当程序意外退出时，可以去掉通知栏上显示的图标
1.创建TestNotificationActivity activity类,
package com.notioni.test.notification;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
public class TestNotificationActivity extends Activity implementsView.OnClickListener{
/** Called when the activity is first created. */
private boolean mStart = false;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
int[] ids = {R.id.btnShow,R.id.btnUpdate,R.id.btnRemove};
for(int i = 0; i < ids.length; i++){
findViewById(ids[i]).setOnClickListener(this);
}
mStart = false;
}
@Override
public void onClick(View v) {
switch(v.getId()){
case R.id.btnShow://显示通知栏
mStart = true;
sendMsgToService(NotificationService.KEY_COMMAND_SHOW,mStart);
break;
case R.id.btnUpdate://修改通知栏内容
sendMsgToService(NotificationService.KEY_COMMAND_UPDATE,!mStart);
break;
case R.id.btnRemove:
mStart = false;//移除通知栏
sendMsgToService(NotificationService.KEY_COMMAND_REMOVE,mStart);
break;
}
}
@Override
protected void onDestroy() {
mStart = false;
sendMsgToService(NotificationService.KEY_COMMAND_REMOVE,mStart);
super.onDestroy();
}
private void sendMsgToService(String cmd,boolean isStart){
Intent intent = new Intent(this,NotificationService.class);
intent.setAction(NotificationService.ACTION_NOTIFICATION_CONTROL);
intent.putExtra(NotificationService.COMMAND_KEY, cmd);
intent.putExtra(NotificationService.TIME_KEY, isStart);
startService(intent);
}
}
2.main.xml 显示几个button，用来演示效果
<?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" >
<Button
android:id="@+id/btnShow"
android:layout_width="fill_parent"
android:layout_height="100dip"
android:text="@string/notification_show"
/>
<Button
android:id="@+id/btnUpdate"
android:layout_width="fill_parent"
android:layout_height="100dip"
android:text="@string/notification_update"
/>
<Button
android:id="@+id/btnRemove"
android:layout_width="fill_parent"
android:layout_height="100dip"
android:text="@string/notification_remove"
/>
</LinearLayout>
3.NotificationService.java
对Notification显示，修改，移除操作的核心类
package com.notioni.test.notification;
import android.app.Notification;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Intent;
import android.os.IBinder;
import android.os.SystemClock;
import android.util.Log;
import android.widget.RemoteViews;
public class NotificationService extends Service {
private static final String TAG = "NotificationService";
public static final String ACTION_NOTIFICATION_CONTROL ="action_notification_control";
public static final String COMMAND_KEY = "cmd_key";
public static final String KEY_COMMAND_SHOW = "show_notification";
public static final String KEY_COMMAND_UPDATE = "update_notification";
public static final String KEY_COMMAND_REMOVE = "remove_notification";
public static final String TIME_KEY = "time_key";
public static final int NOTIFICATIN_ID = 100;
private Notification mNotification;
private long mTime;
@Override
public IBinder onBind(Intent intent) {
// TODO Auto-generated method stub
return null;
}
@Override
public void onCreate() {
super.onCreate();
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
String action = intent.getAction();
//Log.i(TAG, "[onStartCommand] action:"+action);
if(ACTION_NOTIFICATION_CONTROL.equals(action)){
String cmd = intent.getStringExtra(COMMAND_KEY);
boolean isStart = intent.getBooleanExtra(TIME_KEY, false);
Log.i(TAG, "[onStartCommand] action:"+action+",cmd:"+cmd+",isStart:"+isStart);
if(KEY_COMMAND_SHOW.equals(cmd)){
showNotification(isStart);
}else if(KEY_COMMAND_UPDATE.equals(cmd)){
updateNotification(isStart);
}else if(KEY_COMMAND_REMOVE.equals(cmd)){
removeNotification();
}
}else{
Log.e(TAG, "illegality action:"+action);
}
return super.onStartCommand(intent, flags, startId);
}
/*
* 显示在通知栏
*/
private void showNotification(boolean isStart){
createNotification(isStart);
}
/*
* 修改通知栏显示
*/
private void updateNotification(boolean isStart){
createNotification(isStart);
}
/*
* 从通知栏移除
*/
public void removeNotification(){
stopForeground(true);
mTime = 0;
stopSelf();
}
/*
* 创建Notification对象
*/
public void createNotification(boolean started){
if(mNotification == null){
mNotification = new Notification();
mNotification.icon = R.drawable.ic_launcher;
mNotification.flags |=Notification.FLAG_ONGOING_EVENT;//表示正处于活动中
Intent intent = new Intent(this,TestNotificationActivity.class);
//这里要加入此Flags，作用：当你通过点击通知栏来唤起Activity时，对应的Activity启动模式要为android:launchMode="singleTop"
//于此Flag一起使用，可以保证你要启动的Activity不会重新启动，在一个堆栈只有一个对应的实例对象
//使用这个标志，如果正在启动的Activity的Task已经在运行的话，那么，新的Activity将不会启动；代替的，当前Task会简单的移入前台。
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, 0);
mNotification.contentIntent = pendingIntent;
RemoteViews contentView = new RemoteViews(getPackageName(), R.layout.notification_layout);
contentView.setImageViewResource(R.id.icon, R.drawable.ic_launcher);
mNotification.contentView = contentView;
mTime = SystemClock.elapsedRealtime();
}
long time = mTime;
mNotification.contentView.setChronometer(R.id.text1, time, null, started);
mNotification.contentView.setTextViewText(R.id.text2, getString(started?R.string.time_running:R.string.time_pause));
//使用服务来启动通知栏，这样的好处时，
//1.当应用程序在后台运行时，startForeground可以使本应用优先级提高，不至于被系统杀掉
//2.当应用被异常挂掉时，可以保证通知栏对应的图标被系统移除
startForeground(NOTIFICATIN_ID, mNotification);
}
}
4. notification_layout.xml文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:baselineAligned="false"
android:gravity="center_vertical"
android:layout_width="match_parent"
android:layout_height="65sp"
android:background="@android:drawable/status_bar_item_background"
android:id="@+id/layoutMain"
>
<ImageView android:id="@+id/icon"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingLeft="4dip"
android:layout_marginRight="6dip" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
>
<Chronometer android:id="@+id/text1"
android:textColor="?android:attr/textColorPrimaryInverse"
android:textStyle="bold"
android:textSize="18sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:singleLine="true"
/>
<TextView android:id="@+id/text2"
android:textColor="#ff6b6b6b"
android:textSize="14sp"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:singleLine="true"
/>
</LinearLayout>
</LinearLayout>
5.AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.notioni.test.notification"
android:versionCode="1"
android:versionName="1.0" >
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:name=".TestNotificationActivity"
android:launchMode="singleTop"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service android:name=".NotificationService" android:exported="false"></service>
</application>
</manifest>
总结：通知栏采用Service中的startForeground方法去显示到状态栏，
而不采用NotificationManager中的notify的好处有以下两点
1. 当应用程序转入后台运行时startForeground方法可以提高应用程序的运行等级，不至于被系统杀掉
2. 当应用程序由于异常或其他未知的情况下，终止，ActivityManagerService会移除通知栏的图标，不会导致程序已经关闭而图标还显示在通知栏
对startForeground的简单分析说明，此方法会调用ActivityManagerService.java类的setServiceForeground方法，此方法会保存Notification对象，并调用NotificationManger中的notify将通知显示到状态栏，然后设置Service是forground= ture
当应用程序异常退出时ActivityManagerService会监听到应用死亡，根据保存的Notification对象可以去掉通知栏上的显示图标