Enable Linux terminal app via developer settings

Bug: 369246712
Test: `atest SettingsRoboTests`, try toggle the option, \
  and try search with 'Linux'.
Flag: RELEASE_AVF_SUPPORT_CUSTOM_VM_WITH_PARAVIRTUALIZED_DEVICES
Change-Id: Ibdcf00de04f09fe5b03ba53857904945354ed844

src/com/android/settings/development/DevelopmentSettingsDashboardFragment.java

@@ -676,6 +676,7 @@ public class DevelopmentSettingsDashboardFragment extends RestrictedDashboardFra
         controllers.add(new WirelessDebuggingPreferenceController(context, lifecycle));
         controllers.add(new AdbAuthorizationTimeoutPreferenceController(context));
         controllers.add(new LocalTerminalPreferenceController(context));
+        controllers.add(new LinuxTerminalPreferenceController(context));
         controllers.add(new BugReportInPowerPreferenceController(context));
         controllers.add(new AutomaticSystemServerHeapDumpPreferenceController(context));
         controllers.add(new MockLocationAppPreferenceController(context, fragment));

src/com/android/settings/development/LinuxTerminalPreferenceController.java

@@ -0,0 +1,127 @@
+/*
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.development;
+
+import android.content.Context;
+import android.content.pm.PackageManager;
+import android.text.TextUtils;
+import android.util.Log;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.annotation.VisibleForTesting;
+import androidx.preference.Preference;
+import androidx.preference.PreferenceScreen;
+import androidx.preference.TwoStatePreference;
+
+import com.android.settings.R;
+import com.android.settings.core.PreferenceControllerMixin;
+import com.android.settingslib.development.DeveloperOptionsPreferenceController;
+
+public class LinuxTerminalPreferenceController extends DeveloperOptionsPreferenceController
+        implements Preference.OnPreferenceChangeListener, PreferenceControllerMixin {
+    private static final String TAG = "LinuxTerminalPrefCtrl";
+
+    private static final String ENABLE_TERMINAL_KEY = "enable_linux_terminal";
+
+    @NonNull
+    private final PackageManager mPackageManager;
+
+    @Nullable
+    private final String mTerminalPackageName;
+
+    public LinuxTerminalPreferenceController(@NonNull Context context) {
+        super(context);
+        mPackageManager = mContext.getPackageManager();
+
+        String packageName = mContext.getString(R.string.config_linux_terminal_app_package_name);
+        mTerminalPackageName =
+                isPackageInstalled(mPackageManager, packageName) ? packageName : null;
+
+        Log.d(TAG, "Terminal app package name=" + packageName + ", isAvailable=" + isAvailable());
+    }
+
+    // Avoid lazy initialization because this may be called before displayPreference().
+    @Override
+    public boolean isAvailable() {
+        // Returns true only if the terminal app is installed which only happens when the build flag
+        // RELEASE_AVF_SUPPORT_CUSTOM_VM_WITH_PARAVIRTUALIZED_DEVICES is true.
+        // TODO(b/343795511): Add explicitly check for the flag when it's accessible from Java code.
+        return getTerminalPackageName() != null;
+    }
+
+    @Override
+    @NonNull
+    public String getPreferenceKey() {
+        return ENABLE_TERMINAL_KEY;
+    }
+
+    @Override
+    public void displayPreference(@NonNull PreferenceScreen screen) {
+        super.displayPreference(screen);
+        mPreference.setEnabled(isAvailable());
+    }
+
+    @Override
+    public boolean onPreferenceChange(
+                @NonNull Preference preference, @NonNull Object newValue) {
+        String packageName = getTerminalPackageName();
+        if (packageName == null) {
+            return false;
+        }
+
+        boolean terminalEnabled = (Boolean) newValue;
+        int state = terminalEnabled
+                ? PackageManager.COMPONENT_ENABLED_STATE_ENABLED
+                : PackageManager.COMPONENT_ENABLED_STATE_DEFAULT;
+        mPackageManager.setApplicationEnabledSetting(packageName, state, /* flags=*/ 0);
+        ((TwoStatePreference) mPreference).setChecked(terminalEnabled);
+        return true;
+    }
+
+    @Override
+    public void updateState(@NonNull Preference preference) {
+        String packageName = getTerminalPackageName();
+        if (packageName == null) {
+            return;
+        }
+
+        boolean isTerminalEnabled = mPackageManager.getApplicationEnabledSetting(packageName)
+                == PackageManager.COMPONENT_ENABLED_STATE_ENABLED;
+        ((TwoStatePreference) mPreference).setChecked(isTerminalEnabled);
+    }
+
+    // Can be mocked for testing
+    @VisibleForTesting
+    @Nullable
+    String getTerminalPackageName() {
+        return mTerminalPackageName;
+    }
+
+    private static boolean isPackageInstalled(PackageManager manager, String packageName) {
+        if (TextUtils.isEmpty(packageName)) {
+            return false;
+        }
+        try {
+            return manager.getPackageInfo(
+                    packageName,
+                    PackageManager.MATCH_ALL | PackageManager.MATCH_DISABLED_COMPONENTS) != null;
+        } catch (PackageManager.NameNotFoundException e) {
+            return false;
+        }
+    }
+}