今天老大要求项目中增加双击退出程序的功能, 查了下大神们的博客, 随手记录下来:

  //记录用户首次点击返回键的时间
  private long firstTime = 0;

/**实现双击返回键退出程序
 * 方法一
 * 通过监听keyUp
 */
@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_UP) {
        long secondTime = System.currentTimeMillis();
        if (secondTime - firstTime > 2000) {
            Toast.makeText(IndexActivity.this, "再按一次退出应用", Toast.LENGTH_SHORT).show();
            firstTime = secondTime;
            return true;
        } else {
            System.exit(0); // 退出程序但 没有杀死进程
        }
    }
    return super.onKeyUp(keyCode, event);
}



/** 方法二
 * 监听keyDown
 */
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
    if (keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN) {
        long secondTime = System.currentTimeMillis();
        if (secondTime - firstTime > 2000) {
            Toast.makeText(IndexActivity.this, "再按一次退出程序", Toast.LENGTH_SHORT).show();
            firstTime = secondTime;
        } else {  
            finish();
            System.exit(0);
        }
        return true;
    }
    return super.onKeyDown(keyCode, event);
}