什么是MVP，为什么要用MVP？
网上介绍MVP的很多，百度一下你就知道，至于为什么要用MVP，当然是由于它的优势了：
1.代码简洁
此处的简洁是逻辑的简洁，而不是代码本身 举个栗子
image
比如购物车界面，有很多请求网络的地方：获取购物车商品列表、购物车商品的删除、购物车商品的购买等等， 这么多网络请求，如果都写在一个Activity，而且还有大量逻辑判断，那这个Activity的行数~ 看着就让人头痛， 即便写了注释，维护起来也是比较麻烦的
2.降低耦合，方便维护
MVP的使用，使Activity中的网络请求剥离出来 成为model、presenter，model只负责网络的请求、pesenter负责处理请求网络后的数据处理：加载中 成功 or 失败 取消加载；最后View进行界面的展示
整体的mvp结构图
image.png
Start：介绍一下BaseMvpActivity
MVP的Activity基类：纯粹的 MVP 包装，不要增加任何View层基础功能 如果要添加基类功能，建议写一个所有activity的基类添加
public abstract class BaseMvpActivity<P extends IPresenter> extends Activity implements BaseView {
protected P mPresenter;
protected abstract P createPresenter();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mPresenter = createPresenter();
if (mPresenter == null) {
throw new NullPointerException("Presenter is null! Do you return null in createPresenter()?");
}
mPresenter.onMvpAttachView(this, savedInstanceState);
}
@Override
protected void onStart() {
super.onStart();
if (mPresenter != null) {
mPresenter.onMvpStart();
}
}
@Override
protected void onResume() {
super.onResume();
if (mPresenter != null) {
mPresenter.onMvpResume();
}
}
@Override
protected void onPause() {
super.onPause();
if (mPresenter != null) {
mPresenter.onMvpPause();
}
}
@Override
protected void onStop() {
super.onStop();
if (mPresenter != null) {
mPresenter.onMvpStop();
}
}
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
if (mPresenter != null) {
mPresenter.onMvpSaveInstanceState(outState);
}
}
@Override
protected void onDestroy() {
super.onDestroy();
if (mPresenter != null) {
mPresenter.onMvpDetachView(false);
mPresenter.onMvpDestroy();
}
}
}
在这里有人会觉得生命周期怎么会出现onMvpStart 或者onMvpResume等等
下面来解释一下MVP的生命周期：
就是为了定义P层生命周期与 V层同步
public interface IPresenter<V extends BaseView> {
void onMvpAttachView(V view, Bundle savedInstanceState);
void onMvpStart();
void onMvpResume();
void onMvpPause();
void onMvpStop();
void onMvpSaveInstanceState(Bundle savedInstanceState);
void onMvpDetachView(boolean retainInstance);
void onMvpDestroy();
}
接下来 我们会用到WeakReference类从字面上了解 他的意思是弱引用
关于 弱引用，强引用、软引用、虚引用，可以参考
https://www.cnblogs.com/gudi/p/6403953.html
public class BasePresenter<V extends BaseView> implements IPresenter<V> {
private WeakReference<V> viewRef;
protected V getView() {
return viewRef.get();
}
protected boolean isViewAttached() {
return viewRef != null && viewRef.get() != null;
}
private void attach(V view, Bundle savedInstanceState) {
viewRef = new WeakReference<V>(view);
}
@Override
public void onMvpAttachView(V view, Bundle savedInstanceState) {
attach(view, savedInstanceState);
}
@Override
public void onMvpStart() {
}
@Override
public void onMvpResume() {
}
@Override
public void onMvpPause() {
}
@Override
public void onMvpStop() {
}
@Override
public void onMvpSaveInstanceState(Bundle savedInstanceState) {
}
private void _detach(boolean retainInstance) {
if (viewRef != null) {
viewRef.clear();
viewRef = null;
}
}
@Override
public void onMvpDetachView(boolean retainInstance) {
_detach(retainInstance);
}
@Override
public void onMvpDestroy() {
}
}
接下来就是 view和model绑定处理数据
public class MainPresenterImpl extends BasePresenter<MainContract.IMainView> implements MainContract.IMainPresenter {
private LoginMobel mMobel;
public MainPresenterImpl() {
mMobel = new LoginMobel();
}
@Override
public void main(String username, String password, String token) {
//先进行非空判断
if (isViewAttached()) {
handleLogin(getView(), username, password, token);
}
}
@Override
public void login(String username, String password, String token) {
//先进行非空判断
if (isViewAttached()) {
Login(getView(), username, password, token);
}
}
private void Login(final MainContract.IMainView view, String username, String password, String token) {
mMobel.login(username, password, token, new StringCallbackAdapter() {
@Override
public void onError(Call call, Exception e, int id) {
super.onError(call, e, id);
view.loginSuccess();
}
@Override
public void onResponse(String response, int id) {
super.onResponse(response, id);
view.loginFailed(response);
}
});
}
private void handleLogin(final MainContract.IMainView view, String username, String password, String token) {
mMobel.login(username, password, token, new StringCallbackAdapter() {
@Override
public void onError(Call call, Exception e, int id) {
super.onError(call, e, id);
view.mainSuccess();
}
@Override
public void onResponse(String response, int id) {
super.onResponse(response, id);
view.mainFailed(response);
}
});
}
}
使用
public class MainActivity extends BaseMvpActivity<MainContract.IMainPresenter> implements MainContract.IMainView {
@Override
protected MainContract.IMainPresenter createPresenter() {
return new MainPresenterImpl();
}
mPresenter.main(username, password, token);
@Override
public void mainSuccess() {
Toast.makeText(this, "mainSuccess", Toast.LENGTH_SHORT).show();
}
@Override
public void mainFailed(String msg) {
Toast.makeText(this, "mainFailed", Toast.LENGTH_SHORT).show();
}
时间有限，暂时就先这样，具体可下载Demo查看 ↓
本Demo：https://gitee.com/oubajunping/androidzhimvprumen
MVP快速生成类的插件： https://github.com/githubwing/MVPHelper
