Android Activity/Service/Broadcaster三大元件之間互相呼叫

Ruthless發表於2013-06-21
AndroidAST元件

我們研究兩個問題，
1、Service如何透過Broadcaster更改activity的一個TextView。
(研究這個問題，考慮到Service從伺服器端獲得訊息之後，將msg返回給activity)

2、Activity如何透過Binder呼叫Service的一個方法。
(研究這個問題，考慮到與伺服器端互動的動作，打包至Service，Activity只呈現介面，呼叫Service的方法)

結構圖見如下：

效果圖如下：

點選“start service”按鈕，啟動Service，然後更改Activity的UI。

點選“send msg to server”按鈕呼叫Service的方法，顯示NotificationBar

程式碼：
1、新建一個MyService類，繼承Service

package com.ljq.activity;
 
 
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.app.Service;
import android.content.Context;
import android.content.Intent;
import android.graphics.Color;
import android.os.Binder;
import android.os.IBinder;
 
public class MyService extends Service {
 private NotificationManager notificationManager = null;
 private final IBinder binder = new LocalBinder();
 
 @Override
 public void onCreate() {
  sendMsgtoActivty("Service is oncreating.\n");
 }
 
 @Override
 public IBinder onBind(Intent intent) {
  String msg = "Activity is sendding message to service,\n Service send msg to server!\n";
  sendMsgtoActivty(msg);
  return binder;
 }
 
 /**
  * 把資訊傳遞給activity
  * 
  * @param msg
  */
 private void sendMsgtoActivty(String msg) {
  Intent intent = new Intent("com.android.Yao.msg");
  intent.putExtra("msg", msg);
  this.sendBroadcast(intent);
 }
  
 @Override
 public void onDestroy() {
  super.onDestroy();
  if(notificationManager!=null){
   notificationManager.cancel(0);
   notificationManager=null;
  }
 }
 
 /**
  * 在狀態列顯示通知
  * 
  * @param msg
  */
 private void showNotification(String msg) {
  notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
  // 定義Notification的各種屬性   
  Notification notification =new Notification(R.drawable.icon,   
          "A Message Coming!", System.currentTimeMillis()); 
  //FLAG_AUTO_CANCEL   該通知能被狀態列的清除按鈕給清除掉
  //FLAG_NO_CLEAR      該通知不能被狀態列的清除按鈕給清除掉
  //FLAG_ONGOING_EVENT 通知放置在正在執行
  //FLAG_INSISTENT     是否一直進行，比如音樂一直播放，知道使用者響應
  notification.flags |= Notification.FLAG_ONGOING_EVENT; // 將此通知放到通知欄的"Ongoing"即"正在執行"組中   
  notification.flags |= Notification.FLAG_NO_CLEAR; // 表明在點選了通知欄中的"清除通知"後，此通知不清除，經常與FLAG_ONGOING_EVENT一起使用   
  notification.flags |= Notification.FLAG_SHOW_LIGHTS;   
  //DEFAULT_ALL     使用所有預設值，比如聲音，震動，閃屏等等
  //DEFAULT_LIGHTS  使用預設閃光提示
  //DEFAULT_SOUNDS  使用預設提示聲音
  //DEFAULT_VIBRATE 使用預設手機震動，需加上<uses-permission android:name="android.permission.VIBRATE" />許可權
  notification.defaults = Notification.DEFAULT_LIGHTS; 
  //疊加效果常量
  //notification.defaults=Notification.DEFAULT_LIGHTS|Notification.DEFAULT_SOUND;
  notification.ledARGB = Color.BLUE;   
  notification.ledOnMS =5000; //閃光時間，毫秒
   
  // 設定通知的事件訊息   
  //Intent notificationIntent =new Intent(MainActivity.this, MainActivity.class); // 點選該通知後要跳轉的Activity   
  Intent notificationIntent = new Intent(getApplicationContext(), MainActivity.class); // 載入類，如果直接透過類名，會在點選時重新載入頁面，無法恢復最後頁面狀態。
  notificationIntent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);
  PendingIntent contentItent = PendingIntent.getActivity(this, 0, notificationIntent, 0);   
  notification.setLatestEventInfo(this, "Message", "Message:" + msg, contentItent);
   
  // 把Notification傳遞給NotificationManager   
  notificationManager.notify(0, notification);
     
 }
  
 /**
  * 從activity獲取資訊
  * 
  * @param msg
  */
 public void receiverMsgtoActivity(String msg){
  sendMsgtoActivty("\n receiverMsgtoActivity:"+msg);
 }
 
 public void sendMsgtoServer(String msg) {
  showNotification(msg);
 }
 
 public class LocalBinder extends Binder {
  public MyService getService() {
   return MyService.this;
  }
 }
 
}

2、新建MyBroadcastreceiver類，繼承BroadcastReceiver，用來傳送Intent啟動服務

package com.ljq.activity;
 
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
 
/**
 * 傳送Intent啟動服務
 * 
 * @author jiqinlin
 *
 */
public class MyBroadcastreceiver extends BroadcastReceiver {
 @Override
 public void onReceive(Context context, Intent intent) {
  Intent service = new Intent(context, MyService.class);
  context.startService(service);
 }
 
