android.os.NetworkOnMainThreadException

问题

android.os.NetworkOnMainThreadException

详细问题

核心代码如下：

import android.os.Bundle;import androidx.appcompat.app.AppCompatActivity;import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.List;public class HomeActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_home);try {getData();} catch (IOException e) {e.printStackTrace();}}private List<MyDataType> getData() throws IOException {String apiUrl = "http://api-url";URL url = new URL(apiUrl);HttpURLConnection connection = (HttpURLConnection) url.openConnection();// 设置请求方法为GETconnection.setRequestMethod("GET");// 获取响应代码int responseCode = connection.getResponseCode();if (responseCode == HttpURLConnection.HTTP_OK) {// 读取响应内容BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));StringBuilder response = new StringBuilder();String line;while ((line = reader.readLine()) != null) {response.append(line);}reader.close();// 将响应内容转换为Weather对象列表（这里的实现取决于你的服务端返回的数据结构）List<MyDataType> dataList = parseResponse(response.toString());return dataList;} else {// 处理错误情况System.out.println("HTTP request failed with code: " + responseCode);return null;}}// 解析响应内容，将其转换为Weather对象列表private static List<MyDataType> parseResponse(String response) {// 这里需要根据实际情况解析返回的数据，将其转换为Weather对象列表// 请根据你的实际返回数据结构进行实现// 示例实现可能需要使用 JSON 解析库（如 Jackson、Gson）来处理 JSON 数据return null;}
}

控制台报错信息如下：

2024-01-14 11:57:54.617 12108-12108/com.example.assistingagriculture E/AndroidRuntime: FATAL EXCEPTION: mainProcess: com.example.assistingagriculture, PID: 12108android.os.NetworkOnMainThreadExceptionat android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1605)at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:116)at java.net.SocketOutputStream.write(SocketOutputStream.java:161)at com.android.okhttp.okio.Okio$1.write(Okio.java:78)at com.android.okhttp.okio.AsyncTimeout$1.write(AsyncTimeout.java:157)at com.android.okhttp.okio.RealBufferedSink.flush(RealBufferedSink.java:222)at com.android.okhttp.internal.http.Http1xStream.finishRequest(Http1xStream.java:163)at com.android.okhttp.internal.http.HttpEngine.readNetworkResponse(HttpEngine.java:748)at com.android.okhttp.internal.http.HttpEngine.readResponse(HttpEngine.java:622)at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:475)at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:411)at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponseCode(HttpURLConnectionImpl.java:542)at com.example.assistingagriculture.HomeActivity.getNearestLongitudeAndLatitude(HomeActivity.java:117)at com.example.assistingagriculture.HomeActivity.lambda$requestLocation$0$com-example-assistingagriculture-HomeActivity(HomeActivity.java:79)at com.example.assistingagriculture.HomeActivity$$ExternalSyntheticLambda1.onSuccess(Unknown Source:4)at com.google.android.gms.tasks.zzn.run(com.google.android.gms:play-services-tasks@@17.2.0:4)at android.os.Handler.handleCallback(Handler.java:938)at android.os.Handler.dispatchMessage(Handler.java:99)at android.os.Looper.loop(Looper.java:223)at android.app.ActivityThread.main(ActivityThread.java:7656)at java.lang.reflect.Method.invoke(Native Method)at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
2024-01-14 11:57:54.627 12108-12108/? I/Process: Sending signal. PID: 12108 SIG: 9

解决方案

步骤1、在项目目录\app\src\main\AndroidManifest.xml中添加

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

具体操作如下图所示：

解释：数据请求设计网络访问，需要为项目配置网络权限

步骤2、对于上述代码修改，具体修改如下：

import android.os.AsyncTask;
import android.os.Bundle;
import androidx.appcompat.app.AppCompatActivity;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.List;public class HomeActivity extends AppCompatActivity {@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_home);// 此处需修改，添加如下行代码 作用：启动异步任务new GetDataAsyncTask().execute(); }// 此处需修改，添加如下类代码 作用：构造异步任务类private class GetDataAsyncTask extends AsyncTask<Void, Void, List<MyDataType>> {@Overrideprotected List<MyDataType> doInBackground(Void... voids) {try {return getData();} catch (IOException e) {e.printStackTrace();return null;}}@Overrideprotected void onPostExecute(List<MyDataType> result) {// 在UI线程中处理获取到的数据if (result != null) {// 处理数据} else {// 处理错误情况}}}private List<MyDataType> getData() throws IOException {String apiUrl = "http://api-url";URL url = new URL(apiUrl);HttpURLConnection connection = (HttpURLConnection) url.openConnection();// 设置请求方法为GETconnection.setRequestMethod("GET");// 获取响应代码int responseCode = connection.getResponseCode();if (responseCode == HttpURLConnection.HTTP_OK) {// 读取响应内容BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));StringBuilder response = new StringBuilder();String line;while ((line = reader.readLine()) != null) {response.append(line);}reader.close();// 将响应内容转换为Weather对象列表return parseResponse(response.toString());} else {// 处理错误情况System.out.println("HTTP request failed with code: " + responseCode);return null;}}// 解析响应内容，将其转换为Weather对象列表private static List<MyDataType> parseResponse(String response) {// 实现解析逻辑return null;}
}

问题原因

这个错误是由于笔者在主线程（UI线程）上进行了网络操作，而Android不允许在主线程上执行耗时的网络操作，因为这可能会导致应用界面的卡顿。

解决方案

将网络操作移到后台线程上执行即可。使用异步任务 (AsyncTask) 或者 Thread 来执行网络请求，将网络请求放在 doInBackground 方法中。

参考文献

How can I fix ‘android.os.NetworkOnMainThreadException’?

部分内容参考chatgpt

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