Android学习日记（二）：
广播：标准广播 有序广播（可以截断）
一、接收系统广播

    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.coon.CONNECTIVITY_CHANGE");
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver,intentFilter);
    }
     @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }

    class NetworkChangeReceiver extends BroadcastReceiver {

        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectionManager = (ConnectivityManager)
                    getSystemService(Context.CONNECTIVITY_SERVICE);
            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();
            }
        }
    }

IntentFilter的实例addAction android.net.coon.CONNECTIVITY_CHANGE
监听网络变化
在AndroidMainfest.xml中加入

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

二、自定义广播
在AndroidMainfest.xml中加入

        <receiver
            android:name=".MyBroadcastReceiver"
            android:enabled="true"
            android:exported="true">
            <intent-filter>
                <action android:name="com.sun.broadcasttest.MY_BROADCAST"/>
            </intent-filter>
        </receiver>

可以用Intent传数据

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

三、有序广播

Intent intent = new Intent("com.sun.broadcasttest.MY_BROADCAST");
sendOrderBroadcast(intent,null)

四、本地广播
优势：
安全，比全局广播高效。