5. 廣播

5.1 廣播

5.2 接收系統廣播

5.2.1 動態註冊監聽網路變化

public class MainActivity extends AppCompatActivity {
    private IntentFilter intentFilter;

    private NetworkChangeReceiver networkChangeReceiver;

    /**
     * 1.定義了一個內部類，繼承自BroadcastReceiver類，重寫接收到廣播後的執行方法
     */
    class NetworkChangeReceiver extends BroadcastReceiver {

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

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

        /**
         * 2.建立一個IntentFilter類例項，新增一個值為如下的action（因為當系統網路發生變化時發出的就是此值的廣播）
         */
        intentFilter = new IntentFilter();
        intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");
        /**
         * 3.建立一個自定義廣播接收器類例項，然後呼叫registerReceiver進行註冊。
         */
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver, intentFilter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        /**
         * 4.動態註冊的廣播接收器最後都要取消註冊，不管是在哪個方法中
         */
        unregisterReceiver(networkChangeReceiver);
    }
}
 

@Override
public void onReceive(Context context, Intent intent) {
    //首先通過getSystemService()方法得到ConnectivityManager的例項，這是系統服務類，專門用於管理網路連線
    ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
    //然後通過它的getActiveNetworkInfo()方法得到NetworkInfo例項
    NetworkInfo network = connectivityManager.getActiveNetworkInfo();
    //最後判斷是否有網路
    if (network != null && network.isAvailable()) {
        Toast.makeText(context, "網路可用", Toast.LENGTH_SHORT).show();
    } else {
        Toast.makeText(context, "網路不可用", Toast.LENGTH_SHORT).show();
    }
}
 

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

5.2.2 靜態註冊實現開機啟動

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.jastar.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: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>
        <!--通過receiver標籤來靜態註冊廣播接收器-->
        <receiver android:name=".receiver.BootCompleteReceiver">
            <intent-filter>
                <!--在此新增要監聽的廣播action-->
                <action android:name="android.intent.action.BOOT_COMPLETED"></action>
            </intent-filter>
        </receiver>
    </application>

</manifest>

5.3 傳送自定義廣播

5.3.1 傳送標準廣播

Intent intent=new Intent("com.jastar.broadcasttest.MY_BROADCAST");
sendBroadcast(intent);

5.3.2 傳送有序廣播

Intent intent = new Intent("com.jastar.broadcasttest.MY_BROADCAST");
//第一個引數為intent，第二個引數為與許可權有關的字串
sendOrderedBroadcast(intent, null);

5.4 本地廣播