广播：四大组件之一，你的应用可以使用它对外部事件进行过滤只对感兴趣的外部事件（如当电话呼入时，或者数据网络可用时）进行接收并作出响应，广播接收器没有用户界面。然而，它们可以启动一个activity或serice来响应它们接收到的消息，或者用NotificationManager来通知用户。通知可以用很多种方式来吸引用户的注意力——闪动背灯、震动、播放声音等。一般来说是在状态栏上放一个持久的图标，用户可以打开它并获取消息。
- 想要拦截的广播
- 拦截到广播之后做得动作
- 注册广播
- 取消注册
package com.example.bbw.broadcastdemo;
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.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Toast;
public class MainActivity extends AppCompatActivity {
private IntentFilter intentFilter;
private NetworkChangeReceiver receiver;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
intentFilter = new IntentFilter();
intentFilter.addAction("android.net.conn.CONNECTIVITY_CHANGE");//决定拦截哪条广播
receiver = new NetworkChangeReceiver();
registerReceiver(receiver,intentFilter);//注册
}
@Override
protected void onDestroy() {
super.onDestroy();
unregisterReceiver(receiver);//取消注册
}
private class NetworkChangeReceiver extends BroadcastReceiver{
@Override
public void onReceive(Context context, Intent intent) {
ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isAvailable()){
Toast.makeText(getApplicationContext(),"network is available",Toast.LENGTH_SHORT).show();
}else{
Toast.makeText(getApplicationContext(),"network is unavailable",Toast.LENGTH_SHORT).show();
}
}
}
}
取得权限：
<uses-permission android:name="android.permission.ACCE SS_NETWORK_STATE"/>
