Android中定时器Timer和TimerTask的启动，停止，暂停，继续等操作实例

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：

[java] view plaincopyprint?

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。）

[java] view plaincopyprint?

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

[java] view plaincopyprint?

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);

}

}

}