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
<?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>
源码下载：
http://download.csdn.net/detail/yang_hui1986527/3922447
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