Android--广播的研究

浏览数：26 / 时间：2015年06月11日

Android中的广播大致有两种：有序广播和标准广播。标准广播是一种完全异步执行的广播，广播发出后，广播接收器几乎都会在同一时刻接收到这条广播消息，因此它们之间没有任何先后顺序而言，这种广播的执行效率较高，但是也以为这它是无法被截断的。有序广播是一种同步执行的广播，广播发出后，同一时刻只会有一个广播接收器接收到广播，当这个广播接收器中的逻辑执行完毕后才会继续传播消息。并且前面的广播可以截断正在传播的广播。

下面看一个标准广播的例子：

1.先建立一个接收类，要继承BroadcastReciver类：

package org.lxh.demo;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class MyBroadcastReceiver extends BroadcastReceiver {

	@Override
	public void onReceive(Context context, Intent intent) {
		Toast.makeText(context, "received in MyBroadcastReceiver",
				Toast.LENGTH_SHORT).show();

	}

}


2.配置AndroidManifest.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest 
	xmlns:android="http://schemas.android.com/apk/res/android"
	package="org.lxh.demo" 
	android:versionCode="1" 
	android:versionName="1.0">
	<uses-sdk android:minSdkVersion="10" />
	<application 
		android:icon="@drawable/icon" 
		android:label="@string/app_name">
		<activity 
			android:name=".Hello" 
			android:label="@string/app_name">
			<intent-filter>
				<action android:name="android.intent.action.MAIN" />
				<category android:name="android.intent.category.LAUNCHER" />
			</intent-filter>
		</activity>
		<receiver android:name="org.lxh.demo.MyBroadcastReceiver">
		    <intent-filter>
		        <action android:name="com.example.broadcast.MY_BROADCASTTEST"/>
		    </intent-filter>
		</receiver>	
		    </application>
	
</manifest>

即：

<receiver android:name="org.lxh.demo.MyBroadcastReceiver">
		    <intent-filter>
		        <action android:name="com.example.broadcast.MY_BROADCASTTEST"/>
		    </intent-filter>
		</receiver>


3。发送程序：

package org.lxh.demo;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnFocusChangeListener;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class Hello extends Activity {
	private Button btn=null;
	
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState); // 生命周期方法
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		super.setContentView(R.layout.main); // 设置要使用的布局管理器
		this.btn=(Button)super.findViewById(R.id.mybtn);
		this.btn.setOnClickListener(new ClickListenerImpl());

	}
	private class ClickListenerImpl implements OnClickListener{

		public void onClick(View arg0) {
			Intent intent=new Intent("com.example.broadcast.MY_BROADCASTTEST");
			sendBroadcast(intent);
			
		}
		
	}
}


运行如下：

技术分享

下面我们再建立一个广播接收类：

package org.lxh.demo;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class AnotherBroadcastReceiver extends BroadcastReceiver {

	@Override
	public void onReceive(Context context, Intent intent) {
		Toast.makeText(context, "received in AnotherBroadcastReceiver",
				Toast.LENGTH_SHORT).show();

	}

}


再配置一次AndroidManifest.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<manifest 
	xmlns:android="http://schemas.android.com/apk/res/android"
	package="org.lxh.demo" 
	android:versionCode="1" 
	android:versionName="1.0">
	<uses-sdk android:minSdkVersion="10" />
	<application 
		android:icon="@drawable/icon" 
		android:label="@string/app_name">
		<activity 
			android:name=".Hello" 
			android:label="@string/app_name">
			<intent-filter>
				<action android:name="android.intent.action.MAIN" />
				<category android:name="android.intent.category.LAUNCHER" />
			</intent-filter>
		</activity>
		<receiver android:name="org.lxh.demo.MyBroadcastReceiver">
		    <intent-filter>
		        <action android:name="com.example.broadcast.MY_BROADCASTTEST"/>
		    </intent-filter>
		</receiver>	
		<receiver android:name="org.lxh.demo.AnotherBroadcastReceiver">
		    <intent-filter>
		        <action android:name="com.example.broadcast.MY_BROADCASTTEST"/>
		    </intent-filter>
		</receiver>	
		    </application>
	
</manifest>


两个广播接收器过滤同一个广播，所以他们会同时收到此广播，运行如下：

技术分享技术分享

即先显示第一个注册的广播，后显示第二个。我们考虑如何改变接收的顺序？可以设置优先级<intent-filter android:priority="100">：

<receiver android:name="org.lxh.demo.MyBroadcastReceiver">
		    <intent-filter>
		        <action android:name="com.example.broadcast.MY_BROADCASTTEST"/>
		    </intent-filter>
		</receiver>	
		<receiver android:name="org.lxh.demo.AnotherBroadcastReceiver">
		    <intent-filter android:priority="100">
		        <action android:name="com.example.broadcast.MY_BROADCASTTEST"/>
		    </intent-filter>
		</receiver>

此时运行接收顺序就反过来了。下面考虑如何不让第二个接收器接收到广播？我们可以再第一个接收器内写入abortBroadcast();即：

package org.lxh.demo;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.widget.Toast;

public class AnotherBroadcastReceiver extends BroadcastReceiver {

	@Override
	public void onReceive(Context context, Intent intent) {
		Toast.makeText(context, "received in AnotherBroadcastReceiver",
				Toast.LENGTH_SHORT).show();
		abortBroadcast();

	}

}

此时运行会报错：

04-22 01:48:58.187: E/BroadcastReceiver(435): BroadcastReceiver trying to return result during a non-ordered broadcast
04-22 01:48:58.187: E/BroadcastReceiver(435): java.lang.RuntimeException: BroadcastReceiver trying to return result during a non-ordered broadcast
04-22 01:48:58.187: E/BroadcastReceiver(435):  at android.content.BroadcastReceiver.checkSynchronousHint(BroadcastReceiver.java:451)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at android.content.BroadcastReceiver.abortBroadcast(BroadcastReceiver.java:374)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at org.lxh.demo.AnotherBroadcastReceiver.onReceive(AnotherBroadcastReceiver.java:14)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at android.app.ActivityThread.handleReceiver(ActivityThread.java:1794)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at android.app.ActivityThread.access$2400(ActivityThread.java:117)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:981)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at android.os.Handler.dispatchMessage(Handler.java:99)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at android.os.Looper.loop(Looper.java:123)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at android.app.ActivityThread.main(ActivityThread.java:3683)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at java.lang.reflect.Method.invokeNative(Native Method)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at java.lang.reflect.Method.invoke(Method.java:507)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-22 01:48:58.187: E/BroadcastReceiver(435):  at dalvik.system.NativeStart.main(Native Method)

提示这是一个没有顺序的广播。怎么改正呢？只需将发送广播的程序改为sendOrderedBroadcast(intent, null);：

package org.lxh.demo;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnFocusChangeListener;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class Hello extends Activity {
	private Button btn=null;
	
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState); // 生命周期方法
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		super.setContentView(R.layout.main); // 设置要使用的布局管理器
		this.btn=(Button)super.findViewById(R.id.mybtn);
		this.btn.setOnClickListener(new ClickListenerImpl());

	}
	private class ClickListenerImpl implements OnClickListener{

		public void onClick(View arg0) {
			Intent intent=new Intent("com.example.broadcast.MY_BROADCASTTEST");
			//sendBroadcast(intent);
			sendOrderedBroadcast(intent, null);
			
		}
		
	}
}


此时再运行实例，只会显示第一条Toast：

技术分享

并且不会报错。


 


 

 

 

 

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