java - 我只想通过android发送get请求，但它不起作用，我的代码如下，

Question

  public void sendGET(String GET_URL) throws IOException {
    try {
        URL obj = new URL(GET_URL);
        HttpURLConnection con = (HttpURLConnection) obj.openConnection();
        con.setRequestMethod("GET");
        con.setRequestProperty("User-Agent", USER_AGENT);
        int responseCode = con.getResponseCode();
    }
    catch (IOException e) {
        e.printStackTrace();
    }
}

这是我为获取请求编写的方法。
在我的情况下，GET_URL是一个字符串，其值GET_URL = 192.168.4.1？value = 1。
我在按钮单击时调用了此方法，但在android中却无法正常工作。
注意：我的apk编译时没有任何错误，它也可以运行，但是get请求不起作用。
按钮代码如下，

    led1on.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            try{
                sendGET("http://192.168.4.1/?linker=1");
                Toast.makeText(getApplicationContext(),
                        "Led1 ON Clicked!", Toast.LENGTH_SHORT).show();
            }
            catch (IOException e){

            }
        }
    });

崩溃日志在这里：
07-29 16：10：07.352 3459-3459 / com.example.samiullah.esp8266 E / AndroidRuntime：FATAL EXCEPTION：main
                                                                             进程：com.example.samiullah.esp8266，PID：3459
                                                                             android.os.NetworkOnMainThreadException
                                                                                 在android.os.StrictMode $ AndroidBlockGuardPolicy.onNetwork（StrictMode.java:1273）
                                                                                 在libcore.io.BlockGuardOs.connect（BlockGuardOs.java:110）
                                                                                 在libcore.io.IoBridge.connectErrno（IoBridge.java:137）
                                                                                 在libcore.io.IoBridge.connect（IoBridge.java:122）
                                                                                 在java.net.PlainSocketImpl.connect（PlainSocketImpl.java:183）
                                                                                 在java.net.PlainSocketImpl.connect（PlainSocketImpl.java:452）
                                                                                 在java.net.Socket.connect（Socket.java:884）
                                                                                 在com.android.okhttp.internal.Platform.connectSocket（Platform.java:117）
                                                                                 在com.android.okhttp.internal.http.SocketConnector.connectRawSocket（SocketConnector.java:160）
                                                                                 在com.android.okhttp.internal.http.SocketConnector.connectCleartext（SocketConnector.java:67）
                                                                                 在com.android.okhttp.Connection.connect（Connection.java:152）
                                                                                 在com.android.okhttp.Connection.connectAndSetOwner（Connection.java:185）
                                                                                 在com.android.okhttp.OkHttpClient $ 1.connectAndSetOwner（OkHttpClient.java:128）
                                                                                 在com.android.okhttp.internal.http.HttpEngine.nextConnection（HttpEngine.java:341）
                                                                                 在com.android.okhttp.internal.http.HttpEngine.connect（HttpEngine.java:330）
                                                                                 在com.android.okhttp.internal.http.HttpEngine.sendRequest（HttpEngine.java:248）
                                                                                 在com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute（HttpURLConnectionImpl.java:433）
                                                                                 在com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse（HttpURLConnectionImpl.java:384）
                                                                                 在com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponseCode（HttpURLConnectionImpl.java:497）
                                                                                 在com.example.samiullah.esp8266.MainActivity.sendGET（MainActivity.java:110）
                                                                                 在com.example.samiullah.esp8266.MainActivity $ 1.onClick（MainActivity.java:29）
                                                                                 在android.view.View.performClick（View.java:5198）
                                                                                 在android.view.View $ PerformClick.run（View.java:21147）
                                                                                 在android.os.Handler.handleCallback（Handler.java:739）
                                                                                 在android.os.Handler.dispatchMessage（Handler.java:95）
                                                                                 在android.os.Looper.loop（Looper.java:148）
                                                                                 在android.app.ActivityThread.main（ActivityThread.java:5417）
                                                                                 在java.lang.reflect.Method.invoke（本机方法）
                                                                                 在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run（ZygoteInit.java:726）
                                                                                 在com.android.internal.os.ZygoteInit.main（ZygoteInit.java:616）
07-29 16：10：09.956 3459-3459 / com.example.samiullah.esp8266 I / Process：正在发送信号。 PID：3459 SIG：9

Answer 1

在您的AndroidMenifest.xml中，添加

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

我看到了您的日志，对于不熟悉android的人来说这是一个常见问题。尝试

new Thread(() -> sendGET("http://192.168.4.1/?linker=1")).start();

这不是一个好方法，但是可以解决您的问题。看看 How do I fix android.os.NetworkOnMainThreadException?