要在Android中监听网络状态变化，可以使用ConnectivityManager类和广播接收器来实现。以下是一个简单的示例代码：
1. 添加权限
首先，在AndroidManifest.xml文件中添加必要的权限：
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>2. 创建一个BroadcastReceiver
创建一个继承BroadcastReceiver的类，以便监听网络状态的变化：
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.widget.Toast;
public class NetworkChangeReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {
ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
boolean isConnected = activeNetwork != null && activeNetwork.isConnectedOrConnecting();
if (isConnected) {
Toast.makeText(context, "Network Connected", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(context, "Network Disconnected", Toast.LENGTH_SHORT).show();
}
}
}3. 注册BroadcastReceiver
在AndroidManifest.xml文件中注册BroadcastReceiver：
<receiver android:name=".NetworkChangeReceiver">
<intent-filter>
<action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
</intent-filter>
</receiver>4. 在Activity中动态注册（可选）
你也可以在你的Activity中动态注册BroadcastReceiver：
import android.content.IntentFilter;
import android.net.ConnectivityManager;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
public class MainActivity extends AppCompatActivity {
private NetworkChangeReceiver networkChangeReceiver = new NetworkChangeReceiver();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
@Override
protected void onResume() {
super.onResume();
IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
registerReceiver(networkChangeReceiver, filter);
}
@Override
protected void onPause() {
super.onPause();
unregisterReceiver(networkChangeReceiver);
}
}通过上述步骤，你可以在Android应用中监听网络状态变化并做出相应的处理。这个方法使用了广播接收器，可以在网络状态变化时实时地检测到，并通过Toast显示当前网络的连接状态。
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