大四实习准备5_android广播机制

2021-07-05 01:44:15

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();

             }

         }

     }

 }

MainActivity.class

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();

     }

 }

BootCompleted.class 广播接收器

 <?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>

AndroidManifest.xml 这里需对开机启动做权限声明&静态注册广播

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);

             }

         });

     }

 }

MainActivity.class

 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();

     }

 }

diy_broadcastReceiver.class

 <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>

activity_main.xml

 <?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>

AndroidManifest.xml

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

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

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