下面是一個在Android中使用定時器Timer和TimerTask的啟動，停止，暫停，繼續等操作的demo。
需要注意的問題主要有兩點：
1、Timer和TimerTask在呼叫cancel()取消後不能再執行 schedule語句，否則提示出錯，提示如下：

D/AndroidRuntime( 6672): Shutting down VM  
W/dalvikvm( 6672): threadid=1: thread exiting with uncaught exception (group=0x40018560)  
E/AndroidRuntime( 6672): FATAL EXCEPTION: main  
E/AndroidRuntime( 6672): java.lang.IllegalStateException: Timer was canceled  
E/AndroidRuntime( 6672):    at java.util.Timer.scheduleImpl(Timer.java:563)  
E/AndroidRuntime( 6672):    at java.util.Timer.schedule(Timer.java:483)  
E/AndroidRuntime( 6672):    at com.snowdream.timerdemo.TimerDemoActivity$2.onClick(TimerDemoActivity.java:73)  
E/AndroidRuntime( 6672):    at android.view.View.performClick(View.java:2501)  
E/AndroidRuntime( 6672):    at android.view.View$PerformClick.run(View.java:9107)  
E/AndroidRuntime( 6672):    at android.os.Handler.handleCallback(Handler.java:587)  
E/AndroidRuntime( 6672):    at android.os.Handler.dispatchMessage(Handler.java:92)  
E/AndroidRuntime( 6672):    at android.os.Looper.loop(Looper.java:130)  
E/AndroidRuntime( 6672):    at android.app.ActivityThread.main(ActivityThread.java:3835)  
E/AndroidRuntime( 6672):    at java.lang.reflect.Method.invokeNative(Native Method)  
E/AndroidRuntime( 6672):    at java.lang.reflect.Method.invoke(Method.java:507)  
E/AndroidRuntime( 6672):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)  
E/AndroidRuntime( 6672):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)  
E/AndroidRuntime( 6672):    at dalvik.system.NativeStart.main(Native Method)  
W/ActivityManager(  154):   Force finishing activity com.snowdream.timerdemo/.TimerDemoActivity  
W/ActivityManager(  154): Activity pause timeout for HistoryRecord{40550560 com.snowdream.timerdemo/.TimerDemoActivity}  
W/ActivityManager(  154): Activity destroy timeout for HistoryRecord{40550560 com.snowdream.timerdemo/.TimerDemoActivity}  
D/dalvikvm(  800): GC_EXPLICIT freed 13K, 58% free 3127K/7431K, external 0K/0K, paused 70ms  
D/dalvikvm(  562): GC_EXPLICIT freed 59K, 51% free 2935K/5959K, external 245K/512K, paused 84ms  
I/ActivityManager(  154): Start proc com.android.email for service com.android.email/.service.MailService: pid=6691 uid=10019 gids={3003, 1015}  
 

2、只能在UI主執行緒中更新控制元件/元件。在其他執行緒中，更新控制元件/元件，會提示出錯，提示如下： 
（注：這種情況下，可以通過Hander傳送訊息的方式來更新控制元件/元件，詳情參考例子。）

E/AndroidRuntime( 6309): android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.  
E/AndroidRuntime( 6309):    at android.view.ViewRoot.checkThread(ViewRoot.java:2941)  
E/AndroidRuntime( 6309):    at android.view.ViewRoot.invalidateChild(ViewRoot.java:643)  
E/AndroidRuntime( 6309):    at android.view.ViewRoot.invalidateChildInParent(ViewRoot.java:669)  
E/AndroidRuntime( 6309):    at android.view.ViewGroup.invalidateChild(ViewGroup.java:2511)  
E/AndroidRuntime( 6309):    at android.view.View.invalidate(View.java:5296)  
E/AndroidRuntime( 6309):    at android.widget.TextView.checkForRelayout(TextView.java:5533)  
E/AndroidRuntime( 6309):    at android.widget.TextView.setText(TextView.java:2730)  
E/AndroidRuntime( 6309):    at android.widget.TextView.setText(TextView.java:2598)  
E/AndroidRuntime( 6309):    at android.widget.TextView.setText(TextView.java:2573)  
E/AndroidRuntime( 6309):    at com.snowdream.timerdemo.TimerDemoActivity$1.run(TimerDemoActivity.java:48)  
E/AndroidRuntime( 6309):    at java.util.Timer$TimerImpl.run(Timer.java:284)  
 

Demo原始碼如下： TimerDemoActivity.java

package com.snowdream.timerdemo;

