MVP架构设计-初探

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1.什么是MVP?

简单理解:就是通过Presenter将View和Model解耦

M —>Model 包括:与数据相关都属于M层(例如:数据库、文件、网络、数据解析、数据保存......)
V —>View 包括:在MVC中View只是一个单纯视图,但是在MVP中(例如:Activity、Fragment、布局)
P —>Presenter 包括:调度,通过P层将我们的View层和Model层进行关联转换

2.MVP和设计模式有什么区别?

举例说明:北京国贸三期(整体架构) --- MVP
国贸三期中 窗户设计、电梯设计、走廊设计 ...... 相当于设计模式 --- 针对具体的问题或者场景提出不同的解决方案。

3.MVP架构交互过程

4. 简单MVP登录案例


public interface MainView {
    public void onLoginResult(String result);
}
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public class MainActivity extends AppCompatActivity implements MainView {
private MainPresenter mainPresenter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        this.mainPresenter = new MainPresenter(this);
    }

    /**
     * 其实在Android当中,本身就是一个非常典型的MVC架构
     * 在Android MVC中
     * M代表:数据
     * C代表:activity或者Fragment
     * V代表:视图
     */
    //MVP适合大项目
    //MVP更加便于团队开发
    public void click(View v){
        this.mainPresenter.login("kpioneer","123456");
    }

    @Override
    public void onLoginResult(String result) {
      Toast.makeText(this,result, Toast.LENGTH_LONG).show();
    }
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/**
 * Created by Xionghu on 2017/7/11.
 * Desc: M层(数据、网络)
 */

public class MainModel {
    public void login(String username, String pwd, final HttpUtils.OnHttpResultListener onHttpResultListener){
        HttpTask httpTask = new HttpTask(new HttpUtils.OnHttpResultListener() {
            @Override
            public void onResult(String result) {
                //解析数据
                //更新UI
                onHttpResultListener.onResult(result);
            }
        });
        httpTask.execute(username,pwd,"http://www.baidu.com");
    }
}
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public class MainPresenter {

    private  MainView mainView;
    private  MainModel mainModel;

    public MainPresenter(MainView mainView) {
        this.mainView  = mainView;
        this.mainModel =  new MainModel();
    }

    public void login(String userName, String pwd){
        this.mainModel.login(userName, pwd, new HttpUtils.OnHttpResultListener() {
            @Override
            public void onResult(String result) {
                mainView.onLoginResult(result);
            }
        });
    }
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5.分析简单MVP登录案例的问题?

问题1

假设Activty意外关闭,这个时候网络请求还在进行,当数据返回的时候,发现Activity(或者Fragment) 挂掉了将会造成内存泄漏。


    解决办法:MainPresenter提供一个销毁mainView的方法

      问题2:
      项目开发当中Activity或者Fragment数量很庞大 Presenter相关类将会造成代码冗余。

      解决办法:  单独抽象出来(引出抽象类)
      抽象类设计MVP架构
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抽象 AbsMvpPresenter


public abstract class AbsMvpPresenter<V extends IMvpView> {


    private V view;

    public V getView() {
        return view;
    }


    /**
     * 绑定
     * @param view
     */
    public void attachView(V view) {
        this.view = view;
    }

    /**
     * 解决绑定
     */
    public void detachView(){
        this.view =null;
    }
}
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public interface IMvpView {
}
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public class MainPresenter extends AbsMvpPresenter<MainView> {

    private MainModel mainModel;

    public MainPresenter() {
        this.mainModel =  new MainModel();
    }

    public void login(String userName, String pwd){
        this.mainModel.login(userName, pwd, new HttpUtils.OnHttpResultListener() {
            @Override
            public void onResult(String result) {
                if(getView()!=null){
                    getView().onLoginResult(result);
                }

            }
        });
    }

}
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public abstract class MvpActivity<V extends IMvpView, P extends AbsMvpPresenter<V>> extends Activity {
    private P presenter;
    private V view;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (presenter == null) {
            this.presenter = bindPresenter();
        }
        if (view == null) {
            this.view = bindView();
            this.presenter.attachView(this.view);
        }

