context context, final AttributeSet attrs) {
-        super(context, attrs);
-    }
-
-    @Override
-    public CharSequence getSummary() {
-        return getContext().getString(state.messageResourceId);
-    }
-
-    @Override
-    public CharSequence getTitle() {
-        return getContext().getString(R.string.module_installer_title);
-    }
-
-    @Override
-    protected void onClick() {
-        setState(State.WORKING);
-        Application.getAsyncWorker().supplyAsync(Application.getModuleLoader()::download).whenComplete(this::onDownloadResult);
-    }
-
-    @SuppressLint("ApplySharedPref")
-    private void onDownloadResult(final Integer result, @Nullable final Throwable throwable) {
-        if (throwable != null) {
-            setState(State.FAILURE);
-            Toast.makeText(getContext(), ErrorMessages.get(throwable), Toast.LENGTH_LONG).show();
-        } else if (result == OsConstants.ENOENT)
-            setState(State.NOTFOUND);
-        else if (result == OsConstants.EXIT_SUCCESS) {
-            setState(State.SUCCESS);
-            Application.getSharedPreferences().edit().remove("disable_kernel_module").commit();
-            Application.getAsyncWorker().runAsync(() -> {
-                final Intent restartIntent = new Intent(getContext(), SettingsActivity.class);
-                restartIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
-                restartIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
-                Application.get().startActivity(restartIntent);
-                System.exit(0);
-            });
-        } else
-            setState(State.FAILURE);
-    }
-
-    private void setState(final State state) {
-        if (this.state == state)
-            return;
-        this.state = state;
-        if (isEnabled() != state.shouldEnableView)
-            setEnabled(state.shouldEnableView);
-        notifyChanged();
-    }
-
-    private enum State {
-        INITIAL(R.string.module_installer_initial, true),
-        FAILURE(R.string.module_installer_error, true),
-        WORKING(R.string.module_installer_working, false),
-        SUCCESS(R.string.success_application_will_restart, false),
-        NOTFOUND(R.string.module_installer_not_found, false);
-
-        private final int messageResourceId;
-        private final boolean shouldEnableView;
-
-        State(final int messageResourceId, final boolean shouldEnableView) {
-            this.messageResourceId = messageResourceId;
-            this.shouldEnableView = shouldEnableView;
-        }
-    }
-}
diff --git a/ui/src/main/java/com/wireguard/android/preference/ModuleDownloaderPreference.kt b/ui/src/main/java/com/wireguard/android/preference/ModuleDownloaderPreference.kt
new file mode 100644
index 00000000..6ecebb95
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/preference/ModuleDownloaderPreference.kt
@@ -0,0 +1,69 @@
+/*
+ * Copyright © 2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.preference
+
+import android.annotation.SuppressLint
+import android.content.Context
+import android.content.Intent
+import android.system.OsConstants
+import android.util.AttributeSet
+import android.widget.Toast
+import androidx.preference.Preference
+import com.wireguard.android.Application
+import com.wireguard.android.R
+import com.wireguard.android.activity.SettingsActivity
+import com.wireguard.android.util.ErrorMessages
+import kotlin.system.exitProcess
+
+class ModuleDownloaderPreference(context: Context, attrs: AttributeSet?) : Preference(context, attrs) {
+    private var state = State.INITIAL
+
+    override fun getSummary() = context.getString(state.messageResourceId)
+
+    override fun getTitle() = context.getString(R.string.module_installer_title)
+
+    override fun onClick() {
+        setState(State.WORKING)
+        Application.getAsyncWorker().supplyAsync(Application.getModuleLoader()::download).whenComplete(this::onDownloadResult)
+    }
+
+    @SuppressLint("ApplySharedPref")
+    private fun onDownloadResult(result: Int, throwable: Throwable?) {
+        when {