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;  


public class TimerDemoActivity extends Activity {  
    private static String  TAG = "TimerDemo";  
    private TextView mTextView = null;  
    private Button mButton_start = null;  
    private Button mButton_pause = null;  
    private Timer mTimer = null;  
    private TimerTask mTimerTask = null;  
    private Handler mHandler = null;  
    private static int count = 0;  
    private boolean isPause = false;  
    private boolean isStop = true;  
    private static int delay = 1000;  //1s  
    private static int period = 1000;  //1s  
    private static final int UPDATE_TEXTVIEW = 0;  
      
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.main);  
        mTextView = (TextView)findViewById(R.id.mytextview);   
        mButton_start = (Button)findViewById(R.id.mybutton_start);  
        mButton_pause = (Button)findViewById(R.id.mybutton_pause);  


        mButton_start.setOnClickListener(new Button.OnClickListener() {  
            public void onClick(View v) {  
                if (isStop) {  
                    Log.i(TAG, "Start");  
                } else {  
                    Log.i(TAG, "Stop");  
                }  
  
                isStop = !isStop;  
  
                if (!isStop) {  
                    startTimer();  
                }else {  
                    stopTimer();  
                }  
  
                if (isStop) {  
                    mButton_start.setText(R.string.start);  
                } else {  
                    mButton_start.setText(R.string.stop);  
                }  
            }  
        });  
  
        mButton_pause.setOnClickListener(new Button.OnClickListener() {  
            public void onClick(View v) {  
                if (isPause) {  
                    Log.i(TAG, "Resume");  
                } else {  
                    Log.i(TAG, "Pause");  
                }  
  
                isPause = !isPause;  
  
                if (isPause) {  
                    mButton_pause.setText(R.string.resume);  
                } else {  
                    mButton_pause.setText(R.string.pause);  
                }  
            }  
        });  
          
        mHandler = new Handler(){  
            @Override  
            public void handleMessage(Message msg) {  
                switch (msg.what) {  
                case UPDATE_TEXTVIEW:  
                    updateTextView();  
                    break;  
                default:  
                    break;  
                }  
            }  
        };  
    }  
  
    private void updateTextView(){  
        mTextView.setText(String.valueOf(count));  
    }  
  
    private void startTimer(){  
        if (mTimer == null) {  
            mTimer = new Timer();  
        }  
  
        if (mTimerTask == null) {  
            mTimerTask = new TimerTask() {  
                @Override  
                public void run() {  
                    Log.i(TAG, "count: "+String.valueOf(count));  
                    sendMessage(UPDATE_TEXTVIEW);  
                      
                    do {  
                        try {  
                            Log.i(TAG, "sleep(1000)...");  
                            Thread.sleep(1000);  
                        } catch (InterruptedException e) {  
                        }     
                    } while (isPause);  
                      
                    count ++;    
                }  
            };  
        }  
  
        if(mTimer != null && mTimerTask != null )  
            mTimer.schedule(mTimerTask, delay, period);  
  
    }  
  
    private void stopTimer(){  
        if (mTimer != null) {  
            mTimer.cancel();  
            mTimer = null;  
        }  
        if (mTimerTask != null) {  
            mTimerTask.cancel();  
            mTimerTask = null;  
        }     
        count = 0;  
    }  
      
    public void sendMessage(int id){  
        if (mHandler != null) {  
            Message message = Message.obtain(mHandler, id);     
            mHandler.sendMessage(message);   
        }  
    }  
}  
 

layout-main.xml 

<?xml version="1.0" encoding="utf-8"?>  
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
  android:layout_width="fill_parent"  
  android:layout_height="fill_parent"  
  android:orientation="vertical" >  
  <TextView  
    android:id="@+id/mytextview"  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:gravity="center"  
    android:text="@string/number" />  
  
  <LinearLayout  
    android:layout_width="fill_parent"  
    android:layout_height="wrap_content"  
    android:gravity="center"  
    android:orientation="horizontal" >  
 
  <Button  
    android:id="@+id/mybutton_start"  
    android:layout_width="wrap_content"  
    android:layout_height="wrap_content"  
    android:text="@string/start" />  
 
  <Button  
    android:id="@+id/mybutton_pause"  
    android:layout_width="wrap_content"  
    android:layout_height="wrap_content"  
    android:text="@string/pause" />  
  </LinearLayout>  
</LinearLayout>  

strings.xml

<?xml version="1.0" encoding="utf-8"?>  
<resources>  
  <string name="app_name">TimerDemo</string>  
  <string name="number">0</string>  
  <string name="start">start</string>  
  <string name="stop">stop</string>  
  <string name="pause">pause</string>  
  <string name="resume">resume</string>  
</resources>  

原始碼下載：http://download.csdn.net/detail/yang_hui1986527/3922447