要为仅限现场/内部应用程序添加代理，可以使用以下代码示例：

1. 在AndroidManifest.xml文件中添加以下权限：

2. 创建一个类来设置代理：

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.Network;
import android.net.NetworkCapabilities;
import android.net.NetworkRequest;
import android.util.Log;

import java.lang.reflect.Field;
import java.net.InetSocketAddress;
import java.net.Proxy;
import java.net.ProxySelector;
import java.net.URI;
import java.util.List;

public class ProxyHelper {

    private static final String TAG = "ProxyHelper";

    private static final String PROXY_HOST = "YOUR_PROXY_HOST";
    private static final int PROXY_PORT = YOUR_PROXY_PORT;

    public static void enableProxy(Context context) {
        try {
            // Set HTTP proxy
            System.setProperty("http.proxyHost", PROXY_HOST);
            System.setProperty("http.proxyPort", String.valueOf(PROXY_PORT));
            // Set HTTPS proxy
            System.setProperty("https.proxyHost", PROXY_HOST);
            System.setProperty("https.proxyPort", String.valueOf(PROXY_PORT));

            // Set proxy for the default ProxySelector
            ProxySelector.setDefault(new ProxySelector() {
                @Override
                public List select(URI uri) {
                    return List.of(new Proxy(Proxy.Type.HTTP, new InetSocketAddress(PROXY_HOST, PROXY_PORT)));
                }

                @Override
                public void connectFailed(URI uri, SocketAddress sa, IOException ioe) {
                    Log.e(TAG, "Proxy connect failed");
                }
            });

            // Set proxy for the default Network
            ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkRequest.Builder builder = new NetworkRequest.Builder();
            builder.addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET);
            builder.addTransportType(NetworkCapabilities.TRANSPORT_CELLULAR);
            builder.addTransportType(NetworkCapabilities.TRANSPORT_WIFI);
            NetworkRequest networkRequest = builder.build();
            ConnectivityManager.NetworkCallback networkCallback = new ConnectivityManager.NetworkCallback() {
                @Override
                public void onAvailable(Network network) {
                    try {
                        // Set proxy for the Network
                        Field field = network.getClass().getDeclaredField("mService");
                        field.setAccessible(true);
                        Object obj = field.get(network);
                        Class cls = Class.forName("android.net.INetworkManager");
                        Method method = cls.getDeclaredMethod("setProxy", Network.class, ProxyInfo.class);
                        method.invoke(obj, network, ProxyInfo.buildDirectProxy(PROXY_HOST, PROXY_PORT, null));
                    } catch (Exception e) {
                        Log.e(TAG, "Failed to set proxy for network", e);
                    }
                }
            };
            connectivityManager.registerNetworkCallback(networkRequest, networkCallback);
        } catch (Exception e) {
            Log.e(TAG, "Failed to enable proxy", e);
        }
    }

    public static void disableProxy() {
        // Clear HTTP proxy
        System.clearProperty("http.proxyHost");
        System.clearProperty("http.proxyPort");
        // Clear HTTPS proxy
        System.clearProperty("https.proxyHost");
        System.clearProperty("https.proxyPort");

        // Remove proxy for the default ProxySelector
        ProxySelector.setDefault(ProxySelector.getDefault());

        // Remove proxy for the default Network
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        connectivityManager.unregisterNetworkCallback(networkCallback);
    }
}

3. 在需要启用代理的地方调用 enableProxy() 方法：

ProxyHelper.enableProxy(getApplicationContext());

4. 在需要禁用代理的地方调用 disableProxy() 方法：

ProxyHelper.disableProxy();

注意：上述示例中的 YOUR_PROXY_HOST 和 YOUR_PROXY_PORT 需要替换为实际的代理主机和端口。同时，请确保您的应用程序具有访问网络的权限。