Android 通知栏用法例子

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>

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>

</intent-filter>

</activity>

</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