Android ViewModel+liveData+lifecycle+databinding打造MVVM

Google JetPack

最近google推出JetPack官方架構組件，最近有時間在網上看了不少相似的文章，對ViewModel和lifeCycle有了大概的瞭解，谷歌意在使用這些組件完成代碼解耦，實現數據驅動UI的模式，可是尚未深刻的瞭解，效率優先，仍是動手才能看到這些架構組件具體是怎樣的使用，來實現簡單的MVVM模式。 每一個組件的單獨使用網上有不少文章，你們能夠自行去查看，我也是拿來主義，直接上代碼。

MVVM設計模式：

網絡請求：

接口使用的網上一位大神測試用的接口，UI也是直接使用，本人較懶，請求使用流行的Retrofit2+rxjava2，將其封裝在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);
    }
}

複製代碼

lifeCycle綁定頁面生命週期

此處的Presenter用於將ViewModel中的業務綁定到不一樣的生命週期中去執行業務邏輯。

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;
        }
    }

    @Override
    public void onCreate(@Nullable LifecycleOwner owner) {

    }

    @Override
    public void onDestroy(@Nullable LifecycleOwner owner) {

    }

    @Override
    public void onStart(@Nullable LifecycleOwner owner) {

    }

    @Override
    public void onResume(@Nullable LifecycleOwner owner) {

    }

    @Override
    public void onPause(@Nullable LifecycleOwner owner) {

    }

    @Override
    public void onStop(@Nullable LifecycleOwner owner) {

    }

    @Override
    public void onLifecycleChanged(@Nullable LifecycleOwner owner, @Nullable Lifecycle.Event event) {

    }
}

複製代碼

這裏ILifeCycle接口用來繼承LifecycleObserver，SupportActivity內部已經實現了LifecycleOwner接口用來獲取lifeCycle，加入LifecycleObserver來添加觀察者來響應不一樣的生命週期。

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);
}
複製代碼

還有此處的BasePresenter用來綁定ViewModel，實現其中的業務邏輯。

public abstract class BasePresenter<M extends ViewModel> {
    protected M mViewModel;

    public BasePresenter(M viewModel) {
        if (viewModel != null) {
            this.mViewModel = viewModel;
        }
    }
}
複製代碼

下面是將lifeCycle和databinding寫入BaseActivity中比較簡單，沒有集成過多的其餘組件。 getLifecycle().addObserver(mLifeCycle);將不一樣頁面的生命週期邏輯綁定到不一樣頁面中， mLifeCycle.addPresenter(mPresenter);將業務處理部分加入到生面週期中，用於在不一樣的生命週期中處理不一樣的業務。 startListenerData();此處用於實現ViewModel數據返回View進行響應刷新的邏輯。

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;

    @Override
    public 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();
}
複製代碼

下面看下在Activity中的具體實現： ImageViewModel中就是具體的業務邏輯的實現與數據的綁定； MainLifeCycle是該頁面的生命週期，presenter在不一樣的生命週期實現不一樣的處理。

public class MainActivity extends BaseActivity<MainLifeCycle, ActivityMainBinding, ImagePresenter> {
    private ProgressDialog mProgressDialog;
    private ImageViewModel baseViewModel;

    @Override
    protected void initView() {
        mLifeCycle = new MainLifeCycle(this);
        mProgressDialog = new ProgressDialog(this);
        mProgressDialog.setMessage("加載中");
        baseViewModel = ViewModelProviders.of(this).get(ImageViewModel.class);
        dataBinding.setClick(new ClickHandler());
        //將presener綁定生命週期
        mPresenter = new ImagePresenter(baseViewModel);
        mProgressDialog.show();
    }

    @Override
    protected int getLayoutRes() {
        return R.layout.activity_main;
    }

    @Override
    protected void startListenerData() {
        baseViewModel.getMutableLiveData().observe(this, new Observer<Data<ImageBean.ImagesBean>>() {
            @Override
            public 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);
    }

    @Override
    public void onStart(@Nullable LifecycleOwner owner) {
        Log.e("MainActivity", "onCreate");
        mPresenter.loadImage();
    }
}
複製代碼

好了，簡單的mvvm模式大概就是這樣，本人能力有限，有不少不足之處，若有大神請指摘，下面貼出代碼的GitHub地址：github.com/ale0201/mvv…