Android笔记之ViewModel的使用示例

依赖

implementation 'android.arch.lifecycle:extensions:1.1.1'
implementation 'com.squareup.retrofit2:retrofit:2.5.0'
implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
implementation 'com.squareup.retrofit2:adapter-rxjava2:2.5.0'
implementation 'io.reactivex.rxjava2:rxjava:2.2.8'
implementation 'io.reactivex.rxjava2:rxandroid:2.1.1'

android.arch.lifecycle:extensions:1.1.1用于引用ViewModelProviders

ViewModelProviders官方文档

EyeKeyService.java

package com.bu_ish.viewmodeltest.service;import com.bu_ish.viewmodeltest.reply.FaceCheckingReply;
import com.bu_ish.viewmodeltest.reply.FacesComparingReply;import io.reactivex.Single;
import retrofit2.http.Field;
import retrofit2.http.FormUrlEncoded;
import retrofit2.http.GET;
import retrofit2.http.POST;
import retrofit2.http.Query;public interface EyeKeyService {String BASE_URL = "http://api.eyekey.com/face/";String APP_ID = "f89ae61fd63d4a63842277e9144a6bd2";String APP_KEY = "af1cd33549c54b27ae24aeb041865da2";@FormUrlEncoded@POST("Check/checking")Single<FaceCheckingReply> checkFace(@Field("app_id") String appId, @Field("app_key") String appKey, @Field("url") String url);@GET("Match/match_compare")Single<FacesComparingReply> compareFaces(@Query("app_id") String appId, @Query("app_key") String appKey, @Query("face_id1") String faceId1, @Query("face_id2") String faceId2);
}

EyeKeyRepository.java

package com.bu_ish.viewmodeltest.view_model;import com.bu_ish.viewmodeltest.service.EyeKeyService;
import com.bu_ish.viewmodeltest.reply.FaceCheckingReply;
import com.bu_ish.viewmodeltest.reply.FacesComparingReply;import io.reactivex.Single;
import io.reactivex.android.schedulers.AndroidSchedulers;
import io.reactivex.schedulers.Schedulers;
import retrofit2.Retrofit;
import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory;
import retrofit2.converter.gson.GsonConverterFactory;public class EyeKeyRepository {private static EyeKeyRepository instance = new EyeKeyRepository();private EyeKeyService service;private EyeKeyRepository() {Retrofit retrofit = new Retrofit.Builder().baseUrl(EyeKeyService.BASE_URL).addConverterFactory(GsonConverterFactory.create()).addCallAdapterFactory(RxJava2CallAdapterFactory.create()).build();service = retrofit.create(EyeKeyService.class);}public static EyeKeyRepository getInstance() {return instance;}public Single<FaceCheckingReply> checkFace(String url) {return setScheduler(service.checkFace(EyeKeyService.APP_ID, EyeKeyService.APP_KEY, url));}public Single<FacesComparingReply> compareFaces(String faceId1, String faceId2) {return setScheduler(service.compareFaces(EyeKeyService.APP_ID, EyeKeyService.APP_KEY, faceId1, faceId2));}private Single setScheduler(Single single) {return single.subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());}
}

EyeKeyViewModel.java

package com.bu_ish.viewmodeltest.view_model;import android.arch.lifecycle.MutableLiveData;
import android.arch.lifecycle.ViewModel;import com.bu_ish.viewmodeltest.observer.ReplyObserver;
import com.bu_ish.viewmodeltest.reply.FaceCheckingReply;
import com.bu_ish.viewmodeltest.reply.FacesComparingReply;public class EyeKeyViewModel extends ViewModel {public MutableLiveData<FaceCheckingReply> faceCheckingReply1Data = new MutableLiveData<>();public MutableLiveData<FaceCheckingReply> faceCheckingReply2Data = new MutableLiveData<>();public MutableLiveData<FacesComparingReply> facesComparingReplyData = new MutableLiveData<>();private DialogViewModel dialogViewModel;private EyeKeyRepository eyeKeyRepository;public EyeKeyViewModel(DialogViewModel dialogViewModel) {this.dialogViewModel = dialogViewModel;eyeKeyRepository = EyeKeyRepository.getInstance();}public void checkFace1(String url) {eyeKeyRepository.checkFace(url).subscribe(new ReplyObserver<FaceCheckingReply>(dialogViewModel) {@Overridepublic void onReply(FaceCheckingReply reply) {faceCheckingReply1Data.setValue(reply);}});}public void checkFace2(String url) {eyeKeyRepository.checkFace(url).subscribe(new ReplyObserver<FaceCheckingReply>(dialogViewModel) {@Overridepublic void onReply(FaceCheckingReply reply) {faceCheckingReply2Data.setValue(reply);}});}public void compareFaces(String faceId1, String faceId2) {eyeKeyRepository.compareFaces(faceId1, faceId2).subscribe(new ReplyObserver<FacesComparingReply>(dialogViewModel) {@Overridepublic void onReply(FacesComparingReply reply) {facesComparingReplyData.setValue(reply);}});}
}

ReplyObserver.java

package com.bu_ish.viewmodeltest.observer;import com.bu_ish.viewmodeltest.reply.BaseReply;
import com.bu_ish.viewmodeltest.view_model.DialogViewModel;import io.reactivex.SingleObserver;
import io.reactivex.disposables.Disposable;public abstract class ReplyObserver<T extends BaseReply> implements SingleObserver<T> {public abstract void onReply(T reply);private DialogViewModel dialogViewModel;public ReplyObserver(DialogViewModel dialogViewModel) {this.dialogViewModel = dialogViewModel;}@Overridepublic void onSubscribe(Disposable d) {dialogViewModel.showProgressData.setValue(true);}@Overridepublic void onSuccess(T reply) {dialogViewModel.showProgressData.setValue(false);String code = reply.getResCode();if (code.equals("0000")) {onReply(reply);} else {dialogViewModel.showErrorData.setValue(reply);}}@Overridepublic void onError(Throwable e) {dialogViewModel.showProgressData.setValue(false);dialogViewModel.showExceptionData.setValue(e);}
}

EyeKeyViewModelFactory.java

package com.bu_ish.viewmodeltest.view_model;import android.arch.lifecycle.ViewModel;
import android.arch.lifecycle.ViewModelProvider;
import android.support.annotation.NonNull;public class EyeKeyViewModelFactory implements ViewModelProvider.Factory {private DialogViewModel dialogViewModel;public EyeKeyViewModelFactory(DialogViewModel dialogViewModel) {this.dialogViewModel = dialogViewModel;}@NonNull@Overridepublic <T extends ViewModel> T create(@NonNull Class<T> modelClass) {return (T) new EyeKeyViewModel(dialogViewModel);}
}

DialogViewModel.java

package com.bu_ish.viewmodeltest.view_model;import android.arch.lifecycle.MutableLiveData;
import android.arch.lifecycle.ViewModel;import com.bu_ish.viewmodeltest.reply.BaseReply;public class DialogViewModel extends ViewModel {public MutableLiveData<Boolean> showProgressData = new MutableLiveData<>();public MutableLiveData<BaseReply> showErrorData = new MutableLiveData<>();public MutableLiveData<Throwable> showExceptionData = new MutableLiveData<>();
}

使用ViewModel的好处

即使发生配置变更（Configuration Change），ViewModel中的数据依然存在

所以，使用ViewModel后，也就不需要考虑onSaveInstanceState这类操作了^_^

参考博文

MVVM 架构,ViewModel和LiveData(一)

完整Demo

链接：https://pan.baidu.com/s/1TwY9OZTaQPk1eCn7vSz4fA，提取码：x0fy