+            throwable != null -> {
+                setState(State.FAILURE)
+                Toast.makeText(context, ErrorMessages.get(throwable), Toast.LENGTH_LONG).show()
+            }
+            result == OsConstants.ENOENT -> setState(State.NOTFOUND)
+            result == OsConstants.EXIT_SUCCESS -> {
+                setState(State.SUCCESS)
+                Application.getSharedPreferences().edit().remove("disable_kernel_module").commit()
+                Application.getAsyncWorker().runAsync {
+                    val restartIntent = Intent(context, SettingsActivity::class.java)
+                    restartIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP)
+                    restartIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+                    Application.get().startActivity(restartIntent)
+                    exitProcess(0)
+                }
+            }
+            else -> setState(State.FAILURE)
+        }
+    }
+
+    private fun setState(state: State) {
+        if (this.state == state) return
+        this.state = state
+        if (isEnabled != state.shouldEnableView) isEnabled = state.shouldEnableView
+        notifyChanged()
+    }
+
+    private enum class State(val messageResourceId: Int, val shouldEnableView: Boolean) {
+        INITIAL(R.string.module_installer_initial, true),
+        FAILURE(R.string.module_installer_error, true),
+        WORKING(R.string.module_installer_working, false),
+        SUCCESS(R.string.success_application_will_restart, false),
+        NOTFOUND(R.string.module_installer_not_found, false);
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/preference/ToolsInstallerPreference.java b/ui/src/main/java/com/wireguard/android/preference/ToolsInstallerPreference.java
deleted file mode 100644
index 6219ed40..00000000
--- a/ui/src/main/java/com/wireguard/android/preference/ToolsInstallerPreference.java
+++ /dev/null
@@ -1,105 +0,0 @@
-/*
- * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.android.preference;
-
-import android.content.Context;
-import android.util.AttributeSet;
-
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-import com.wireguard.android.util.ToolsInstaller;
-import com.wireguard.util.NonNullForAll;
-
-import androidx.annotation.Nullable;
-import androidx.preference.Preference;
-
-/**
- * Preference implementing a button that asynchronously runs {@code ToolsInstaller} and displays the
- * result as the preference summary.
- */
-
-@NonNullForAll
-public class ToolsInstallerPreference extends Preference {
-    private State state = State.INITIAL;
-
-    public ToolsInstallerPreference(final Context context, final AttributeSet attrs) {
-        super(context, attrs);
-    }
-
-    @Override
-    public CharSequence getSummary() {
-        return getContext().getString(state.messageResourceId);
-    }
-
-    @Override
-    public CharSequence getTitle() {
-        return getContext().getString(R.string.tools_installer_title);
-    }
-
-    @Override
-    public void onAttached() {
-        super.onAttached();
-        Application.getAsyncWorker().supplyAsync(Application.getToolsInstaller()::areInstalled).whenComplete(this::onCheckResult);
-    }
-
-    private void onCheckResult(final int state, @Nullable final Throwable throwable) {
-        if (throwable != null || state == ToolsInstaller.ERROR)
-            setState(State.INITIAL);
-        else if ((state & ToolsInstaller.YES) == ToolsInstaller.YES)
-            setState(State.ALREADY);
-        else if ((state & (ToolsInstaller.MAGISK | ToolsInstaller.NO)) == (ToolsInstaller.MAGISK | ToolsInstaller.NO))
-            setState(State.INITIAL_MAGISK);
-        else if ((state & (ToolsInstaller.SYSTEM | ToolsInstaller.NO)) == (ToolsInstaller.SYSTEM | ToolsInstaller.NO))
-            setState(State.INITIAL_SYSTEM);
-        else
-            setState(State.INITIAL);
-    }
-
-    @Override
-    protected void onClick() {
-        setState(State.WORKING);
-        Application.getAsyncWorker().supplyAsync(Application.getToolsInstaller()::install).whenComplete(this::onInstallResult);
