活動(Activity)，服務(Service)和廣播接收器(BroadcastReceiver)之間的通信

這是一個幫助理解活動(Activity)，服務(Service)和廣播接收器(BroadcastReceiver)很好的練習. 如果能消化這段代碼, 絕對可以增加對活動，服務和廣播接收器的了解.



本應用程序包括一個活動(testActivity)和一個服務(testService), 他們各自有自己的廣播接收器(MyReceiver 和 TestServiceReceiver).

當按下Start按鈕, testActivity會通過意圖(Intent)啟動testService.
在testService的onStartCommand()創建並啟動一個線程(thread), 在線程裡面重複發送廣播(sendBroadcast()), 把當前系統時間送給testActivity 的MyReceiver.
當MyReceiver接收到, 會把接收到的時間和新的系統時間比較, 並把延遲時間顯示出來.

當按下Stop按鈕, testActivity會發送廣播送給testService 的 TestServiceReceiver.
當TestServiceReceiver接收到, 便會停止服務.

testActivity.java

package com.testActivity;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class testActivity extends Activity {
 
 final static String MY_ACTION = "testActivity.MY_ACTION";
 
 TextView textData;
 
 public static final int RQS_STOP_SERVICE = 1;
 MyReceiver myReceiver;
 
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        textData = (TextView)findViewById(R.id.data);
        Button buttonStart = (Button)findViewById(R.id.start);
        Button buttonStop = (Button)findViewById(R.id.stop);
        buttonStart.setOnClickListener(buttonStartOnClickListener);
        buttonStop.setOnClickListener(buttonStopOnClickListener);
    }
    
    @Override
 protected void onStart() {
  // TODO Auto-generated method stub
     myReceiver = new MyReceiver();
     IntentFilter intentFilter = new IntentFilter();
     intentFilter.addAction(MY_ACTION);
     registerReceiver(myReceiver, intentFilter);
  super.onStart();
 }

 @Override
 protected void onStop() {
  // TODO Auto-generated method stub
  unregisterReceiver(myReceiver);
  super.onStop();
 }

 Button.OnClickListener buttonStartOnClickListener
    = new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   Intent intent = new Intent(testActivity.this, com.testActivity.testService.class);
   testActivity.this.startService(intent);
  }};
  
 Button.OnClickListener buttonStopOnClickListener
 = new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   Intent intent = new Intent();
   intent.setAction(testService.MY_ACTION);
   intent.putExtra("RQS", RQS_STOP_SERVICE);
   sendBroadcast(intent);
  }};
  
 private class MyReceiver extends BroadcastReceiver{

  @Override
  public void onReceive(Context arg0, Intent arg1) {
   // TODO Auto-generated method stub
   long timestamp = arg1.getLongExtra("timestamp", 0);
   long curtime = System.currentTimeMillis();
   long delay = curtime - timestamp;
   textData.setText(String.valueOf(timestamp)
     + " : " + String.valueOf(curtime)
     + " delay " + String.valueOf(delay)
     + "(ms)");
  }
  
 }
}

testService.java

package com.testActivity;

import android.app.Service;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.IBinder;
import android.widget.Toast;

public class testService extends Service {

 final static String MY_ACTION = "testService.MY_ACTION";

 TestServiceReceiver testServiceReceiver;
 boolean running;

 @Override
 public void onCreate() {
  // TODO Auto-generated method stub
  Toast.makeText(getBaseContext(), 
    "TestServiceReceiver.onCreate", 
    Toast.LENGTH_LONG).show();
  testServiceReceiver = new TestServiceReceiver();
  super.onCreate();
 }

 @Override
 public IBinder onBind(Intent arg0) {
  // TODO Auto-generated method stub
  return null;
 }

 @Override
 public int onStartCommand(Intent intent, int flags, int startId) {
  // TODO Auto-generated method stub
  Toast.makeText(getBaseContext(), 
    "TestServiceReceiver.onStartCommand", 
    Toast.LENGTH_LONG).show();
  IntentFilter intentFilter = new IntentFilter();
  intentFilter.addAction(MY_ACTION);
  registerReceiver(testServiceReceiver, intentFilter);
  running = true;
  
  MyThread myThread = new MyThread();
  myThread.start();
  
  return super.onStartCommand(intent, flags, startId);
 }
 
 

 @Override
 public void onDestroy() {
  // TODO Auto-generated method stub
  this.unregisterReceiver(testServiceReceiver);
  super.onDestroy();
 }
 
 public class MyThread extends Thread {

  @Override
  public void run() {
   // TODO Auto-generated method stub

   // TODO Auto-generated method stub
   while(running){
    try {
     Thread.sleep(1000);
    } catch (InterruptedException e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }
    Intent intent = new Intent();
    intent.setAction(testActivity.MY_ACTION);
    intent.putExtra("timestamp", System.currentTimeMillis());
    sendBroadcast(intent);
   }
  }

 }
 
 public class TestServiceReceiver extends BroadcastReceiver {

  @Override
  public void onReceive(Context arg0, Intent arg1) {
   // TODO Auto-generated method stub
   int rqs = arg1.getIntExtra("RQS", 0);
   if (rqs == testActivity.RQS_STOP_SERVICE){
    Toast.makeText(getBaseContext(), 
      "TestServiceReceiver.onReceive w/ RQS_STOP_SERVICE", 
      Toast.LENGTH_LONG).show();
    running = false;
    stopSelf();
   }
  }
 }
 
}

main.xml

<?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:text="@string/hello"
    />
<Button  
 android:id="@+id/start"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="- Start -"
    />
<Button  
 android:id="@+id/stop"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    android:text="- Stop -"
    />
<TextView  
 android:id="@+id/data"
    android:layout_width="fill_parent" 
    android:layout_height="wrap_content" 
    />
</LinearLayout>

修改AndroidManifest.xml添加 testService

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

</manifest>