大四实习准备5_android广播机制

2015-5-1

android 广播机制

5.1简介

分为标准广播(Normal broadcasts)(无先后顺序，几乎同时接收，不可截断)和有序广播(Ordered broadcasts)(有先后顺序，可以截断)两种。

5.2接收系统广播

广播接收器对感兴趣的广播进行注册，这样就能监听到对应的广播，并在内部处理相应的逻辑。

注册广播的方式有两种，分别为在代码中注册(动态注册)(缺点：必须在程序启动之后才能接收到广播，因为注册的逻辑是写在onCreat()方法中的)和在AndroidManifest.xml(静态注册)中注册。

创建广播接收器的方法为：新建一个继承自BroadcastReceiver的类，并重写父类的onReceive()方法就行了，监听到广播时对应的处理逻辑就在onReceive()方法中。

5.2.1通过动态注册的方法实现监听网络变化

IntentFilter:组件告诉Android系统自己乐意接收哪些隐式intent(显式的Intent会直接传送到目标组件)

http://blog.csdn.net/today520/article/details/7000048

package com.example.broadcasttest;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

public class MainActivity extends Activity {
    private IntentFilter intentFilter;
    private NetworkChangeReceiver  networkChangeReceiver;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        intentFilter = new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver,intentFilter);
    }
    
    @Override
    protected void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }
    
    class NetworkChangeReceiver extends BroadcastReceiver{//非静态内部类

        @Override
        public void onReceive(Context arg0, Intent arg1) {
            // TODO Auto-generated method stub
            ConnectivityManager connectivityManager = (ConnectivityManager)
                    getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
            if( networkInfo != null && networkInfo.isAvailable() ){
                Toast.makeText(arg0, "network is availbale", Toast.LENGTH_SHORT).show();
            }else{
                Toast.makeText(arg0, "network is unavailbale", Toast.LENGTH_SHORT).show();
            }
        }
        
    }
}

需在在AndroidManifest.xml中声明

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

5.2.2通过静态注册监听开机启动广播

//开机启动广播只能用静态注册来监听(?)

package com.example.broadtest2;

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

public class BootCompleted extends BroadcastReceiver{

    @Override
    public void onReceive(Context arg0, Intent arg1) {
        // TODO Auto-generated method stub
            Toast.makeText(arg0, "开机啦",Toast.LENGTH_SHORT).show();
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.broadtest2"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="20" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <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>
        <receiver 
            android:name=".BootCompleted" >
            <intent-filter> 
                 <action android:name="android.intent.action.BOOT_COMPLETED" />   
            </intent-filter>
        </receiver>
    </application>
    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED"/>
</manifest>

这里MainActivity.class中不用写跟广播有关系的内容。

5.3发送自定义广播

5.3.1发送标准广播

Intent intent = new Intent("lalala");//自定义的广播名
intent.putExtra("key", "get lalala BroadCast~");//可以附带些数据
sendBroadcast(intent);

例子：采用静态注册的方法，点击按钮发送一个自定义的广播，MainActivity中就是发送了下广播，没有直接涉及到diy_broadcastReceiver.class。

package com.example.broadcasttest;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {

    Button bt; 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bt = (Button) findViewById(R.id.button1);
        bt.setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                Intent intent = new Intent("lalala");
                intent.putExtra("key", "get lalala BroadCast~");
                sendBroadcast(intent);
            }
        });
    }
}

package com.example.broadcasttest;

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

public class diy_broadcastReceiver extends BroadcastReceiver{

    @Override
    public void onReceive(Context arg0, Intent arg1) {
        // TODO Auto-generated method stub
        String s = arg1.getExtras().getString("key");//或者arg1.getStringExtra("key");
        Toast.makeText(arg0, s, Toast.LENGTH_SHORT).show();
    }

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="${relativePackage}.${activityClass}" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="19dp"
        android:text="Send BroadCast" />

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.broadcasttest"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="20" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <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>
        <receiver
            android:name=".diy_broadcastReceiver" >
            <intent-filter>
                <action android:name="lalala" />
            </intent-filter>            
        </receiver>
    </application>

</manifest>

别的应用，如果静态注册了同样的广播，也会进行相应的操作。

问题：

一个广播接收器注册了多个广播，怎样根据广播来源的不同，进行不同的操作？

 5.3.2发送有序广播

//..........