MVP设计模式的源码，有一段逻辑看不懂，求解

[gramyang]

http://p.codekk.com/detail/Android/GeekGhost/Ghost
最近在学习这个开源的App的源码，整体项目是可以正常运行的，整个项目采用的是MVP设计模式，其中App打开时的欢迎界面有一段运行逻辑实在搞不明白，特请教各位大神。

具体代码如下：

WelcomeActivity

package com.zcy.ghost.vivideo.ui.activitys;

import android.os.Bundle;

import com.zcy.ghost.vivideo.R;
import com.zcy.ghost.vivideo.base.BaseActivity;
import com.zcy.ghost.vivideo.presenter.WelcomePresenter;
import com.zcy.ghost.vivideo.ui.view.WelcomeView;

import butterknife.BindView;
import butterknife.ButterKnife;

public class WelcomeActivity extends BaseActivity {

@BindView(R.id.welcome_view)
WelcomeView welcomeView;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_welcome);
unbinder = ButterKnife.bind(this);
mPresenter = new WelcomePresenter(welcomeView);
}
}

这个是App刚打开时的欢迎界面，逻辑比较简单

WelcomePresenter

package com.zcy.ghost.vivideo.presenter;

import android.support.annotation.NonNull;

import com.zcy.ghost.vivideo.base.RxPresenter;
import com.zcy.ghost.vivideo.presenter.contract.WelcomeContract;
import com.zcy.ghost.vivideo.utils.RxUtil;
import com.zcy.ghost.vivideo.utils.StringUtils;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;

import rx.Observable;
import rx.Subscription;
import rx.functions.Action1;

/**
* Description: WelcomePresenter
* Creator: yxc
* date: 2016/9/22 13:17
*/
public class WelcomePresenter extends RxPresenter implements WelcomeContract.Presenter {
WelcomeContract.View mView;
private static final int COUNT_DOWN_TIME = 2200;

public WelcomePresenter(@NonNull WelcomeContract.View oneView) {
mView = StringUtils.checkNotNull(oneView);
mView.setPresenter(this);
getWelcomeData();
}

@Override
public void getWelcomeData() {
// Subscription rxSubscription = RetrofitHelper.getVideoApi().getHomePage()
// .compose(RxUtil.<VideoHttpResponse<VideoRes>>rxSchedulerHelper())
// .compose(RxUtil.<VideoRes>handleResult())
// .subscribe(new Action1<VideoRes>() {
// @Override
// public void call(final VideoRes res) {
// if (res != null) {
// if (mView.isActive()) {
// mView.showContent(res);
// }
// }
// startCountDown();
// }
// }, new Action1<Throwable>() {
// @Override
// public void call(Throwable throwable) {
// startCountDown();
// }
// });
// addSubscrebe(rxSubscription);
mView.showContent(getImgData());
startCountDown();
}

private void startCountDown() {
Subscription rxSubscription = Observable.timer(COUNT_DOWN_TIME, TimeUnit.MILLISECONDS)
.compose(RxUtil.<Long>rxSchedulerHelper())
.subscribe(new Action1<Long>() {
@Override
public void call(Long aLong) {
mView.jumpToMain();
}
});
addSubscrebe(rxSubscription);
}

private List<String> getImgData() {
List<String> imgs = new ArrayList<>();
imgs.add("file:///android_asset/a.jpg");
imgs.add("file:///android_asset/b.jpg");
imgs.add("file:///android_asset/c.jpg");
// imgs.add("file:///android_asset/d.jpg");
imgs.add("file:///android_asset/e.jpg");

imgs.add("file:///android_asset/f.jpg");
imgs.add("file:///android_asset/g.jpg");
return imgs;
}

}

这个是欢迎界面的presenter，注意里面的mView.showContent(getImgData())这行代码

WelcomeView

package com.zcy.ghost.vivideo.ui.view;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.ImageView;

import com.google.common.base.Preconditions;
import com.zcy.ghost.vivideo.R;
import com.zcy.ghost.vivideo.base.RootView;
import com.zcy.ghost.vivideo.component.ImageLoader;
import com.zcy.ghost.vivideo.presenter.contract.WelcomeContract;
import com.zcy.ghost.vivideo.ui.activitys.WelcomeActivity;
import com.zcy.ghost.vivideo.utils.EventUtil;
import com.zcy.ghost.vivideo.utils.JumpUtil;
import com.zcy.ghost.vivideo.utils.StringUtils;

import java.util.List;

import butterknife.BindView;
import butterknife.ButterKnife;


