Hey there! Let's break down the implementation for both of your requirements—since you're working with a system-signed Android app, you have access to privileged APIs that regular apps don't, making these tasks totally feasible.

First, we'll build a button that checks the current TTS state and toggles it with a tap. Here's a step-by-step approach:

Step 1: Check if TTS is Enabled #

To determine if the system has an active TTS engine configured, read from secure system settings:

private boolean isTTSEnabled(Context context) {
    String defaultEngine = Settings.Secure.getString(context.getContentResolver(), Settings.Secure.TTS_DEFAULT_ENGINE);
    return defaultEngine != null && !defaultEngine.isEmpty();
}

Step 2: Toggle TTS State on Button Click #

As a system-signed app, you can modify secure settings to enable/disable the default TTS engine. Here's the click listener logic:

Button ttsToggleButton = findViewById(R.id.tts_toggle_btn);
TextToSpeech ttsInstance = null;

ttsToggleButton.setOnClickListener(v -> {
    boolean isEnabled = isTTSEnabled(getApplicationContext());
    
    if (isEnabled) {
        // Disable TTS: Clear the default engine
        Settings.Secure.putString(getContentResolver(), Settings.Secure.TTS_DEFAULT_ENGINE, "");
        // Stop ongoing playback and clean up the TTS instance
        if (ttsInstance != null) {
            ttsInstance.stop();
            ttsInstance.shutdown();
            ttsInstance = null;
        }
        ttsToggleButton.setText("Enable TTS");
    } else {
        // Enable TTS: Initialize with the first available engine
        ttsInstance = new TextToSpeech(getApplicationContext(), status -> {
            if (status == TextToSpeech.SUCCESS) {
                List<TextToSpeech.EngineInfo> engines = ttsInstance.getEngines();
                if (!engines.isEmpty()) {
                    Settings.Secure.putString(getContentResolver(), Settings.Secure.TTS_DEFAULT_ENGINE, engines.get(0).name);
                    // Optional: Set default language (handle unsupported cases)
                    int langResult = ttsInstance.setLanguage(Locale.getDefault());
                    if (langResult == TextToSpeech.LANG_MISSING_DATA || langResult == TextToSpeech.LANG_NOT_SUPPORTED) {
                        Log.w("TTS", "Default language not supported");
                    }
                }
            }
        });
        ttsToggleButton.setText("Disable TTS");
    }
});

Required Permission #

Add this to your app's AndroidManifest.xml (only system-signed apps can use this permission):

<uses-permission android:name="android.permission.WRITE_SECURE_SETTINGS" />

Regular apps can't modify system settings directly, so we'll use a broadcast-based approach to let them signal your system app to perform these actions.

Triggering TTS Toggle #

1. Register a Custom Broadcast Receiver in your system app's manifest (use a custom permission to restrict access to trusted apps):

<receiver android:name=".TTSToggleReceiver"
          android:permission="com.your.system.app.PERMISSION_TOGGLE_TTS">
    <intent-filter>
        <action android:name="com.your.system.app.ACTION_TOGGLE_TTS" />
    </intent-filter>
</receiver>

<!-- Define your custom restricted permission -->
<permission android:name="com.your.system.app.PERMISSION_TOGGLE_TTS"
            android:protectionLevel="signatureOrSystem" />

2. Implement the Receiver to handle the toggle logic:

public class TTSToggleReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // Reuse the isTTSEnabled and toggle logic from Section 1 here
        boolean isEnabled = isTTSEnabled(context);
        // ... perform the TTS toggle action ...
    }
}

3. Other Apps Send the Broadcast (they need to declare your custom permission in their manifest):

Intent toggleIntent = new Intent("com.your.system.app.ACTION_TOGGLE_TTS");
context.sendBroadcast(toggleIntent);

Enabling/Disabling TalkBack #

TalkBack is an accessibility service, so we'll manipulate secure settings to toggle it. Note that TalkBack's component name may vary by manufacturer—adjust if needed:

private void toggleTalkBack(Context context) {
    AccessibilityManager am = (AccessibilityManager) context.getSystemService(Context.ACCESSIBILITY_SERVICE);
    // Stock Android TalkBack component; adjust for custom skins
    ComponentName talkBackComponent = new ComponentName("com.google.android.marvin.talkback", 
                                                        "com.google.android.marvin.talkback.TalkBackService");
    
    boolean isTalkBackEnabled = am.isEnabled() && am.getEnabledAccessibilityServices().contains(talkBackComponent);
    
    String enabledServices = Settings.Secure.getString(context.getContentResolver(), Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES);
    if (isTalkBackEnabled) {
        // Disable TalkBack: Remove its component from the enabled list
        String updatedServices = enabledServices.replace(talkBackComponent.flattenToString(), "").replace("::", ":");
        Settings.Secure.putString(context.getContentResolver(), Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES, updatedServices);
        // Turn off accessibility if no other services are active (optional)
        if (updatedServices.isEmpty()) {
            Settings.Secure.putInt(context.getContentResolver(), Settings.Secure.ACCESSIBILITY_ENABLED, 0);
        }
    } else {
        // Enable TalkBack: Add its component to the enabled list
        String updatedServices = enabledServices.isEmpty() 
            ? talkBackComponent.flattenToString() 
            : enabledServices + ":" + talkBackComponent.flattenToString();
        Settings.Secure.putString(context.getContentResolver(), Settings.Secure.ENABLED_ACCESSIBILITY_SERVICES, updatedServices);
        Settings.Secure.putInt(context.getContentResolver(), Settings.Secure.ACCESSIBILITY_ENABLED, 1);
    }
}

You can expose this TalkBack toggle via the same broadcast receiver pattern used for TTS.

Key Notes #

• Manufacturer Variations: TalkBack's package name might differ on non-stock Android. Use am.getInstalledAccessibilityServices() to fetch all available accessibility services and find the correct component.
• System Signature: All these operations require your app to be signed with the system's platform key and have the necessary permissions.
• User Experience: Always notify users when toggling accessibility features, as they drastically change device interaction.

内容的提问来源于stack exchange，提问作者Alien Geography