-    }
-
-    private void onInstallResult(final Integer result, @Nullable final Throwable throwable) {
-        if (throwable != null)
-            setState(State.FAILURE);
-        else if ((result & (ToolsInstaller.YES | ToolsInstaller.MAGISK)) == (ToolsInstaller.YES | ToolsInstaller.MAGISK))
-            setState(State.SUCCESS_MAGISK);
-        else if ((result & (ToolsInstaller.YES | ToolsInstaller.SYSTEM)) == (ToolsInstaller.YES | ToolsInstaller.SYSTEM))
-            setState(State.SUCCESS_SYSTEM);
-        else
-            setState(State.FAILURE);
-    }
-
-    private void setState(final State state) {
-        if (this.state == state)
-            return;
-        this.state = state;
-        if (isEnabled() != state.shouldEnableView)
-            setEnabled(state.shouldEnableView);
-        notifyChanged();
-    }
-
-    private enum State {
-        INITIAL(R.string.tools_installer_initial, true),
-        ALREADY(R.string.tools_installer_already, false),
-        FAILURE(R.string.tools_installer_failure, true),
-        WORKING(R.string.tools_installer_working, false),
-        INITIAL_SYSTEM(R.string.tools_installer_initial_system, true),
-        SUCCESS_SYSTEM(R.string.tools_installer_success_system, false),
-        INITIAL_MAGISK(R.string.tools_installer_initial_magisk, true),
-        SUCCESS_MAGISK(R.string.tools_installer_success_magisk, false);
-
-        private final int messageResourceId;
-        private final boolean shouldEnableView;
-
-        State(final int messageResourceId, final boolean shouldEnableView) {
-            this.messageResourceId = messageResourceId;
-            this.shouldEnableView = shouldEnableView;
-        }
-    }
-}
diff --git a/ui/src/main/java/com/wireguard/android/preference/ToolsInstallerPreference.kt b/ui/src/main/java/com/wireguard/android/preference/ToolsInstallerPreference.kt
new file mode 100644
index 00000000..f7dd932d
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/preference/ToolsInstallerPreference.kt
@@ -0,0 +1,71 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.preference
+
+import android.content.Context
+import android.util.AttributeSet
+import androidx.preference.Preference
+import com.wireguard.android.Application
+import com.wireguard.android.R
+import com.wireguard.android.util.ToolsInstaller
+
+/**
+ * Preference implementing a button that asynchronously runs `ToolsInstaller` and displays the
+ * result as the preference summary.
+ */
+class ToolsInstallerPreference(context: Context, attrs: AttributeSet?) : Preference(context, attrs) {
+    private var state = State.INITIAL
+
+    override fun getSummary() = context.getString(state.messageResourceId)
+
+    override fun getTitle() = context.getString(R.string.tools_installer_title)
+
+    override fun onAttached() {
+        super.onAttached()
+        Application.getAsyncWorker().supplyAsync(Application.getToolsInstaller()::areInstalled).whenComplete(this::onCheckResult)
+    }
+
+    private fun onCheckResult(state: Int, throwable: Throwable?) {
+        when {
+            throwable != null || state == ToolsInstaller.ERROR -> setState(State.INITIAL)
+            state and ToolsInstaller.YES == ToolsInstaller.YES -> setState(State.ALREADY)
+            state and (ToolsInstaller.MAGISK or ToolsInstaller.NO) == ToolsInstaller.MAGISK or ToolsInstaller.NO -> setState(State.INITIAL_MAGISK)
+            state and (ToolsInstaller.SYSTEM or ToolsInstaller.NO) == ToolsInstaller.SYSTEM or ToolsInstaller.NO -> setState(State.INITIAL_SYSTEM)
+            else -> setState(State.INITIAL)
+        }
+    }
+
+    override fun onClick() {
+        setState(State.WORKING)
+        Application.getAsyncWorker().supplyAsync { Application.getToolsInstaller().install() }.whenComplete { result: Int, throwable: Throwable? -> onInstallResult(result, throwable) }
+    }
+
+    private fun onInstallResult(result: Int, throwable: Throwable?) {
+        when {
+            throwable != null -> setState(State.FAILURE)
