Android學習筆記（四） 定時器Timer

標籤：

  Android考慮到安全執行緒問題，不允許線上程中執行UI線程。

所以線上程中不允許有UI操作

可以利用Handler機制來接收Timer每隔一秒發出的資訊，也可以直接利用handler機制的

1、方法一:Handler+Thread

 

package com.example.yuyin_lixian;import android.os.Bundle;import android.app.Activity;import android.view.Menu;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.util.Log;import android.view.View;import android.widget.Button;import android.widget.TextView;     /** * handler定時器 * * @author Smalt * */public class MainActivity extends Activity {    TextView tvShow;    private int i = 0;         @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        tvShow = (TextView) findViewById(R.id.textView1);        new Thread(new ThreadShow()).start();    }         // handler類接收資料    Handler handler = new Handler() {        public void handleMessage(Message msg) {            if (msg.what == 1) {                tvShow.setText(Integer.toString(i++));                System.out.println("receive....");            }        };    };         // 線程類    class ThreadShow implements Runnable {             @Override        public void run() {            // TODO Auto-generated method stub            while (true) {                try {                    Thread.sleep(1000);   //每隔一秒執行一次                    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...");                }            }        }    }}

 

2、方法二:Handler類內建的postDelyed

其中使用PostDelayed方法，1秒後調用此Runnable對象
handler.postDelayed(runnable, 1000); 實際上也就實現了一個1s的一個定時器

如果想要關閉此定時器，可以這樣操作
handler.removeCallbacks(runnable);

package com.example.yuyin_lixian;import android.app.Activity;  import android.os.Bundle;  import android.os.Handler;  import android.widget.TextView;    /**  * handler定時器使用postDelyed實現  *   * @author Smalt  *   */  public class MainActivity extends Activity {      TextView tvShow;      private int i = 0;      private int TIME = 1000;        @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);          tvShow = (TextView) findViewById(R.id.textView1);          handler.postDelayed(runnable, TIME); //每隔1s執行      }        Handler handler = new Handler();      Runnable runnable = new Runnable() {            @Override          public void run() {              // handler內建方法實現定時器              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...");              }          }      };    }

 

3、方法二:Handler+Timer+TimerTask

 

package com.example.yuyin_lixian;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;    /**  * 定時器實現:Handler+Timer+TimerTask  *   * @author Smalt  *   */  public class MainActivity extends Activity {      TextView tvShow;      private int i = 0;      private int TIME = 1000;        @Override      public void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);          tvShow = (TextView) findViewById(R.id.textView1);          timer.schedule(task, 1000, 1000); // 1s後執行task,經過1s再次執行      }        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:發送訊息              Message message = new Message();              message.what = 1;              handler.sendMessage(message);          }      };  }

Android學習筆記（四） 定時器Timer