BroadCastTest

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学习目的：1.了解标准广播 有序广播区别(简单，不赘述) 2.接收系统广播 3,发送自定义广播 4.使用本地广播

2.接收系统广播


1.动态注册监听网络变化

  • 需要声明权限
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<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.broadcasttest">

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
>
  • 新建NetworkChangeReceiver类 
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    public class MainActivity extends AppCompatActivity {


       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");//当网络发生变化  系统发出值/为android.net.conn.CONNECTIVITY_CHANGE的广播  要监听什么广播就加什么action
            networkChangeReceiver = new NetworkChangeReceiver();//新建NetworkChangeReceiver实例
            registerReceiver(networkChangeReceiver, intentFilter);//对其进行注册

        }

        @Override
        protected void onDestroy() {
            super.onDestroy();
            unregisterReceiver(networkChangeReceiver);//动态注册的的广播接收器一定要取消注册
              }


    class NetworkChangeReceiver extends BroadcastReceiver {

           @Override
          public void onReceive(Context context, Intent intent) {
               Toast.makeText(content,"network changes",Toast.LENGTH_SHORT).show();
            }

优化（告诉用户有网还是没网）


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class NetworkChangeReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectionManager = (ConnectivityManager)
                    getSystemService(Context.CONNECTIVITY_SERVICE);//ConnectivityManager 系统服务类 专门管理网络getSystemService获得NetworkInfo实例
            NetworkInfo networkInfo = connectionManager.getActiveNetworkInfo();//
            if (networkInfo != null && networkInfo.isAvailable()) {
                Toast.makeText(context, "network is available",
                        Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(context, "network is unavailable",
                        Toast.LENGTH_SHORT).show();
            }

        }
    }

2.静态注册监听网路变化
直接NEW-other-BoardCastReceriver

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public class BoardCompelteReceiver extends BroadcastReceiver {

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

    }

}

添加权限(部分自动生成)

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

    <receiver
            android:name=".BootCompleteReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />//系统启动时会发android.intent.action.BOOT_COMPLETED值得广播
            </intent-filter>
        </receiver>

3,发送自定义广播


1.发送标准广播
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public class MyBroadcastReceiver extends BroadcastReceiver {

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

}

添加权限
```text
<receiver
            android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter android:priority="100">
                <action android:name="com.example.broadcasttest.MY_BROADCAST"/>
            </intent-filter>
        </receiver>

```     
按钮启动
```java
Button button = (Button) findViewById(R.id.button);
      button.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
              Intent intent = new Intent("com.example.broadcasttest.MY_BROADCAST");
              sendBroadcast(intent);
          }
      });   

<h3>2.发送有序广播</h3>
改一行代码
```java
sendOrderedBroadcast(intent,null);//这时广播接收器有先后顺序

如何定义先后顺序

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<receiver
           android:name=".MyBroadcastReceiver"
           android:enabled="true"
           android:exported="true">
           <intent-filter android:priority="100">//100优先级最高
               <action android:name="com.example.broadcasttest.MY_BROADCAST"/>
           </intent-filter>

是否允许继续传递

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ublic void onReceive(Context context, Intent intent) {
        Toast.makeText(context, "received in MyBroadcastReceiver", Toast.LENGTH_SHORT).show();
        abortBroadcast();//表示截断
    }

4.使用本地广播


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ublic class MainActivity extends AppCompatActivity {

    private IntentFilter intentFilter;

    private LocalReceiver localReceiver;

    private LocalBroadcastManager localBroadcastManager;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        localBroadcastManager = LocalBroadcastManager.getInstance(this); // 获取实例
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("com.example.broadcasttest.LOCAL_BROADCAST");
                localBroadcastManager.sendBroadcast(intent); // 发送本地广播
            }
        });
        intentFilter = new IntentFilter();
        intentFilter.addAction("com.example.broadcasttest.LOCAL_BROADCAST");//当网络发生变化  系统发出值/为android.net.conn.CONNECTIVITY_CHANGE的广播  要监听什么广播就加什么action
        localReceiver = new LocalReceiver();//新建NetworkChangeReceiver实例
        localBroadcastManager.registerReceiver(localReceiver, intentFilter); // 注册本地广播监听器
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();

        localBroadcastManager.unregisterReceiver(localReceiver);
    }

    class LocalReceiver extends BroadcastReceiver {

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

    }

本地广播的优势


不用担心机密数据泄露
其他程序将广播发送到我们程序内部
比全局广播更高效