Android click the Back key twice to listen to exit the program

This Blog has documented how to exit the program by clicking the Back key twice

The effect is as follows:

Let’s do it this way

	@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
   		return super.onKeyDown(keyCode, event);
    }

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Then explain what these two methods do: onKeyDown() is triggered when a key is pressed, but not handled by any view within the Activity. By default, pressing KEYCODE_BACK returns to the previous Activity.

OnKeyUp () : Emitted when a key is pressed and released, but not handled by any view within the Activity. By default, nothing is done, simply giving false as the return value.

The implementation code

	/** * First time click on back */
    private Long mExitTime = 0L;


	@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN) {
            if (System.currentTimeMillis() - mExitTime > 2000) {
                Toast.makeText(this."Press exit again.", Toast.LENGTH_SHORT).show();
                mExitTime = System.currentTimeMillis();
            } else {
                finish();
                System.exit(0);
            }
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }

Copy the code

This is generally done in this way

The above