+            result and (ToolsInstaller.YES or ToolsInstaller.MAGISK) == ToolsInstaller.YES or ToolsInstaller.MAGISK -> setState(State.SUCCESS_MAGISK)
+            result and (ToolsInstaller.YES or ToolsInstaller.SYSTEM) == ToolsInstaller.YES or ToolsInstaller.SYSTEM -> setState(State.SUCCESS_SYSTEM)
+            else -> setState(State.FAILURE)
+        }
+    }
+
+    private fun setState(state: State) {
+        if (this.state == state) return
+        this.state = state
+        if (isEnabled != state.shouldEnableView) isEnabled = state.shouldEnableView
+        notifyChanged()
+    }
+
+    private enum class State(val messageResourceId: Int, val shouldEnableView: Boolean) {
+        INITIAL(R.string.tools_installer_initial, true),
+        ALREADY(R.string.tools_installer_already, false),
+        FAILURE(R.string.tools_installer_failure, true),
+        WORKING(R.string.tools_installer_working, false),
+        INITIAL_SYSTEM(R.string.tools_installer_initial_system, true),
+        SUCCESS_SYSTEM(R.string.tools_installer_success_system, false),
+        INITIAL_MAGISK(R.string.tools_installer_initial_magisk, true),
+        SUCCESS_MAGISK(R.string.tools_installer_success_magisk, false);
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/preference/VersionPreference.java b/ui/src/main/java/com/wireguard/android/preference/VersionPreference.java
deleted file mode 100644
index b5c7c5e8..00000000
--- a/ui/src/main/java/com/wireguard/android/preference/VersionPreference.java
+++ /dev/null
@@ -1,74 +0,0 @@
-/*
- * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.android.preference;
-
-import android.content.ActivityNotFoundException;
-import android.content.Context;
-import android.content.Intent;
-import android.net.Uri;
-import android.util.AttributeSet;
-
-import com.wireguard.android.Application;
-import com.wireguard.android.BuildConfig;
-import com.wireguard.android.R;
-import com.wireguard.android.backend.Backend;
-import com.wireguard.android.backend.GoBackend;
-import com.wireguard.android.backend.WgQuickBackend;
-import com.wireguard.util.NonNullForAll;
-
-import java.util.Locale;
-
-import androidx.annotation.Nullable;
-import androidx.preference.Preference;
-
-@NonNullForAll
-public class VersionPreference extends Preference {
-    @Nullable private String versionSummary;
-
-    public VersionPreference(final Context context, final AttributeSet attrs) {
-        super(context, attrs);
-
-        Application.getBackendAsync().thenAccept(backend -> {
-            versionSummary = getContext().getString(R.string.version_summary_checking, getBackendPrettyName(context, backend).toLowerCase(Locale.ENGLISH));
-            Application.getAsyncWorker().supplyAsync(backend::getVersion).whenComplete((version, exception) -> {
-                versionSummary = exception == null
-                        ? getContext().getString(R.string.version_summary, getBackendPrettyName(context, backend), version)
-                        : getContext().getString(R.string.version_summary_unknown, getBackendPrettyName(context, backend).toLowerCase(Locale.ENGLISH));
-                notifyChanged();
-            });
-        });
-    }
-
-    private static String getBackendPrettyName(final Context context, final Backend backend) {
-        if (backend instanceof WgQuickBackend)
-            return context.getString(R.string.type_name_kernel_module);
-        if (backend instanceof GoBackend)
-            return context.getString(R.string.type_name_go_userspace);
-        return "";
-    }
-
-    @Nullable
-    @Override
-    public CharSequence getSummary() {
-        return versionSummary;
-    }
-
-    @Override
-    public CharSequence getTitle() {
-        return getContext().getString(R.string.version_title, BuildConfig.VERSION_NAME);
-    }
-
-    @Override
-    protected void onClick() {
-        final Intent intent = new Intent(Intent.ACTION_VIEW);
-        intent.setData(Uri.parse("https://www.wireguard.com/"));
-        try {
-            getContext().startActivity(intent);
-        } catch (final ActivityNotFoundException ignored) {
