How can I programmatically start and stop an Acces

问题:

Background

I have an app that has an AccessibilityService. Android seems to keep AccessibilityServices running all the time, but I only need mine to run sometimes. (Specifically, if a user opens my app and turns it off, the AccessibilityService is no longer needed.)

If my AccessibilityService is running when it isn't needed, it's wasting the device's RAM and CPU, and I want to avoid doing this to my users if possible.

Question

How can I programmatically start and stop my AccessibilityService?

Note that I am not asking to programmatically enable or disable the AccessibilityService in Android's accessibility settings; this is just about starting and stopping it when it's already enabled.

What I've tried (stopping the AccessibilityService)

• Disabling the AccessibilityService component using the following:

  PackageManager.setComponentEnabledSetting(
      accessibilityServiceName,
      PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
      0
  );
  

  This killed the entire application, including the AccessibilityService. Also, after rebooting the phone, the AccessibilityService was no longer visible in the Android accessibility settings. (It seems that the component needs to be re-enabled followed by restarting the phone in order to get it to show up again.)

• Disabling the AccessibilityService component using the following:

  PackageManager.setComponentEnabledSetting(
      accessibilityServiceName,
      PackageManager.COMPONENT_ENABLED_STATE_DISABLED,
      PackageManager.DONT_KILL_APP
  );
  

  This didn't stop the AccessibilityService.

• Stopping the AccessibilityService using Context.stopService() and Service.stopSelf(). These didn't stop the service, presumably because the OS is bound to it.

• Killing the AccessibilityService's process using Process.killProcess(). However, the service was soon after restarted and reconnected, presumably because the OS is bound to it.

• Unregistering for accessibility events using AccessibilityService.setServiceInfo(new AccessibilityServiceInfo()). This stops the service from getting accessibility events, but the service still runs in the background.

Related questions

• Can accessibility service be stopped or killed?

  This one is only about stopping the service. I want to be able to start the service again once it's stopped.

回答1:

Taken from the Lifecycle section of the AccessibilityService documentation:

The lifecycle of an accessibility service is managed exclusively by the system and follows the established service life cycle. Starting an accessibility service is triggered exclusively by the user explicitly turning the service on in device settings. After the system binds to a service, it calls onServiceConnected(). This method can be overriden by clients that want to perform post binding setup.

An accessibility service stops either when the user turns it off in device settings or when it calls disableSelf() (In Android 7.0 (API 24) and later).

回答2:

As stated in Sam's answer, the lifecycle of an AccessibilityService is managed exclusively by the system, so you can't kill it.

But apart resource optimization aims, if you still need to start/stop the AccessibilityService from operating in some circumstances, you can simply use the good old SharedPreferences.

Your Service's onAccessibilityEvent should be:

@Override
public void onAccessibilityEvent(AccessibilityEvent event) {
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getBaseContext());

    if (prefs.getBoolean("isServiceEnabled", true)){
        /*
        * Your code goes here
        */
    }
}

When you want to "switch off/on" the service you can do it by simply writing this in some button's onClickListener or somewhere else according to your needs:

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);

prefs.edit().putBoolean("isServiceEnabled", false).apply(); // disable

prefs.edit().putBoolean("isServiceEnabled", true).apply();  // enable