【android学习随笔】android广播机制

android

广播类型简介

标准广播

异步执行，无序，效率高，但是无法截断

有序广播

同步执行，有序，效率低，优先级高会先收到消息，并且可以截断正在传递的广播

接受系统广播

例如：电池低电量，手机开启，时间时区变化，网络变化

动态注册监听网络变化

优点：可以灵活使用，自由的在周期内控制监听的注册和注销
缺点：只能在程序的周期内使用

添加广播接收器

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public class NetworkChangeReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // 获取系统服务类的实例 getSystemService
        ConnectivityManager connectionManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        // 获取 NetworkInfo 实例
        NetworkInfo networkInfo = connectionManager.getActiveNetworkInfo();
        // 用NetworkInfo实例下的方法isAvailable()是否开启进行判断输出
        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();
        }
    }
}

添加动态注册监听网络广播

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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();                              // 创建IntentFilter实例
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE"); // 添加 android.net.conn.CONNECTIVITY_CHANGE 监听action为网络发生变化的广播
        networkChangeReceiver = new NetworkChangeReceiver();            // 创建 NetworkChangeReceiver 实例
        registerReceiver(networkChangeReceiver, intentFilter);          // 进行注册，完成监听功能
    }

    // 在活动销毁周期，注销掉已注册的监听，动态注册的必做此步骤
    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }
}

静态注册实现开机启动

优点：可以在程序外启动
缺点：不灵活
注：8.0以上自定义静态注册被限制,尽量使用动态注册,系统广播，例如开机启动一些未被限制的可以静态注册

创建广播接收器

可以使用 Android Studio 提供的快捷方式来创建一个广播接收器，右击 com.example.broadcasttest 包→New→Other→Broadcast Receiver，Exported 属性表示是否 允许这个广播接收器接收本程序以外的广播，Enabled 属性表示是否启用这个广播接收器。

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public class BootCompleteReceiver extends BroadcastReceiver {
    static final String action_boot ="android.intent.action.BOOT_COMPLETED";
    @Override
    public void onReceive(Context context, Intent intent) {
        if (intent.getAction().equals(action_boot)){
            Intent mBootIntent = new Intent(context, MainActivity.class);
            // 下面这句话必须加上才能开机自动运行app的界面
            mBootIntent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            context.startActivity(mBootIntent);
        }
    }
}

在AndroidManifest.xml添加权限和动作

添加权限 <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
添加自动添加的receiver内添加 intentFilter 动作

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<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.shifeng.broadcasttest">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver
            android:name=".BootCompleteReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.BOOT_COMPLETED" />
            </intent-filter>
        </receiver>
    </application>

</manifest>

接受自定义广播

发送标准广播

定义广播接收器

新建类MyBroadcastReceiver继承BroadcastReceiver，重写onReceive方法

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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();
    }
}

添加动态注册和触发事件

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public class MainActivity extends AppCompatActivity {

    private IntentFilter myIntentFilter;

    private MyBroadcastReceiver myBroadcastReceiver;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 动态注册部分
        myIntentFilter = new IntentFilter();
        myIntentFilter.addAction("com.example.MY_BROADCAST");
        myBroadcastReceiver = new MyBroadcastReceiver();
        registerReceiver(myBroadcastReceiver, myIntentFilter);
        // button事件触发部分
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent("com.example.MY_BROADCAST");
                sendBroadcast(intent);
            }
        });
    }

    // 在活动销毁周期，注销掉已注册的监听，动态注册的必做此步骤
    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(myBroadcastReceiver);
    }
}

本地广播

定义广播接收器

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public class LocalReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        Toast.makeText(context,"hello local", Toast.LENGTH_SHORT).show();
    }
}

添加动态注册和触发事件

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public 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.LOCAL_BROADCAST");
                localBroadcastManager.sendBroadcast(intent); // 发送本地广播
            }
        });
        intentFilter = new IntentFilter();
        intentFilter.addAction("com.example.LOCAL_BROADCAST");
        localReceiver = new LocalReceiver();
        localBroadcastManager.registerReceiver(localReceiver, intentFilter); // 注 册本地广播监听器
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        localBroadcastManager.unregisterReceiver(localReceiver);
    }

}