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android-如何使用viewmodel在oncreate中处理http调用,而oncreate不会在屏幕上被调用旋转?

android

Feroz Siddiqui · 技术社区 · 6 年前

是的。在创建一个活动时加载数据的基本场景。因此,我试图加载数据,一旦我打开我的活动,但当我改变屏幕方向,它会再次调用。

下面是我改造的rest客户

public class MyRestApiClient {
    private static Retrofit retrofit = null;

    public static Retrofit getClient() {

        HttpLoggingInterceptor interceptor = new HttpLoggingInterceptor();
        interceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
        OkHttpClient client = new OkHttpClient.Builder().addInterceptor(interceptor).connectTimeout(30,TimeUnit.SECONDS).readTimeout(30,TimeUnit.SECONDS).build();
        Gson gson = new GsonBuilder().setDateFormat("yyyy-MM-dd HH:mm:ss").create();

        retrofit = new Retrofit.Builder()
                .baseUrl("http://localhost:8080/rest/")
                .addConverterFactory(GsonConverterFactory.create(gson))
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .client(client)

                .build();



        return retrofit;
    }
}

下面是用于加载数据的resturl接口

   public interface MyRestUrlInterface {
    @GET("user/{user_id}")
        Call<Object> getData(@Path("user_id") String user_id);
    }

下面是我的ViewModel类:

public class MyViewModelObserver  extends ViewModel {

    private MutableLiveData<Object> httpCallBackObserver;

    public MutableLiveData<Object> getHttpCallBackObserver() {
        if (httpCallBackObserver == null) {
            httpCallBackObserver = new MutableLiveData<Object>();
        }
        return httpCallBackObserver;
    }
}

以下是我的活动代码:

public class MyActivity extends AppCompatActivity {
 private static final String TAG = "MyActivity" ;

 MyRestUrlInterface restUrlInterface;
 public MyViewModelObserver myViewModelObserver;

@Override   
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        restUrlInterface = MyRestApiClient.getClient().create(MyRestUrlInterface.class);
        myViewModelObserver = ViewModelProviders.of(this).get(MyViewModelObserver.class);
        myViewModelObserver.getHttpCallBackObserver().observe(this, getData());
        //load data via http
        Call<Object> call = restUrlInterface.getData("123");
        call.enqueue(new Callback<Object>() {
            @Override
            public void onResponse(Call<Object> call, Response<Object> response) {
             myViewModelObserver.getHttpCallBackObserver().setValue(response.body());
            }

            @Override
            public void onFailure(Call<Object> call, Throwable t) {

            }
        });

        }


private Observer<Object> getData(){
        return new Observer<Object>() {
            @Override
            public void onChanged(@Nullable final Object responseString) {
                Log.d(TAG,"***** Loaded Data --- "+responseString);

            }
        };
    }
}

如何使用视图模型,使其在屏幕方向更改时不再进行http调用

建议答案:

public class MyViewModelObserver  extends ViewModel {

    private MutableLiveData<Object> httpCallBackObserver;

    public MutableLiveData<Object> getHttpCallBackObserver() {
        if (httpCallBackObserver == null) {
            httpCallBackObserver = new MutableLiveData<Object>();
            loadData();

        }
        return httpCallBackObserver;
    }
    private void loadData(){
    Call<Object> call = restUrlInterface.getData("123");
            call.enqueue(new Callback<Object>() {
                @Override
                public void onResponse(Call<Object> call, Response<Object> response) {
                 myViewModelObserver.getHttpCallBackObserver().setValue(response.body());
                }

                @Override
                public void onFailure(Call<Object> call, Throwable t) {

                }
            });
    }
}

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