/**
* Description: WelcomeView
* Creator: yxc
* date: 2016/9/22 13:20
*/
public class WelcomeView extends RootView implements WelcomeContract.View {

private WelcomeContract.Presenter mPresenter;

@BindView(R.id.iv_welcome_bg)
ImageView ivWelcomeBg;

public WelcomeView(Context context) {
super(context);
init();
}


public WelcomeView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}

private void init() {
mContext = getContext();
inflate(mContext, R.layout.activity_welcome_view, this);
unbinder = ButterKnife.bind(this);
mActive = true;
}

@Override
public void setPresenter(WelcomeContract.Presenter presenter) {
mPresenter = Preconditions.checkNotNull(presenter);
}

@Override
public void showError(String msg) {
EventUtil.showToast(mContext, msg);
}

@Override
public boolean isActive() {
return mActive;
}

@Override
public void showContent(List<String> list) {
if (list != null) {
int page = StringUtils.getRandomNumber(0, list.size() - 1);
ImageLoader.load(mContext, list.get(page), ivWelcomeBg);
ivWelcomeBg.animate().scaleX(1.12f).scaleY(1.12f).setDuration(2000).setStartDelay(100).start();
}

}

@Override
public void jumpToMain() {
JumpUtil.go2MainActivity(mContext);
((WelcomeActivity) mContext).overridePendingTransition(android.R.anim.fade_in, android.R.anim.fade_out);
}
}

这个是欢迎界面的View，注意里面的showContent方法

接口的代码

WelcomeContract

package com.zcy.ghost.vivideo.presenter.contract;


import com.zcy.ghost.vivideo.base.BasePresenter;
import com.zcy.ghost.vivideo.base.BaseView;

import java.util.List;

/**
* Description: WelcomeContract
* Creator: yxc
* date: 2016/9/22 13:16
*/
public interface WelcomeContract {

interface View extends BaseView<Presenter> {

boolean isActive();

void showContent(List<String> list);

void jumpToMain();
}

interface Presenter extends BasePresenter {
void getWelcomeData();
}
}

问题如下：
presenter里面调用的mView.showContent(getImgData())，里面mView是接口的实例，接口里面的showContent方法是空方法，但是从App运行的样子来看，这里调用的方法应该是View里面的showContent方法，请问这个是怎么实现的？逻辑是什么？
在此先谢谢各位大神的关注和讲解！！

[幻影宇寰]

通过看代码逻辑应该很好理解呀，就是通过定义些接口也就是所谓的行为来告诉你我有这些功能，让具体的实例去实现。还有你所说的空方法在哪，我看代码中有实现这个接口呀

@Override
    public void showContent(List<String> list) {
        if (list != null) {
            int page = StringUtils.getRandomNumber(0, list.size() - 1);
            ImageLoader.load(mContext, list.get(page), ivWelcomeBg);
            ivWelcomeBg.animate().scaleX(1.12f).scaleY(1.12f).setDuration(2000).setStartDelay(100).start();
        }

    }

[科幻宇宙]

首先要理解MVP模式，该项目用的是MVP模式， Presenter负责业务逻辑，WelcomeActivity的逻辑就是加载图片，并显示。由 WelcomePresenter的如下方法完成 @Override public void getWelcomeData() { mView.showContent(getImgData()); startCountDown(); } 为什么要调mView.showContent()？ View负责显示内容。 你可以看到WelcomeActivity的定义 实现了 WelcomeContract.View里的接口showContent() ， public class WelcomeActivity extends BaseMvpActivity<WelcomePresenter> implements WelcomeContract.View { .... @Override public void showContent(List<String> list) { if (list != null) { int page = StringUtils.getRandomNumber(0, list.size() - 1); ImageLoader.load(mContext, list.get(page), ivWelcomeBg); ivWelcomeBg.animate().scaleX(1.12f).scaleY(1.12f).setDuration(2000).setStartDelay(100).start(); } } } 就这么简单哈

[Perfect411_111]

这个你要看下多态的概念， public WelcomePresenter(@NonNull WelcomeContract.View oneView) { mView = StringUtils.checkNotNull(oneView); mView.setPresenter(this); getWelcomeData(); } 这里是有赋值的，指向一个具体对象，而不是接口

[邹言]

mView就是WelcomeView，是通过activity里onCreate的这句mPresenter = new WelcomePresenter(welcomeView);传过去的 WelcomeView实现了WelcomeContract.View，在presenter中调用这句 mView.showContent(getImgData())就是调用了WelcomeView的showContent方法。这个做法类似接口回调