Android 中的 Retrofit GET 请求出错

Question

我正在开发 Android 应用程序。在我的应用程序中，我正在使用 Retrofit 网络库连接服务器。这是我第一次使用改造。在我使用 Volley 之前。所以在我在实际项目中使用改造之前，我正在测试它向服务器发出一个简单的获取请求。

我在 Gradle

中安装了改造

compile 'com.squareup.retrofit2:retrofit:2.1.0'
compile 'com.squareup.retrofit2:converter-gson:2.1.0'

我为改造请求创建了一个接口

public interface RetrofitService {
    @GET("test")
    Call<ChildCategoryItem> repoContributors();

    public static final Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(LinkConfig.API_END_POINT)
            .addConverterFactory(GsonConverterFactory.create())
            .build();
}

我在 activity 中提出了这样的请求

 private void makeRetrofitRequest()
    {
        try{
            RetrofitService service = RetrofitService.retrofit.create(RetrofitService.class);
            Call<ChildCategoryItem> call = service.repoContributors();
            String result = call.execute().body().toString();
            Toast.makeText(getBaseContext(),result,Toast.LENGTH_SHORT).show();
        }
        catch (IOException e)
        {
            Toast.makeText(getBaseContext(),"Exception",Toast.LENGTH_SHORT).show();
        }
    }

服务器正在返回此 json 数据

{"id":1,"name":"name","mm_name":"mm_name"}

这是我的 ChildCategoryItem class

public class ChildCategoryItem {
    private int Id;
    private String Name;
    private String MmName;
    private int ParentId;

    public void setId(int id)
    {
        this.Id = id;
    }
    public int getId()
    {
        return this.Id;
    }
    public void setName(String name)
    {
        this.Name = name;
    }
    public String getName()
    {
        return this.Name;
    }
    public void setMmName(String mmName)
    {
        this.MmName = mmName;
    }
    public String getMmName()
    {
        return this.MmName;
    }
    public void setParentId(int id)
    {
        this.ParentId = id;
    }
    public int getParentId()
    {
        return this.ParentId;
    }


    public static ChildCategoryItem fromJson(JSONObject json)
    {
        try{
            ChildCategoryItem item = new ChildCategoryItem();
            item.setId(json.getInt("id"));
            item.setName(json.getString("name"));
            item.setMmName(json.getString("mm_name"));
            return item;
        }
        catch (JSONException e)
        {
            return null;
        }
    }
}

当我运行时，它给我这个错误

08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime: FATAL EXCEPTION: main
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{mmbookhub.com.mmbookhub/mmbookhub.com.mmbookhub.ContributeActivity}: android.os.NetworkOnMainThreadException
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread.access0(ActivityThread.java:141)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5103)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:525)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:  Caused by: android.os.NetworkOnMainThreadException
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1133)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at libcore.io.IoBridge.connectErrno(IoBridge.java:144)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at libcore.io.IoBridge.connect(IoBridge.java:112)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at java.net.Socket.connect(Socket.java:842)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.AndroidPlatform.connectSocket(AndroidPlatform.java:55)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.io.RealConnection.connectSocket(RealConnection.java:185)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.io.RealConnection.buildConnection(RealConnection.java:170)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.io.RealConnection.connect(RealConnection.java:111)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.http.StreamAllocation.findConnection(StreamAllocation.java:187)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:123)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.http.StreamAllocation.newStream(StreamAllocation.java:93)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.http.HttpEngine.connect(HttpEngine.java:296)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.internal.http.HttpEngine.sendRequest(HttpEngine.java:248)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.RealCall.getResponse(RealCall.java:243)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.RealCall$ApplicationInterceptorChain.proceed(RealCall.java:201)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.RealCall.getResponseWithInterceptorChain(RealCall.java:163)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at okhttp3.RealCall.execute(RealCall.java:57)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at retrofit2.OkHttpCall.execute(OkHttpCall.java:174)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at retrofit2.ExecutorCallAdapterFactory$ExecutorCallbackCall.execute(ExecutorCallAdapterFactory.java:89)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at mmbookhub.com.mmbookhub.ContributeActivity.makeRetrofitRequest(ContributeActivity.java:505)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at mmbookhub.com.mmbookhub.ContributeActivity.onCreate(ContributeActivity.java:84)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.Activity.performCreate(Activity.java:5133)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread.access0(ActivityThread.java:141) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:99) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5103) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:525) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
08-20 05:24:41.195 1341-1341/mmbookhub.com.mmbookhub E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method) 
08-20 05:24:41.231 398-410/system_process W/ActivityManager:   Force finishing activity mmbookhub.com.mmbookhub/.ContributeActivity
08-20 05:24:41.231 398-410/system_process W/ActivityManager:   Force finishing activity mmbookhub.com.mmbookhub/.MainActivity

