仿UC点击两次返回键退出程序
应用场景:点击两次Back键退出程序
效果图:
实现原理:onKeyDown()会捕获当前点击事件,如果当前keyCode等于BACK事件值就会执行exit()方法。在exit()方法中,首先判断isExit的值,如果为false的话,则置为true,同时会弹出提示,并在3000毫秒(3秒)后发出一个消息,在Handler中接收到消息后将isExit值还原成false。如果在发送消息间隔的3秒内,再次按了BACK键,则再次执行exit方法,此时isExit的值已为true,则会执行退出程序的方法。
实现步骤:
1、定义一个boolean型的变量,默认值为false
private boolean isExit = false;
2、覆写Activity中onKeyDown()方法
@Override public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK)// 当keyCode等于退出事件值时 { exit(); return false; } else { return super.onKeyDown(keyCode, event); } }
3、封装exit()方法
private void exit() { if (isExit) { // ACTION_MAIN with category CATEGORY_HOME 启动主屏幕 Intent intent = new Intent(Intent.ACTION_MAIN); intent.addCategory(Intent.CATEGORY_HOME); startActivity(intent); System.exit(0);// 使虚拟机停止运行并退出程序 } else { isExit = true; Toast.makeText(TwoTimesBackActivity.this, "再按一次退出", Toast.LENGTH_SHORT).show(); mHandler.sendEmptyMessageDelayed(0, 3000);// 3秒后发送消息 } }
4、创建Handler对象,用来处理消息
Handler mHandler = new Handler() { @Override public void handleMessage(Message msg)//处理消息 { super.handleMessage(msg); isExit = false; } };
代码如下:
public class TwoTimesBackActivity extends Activity { private boolean isExit = false; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK)// 当keyCode等于退出事件值时 { exit(); return false; } else { return super.onKeyDown(keyCode, event); } } private void exit() { if (isExit) { // ACTION_MAIN with category CATEGORY_HOME 启动主屏幕 Intent intent = new Intent(Intent.ACTION_MAIN); intent.addCategory(Intent.CATEGORY_HOME); startActivity(intent); System.exit(0);// 使虚拟机停止运行并退出程序 } else { isExit = true; Toast.makeText(TwoTimesBackActivity.this, "再按一次退出", Toast.LENGTH_SHORT).show(); mHandler.sendEmptyMessageDelayed(0, 3000);// 3秒后发送消息 } } Handler mHandler = new Handler() { @Override public void handleMessage(Message msg)//处理消息 { super.handleMessage(msg); isExit = false; } }; }