中山阿里云代理商：android 判断有无网络

在Android中，可以通过以下方法判断是否有网络连接：

1. 使用系统服务ConnectivityManager：

ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
boolean isConnected = networkInfo != null && networkInfo.isConnected();

2. 检查网络连接的类型：

ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
boolean isConnected = networkInfo != null && networkInfo.isConnected();
if (isConnected) {
    int networkType = networkInfo.getType();
    boolean isWiFi = networkType == ConnectivityManager.TYPE_WIFI;
    boolean isMobile = networkType == ConnectivityManager.TYPE_MOBILE;
    // 根据需要进行处理
}

3. 监听网络连接状态的变化：

首先，在AndroidManifest.xml文件中添加权限：

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

然后，在Activity或Fragment中注册广播接收器：

private NetworkChangeReceiver networkChangeReceiver;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    
    networkChangeReceiver = new NetworkChangeReceiver();
    IntentFilter intentFilter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
    registerReceiver(networkChangeReceiver, intentFilter);
}

@Override
protected void onDestroy() {
    super.onDestroy();

    unregisterReceiver(networkChangeReceiver);
}

public class NetworkChangeReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        if (ConnectivityManager.CONNECTIVITY_ACTION.equals(intent.getAction())) {
            ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
            boolean isConnected = networkInfo != null && networkInfo.isConnected();
            // 根据需要进行处理
        }
    }
}

通过以上方法，可以判断Android设备是否有网络连接。

在Android设备上，可以通过ConnectivityManager来判断是否有网络连接。以下是一个示例代码：

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;

public class NetworkUtil {

    public static boolean isNetworkAvailable(Context context) {
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        if (connectivityManager != null) {
            NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
            return activeNetworkInfo != null && activeNetworkInfo.isConnected();
        }
        return false;
    }
}

然后在需要判断网络连接的地方调用isNetworkAvailable方法即可，例如：

if (NetworkUtil.isNetworkAvailable(context)) {
    // 有网络连接
} else {
    // 没有网络连接
}

请注意，在使用此方法之前，请确保添加了相应的网络权限到AndroidManifest.xml文件中：

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