下面是一个在Android中使用定时器Timer和TimerTask的启动，停止，暂停，继续等操作的demo。

需要注意的问题主要有两点：

1、Timer和TimerTask在调用cancel()取消后不能再执行 schedule语句，否则提示出错，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主线程中更新控件/组件。在其他线程中，更新控件/组件，会提示出错，提示如下：

（注：这种情况下，可以通过Hander发送消息的方式来更新控件/组件，详情参考例子。）

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源码如下：

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