Android 通知欄用法例子

當程序意外退出時，可以去掉通知欄上顯示的圖標

 

1.創建TestNotificationActivity activity類,

 

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 implements View.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://顯示通知欄

mStart = true;

sendMsgToService(NotificationService.KEY_COMMAND_SHOW,mStart);

break;

case R.id.btnUpdate://修改通知欄內容

sendMsgToService(NotificationService.KEY_COMMAND_UPDATE,!mStart);

break;

case R.id.btnRemove:

mStart = false;//移除通知欄

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 顯示幾個button，用來演示效果

 

<?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

對Notification顯示，修改，移除操作的核心類

 

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);

}

 

/*

* 顯示在通知欄

*/

private void showNotification(boolean isStart){

createNotification(isStart);

}

 

/*

* 修改通知欄顯示

*/

private void updateNotification(boolean isStart){

createNotification(isStart);

}

 

/*

* 從通知欄移除

*/

public void removeNotification(){

stopForeground(true);

mTime = 0;

stopSelf();

}

 

/*

* 創建Notification對象

*/

public void createNotification(boolean started){

if(mNotification == null){

mNotification = new Notification();

mNotification.icon = R.drawable.ic_launcher;

mNotification.flags |=Notification.FLAG_ONGOING_EVENT;//表示正處於活動中

 

Intent intent = new Intent(this,TestNotificationActivity.class);

//這裡要加入此Flags，作用：當你通過點擊通知欄來喚起Activity時，對應的Activity啟動模式要為android:launchMode="singleTop"

//於此Flag一起使用，可以保證你要啟動的Activity不會重新啟動，在一個堆棧只有一個對應的實例對象

//使用這個標志，如果正在啟動的Activity的Task已經在運行的話，那麼，新的Activity將不會啟動；代替的，當前Task會簡單的移入前台。

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));

 

//使用服務來啟動通知欄，這樣的好處時，

//1.當應用程序在後台運行時，startForeground可以使本應用優先級提高，不至於被系統殺掉

//2.當應用被異常掛掉時，可以保證通知欄對應的圖標被系統移除

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>

 

 

總結：通知欄采用Service中的startForeground方法去顯示到狀態欄，

而不采用NotificationManager中的notify的好處有以下兩點

1. 當應用程序轉入後台運行時startForeground方法可以提高應用程序的運行等級，不至於被系統殺掉

2. 當應用程序由於異常或其他未知的情況下，終止，ActivityManagerService會移除通知欄的圖標，不會導致程序已經關閉而圖標還顯示在通知欄

 

對startForeground的簡單分析說明，此方法會調用ActivityManagerService.java類的setServiceForeground方法，此方法會保存Notification對象，並調用NotificationManger中的notify將通知顯示到狀態欄，然後設置Service是forground= ture

當應用程序異常退出時ActivityManagerService會監聽到應用死亡，根據保存的Notification對象可以去掉通知欄上的顯示圖標