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 {
    @Override
    protected 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GET
        connection.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: main
    Process: com.example.assistingagriculture, PID: 12108
    android.os.NetworkOnMainThreadException
        at 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：
在这里插入图片描述

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 {
    @Override
    protected 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>> {
        @Override
        protected List<MyDataType> doInBackground(Void... voids) {
            try {
                return getData();
            } catch (IOException e) {
                e.printStackTrace();
                return null;
            }
        }

        @Override
        protected 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GET
        connection.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;
    }
}