Close application and launch home screen on Androi

Question

I have two different activities. The first launches the second one. In the second activity, I call System.exit(0) in order to force the application to close, but the first activity is automatically displayed instead of the application returning to the home screen. How can I avoid this, and get the application to return to the home screen?

Answer 1

Android has a mechanism in place to close an application safely per its documentation. In the last Activity that is exited (usually the main Activity that first came up when the application started) just place a couple of lines in the onDestroy() method. The call to System.runFinalizersOnExit(true) ensures that all objects will be finalized and garbage collected when the the application exits. For example:

public void onDestroy() {
    super.onDestroy();

    /*
     * Notify the system to finalize and collect all objects of the
     * application on exit so that the process running the application can
     * be killed by the system without causing issues. NOTE: If this is set
     * to true then the process will not be killed until all of its threads
     * have closed.
     */
    System.runFinalizersOnExit(true);

    /*
     * Force the system to close the application down completely instead of
     * retaining it in the background. The process that runs the application
     * will be killed. The application will be completely created as a new
     * application in a new process if the user starts the application
     * again.
     */
    System.exit(0);
}

Finally Android will not notify an application of the HOME key event, so you cannot close the application when the HOME key is pressed. Android reserves the HOME key event to itself so that a developer cannot prevent users from leaving their application.

Answer 2

Say you have activity stack like A>B>C>D>E. You are at activity D, and you want to close your app. This is what you wil do -

In Activity from where you want to close (Activity D)-

Intent intent = new Intent(D.this,A.class);
intent.putExtra("exit", "exit");
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP| Intent.FLAG_ACTIVITY_SINGLE_TOP);
startActivity(intent);

In your RootActivity (ie your base activity, here Activity A) -

@Override
    protected void onNewIntent(Intent intent) {
        super.onNewIntent(intent);
        if (intent.hasExtra("exit")) {
            setIntent(intent);
        }
    }

    @Override
    protected void onResume() {
        super.onResume();
        if (getIntent() != null) {
            if (("exit").equalsIgnoreCase(getIntent().getStringExtra(("exit")))) {
                onBackPressed();
            }
        }
    }

onNewIntent is used because if activity is alive, it will get the first intent that started it. Not the new one. For more detail - Documentation

Answer 3

When you launch the second activity, finish() the first one immediately:

startActivity(new Intent(...));
finish();

Answer 4

Start the second activity with startActivityForResult and in the second activity return a value, that once in the onActivityResult method of the first activity closes the main application. I think this is the correct way Android does it.

Answer 5

I use this:

1) The parent activity call the secondary activity with the method "startActivityForResult"

2) In the secondary activity when is closing:

int exitCode = 1; // Select the number you want
setResult(exitCode);
finish();

3) And in the parent activity override the method "onActivityResult":

public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    int exitCode = 1;
    if(resultCode == exitCode) {
        super.setResult(exitCode); // use this if you have more than 2 activities
        finish();
    }
}

This works fine for me.

Answer 6

Use the finish method. It is the simpler and easier method.

this.finish();