广播的基本使用，判断是否有可用网络，并弹出设置窗口

1、MainActivity

package lpc.com.project521;
import android.app.Activity;
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.os.Bundle;
import android.provider.Settings;
import android.widget.Toast;
public class MainActivity extends Activity {
    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");//android.net.conn.CONNECTIVITY_CHANGE是网络发生变化时的事件，将此事件和自定义的广播绑定之后，当发生网络状态改变的情况，就会调用自定义广播里的操作，此处是跳出设置窗口
        networkChangeReceiver = new NetworkChangeReceiver();
        registerReceiver(networkChangeReceiver,intentFilter);
    }
    private class NetworkChangeReceiver extends BroadcastReceiver{
        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager connectivityManager = (ConnectivityManager)
                    getSystemService(CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
            if (networkInfo !=null && networkInfo.isAvailable()){
                Toast.makeText(context,"网络可用",Toast.LENGTH_SHORT).show();
            }else {
                Toast.makeText(context,"网络不可用，请设置网络",Toast.LENGTH_SHORT).show();
                intent =  new Intent(Settings.ACTION_SETTINGS);
                startActivity(intent);
            }
        }
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }
}

2、manifest文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="lpc.com.project521">
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
    <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>
    </application>
</manifest>

运行结果，当开启网络时，提示网络可用，当网络不可用（wifi和移动网络都不可用时，弹出网络不可用，并弹出设置 窗口）

来自为知笔记(Wiz)