定时器Android

来源：互联网发布：黑客使用的linux发行版编辑：程序博客网时间：2024/05/16 00:40

定时器postDelayed的实现
这是一种可以创建多线程消息的函数
使用方法：
1，首先创建一个Handler对象
Handler handler=new Handler();
2，然后创建一个Runnable对象
Runnable runnable=new Runnable(){
@Override
public void run() {
// TODO Auto-generated method stub
//要做的事情，这里再次调用此Runnable对象，以实现每两秒实现一次的定时器操作
handler.postDelayed(this, 2000);
}
};
3，使用PostDelayed方法，两秒后调用此Runnable对象
handler.postDelayed(runnable, 2000);
实际上也就实现了一个2s的一个定时器
4，如果想要关闭此定时器，可以这样操作
handler.removeCallbacks(runnable);

当然，你也可以做一个闹钟提醒延时的函数试试，比如，先用MediaPlayer播放闹钟声音，
如果不想起，被停止播放之后，下次就5分钟后再播放，再被停止的话，下次就4分钟后播放，
………………
只要更改延时的时间就可以实现了，用一个static对象的话会比较容易操作。

错误的定时器写法一：

@Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.fragment_main);        final TextView tv = (TextView) findViewById(R.id.tv);        tvShow = (TextView) findViewById(R.id.tv_show);        new Handler().postDelayed(new Runnable() {            @Override            public void run() {                // TODO Auto-generated method stub                int i = 0;                tv.setText(""+i+"");                System.out.println("i--->" + i);            }        }, 1000);    }

直接使用new Handler().postDelayed();这种方式无法实现定时器操作。原因我也没分析出来。
错误的定时器写法二：

    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        requestWindowFeature(Window.FEATURE_NO_TITLE);        setContentView(R.layout.fragment_main);        tvShow = (TextView) findViewById(R.id.tv_show);        new Thread(new ThreadShow()).start();      } // 线程类      class ThreadShow implements Runnable {        @Override        public void run() {            // TODO Auto-generated method stub            while (true) {                try {                    Thread.sleep(1000);                    tvShow.setText(Integer.toString(i++));                     System.out.println("send...");                } catch (Exception e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                    System.out.println("thread error...");                }            }        }    }

线程类中无法操作控件元素TextView。所以需要接住Message类来传递给Handler类。
以下三种是正确的定时器写法。
方法一:Handler+Thread

package com.xunfang.handerDemo;  import android.app.Activity;  import android.os.Bundle;  import android.os.Handler;  import android.os.Message;  import android.widget.TextView;  /**  * handler定时器  *   * @author Smalt  *   */  public class HanderDemoActivity extends Activity {      TextView tvShow;      private int i = 0;      @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);          tvShow = (TextView) findViewById(R.id.tv_show);          new Thread(new ThreadShow()).start();      }      // handler类接收数据      Handler handler = new Handler() {          public void handleMessage(Message msg) {              if (msg.what == 1) {                  tvShow.setText(Integer.toString(i++));                  System.out.println("receive....");              }          };      };      // 线程类      class ThreadShow implements Runnable {          @Override          public void run() {              // TODO Auto-generated method stub              while (true) {                  try {                      Thread.sleep(1000);                      Message msg = new Message();                      msg.what = 1;                      handler.sendMessage(msg);                      System.out.println("send...");                  } catch (Exception e) {                      // TODO Auto-generated catch block                      e.printStackTrace();                      System.out.println("thread error...");                  }              }          }      }  }

方法二:Handler类自带的postDelyed

package com.xunfang.handerDemo;  import android.app.Activity;  import android.os.Bundle;  import android.os.Handler;  import android.widget.TextView;  /**  * handler定时器使用postDelyed实现  *   * @author Smalt  *   */  public class HanderDemoActivity extends Activity {      TextView tvShow;      private int i = 0;      private int TIME = 1000;      @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);          tvShow = (TextView) findViewById(R.id.tv_show);          handler.postDelayed(runnable, TIME); //每隔1s执行      }      Handler handler = new Handler();      Runnable runnable = new Runnable() {          @Override          public void run() {              // handler自带方法实现定时器              try {                  handler.postDelayed(this, TIME);                  tvShow.setText(Integer.toString(i++));                  System.out.println("do...");              } catch (Exception e) {                  // TODO Auto-generated catch block                  e.printStackTrace();                  System.out.println("exception...");              }          }      };  }

方法三:Handler+Timer+TimerTask

package com.xunfang.handerDemo;  import java.util.Timer;  import java.util.TimerTask;  import android.app.Activity;  import android.os.Bundle;  import android.os.Handler;  import android.os.Message;  import android.widget.TextView;  /**  * 定时器实现:Handler+Timer+TimerTask  *   * @author Smalt  *   */  public class HanderDemoActivity extends Activity {      TextView tvShow;      private int i = 0;      private int TIME = 1000;      @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.main);          tvShow = (TextView) findViewById(R.id.tv_show);          timer.schedule(task, 1000, 1000); // 1s后执行task,经过1s再次执行      }      Handler handler = new Handler() {          public void handleMessage(Message msg) {              if (msg.what == 1) {                  tvShow.setText(Integer.toString(i++));              }              super.handleMessage(msg);          };      };      Timer timer = new Timer();      TimerTask task = new TimerTask() {          @Override          public void run() {              // 需要做的事:发送消息              Message message = new Message();              message.what = 1;              handler.sendMessage(message);          }      };  }

0 0