-        }
-    }
-
-}
diff --git a/ui/src/main/java/com/wireguard/android/preference/VersionPreference.kt b/ui/src/main/java/com/wireguard/android/preference/VersionPreference.kt
new file mode 100644
index 00000000..6c5284ec
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/preference/VersionPreference.kt
@@ -0,0 +1,57 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.preference
+
+import android.content.ActivityNotFoundException
+import android.content.Context
+import android.content.Intent
+import android.net.Uri
+import android.util.AttributeSet
+import androidx.preference.Preference
+import com.wireguard.android.Application
+import com.wireguard.android.BuildConfig
+import com.wireguard.android.R
+import com.wireguard.android.backend.Backend
+import com.wireguard.android.backend.GoBackend
+import com.wireguard.android.backend.WgQuickBackend
+import java.util.Locale
+
+class VersionPreference(context: Context, attrs: AttributeSet?) : Preference(context, attrs) {
+    private var versionSummary: String? = null
+
+    override fun getSummary() = versionSummary
+
+    override fun getTitle() = context.getString(R.string.version_title, BuildConfig.VERSION_NAME)
+
+    override fun onClick() {
+        val intent = Intent(Intent.ACTION_VIEW)
+        intent.data = Uri.parse("https://www.wireguard.com/")
+        try {
+            context.startActivity(intent)
+        } catch (_: ActivityNotFoundException) {
+        }
+    }
+
+    companion object {
+        private fun getBackendPrettyName(context: Context, backend: Backend) = when (backend) {
+            is WgQuickBackend -> context.getString(R.string.type_name_kernel_module)
+            is GoBackend -> context.getString(R.string.type_name_go_userspace)
+            else -> ""
+        }
+    }
+
+    init {
+        Application.getBackendAsync().thenAccept { backend: Backend ->
+            versionSummary = getContext().getString(R.string.version_summary_checking, getBackendPrettyName(context, backend).toLowerCase(Locale.ENGLISH))
+            Application.getAsyncWorker().supplyAsync(backend::getVersion).whenComplete { version, exception ->
+                versionSummary = if (exception == null)
+                    getContext().getString(R.string.version_summary, getBackendPrettyName(context, backend), version)
+                else
+                    getContext().getString(R.string.version_summary_unknown, getBackendPrettyName(context, backend).toLowerCase(Locale.ENGLISH))
+                notifyChanged()
+            }
+        }
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/preference/ZipExporterPreference.java b/ui/src/main/java/com/wireguard/android/preference/ZipExporterPreference.java
deleted file mode 100644
index 0740787f..00000000
--- a/ui/src/main/java/com/wireguard/android/preference/ZipExporterPreference.java
+++ /dev/null
@@ -1,121 +0,0 @@
-/*
- * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
- * SPDX-License-Identifier: Apache-2.0
- */
-
-package com.wireguard.android.preference;
-
-import android.Manifest;
-import android.content.Context;
-import android.content.pm.PackageManager;
-import android.util.AttributeSet;
-import android.util.Log;
-
-import com.google.android.material.snackbar.Snackbar;
-import com.wireguard.android.Application;
-import com.wireguard.android.R;
-import com.wireguard.android.model.ObservableTunnel;
-import com.wireguard.android.util.DownloadsFileSaver;
-import com.wireguard.android.util.DownloadsFileSaver.DownloadsFile;
-import com.wireguard.android.util.ErrorMessages;
-import com.wireguard.android.util.FragmentUtils;
-import com.wireguard.config.Config;
-import com.wireguard.util.NonNullForAll;
-
-import java.nio.charset.StandardCharsets;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.zip.ZipEntry;
-import java.util.zip.ZipOutputStream;
-
-import androidx.annotation.Nullable;
-import androidx.preference.Preference;
-import java9.util.concurrent.CompletableFuture;
-
-/**
- * Preference implementing a button that asynchronously exports config zips.
