Android中“再按一次返回键退出程序”实现

    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); 

    }