BroadCastReceiver

• res/layout/activity_main.xml

01 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
02     xmlns:tools="http://schemas.android.com/tools"
03     android:layout_width="match_parent"
04     android:layout_height="match_parent"
05     android:paddingBottom="@dimen/activity_vertical_margin"
06     android:paddingLeft="@dimen/activity_horizontal_margin"
07     android:paddingRight="@dimen/activity_horizontal_margin"
08     android:paddingTop="@dimen/activity_vertical_margin"
09     android:orientation="vertical"
10     tools:context=".MainActivity" >
11
12     <TextView
13         android:layout_width="wrap_content"
14         android:layout_height="wrap_content"
15         android:gravity="center_horizontal"
16         android:layout_gravity="center_horizontal"
17         android:text="Received Broadcasts" />
18     <Button
19         android:id="@+id/btnSendBroadcast"
20         android:layout_width="wrap_content"
21         android:layout_height="wrap_content"
22         android:gravity="center_horizontal"
23         android:layout_gravity="center_horizontal"
24         android:text="Send Broadcast"
25         />
26     <EditText
27         android:id="@+id/etReceivedBroadcast"
28         android:layout_width="match_parent"
29         android:layout_height="wrap_content"
30
31         />
32
33 </LinearLayout>

( 2 ) 扩展 BroadcastReceiver

• 创建一个叫做MyReceiver的对象，继承BroadcastReceiver.
• 重写 onReceive() 方法，在EditText中打印intent的活动名称.

• /src/com/hmkcode/android/MyReceiver.java

01 package com.hmkcode.android;
02
03 import android.content.BroadcastReceiver;
04 import android.content.Context;
05 import android.content.Intent;
06
07 public class MyReceiver extends BroadcastReceiver{
08
09     @Override
10     public void onReceive(Context context, Intent intent) {
11          MainActivity mainActivity = ((MyApplication) context.getApplicationContext()).mainActivity;
12          mainActivity.etReceivedBroadcast.append("broadcast: "+intent.getAction()+"\n");
13     }
14
15 }

( 3 ) 发送广播

• 发送广播创建一个包含活动名称的Intent，将它传递给sendBroadcast()。

Intent i = new Intent("com.hmkcode.android.USER_ACTION");
sendBroadcast(i);

( 4 ) 通过Java或XML方式注册BroadcastReceiver

你可以通过java代码动态注册或在Manifest xml文件中进行注册。

• 使用Java代码
  

• 创建BroadcastReceiver类的实例MyReceiver和IntentFilter实例并将他们传递给registerReceiver()方法

@Override
    protected void onResume() {
        super.onResume();
        registerReceiver(new MyReceiver(), 
         new IntentFilter("com.hmkcode.android.USER_ACTION"));

    }

• 在Manifest XML 文件中配置
  

• 另外你可以在manifest文件中注册接收器

1 <receiver android:name="com.hmkcode.android.MyReceiver" >
2     <intent-filter>
3         <action android:name="com.hmkcode.android.USER_ACTION" />
4     </intent-filter>
5 </receiver>

( 5 ) Activity Class

• /src/com/hmkcode/android/MainActivity.java

01 package com.hmkcode.android;
02
03 import android.os.Bundle;
04 import android.app.Activity;
05 import android.content.Intent;
06 import android.content.IntentFilter;
07 import android.view.View;
08 import android.view.View.OnClickListener;
09 import android.widget.Button;
10 import android.widget.EditText;
11
12
13 public class MainActivity extends Activity implements OnClickListener {
14
15     MyReceiver myReceiver;
16     IntentFilter intentFilter;
17     EditText etReceivedBroadcast;
18     Button btnSendBroadcast;
19     @Override
20     protected void onCreate(Bundle savedInstanceState) {
21         super.onCreate(savedInstanceState);
22         setContentView(R.layout.activity_main);
23
24         etReceivedBroadcast = (EditText) findViewById(R.id.etReceivedBroadcast);
25         btnSendBroadcast = (Button) findViewById(R.id.btnSendBroadcast);
26
27         //keep reference to Activity context
28         MyApplication myApplication = (MyApplication) this.getApplicationContext();
29         myApplication.mainActivity = this;
30
31         btnSendBroadcast.setOnClickListener(this);
32
33         myReceiver = new MyReceiver();
34         intentFilter = new IntentFilter("com.hmkcode.android.USER_ACTION");
35     }
36
37     @Override
38     protected void onResume() {
39         super.onResume();
40         registerReceiver(myReceiver, intentFilter);
41
42     }
43     @Override
44     protected void onPause() {
45         super.onPause();
46         unregisterReceiver(myReceiver);
47     }
48
49
50     @Override
51     public void onClick(View view) {
52
53         Intent intnet = new Intent("com.hmkcode.android.USER_ACTION");
54         sendBroadcast(intnet);
55
56     }
57
58 }

( 6 ) Manifest.XML

01 <?xml version="1.0" encoding="utf-8"?>
02 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
03     package="com.hmkcode.android"
04     android:versionCode="1"
05     android:versionName="1.0" >
06
07     <uses-sdk
08         android:minSdkVersion="8"
09         android:targetSdkVersion="17" />
10
11     <application
12         android:name="com.hmkcode.android.MyApplication"
13         android:allowBackup="true"
14         android:icon="@drawable/ic_launcher"
15         android:label="@string/app_name"
16         android:theme="@style/AppTheme" >
17         <activity
18             android:name="com.hmkcode.android.MainActivity"
19             android:label="@string/app_name" >
20             <intent-filter>
21                 <action android:name="android.intent.action.MAIN" />
22
23                 <category android:name="android.intent.category.LAUNCHER" />
24             </intent-filter>
25         </activity>
26
27         <receiver android:name="com.hmkcode.android.MyReceiver" >
28             <intent-filter>
29                 <action android:name="com.hmkcode.android.USER_ACTION" />
30             </intent-filter>
31         </receiver>
32
33     </application>
34
35 </manifest>

注：如果你想通过Manifest XML文件注册接收器，那么需要从MainActivity类中移除onResume和onPause方法。

( 7 ) 获取Activity Context 的办法

当使用xml注册接收器时，系统将ReceiverResctrictredContext传递给onReceive()方法。为了能在EditText中进行打印，需要获取MainActivity context，因此需要通过扩展Application来持有MainActivity的引用。

01 package com.hmkcode.android;
02
03 import android.app.Application;
04
05 public class MyApplication extends Application {
06
07     @Override
08     public void onCreate() {
09         super.onCreate();
10     }
11
12     MainActivity mainActivity;
13
14 }

注意：我们在Manifest文件中使用了MyApplication。