- */
-
-@NonNullForAll
-public class ZipExporterPreference extends Preference {
-    private static final String TAG = "WireGuard/" + ZipExporterPreference.class.getSimpleName();
-
-    @Nullable private String exportedFilePath;
-
-    public ZipExporterPreference(final Context context, final AttributeSet attrs) {
-        super(context, attrs);
-    }
-
-    private void exportZip() {
-        Application.getTunnelManager().getTunnels().thenAccept(this::exportZip);
-    }
-
-    private void exportZip(final List<ObservableTunnel> tunnels) {
-        final List<CompletableFuture<Config>> futureConfigs = new ArrayList<>(tunnels.size());
-        for (final ObservableTunnel tunnel : tunnels)
-            futureConfigs.add(tunnel.getConfigAsync().toCompletableFuture());
-        if (futureConfigs.isEmpty()) {
-            exportZipComplete(null, new IllegalArgumentException(
-                    getContext().getString(R.string.no_tunnels_error)));
-            return;
-        }
-        CompletableFuture.allOf(futureConfigs.toArray(new CompletableFuture[futureConfigs.size()]))
-                .whenComplete((ignored1, exception) -> Application.getAsyncWorker().supplyAsync(() -> {
-                    if (exception != null)
-                        throw exception;
-                    DownloadsFile outputFile = DownloadsFileSaver.save(getContext(), "wireguard-export.zip", "application/zip", true);
-                    try (ZipOutputStream zip = new ZipOutputStream(outputFile.getOutputStream())) {
-                        for (int i = 0; i < futureConfigs.size(); ++i) {
-                            zip.putNextEntry(new ZipEntry(tunnels.get(i).getName() + ".conf"));
-                            zip.write(futureConfigs.get(i).getNow(null).
-                                    toWgQuickString().getBytes(StandardCharsets.UTF_8));
-                        }
-                        zip.closeEntry();
-                    } catch (final Exception e) {
-                        outputFile.delete();
-                        throw e;
-                    }
-                    return outputFile.getFileName();
-                }).whenComplete(this::exportZipComplete));
-    }
-
-    private void exportZipComplete(@Nullable final String filePath, @Nullable final Throwable throwable) {
-        if (throwable != null) {
-            final String error = ErrorMessages.get(throwable);
-            final String message = getContext().getString(R.string.zip_export_error, error);
-            Log.e(TAG, message, throwable);
-            Snackbar.make(
-                    FragmentUtils.getPrefActivity(this).findViewById(android.R.id.content),
-                    message, Snackbar.LENGTH_LONG).show();
-            setEnabled(true);
-        } else {
-            exportedFilePath = filePath;
-            notifyChanged();
-        }
-    }
-
-    @Override
-    public CharSequence getSummary() {
-        return exportedFilePath == null ?
