Android ViewModel+liveData+lifecycle+databinding打造MVVM

Google JetPack

最近google推出JetPack官方架构组件，最近有时间在网上看了很多类似的文章，对ViewModel和lifeCycle有了大概的了解，谷歌意在使用这些组件完成代码解耦，实现数据驱动UI的模式，但是还没有深入的了解，效率优先，还是动手才能看到这些架构组件具体是怎样的使用，来实现简单的MVVM模式。 每个组件的单独使用网上有很多文章，大家可以自行去查看，我也是拿来主义，直接上代码。

MVVM设计模式：

网络请求：

接口使用的网上一位大神测试用的接口，UI也是直接使用，本人较懒，请求使用流行的Retrofit2+rxjava2，将其封装在BaseModel中：

public class BaseModel {public BaseModel() {}public void getImage(String format, int idx, int n, BaseObserver<ImageBean> observer) {ApiRepertory.getInstance().getService().getImage(format, idx, n).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread()).subscribe(observer);} }复制代码

lifeCycle绑定页面生命周期

此处的Presenter用于将ViewModel中的业务绑定到不同的生命周期中去执行业务逻辑。

public abstract class BaseLifeCycle<P extends BasePresenter> implements ILifeCycle {protected Context mContext;protected P mPresenter;public BaseLifeCycle(Context context) {this.mContext = context;}protected void addPresenter(P mPresenter) {if (mPresenter != null) {this.mPresenter = mPresenter;}}@Overridepublic void onCreate(@Nullable LifecycleOwner owner) {}@Overridepublic void onDestroy(@Nullable LifecycleOwner owner) {}@Overridepublic void onStart(@Nullable LifecycleOwner owner) {}@Overridepublic void onResume(@Nullable LifecycleOwner owner) {}@Overridepublic void onPause(@Nullable LifecycleOwner owner) {}@Overridepublic void onStop(@Nullable LifecycleOwner owner) {}@Overridepublic void onLifecycleChanged(@Nullable LifecycleOwner owner, @Nullable Lifecycle.Event event) {} }复制代码

这里ILifeCycle接口用来继承LifecycleObserver，SupportActivity内部已经实现了LifecycleOwner接口用来获取lifeCycle，加入LifecycleObserver来添加观察者来响应不同的生命周期。

public interface ILifeCycle extends LifecycleObserver {@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)void onCreate(@Nullable LifecycleOwner owner);@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)void onDestroy(@Nullable LifecycleOwner owner);@OnLifecycleEvent(Lifecycle.Event.ON_START)void onStart(@Nullable LifecycleOwner owner);@OnLifecycleEvent(Lifecycle.Event.ON_RESUME)void onResume(@Nullable LifecycleOwner owner);@OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)void onPause(@Nullable LifecycleOwner owner);@OnLifecycleEvent(Lifecycle.Event.ON_STOP)void onStop(@Nullable LifecycleOwner owner);@OnLifecycleEvent(Lifecycle.Event.ON_ANY)void onLifecycleChanged(@Nullable LifecycleOwner owner,@Nullable Lifecycle.Event event); } 复制代码

还有此处的BasePresenter用来绑定ViewModel，实现其中的业务逻辑。

public abstract class BasePresenter<M extends ViewModel> {protected M mViewModel;public BasePresenter(M viewModel) {if (viewModel != null) {this.mViewModel = viewModel;}} } 复制代码

下面是将lifeCycle和databinding写入BaseActivity中比较简单，没有集成过多的其他组件。 getLifecycle().addObserver(mLifeCycle);将不同页面的生命周期逻辑绑定到不同页面中， mLifeCycle.addPresenter(mPresenter);将业务处理部分加入到生面周期中，用于在不同的生命周期中处理不同的业务。 startListenerData();此处用于实现ViewModel数据返回View进行响应刷新的逻辑。

public abstract class BaseActivity<L extends BaseLifeCycle, V extends ViewDataBinding, P extends BasePresenter>extends AppCompatActivity{protected Context mContext;protected L mLifeCycle;protected V dataBinding;protected P mPresenter;@Overridepublic void onCreate(@Nullable Bundle savedInstanceState) {super.onCreate(savedInstanceState);mContext = this;dataBinding = DataBindingUtil.setContentView(this, getLayoutRes());initView();getLifecycle().addObserver(mLifeCycle);mLifeCycle.addPresenter(mPresenter);startListenerData();}protected abstract void startListenerData();protected abstract void initView();protected abstract int getLayoutRes(); } 复制代码

下面看下在Activity中的具体实现： ImageViewModel中就是具体的业务逻辑的实现与数据的绑定； MainLifeCycle是该页面的生命周期，presenter在不同的生命周期实现不同的处理。

public class MainActivity extends BaseActivity<MainLifeCycle, ActivityMainBinding, ImagePresenter> {private ProgressDialog mProgressDialog;private ImageViewModel baseViewModel;@Overrideprotected void initView() {mLifeCycle = new MainLifeCycle(this);mProgressDialog = new ProgressDialog(this);mProgressDialog.setMessage("加载中");baseViewModel = ViewModelProviders.of(this).get(ImageViewModel.class);dataBinding.setClick(new ClickHandler());//将presener绑定生命周期mPresenter = new ImagePresenter(baseViewModel);mProgressDialog.show();}@Overrideprotected int getLayoutRes() {return R.layout.activity_main;}@Overrideprotected void startListenerData() {baseViewModel.getMutableLiveData().observe(this, new Observer<Data<ImageBean.ImagesBean>>() {@Overridepublic void onChanged(@Nullable Data<ImageBean.ImagesBean> imagesBeanData) {if (imagesBeanData.getErrorMsg() != null) {Toast.makeText(mContext, imagesBeanData.getErrorMsg(), Toast.LENGTH_SHORT).show();mProgressDialog.dismiss();return;}dataBinding.setImageBean(imagesBeanData.getData());setTitle(imagesBeanData.getData().getCopyright());mProgressDialog.dismiss();}});}public class MainLifeCycle extends BaseLifeCycle<ImagePresenter> {public MainLifeCycle(Context context) {super(context);}@Overridepublic void onStart(@Nullable LifecycleOwner owner) {Log.e("MainActivity", "onCreate");mPresenter.loadImage();} } 复制代码

好了，简单的mvvm模式大概就是这样，本人能力有限，有很多不足之处，如有大神请指摘，下面贴出代码的GitHub地址：github.com/ale0201/mvv…

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