如何在Android中实现监听系统网络连接状态的打开与关闭？

Android中监听系统网络连接打开或者关闭的实现代码

在Android应用程序开发中，有时需要监听系统网络连接状态的变化，以便及时响应网络状态的改变，当用户打开或关闭Wi-Fi时，应用可能需要执行相应的操作，本文将详细介绍如何在Android中实现对系统网络连接状态变化的监听。

1. 使用BroadcastReceiver监听网络变化

1.1 定义BroadcastReceiver

我们需要定义一个BroadcastReceiver来接收系统广播，监听网络状态的变化，以下是一个简单的例子：

public class NetworkChangeReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        // 获取网络状态信息
        boolean isConnected = intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY, false);
        
        if (isConnected) {
            // 网络已连接
            Log.d("NetworkChangeReceiver", "Network Connected");
        } else {
            // 网络断开
            Log.d("NetworkChangeReceiver", "Network Disconnected");
        }
    }
}

1.2 注册BroadcastReceiver

需要在AndroidManifest.xml文件中注册这个BroadcastReceiver，并指定它要接收的广播类型。

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

1.3 动态注册BroadcastReceiver（可选）

除了在AndroidManifest.xml中静态注册，还可以在代码中动态注册BroadcastReceiver，这种方式在某些情况下更为灵活，例如在特定Activity中监听网络变化。

public class MainActivity extends AppCompatActivity {
    private NetworkChangeReceiver networkChangeReceiver;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        networkChangeReceiver = new NetworkChangeReceiver();
        IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
        registerReceiver(networkChangeReceiver, filter);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }
}

2. 使用ConnectivityManager获取网络状态

虽然BroadcastReceiver可以监听到网络状态的变化，但有时我们还需要主动查询当前的网络状态，这时可以使用ConnectivityManager类。

2.1 获取ConnectivityManager实例

需要获取ConnectivityManager的实例：

ConnectivityManager connectivityManager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

2 检查网络连接状态

可以使用ConnectivityManager的方法来检查当前是否有可用的网络连接，以下是一个示例方法：

public boolean isNetworkConnected(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
    return networkInfo != null && networkInfo.isConnected();
}

3 检查网络类型

如果需要进一步检查网络类型（如Wi-Fi或移动数据），可以使用以下方法：

public String getNetworkType(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
    if (networkInfo == null) {
        return "No network";
    }
    int type = networkInfo.getType();
    switch (type) {
        case ConnectivityManager.TYPE_WIFI:
            return "WiFi";
        case ConnectivityManager.TYPE_MOBILE:
            return "Mobile Data";
        default:
            return "Other";
    }
}

3. 处理网络变化事件

当接收到网络变化广播时，可以在onReceive方法中执行相应的逻辑，更新UI、重新加载数据等，以下是一个示例：

public class NetworkChangeReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        boolean isConnected = isNetworkConnected(context);
        if (isConnected) {
            // 网络已连接，执行相应操作
            Log.d("NetworkChangeReceiver", "Network Connected");
            // 重新加载数据
            // loadData();
        } else {
            // 网络断开，执行相应操作
            Log.d("NetworkChangeReceiver", "Network Disconnected");
            // 显示提示信息
            // showSnackbar("Network Disconnected");
        }
    }
    private boolean isNetworkConnected(Context context) {
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
        return networkInfo != null && networkInfo.isConnected();
    }
}

4. 权限要求

从Android 6.0（API级别23）开始，访问网络状态需要申请权限，需要在AndroidManifest.xml中声明以下权限：

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

如果目标SDK版本大于等于23，还需要在运行时请求权限：

if (ContextCompat.checkSelfPermission(this, Manifest.permission.ACCESS_NETWORK_STATE) != PackageManager.PERMISSION_GRANTED) {
    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.ACCESS_NETWORK_STATE}, REQUEST_CODE);
}

5. 完整示例代码

以下是一个完整的示例代码，展示了如何使用BroadcastReceiver和ConnectivityManager来监听网络状态变化：

public class MainActivity extends AppCompatActivity {
    private NetworkChangeReceiver networkChangeReceiver;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        networkChangeReceiver = new NetworkChangeReceiver();
        IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
        registerReceiver(networkChangeReceiver, filter);
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(networkChangeReceiver);
    }
}

public class NetworkChangeReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        boolean isConnected = isNetworkConnected(context);
        if (isConnected) {
            // 网络已连接，执行相应操作
            Log.d("NetworkChangeReceiver", "Network Connected");
            // 重新加载数据
            // loadData();
        } else {
            // 网络断开，执行相应操作
            Log.d("NetworkChangeReceiver", "Network Disconnected");
            // 显示提示信息
            // showSnackbar("Network Disconnected");
        }
    }
    private boolean isNetworkConnected(Context context) {
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
        return networkInfo != null && networkInfo.isConnected();
    }
}

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.networkchangereceiver">
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <application
        ... >
        <receiver android:name=".NetworkChangeReceiver">
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
            </intent-filter>
        </receiver>
    </application>
</manifest>

通过以上步骤，您可以在Android应用中成功监听系统网络连接状态的变化，并根据需要进行相应的处理。