-                getContext().getString(R.string.zip_export_summary) :
-                getContext().getString(R.string.zip_export_success, exportedFilePath);
-    }
-
-    @Override
-    public CharSequence getTitle() {
-        return getContext().getString(R.string.zip_export_title);
-    }
-
-    @Override
-    protected void onClick() {
-        FragmentUtils.getPrefActivity(this).ensurePermissions(
-                new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
-                (permissions, granted) -> {
-                    if (granted.length > 0 && granted[0] == PackageManager.PERMISSION_GRANTED) {
-                        setEnabled(false);
-                        exportZip();
-                    }
-                });
-    }
-
-}
diff --git a/ui/src/main/java/com/wireguard/android/preference/ZipExporterPreference.kt b/ui/src/main/java/com/wireguard/android/preference/ZipExporterPreference.kt
new file mode 100644
index 00000000..2a77f36c
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/preference/ZipExporterPreference.kt
@@ -0,0 +1,98 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.preference
+
+import android.Manifest
+import android.content.Context
+import android.content.pm.PackageManager
+import android.util.AttributeSet
+import android.util.Log
+import androidx.preference.Preference
+import com.google.android.material.snackbar.Snackbar
+import com.wireguard.android.Application
+import com.wireguard.android.R
+import com.wireguard.android.model.ObservableTunnel
+import com.wireguard.android.util.DownloadsFileSaver
+import com.wireguard.android.util.ErrorMessages
+import com.wireguard.android.util.FragmentUtils
+import com.wireguard.android.util.ObservableSortedKeyedList
+import com.wireguard.config.Config
+import java9.util.concurrent.CompletableFuture
+import java.nio.charset.StandardCharsets
+import java.util.ArrayList
+import java.util.zip.ZipEntry
+import java.util.zip.ZipOutputStream
+
+/**
+ * Preference implementing a button that asynchronously exports config zips.
+ */
+class ZipExporterPreference(context: Context, attrs: AttributeSet?) : Preference(context, attrs) {
+    private var exportedFilePath: String? = null
+
+    private fun exportZip() {
+        Application.getTunnelManager().tunnels.thenAccept(this::exportZip)
+    }
+
+    private fun exportZip(tunnels: List<ObservableTunnel>) {
+        val futureConfigs = tunnels.map { it.configAsync.toCompletableFuture() }.toTypedArray()
+        if (futureConfigs.isEmpty()) {
+            exportZipComplete(null, IllegalArgumentException(
+                    context.getString(R.string.no_tunnels_error)))
+            return
+        }
+        CompletableFuture.allOf(*futureConfigs)
+                .whenComplete { _, exception ->
+                    Application.getAsyncWorker().supplyAsync {
+                        if (exception != null) throw exception
+                        val outputFile = DownloadsFileSaver.save(context, "wireguard-export.zip", "application/zip", true)
+                        try {
+                            ZipOutputStream(outputFile.outputStream).use { zip ->
+                                for (i in futureConfigs.indices) {
+                                    zip.putNextEntry(ZipEntry(tunnels[i].name + ".conf"))
+                                    zip.write(futureConfigs[i].getNow(null)!!.toWgQuickString().toByteArray(StandardCharsets.UTF_8))
+                                }
+                                zip.closeEntry()
+                            }
+                        } catch (e: Exception) {
+                            outputFile.delete()
+                            throw e
+                        }
+                        outputFile.fileName
+                    }.whenComplete(this::exportZipComplete)
+                }
+    }
+
+    private fun exportZipComplete(filePath: String?, throwable: Throwable?) {
+        if (throwable != null) {
+            val error = ErrorMessages.get(throwable)
+            val message = context.getString(R.string.zip_export_error, error)
+            Log.e(TAG, message, throwable)
+            Snackbar.make(
+                    FragmentUtils.getPrefActivity(this).findViewById(android.R.id.content),
+                    message, Snackbar.LENGTH_LONG).show()
+            isEnabled = true
+        } else {
+            exportedFilePath = filePath
+            notifyChanged()
+        }
+    }
+
+    override fun getSummary() = if (exportedFilePath == null) context.getString(R.string.zip_export_summary) else context.getString(R.string.zip_export_success, exportedFilePath)
+
+    override fun getTitle() = context.getString(R.string.zip_export_title)
+
+    override fun onClick() {
+        FragmentUtils.getPrefActivity(this).ensurePermissions(arrayOf(Manifest.permission.WRITE_EXTERNAL_STORAGE)) { _, granted ->
+            if (granted.isNotEmpty() && granted[0] == PackageManager.PERMISSION_GRANTED) {
+                isEnabled = false
+                exportZip()
+            }
+        }
+    }
+
+    companion object {
+        private val TAG = "WireGuard/" + ZipExporterPreference::class.java.simpleName
+    }
+}