    }

    public P getPresenter() {
        return presenter;
    }

    public V getView() {
        return view;
    }



    public abstract P bindPresenter();

    public abstract V bindView();

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if (this.presenter != null) {
            this.presenter.detachView();
        }
    }
}
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public class MainActivity extends MvpActivity<MainView,MainPresenter> implements MainView {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    }

    @Override
    public MainPresenter bindPresenter() {
        return new MainPresenter();
    }

    @Override
    public MainView bindView() {
        return this;
    }

    /**
     * 其实在Android当中,本身就是一个非常典型的MVC架构
     * 在Android MVC中
     * M代表:数据
     * C代表:activity或者Fragment
     * V代表:视图
     */
    //MVP适合大项目
    //MVP更加便于团队开发
    public void click(View v){
        getPresenter().login("kpioneer","123456");
    }

    @Override
    public void onLoginResult(String result) {
      Toast.makeText(this,result, Toast.LENGTH_LONG).show();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
    }
} 
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6.搭建MVP架构


public class MainPresenter extends MvpBasePresenter<MainView> {
    private MainModel mainModel;

    public MainPresenter(Context context) {
        super(context);
        this.mainModel = new MainModel();
    }

    public void login(String username, String pwd) {
        this.mainModel.login(username, pwd, new HttpUtils.OnHttpResultListener() {

            @Override
            public void onResult(String result) {
                if(isAttachView()){
                    getView().onLoginResult(result);
                }

            }
        });
    }
}
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问题:每一次在Presenter中调用方法都需要处理空(isAttachView())判断
假设:50个Activity,20个Presenter,每一个Presenter里面有20个方法,做判断400次?


      解决办法 ----- 动态代理模式
      每当调用这个方法的时候,我就要去监听
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public interface MvpPresenter<V extends MvpView> {

    /**
     * 绑定视图
     * @param view
     */
    public void attachView(V view);

    public void dettachView();
}
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public class MvpBasePresenter<V extends MvpView> implements MvpPresenter<V> {


    private WeakReference<Context> weakContext;
    private WeakReference<V> weakView;
    private V proxyView;

    public MvpBasePresenter(Context context) {
        this.weakContext = new WeakReference<Context>(context);
    }

    public Context getContext() {
        return weakContext.get();
    }

    public V getView() {
        return proxyView;
    }

    /**
     * 用于检测View是否为空对象
     *
     * @return
     */
    public boolean isAttachView() {
        if (this.weakView != null && this.weakView.get() != null) {
            return true;
        }
        return false;
    }

    @Override
    public void attachView(V view) {
        this.weakView = new WeakReference<V>(view);
        MvpViewInvocationHandler invocationHandler = new MvpViewInvocationHandler(this.weakView.get());

        //在这里采用动态代理
        proxyView = (V) Proxy.newProxyInstance(view.getClass().getClassLoader(), view.getClass().getInterfaces(), invocationHandler);
    }

    @Override
    public void dettachView() {
        if (weakView.get() != null) {
            this.weakView.clear();
            this.weakView = null;
        }
    }

    private class MvpViewInvocationHandler implements InvocationHandler {
        private MvpView mvpView;

        public MvpViewInvocationHandler(MvpView mvpView) {
            this.mvpView = mvpView;
        }

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (isAttachView()) {
                return method.invoke(mvpView, args);
            }
            return null;
        }
    }
}
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关键代码


    public void attachView(V view) {
        this.weakView = new WeakReference<V>(view);
        MvpViewInvocationHandler invocationHandler = new MvpViewInvocationHandler(this.weakView.get());

        //在这里采用动态代理
        proxyView = (V) Proxy.newProxyInstance(view.getClass().getClassLoader(), view.getClass().getInterfaces(), invocationHandler);
    }

    private class MvpViewInvocationHandler implements InvocationHandler {
        private MvpView mvpView;

        public MvpViewInvocationHandler(MvpView mvpView) {
            this.mvpView = mvpView;
        }

        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (isAttachView()) {
                return method.invoke(mvpView, args);
            }
            return null;
        }
    }
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Android
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