要连接到Wifi网络，可以使用Android的WifiManager和WifiConfiguration类。以下是一个示例代码，用于连接到指定的Wifi网络：

import android.content.Context;
import android.net.wifi.WifiConfiguration;
import android.net.wifi.WifiManager;
import android.net.wifi.WifiNetworkSpecifier;
import android.os.Build;
import android.os.Handler;
import android.os.Looper;
import android.widget.Toast;

public class WifiConnector {
    private Context context;
    private WifiManager wifiManager;

    public WifiConnector(Context context) {
        this.context = context;
        wifiManager = (WifiManager) context.getApplicationContext().getSystemService(Context.WIFI_SERVICE);
    }

    public void connectToWifi(String ssid, String password) {
        WifiConfiguration wifiConfig = new WifiConfiguration();

        // For WPA/WPA2 network
        wifiConfig.SSID = String.format("\"%s\"", ssid);
        wifiConfig.preSharedKey = String.format("\"%s\"", password);

        int networkId = wifiManager.addNetwork(wifiConfig);
        wifiManager.disconnect();
        wifiManager.enableNetwork(networkId, true);
        wifiManager.reconnect();

        showToast("Connecting to Wifi: " + ssid);
    }

    private void showToast(final String message) {
        new Handler(Looper.getMainLooper()).post(new Runnable() {
            @Override
            public void run() {
                Toast.makeText(context, message, Toast.LENGTH_SHORT).show();
            }
        });
    }
}

要连接到Wifi网络，可以调用connectToWifi方法，并传入要连接的Wifi的SSID和密码。

请注意，在Android 10及更高版本中，使用WifiManager添加网络的方式已被弃用。相反，可以使用WifiNetworkSpecifier类来连接到特定的Wifi网络。以下是一个示例代码，用于在Android 10及更高版本上连接到Wifi网络：

import android.content.Context;
import android.net.wifi.WifiNetworkSpecifier;
import android.net.wifi.WifiTransportLayerSecurityException;
import android.net.wifi.WifiTransportLayerSecurityException.AuthenticationProblem;
import android.net.wifi.WifiTransportLayerSecurityException.CertificateProblem;
import android.net.wifi.WifiTransportLayerSecurityException.SessionTimeout;
import android.net.wifi.WifiTransportLayerSecurityException.UntrustedRoot;

import androidx.annotation.NonNull;

import java.util.concurrent.Executor;
import java.util.concurrent.Executors;

public class WifiConnector {
    private Context context;
    private WifiManager wifiManager;

    public WifiConnector(Context context) {
        this.context = context;
        wifiManager = (WifiManager) context.getApplicationContext().getSystemService(Context.WIFI_SERVICE);
    }

    public void connectToWifi(String ssid, String password) {
        WifiNetworkSpecifier.Builder builder = new WifiNetworkSpecifier.Builder();
        builder.setSsid(ssid);
        builder.setWpa2Passphrase(password);

        WifiNetworkSpecifier wifiNetworkSpecifier = builder.build();

        Executor executor = Executors.newSingleThreadExecutor();
        wifiManager.requestNetwork(wifiNetworkSpecifier, new ConnectToWifiCallback(), executor);
    }

    private class ConnectToWifiCallback extends WifiManager.NetworkCallback {
        @Override
        public void onUnavailable() {
            showToast("Failed to connect to Wifi");
        }

        @Override
        public void onAvailable(@NonNull android.net.Network network) {
            wifiManager.enableNetwork(network);
            wifiManager.connect(network);
            showToast("Connecting to Wifi");
        }

        @Override
        public void onBlockedStatusChanged(boolean blocked) {
            if (blocked) {
                showToast("Wifi network is blocked");
            } else {
                showToast("Wifi network is unblocked");
            }
        }

        @Override
        public void onAuthenticationProblem(@AuthenticationProblem int problem) {
            showToast("Wifi authentication problem: " + problem);
        }

        @Override
        public void onCertificateProblem(@CertificateProblem int problem) {
            showToast("Wifi certificate problem: " + problem);
        }

        @Override
        public void onSessionTimeout() {
            showToast("Wifi session timeout");
        }

        @Override
        public void onUntrustedRoot(@UntrustedRoot int reason) {
            showToast("Wifi untrusted root: " + reason);
        }
    }

    private void showToast(final String message) {
        new Handler(Looper.getMainLooper()).post(new Runnable() {
            @Override
            public void run() {
                Toast.makeText(context, message, Toast.LENGTH_SHORT).show();
            }
        });
    }
}

在这个示例代码中，我们使用了WifiNetworkSpecifier.Builder来创建一个WifiNetworkSpecifier对象，并通过WifiManager的requestNetwork方法来连接到指定的Wifi网络。这个示例代码还包括一些回调方法，用于处理连接过程中可能出现的问题。