Android使用java实现网络连通性检查详解

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import java.net.HttpURLConnection;
import java.net.URL;

public final class NetCheck {

    public interface Callback {
        void onResult(boolean ok);
    }

    /** 对外入口：主线程调用，回调仍在主线程 */
    public static void isOnline(Context ctx, Callback cb) {
        if (!isConnected(ctx)) {
            cb.onResult(false);
            return;
        }
        // 真正发 HTTP 探活
        new PingTask(cb).execute();
    }

    /* ========== 内部实现 ========== */

    /* 1. 系统是否声明已连接 */
    private static boolean isConnected(Context ctx) {
        ConnectivityManager cm = (ConnectivityManager)
                ctx.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo info = cm.getActiveNetworkInfo();
        return info != null && info.isConnected();
    }

    /* 2. 异步探活，避免 ANR */
    private static class PingTask extends AsyncTask<Void, Void, Boolean> {
        private final Callback cb;
        PingTask(Callback cb) { this.cb = cb; }

        @Override
        protected Boolean doInBackground(Void... voids) {
            HttpURLConnection conn = null;
            try {
                // ① 国内通用、响应快；② 支持 HEAD，省流量
                conn = (HttpURLConnection) new URL("https://www.baidu.com").openConnection();
                conn.setRequestMethod("HEAD");
                conn.setConnectTimeout(3_000);
                conn.setReadTimeout(3_000);
                int code = conn.getResponseCode();
                return (code >= 200 && code < 400);
            } catch (Exception e) {
                e.printStackTrace();
                return false;
            } finally {
                if (conn != null) conn.disconnect();
            }
        }

        @Override
        protected void onPostExecute(Boolean ok) {
            cb.onResult(ok);
        }
    }

    private NetCheck() {}
}

NetCheck.isOnline(this, ok -> {
    if (ok) {
        // 真正连网
    } else {
        Toast.makeText(this, "网络不可用", Toast.LENGTH_SHORT).show();
    }
});

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