极简的MVP设计模式配合UI框架

MVP可以实现视图和数据的解耦

image

如图所示 MVP使M与V分离 实现了解耦

定义BaseView 所有视图的通用接口(activity fragment)

public interface BaseView {

    /**
     * 初始化数据
     */
    void loadData();

    /**
     * 更新View的状态
     * @param state
     */
    void updateState(int state);
}

updateState整个方法是由我们来根据网络返回的数据或者来判断整个View的状态,定义了三个状态值,由此来展示loading页面 或者 error的页面

    //加载状态
    public static final int STATUS_LOADING = 100;
    //成功状态
    public static final int STATUS_SUCCESS = 101;
    //失败状态
    public static final int STATUS_ERROR = 102;

接着去定义通用的接口BaseViewImpl

public interface BaseViewImpl<D> extends BaseView{
    
    void attachPre();

    void showData(List<D> list);
}

attachPre 由View来关联相应的Presenter 可以在定义的BaseActivity里调用绑定Presenter

BasePresenter

public interface BasePresenter<V> {
    /**
     * 绑定View
     * @param view
     */
    void attachView(V view);

    /**
     * 解绑View
     */
    void detachView();
}

BasePresenter的实现类 基类

public abstract class BasePresenterImpl<V extends BaseView> implements BasePresenter<V>{

    public Context mContext;
    
    public V mBaseView;

    private CompositeSubscription mCompositeSubscription;

    public BasePresenterImpl(Context context){
        mContext = context;
    }

    @Override
    public void attachView(V view) {
        mBaseView = view;
    }

    @Override
    public void detachView() {
        this.mBaseView = null;
        onUnsubscribe(); //解绑
    }

    /**
     * 加载数据
     */
    public abstract void loadData();

    //RXjava取消注册，以避免内存泄露
    public void onUnsubscribe() {
        if (mCompositeSubscription != null && mCompositeSubscription.hasSubscriptions()) {
            mCompositeSubscription.unsubscribe();
        }
    }

    public void addSubscription(Observable observable, Subscriber subscriber) {
        if (mCompositeSubscription == null) {
            mCompositeSubscription = new CompositeSubscription();
        }
        mCompositeSubscription.add(subscriber);
    }
}

在BasePresenterImpl里绑定View ,由此子类可以根据View来更新状态

MVP就是基类的实现就是这么简单,现在来创建activity来试试手, 首先创建一个BaseActivity,抽取一些公共的代码

public abstract class BaseActivity<T extends BasePresenter,D> extends AppCompatActivity implements BaseViewImpl<D>{
    
    public T mPresenter;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        /**
         * 绑定Presenter
         */
        attachPre();
        View view = initView(LayoutInflater.from(this));
        setContentView(view);
        ButterKnife.bind(this);
        findView(view);
        loadData();
    }

    protected abstract View initView(LayoutInflater from);

    public abstract void findView(View view);

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(mPresenter != null)
            mPresenter.detachView();
        ButterKnife.unbind(this);
    }

    /**
     * error的统一处理
     * @param error
     */
    public void error(Throwable error){
        if(error instanceof NetworkErrorException){
            Toast.makeText(this,"网络错误", Toast.LENGTH_SHORT).show();
        }
    }

}

创建HomeActivity去访问网络以及加载数据

public class HomeActivity extends BaseActivity<HomePresenter, NewsList.NewsEntity> {

    @Bind(R.id.recy)
    RecyclerView mRecy;
    private NewsListAdapter mNewsListAdapter;
    private LoadStuatus mLoadStuatus;

    @Override
    public View initView(LayoutInflater inflater) {
        /**
         * UI框架
         */
        mLoadStuatus = new LoadStuatus(this);
        /**
         * 实现成功页面的View
         */
        mLoadStuatus.addSuccessView(inflater.inflate(R.layout.activity_home, null));
        /**
         * 绑定BaseView来实现页面点击加载
         */
        mLoadStuatus.bindView(this);
        return mLoadStuatus;
    }

    @Override
    public void findView(View view) {
        mRecy.setLayoutManager(new LinearLayoutManager(this));
        mNewsListAdapter = new NewsListAdapter(this);
        mRecy.setAdapter(mNewsListAdapter);
    }

    @Override
    public void attachPre() {
        mPresenter = new HomePresenter(this);
        mPresenter.attachView(this);
    }

    @Override
    public void showData(List<NewsList.NewsEntity> list) {
        mNewsListAdapter.flush(list);
    }

    @Override
    public void loadData() {
        mPresenter.loadData();
    }

    /**
     * 更新页面
     */
    @Override
    public void updateState(int state) {
        mLoadStuatus.updateView(state);
    }
}

这里的loadStuatus是一个帧布局用来存放我们的三个页面

errorPage,LoadPage,SuccessPage都是根据P层的回调来实现

在来看一下P层的实现

public class HomePresenter extends BasePresenterImpl<HomeActivity>{

    public HomePresenter(Context context) {
        super(context);
    }

    @Override
    public void loadData() {
        Subscription subscribe = RetrofitUtils.getinstance(mContext).buildNews().getNews()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(bean -> mBaseView.showData(bean.getNews()), //onNext() 去更新页面
                        error -> {
                            mBaseView.error(error); // 请求网络失败 在BaseActivity定义了公共的处理方法
                            mBaseView.updateState(LoadStuatus.STATUS_ERROR); //更新页面 显示失败的页面
                        },
                        () -> mBaseView.updateState(LoadStuatus.STATUS_SUCCESS));// onComplete 完成页面更新,显示成功的页面
        addSubscription(subscribe);
    }
}

P层很简单 就是访问网络 当请求

接下来看一下我们的UI框架 定义了统一处理页面状态的状态码以及如何去正确的显示页面

public class LoadStuatus extends FrameLayout {
    private static final String TAG = "TAG";
    BaseView nView;
    @Bind(R.id.error)
    View mErrorView;
    @Bind(R.id.loading)
    View mLoadingView;

    View successView;
    //加载状态
    public static final int STATUS_LOADING = 100;
    //成功状态
    public static final int STATUS_SUCCESS = 101;
    //失败状态
    public static final int STATUS_ERROR = 102;

    public LoadStuatus(Context context) {
        this(context, null);
    }

    public LoadStuatus(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public LoadStuatus(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    public void addSuccessView(View view){
        successView = view;
        addView(successView);
        successView.setVisibility(GONE);
    }
    public void bindView(BaseView view) {
        this.nView = view;
        mErrorView.setOnClickListener(v -> {
            if(nView == null)
                throw new NoBindViewException("没有绑定View");
            nView.loadData();
        });
    }

    public void init() {
        View.inflate(getContext(), R.layout.status, this);
        ButterKnife.bind(this);
    }

    public void updateView(int currentStatus) {
        switch (currentStatus) {
            case STATUS_ERROR:
                successView.setVisibility(GONE);
                mErrorView.setVisibility(VISIBLE);
                mLoadingView.setVisibility(GONE);
                break;
            case STATUS_LOADING:
                successView.setVisibility(GONE);
                mErrorView.setVisibility(GONE);
                mLoadingView.setVisibility(VISIBLE);
                break;
            case STATUS_SUCCESS:
                successView.setVisibility(VISIBLE);
                mErrorView.setVisibility(GONE);
                mLoadingView.setVisibility(GONE);
                break;
        }
    }

    public class NoBindViewException extends RuntimeException{
        public NoBindViewException(String info){
            super(info);
        }
    }
}

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