从 api 获取数据后，应用程序中未显示数据

Question

我正在尝试从我的应用程序中的 api 获取数据，但即使我在单独的 UI 线程中执行基于服务器的操作，它也会在下面显示响应。 为什么我的数据没有显示

以下是我在邮递员中的 json 回复：

 [
{
    "term_id": "4",
    "name": "Entertainment"
},
{
    "term_id": "5",
    "name": "Tech & Gadgets"
},
{
    "term_id": "6",
    "name": "Sports"
},
{
    "term_id": "7",
    "name": "Health and Fitness Tips"
}
]

当我的应用程序运行时，它显示以下错误：

2020-02-22 12:40:55.881 16118-16118/com.example.flypped E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.flypped, PID: 16118
android.os.NetworkOnMainThreadException
    at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1513)
    at com.android.org.conscrypt.Platform.blockGuardOnNetwork(Platform.java:415)
    at com.android.org.conscrypt.ConscryptFileDescriptorSocket$SSLInputStream.read(ConscryptFileDescriptorSocket.java:560)
    at okio.InputStreamSource.read(Okio.kt:102)
    at okio.AsyncTimeout$source$1.read(AsyncTimeout.kt:159)
    at okio.RealBufferedSource.request(RealBufferedSource.kt:62)
    at okio.RealBufferedSource.require(RealBufferedSource.kt:55)
    at okio.RealBufferedSource.readHexadecimalUnsignedLong(RealBufferedSource.kt:299)
    at okhttp3.internal.http1.Http1ExchangeCodec$ChunkedSource.readChunkSize(Http1ExchangeCodec.kt:450)
    at okhttp3.internal.http1.Http1ExchangeCodec$ChunkedSource.read(Http1ExchangeCodec.kt:429)
    at okhttp3.internal.connection.Exchange$ResponseBodySource.read(Exchange.kt:279)
    at okio.RealBufferedSource.select(RealBufferedSource.kt:93)
    at okhttp3.internal.Util.readBomAsCharset(Util.kt:256)
    at okhttp3.ResponseBody.string(ResponseBody.kt:187)
    at com.example.flypped.MainActivity$3$1.run(MainActivity.java:241)
    at android.os.Handler.handleCallback(Handler.java:873)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:214)
    at android.app.ActivityThread.main(ActivityThread.java:7156)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:494)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:975)
    Suppressed: android.os.NetworkOnMainThreadException
    at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1513)
    at com.android.org.conscrypt.Platform.blockGuardOnNetwork(Platform.java:415)
    at com.android.org.conscrypt.ConscryptFileDescriptorSocket$SSLInputStream.read(ConscryptFileDescriptorSocket.java:560)
    at okio.InputStreamSource.read(Okio.kt:102)
    at okio.AsyncTimeout$source$1.read(AsyncTimeout.kt:159)
    at okio.RealBufferedSource.request(RealBufferedSource.kt:62)
    at okio.RealBufferedSource.require(RealBufferedSource.kt:55)
    at okio.RealBufferedSource.readHexadecimalUnsignedLong(RealBufferedSource.kt:299)
    at okhttp3.internal.http1.Http1ExchangeCodec$ChunkedSource.readChunkSize(Http1ExchangeCodec.kt:450)
    at okhttp3.internal.http1.Http1ExchangeCodec$ChunkedSource.read(Http1ExchangeCodec.kt:429)
    at okhttp3.internal.Util.skipAll(Util.kt:337)
    at okhttp3.internal.Util.discard(Util.kt:358)
    at okhttp3.internal.http1.Http1ExchangeCodec$ChunkedSource.close(Http1ExchangeCodec.kt:471)
    at okio.ForwardingSource.close(ForwardingSource.kt:34)
    at okhttp3.internal.connection.Exchange$ResponseBodySource.close(Exchange.kt:306)
    at okio.RealBufferedSource.close(RealBufferedSource.kt:461)
    at kotlin.io.CloseableKt.closeFinally(Closeable.kt:56)
    at okhttp3.ResponseBody.string(ResponseBody.kt:186)
            ... 8 more

下面是我的代码：

public class Test extends AppCompatActivity {

RecyclerView recycler;
MenuAdapter adapter;
List<MenuModel> list = new ArrayList<>();
ProgressBar prog;

private static final String URL = "https://www.flypped.com/api/Categoery_api";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test);

    recycler = findViewById(R.id.recycler);
    prog = findViewById(R.id.prog);
    recycler.setHasFixedSize(true);
    recycler.setLayoutManager(new LinearLayoutManager(this));

    getData();
}

private void getData(){

    OkHttpClient client = new OkHttpClient.Builder()
            .readTimeout(20, TimeUnit.SECONDS)
            .writeTimeout(20,TimeUnit.SECONDS)
            .build();

    Request request = new Request.Builder().url(URL).build();

    client.newCall(request).enqueue(new Callback() {

        @Override
        public void onResponse(@NotNull Call call, @NotNull final Response response) throws IOException {

            runOnUiThread(new Runnable() {
                @Override
                public void run() {

                    try {

                        JSONArray jsonArray =  new JSONArray(response.body().string());

                        if(jsonArray.length() > 0){

                            prog.setVisibility(View.INVISIBLE);

                            for(int i =0;i<jsonArray.length();i++){

                                JSONObject jsonObject = jsonArray.getJSONObject(i);

                                String str1 = jsonObject.getString("name");
                                String str2 = jsonObject.getString("term_id");

                                MenuModel model = new MenuModel(str1,str2);
                                list.add(model);
                            }

                            adapter = new MenuAdapter(list,getApplicationContext());
                            recycler.setAdapter(adapter);
                        }

                    } catch (JSONException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            });

        }

        @Override
        public void onFailure(@NotNull Call call, @NotNull final IOException e) {

            runOnUiThread(new Runnable() {
                @Override
                public void run() {

                    prog.setVisibility(View.INVISIBLE);
                    Toast.makeText(getApplicationContext(),e.getMessage(),Toast.LENGTH_SHORT).show();
                }
            });
        }
    });
  }
}

为什么即使我在单独的 UI 线程中使用网络操作也会显示此错误。请让我知道我做错了什么任何帮助将不胜感激。

谢谢

Answer 1

您遇到的问题是因为您试图在主线程上执行网络操作。

如果您查看堆栈跟踪的第一行，您可以看到：

进程：com.example.flypped，PID：16118 android.os.NetworkOnMainThreadException

要解决此问题，您可以在AsyncTask 中运行您的代码。

注意：在 Android R 中已弃用

private class TestTask extends AsyncTask<YOUR PARAMETERS> {

  protected Long doInBackground(Params) {
     //Your logic
 }

 protected void onProgressUpdate(Integer... progress) {
    //Update progress
 }

 protected void onPostExecute(Long result) {

 }
}

要执行 AsyncTask，您可以编写：

new TestTask().execute(YOUR_PARAMS);