}

3、新建MainActivity類，其實是一個activity，用來呈現介面

package com.ljq.activity;
 
import java.util.List;
 
import android.app.Activity;
import android.app.ActivityManager;
import android.content.BroadcastReceiver;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.ServiceConnection;
import android.os.Bundle;
import android.os.IBinder;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
 
public class MainActivity extends Activity implements View.OnClickListener {
 private String msg = "";
 private TextView txtMsg;
 private UpdateReceiver receiver;
 private MyService myService;
 private final static String TAG=MainActivity.class.getSimpleName();
 
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
   
  txtMsg = (TextView) this.findViewById(R.id.txtMsg);
  this.findViewById(R.id.btnStart).setOnClickListener(this);
  this.findViewById(R.id.btnSend).setOnClickListener(this);
   
  //訂閱廣播Intent
  receiver = new UpdateReceiver();
  IntentFilter filter = new IntentFilter();
  filter.addAction("com.android.Yao.msg");
  this.registerReceiver(receiver, filter);
   
  //初始化時啟動服務
  //Intent intent = new Intent(MainActivity.this, MyService.class);
  //this.bindService(intent, conn, BIND_AUTO_CREATE);
 }
  
 @Override
 protected void onDestroy() {
  super.onDestroy();
  //結束服務
  if(conn!=null){
   unbindService(conn);
   myService=null;
  }
    
 }
 
 public class UpdateReceiver extends BroadcastReceiver {
 
  @Override
  public void onReceive(Context context, Intent intent) {
   //獲取service傳過來的資訊
   msg = intent.getStringExtra("msg");
   txtMsg.append(msg);
  }
 }
 
 private ServiceConnection conn = new ServiceConnection() {
  @Override
  public void onServiceConnected(ComponentName name, IBinder service) {
   myService = ((MyService.LocalBinder) service).getService();
   Log.i(TAG, "onServiceConnected myService: "+myService);
  }
 
  @Override
  public void onServiceDisconnected(ComponentName name) {
    myService = null;
  }
 
 };
 
 @Override
 public void onClick(View v) {
  Intent intent = new Intent(MainActivity.this, MyService.class);
  switch (v.getId()) {
  case R.id.btnStart:
   //判斷服務是否啟動
   if(false==isServiceRunning(this, MyService.class.getName())){
    Log.i(TAG, "start "+MyService.class.getSimpleName()+" service");
    this.bindService(intent, conn, BIND_AUTO_CREATE);
   }
   Log.i(TAG, MyService.class.getName()+" run status: "+isServiceRunning(this, MyService.class.getName()));
   break;
  case R.id.btnSend:
   //判斷服務是否啟動
   if(false==isServiceRunning(this, MyService.class.getName())){
    Log.i(TAG, "start "+MyService.class.getSimpleName()+" service");
    this.bindService(intent, conn, BIND_AUTO_CREATE);
   }
    
   Log.i(TAG, MyService.class.getName()+" run status: "+isServiceRunning(this, MyService.class.getName()));
   Log.i(TAG, "onClick myService: "+myService); //第一次啟動服務時此處為null(小編認為雖然服務已啟動成功，但是還沒全部初始化)
    
   if(myService!=null){
       myService.sendMsgtoServer("i am sending msg to server");
       //從activity傳遞資訊給service
       myService.receiverMsgtoActivity("this is a msg");
      }
   break;
  }
 }
  
 /**
  * 判斷服務是否正在執行
  * 
  * @param context
  * @param className 判斷的服務名字：包名+類名
  * @return true在執行 false 不在執行
  */
 public static boolean isServiceRunning(Context context, String className) {
  boolean isRunning = false;
   
  ActivityManager activityManager = (ActivityManager) context
    .getSystemService(Context.ACTIVITY_SERVICE);
  //獲取所有的服務
  List<ActivityManager.RunningServiceInfo> services= activityManager.getRunningServices(Integer.MAX_VALUE);
  if(services!=null&&services.size()>0){
   for(ActivityManager.RunningServiceInfo service : services){
    if(className.equals(service.service.getClassName())){
     isRunning=true;
     break;
    }
   }
  }
 
  return isRunning;
 }
 
}

4、main.xml佈局檔案

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical" android:layout_width="fill_parent"
 android:layout_height="fill_parent">
 <TextView android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:id="@+id/txtMsg" />
 <LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="horizontal"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content">
  <Button android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="start service"
   android:id="@+id/btnStart"/>
  <Button android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="send msg to server"
   android:id="@+id/btnSend"/>
 </LinearLayout>
</LinearLayout>

5、清單檔案AndroidManifest.xml，用來配置元件等資訊

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
      package="com.ljq.activity"
      android:versionCode="1"
      android:versionName="1.0">
    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".MainActivity"
                  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=".MyService"/> 
        <receiver android:name=".MyBroadcastreceiver" />
 
    </application>
    <uses-sdk android:minSdkVersion="7" />
 
</manifest>

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