我的代码有什么问题？我这样请求对吗？

Answer 1

由于 android 在主线程上不支持网络而发生错误，您可以通过将网络调用置于新线程中来解决此问题

或根据您的情况使用以下方法

 call.enqueue(new Callback<ChildCategoryItem>() {
        @Override
        public void onResponse(Call<ChildCategoryItem> call, Response<ChildCategoryItem> response) {

        }

        @Override
        public void onFailure(Call<ChildCategoryItem> call, Throwable t) {
             t.printStackTrace();
        }
    });

Answer 2

您有 2 个选择：

将您的 api 调用放在单独的 Thread

中

String result = call.execute().body().toString(); //put this inside seperate Thread

使用 Retrofit 的 enqueue()。

call.enqueue(new Callback<ChildCategoryItem>() {
    @Override
    public void onResponse(Call<ChildCategoryItem> call, Response<ChildCategoryItem> response) {
           //Here you will get your response.
    }

    @Override
    public void onFailure(Call<ChildCategoryItem> call, Throwable t) {
         t.printStackTrace();
    }
});

您必须检查 this 以获得 NetworkOnMainThreadException

Answer 3

代替 call.execute() 使用 call.enqueue() 发出异步请求。（ui 线程除外）。 execute() 是在同一线程上执行的同步调用，即 ui thread.

Answer 4

正如 Viktor Yakunin 所指出的，您应该完成以下 link 因为主要问题是使网络调用没有 UI 线程。

How to fix android.os.NetworkOnMainThreadException?

根据改造文档

Call instances can be executed either synchronously or asynchronously. Each instance can only be used once, but calling clone() will create a new instance that can be used.

在Android，回调将在主线程上执行。在 JVM 上，回调将发生在执行 HTTP 请求的同一线程上。

对于同步调用，我们使用

call.execute

对于异步调用，我们使用

call.enqueue

我没有使用过 volley，但如果你是从改造开始，我建议你通过这个：

Consuming APIs with Retrofit

对于您的程序，这是最简单的方法：

ChildCategoryItem.java

public class ChildCategoryItem
{
@SerializedName("id")
@Expose
private String id;
@SerializedName("name")
@Expose
private String name;
@SerializedName("mm_name")
@Expose
private String mmName;

/**
 * @return The id
 **/
public String getId()
{
    return id;
}

/**
 * @param id The id
 **/
public void setId(String id)
{
    this.id = id;
}

 /**
 * @return The name
 **/
public String getName()
{
    return name;
}

/**
 * @param name The name
 **/
public void setName(String name)
{
    this.name = name;
}

/**
 * @return The mmName
 **/
public String getMmName()
{
    return mmName;
}

/**
 * @param mmName The mm_name
**/
public void setMmName(String mmName)
{
    this.mmName = mmName;
}
}

MainActivity.java

public class MainActivity extends AppCompatActivity
{

    String result;
    doRetrofit DD;
    Call<ChildCategoryItem> call;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        DD= new doRetrofit();
        DD.execute();
    }

    public class doRetrofit extends AsyncTask
    {
        @Override
        protected Object doInBackground(Object[] objects)
        {
            String baseurl="http://192.168.1.12";
            Retrofit adapter= new Retrofit.Builder().baseUrl(baseurl).addConverterFactory(GsonConverterFactory.create()).build();
            RetrofitService retrofitService=adapter.create(RetrofitService.class);
            Call<ChildCategoryItem> call=retrofitService.repoContributors();
            Response<ChildCategoryItem> c= null;
            try
            {
                c = call.execute();
            } catch (IOException e)
            {
                e.printStackTrace();
            }
            Log.d("<<<<<<<<<Response>>>>>>",c.body().toString());
            ChildCategoryItem child=c.body();
            Log.d("<<<<<<<<<Response>>>>>>",child.getId());
            Log.d("<<<<<<<<<Response>>>>>>",child.getName());
            Log.d("<<<<<<<<<Response>>>>>>",child.getMmName());

            return null;
        }
    }
}

RetrofitService.java

public interface RetrofitService
{
    @GET("/loltry.php")
    Call<ChildCategoryItem> repoContributors();
}

出于好奇，您在哪里以及如何使用 fromJson 方法？

希望这对您有所帮助:)

由于缺乏声誉我无法发表评论，仅供参考：不要在工作线程中使用 toast（即在 Asynctask doInBackground 中）toast 应始终与 UI 线程一起使用。看到这个：

Can't create handler inside thread that has not called Looper.prepare()

Android 中的 Retrofit GET 请求出错

Error in Retrofit GET request in Android

android

retrofit

retrofit2