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在android开发中，对网络状态的监听是非常重要的。比如在WIFI情况下，加载高清的图片。在3G和4G的情况下加载图片质量比较差的图片。那么怎样对android网络状态进行监听呢？

首先加上需要加的权限:

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

然后我们就可以编写一个对网络状态进行判断的工具类：NetUtils

//网络是否可用
public static boolean isNetworkAvailable(Context context) {
    ConnectivityManager mgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo[] info = mgr.getAllNetworkInfo();
    if (info != null) {
        for (int i = 0; i < info.length; i++) {
            if (info[i].getState() == NetworkInfo.State.CONNECTED) {
                return true;
            }
        }
    }
    return false;
}

//网络是否连接
public static boolean isNetworkConnected(Context context) {
    if (context != null) {
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo mNetworkInfo = mConnectivityManager.getActiveNetworkInfo();
        if (mNetworkInfo != null) {
            return mNetworkInfo.isAvailable();
        }
    }
    return false;
}

//是否是WIFI的情况下
public static boolean isWifiConnected(Context context) {
    if (context != null) {
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo mWiFiNetworkInfo = mConnectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
        if (mWiFiNetworkInfo != null) {
            return mWiFiNetworkInfo.isAvailable();
        }
    }
    return false;
}

//3G网络
public static boolean isMobileConnected(Context context) {
    if (context != null) {
        ConnectivityManager mConnectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo mMobileNetworkInfo = mConnectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
        if (mMobileNetworkInfo != null) {
            return mMobileNetworkInfo.isAvailable();
        }
    }
    return false;
}  

这个工具类用来判断网络的一些状态，然后我们需要一个广播接收者，来接收网络的变化

需要在AndroidManifest.xml文件中注册：

   <receiver android:name=".NetStateReceiver">

        <intent-filter>
            <action android:name="android.net.conn.CONNECTIVITY_CHANGE"></action>

        </intent-filter>
    </receiver>

最后就可以着手对网络变化进行监听了：

public class NetStateReceiver extends BroadcastReceiver {

        private final static String ANDROID_NET_CHANGE_ACTION = "android.net.conn.CONNECTIVITY_CHANGE";

        @Override
        public void onReceive(Context context, Intent intent) {
            if (intent.getAction().equalsIgnoreCase(ANDROID_NET_CHANGE_ACTION)) {
                if (NetUtils.isNetworkAvailable(context)) {
                    //Wifi情况下
                    if (NetUtils.isWifiConnected(context)) {
                        Log.d("same_info>>", "net wifi");
                    }
                    //数据流量的情况下
                    else {
                        Log.d("same_info>>", "net data");
                    }
                } else {
                    Log.d("same_info>>", "net error");
                }
            }
        }
    }

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