Android：再按一次退出程序

感觉这种效果比较友好

//两秒内按返回键两次退出程序
    private long exitTime = 0; 

    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
    if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){
    if((System.currentTimeMillis()-exitTime) > 2000){
    Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();
    exitTime = System.currentTimeMillis();
    } else {
    finish();
    System.exit(0);
    }
    return true;
    }
    return super.onKeyDown(keyCode, event);
    } 

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