Android使用Handler实现倒计时功能

本文实例为大家分享了Android实现倒计时功能的具体代码，供大家参考，具体内容如下

1、实现效果

如下图所示：

2、代码实现

新建一个名为CountdownTime的项目，activity_main.xml代码如下：

MainActivity.class代码如下：

public class MainActivity extends AppCompatActivity {

  
  public static final int COUNTDOWN_TIME_CODE = 99999;
  
  public static final int DELAY_MILLIS = 1000;
  
  public static final int MAX_COUNT = 10;
  
  private TextView countdownTimeTextView;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    //初始化文本控件
    countdownTimeTextView = findViewById(R.id.countdownTimeTextView);
    //创建一个handler
    CountdownTimeHandler handler = new CountdownTimeHandler(this);
    //新建一个message
    Message message = Message.obtain();
    message.what = COUNTDOWN_TIME_CODE;
    message.arg1 = MAX_COUNT;
    //第一次发送message
    handler.sendMessageDelayed(message, DELAY_MILLIS);
  }

  public static class CountdownTimeHandler extends Handler {
    
    public static final int MIN_COUNT = 0;
    //创建MainActivity弱引用
    final WeakReference mWeakReference;

    public CountdownTimeHandler(MainActivity activity) {
      this.mWeakReference = new WeakReference<>(activity);
    }

    @Override
    public void handleMessage(Message msg) {
      super.handleMessage(msg);
      //获取对MainActivity的弱引用
      MainActivity activity = mWeakReference.get();
      switch (msg.what) {
 case COUNTDOWN_TIME_CODE:
   int value = msg.arg1;
   activity.countdownTimeTextView.setText(String.valueOf(value--));
   //循环发送消息的控制
   if (value >= MIN_COUNT) {
     Message message = Message.obtain();
     message.what = COUNTDOWN_TIME_CODE;
     message.arg1 = value;
     sendMessageDelayed(message, DELAY_MILLIS);
   }
   break;
      }
    }
  }
}

3、快捷键总结

Ctrl+Alt+F：改变变量的域
Ctrl+Alt+T：surrounded with快捷键
Ctrl+P：查看方法的参数

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持考高分网。