Google在2016年推出了官方的Android MVP架构Demo,本文主要分析一下官方的MVP Demo,并且借由自己的一些经验,提出一些学习过程中,遇到的问题和自己的改进、封装措施。
MVP架构已经推出很多年了,现在已经非常普及了,我在这里就不过多介绍,简单的说,它分为以下三个层次:
在刚刚接触android的时候,或者说,现在依然有很大一部分的APP开发者,在开发过程中,总是习惯在一个Activity、Fragment中几乎完成了所有的功能。例如网络请求、数据加载、业务逻辑处理、界面加载、界面动画。 后来渐渐的我们接触到了MVC、MVP各种官方的框架,懂得了模块的分离、解耦(MVC),懂得了通过依赖于抽象去分离各个模块彻底解耦(MVP)。 但是官方的MVP框架的确已经帮我们做了很多,但是依然不够,接下来,我们基于官方给的MVP框架,结合六大基本原则,去封装更加适宜于项目的MVP框架。 整体设计模式Demo代码
官方Demo怎么去做的?
我们为了方便去分析,我这里简化代码,我们逐步分析,BaseView 和 BasePresenter,BaseView谷歌是这么写的(其实就是view的接口,展示view),以下样例为了理解,我简化处理了部分代码 BaseView.java
package com.itbird.design.principle.mvp.google; /** * Google Demo * Created by itbird on 2022/2/25 */ public interface BaseView<T> { //View中,设置presenter对象,使View可以持有Presenter对象引用 void setPresenter(T presenter); }
BasePresenter
package com.itbird.design.principle.mvp.google; /** * Google Demo * Created by itbird on 2022/2/25 */ public interface BasePresenter { }
TaskDetailContract
package com.itbird.design.principle.mvp.google; /** * Google Demo * Created by itbird on 2022/2/25 */ public interface TaskDetailContract { interface View extends BaseView<Presenter> { //界面UI刷新方法 void updateTextView(String s); } interface Presenter extends BasePresenter { void loadDataFromModel(); } }
TaskGoogleActivity
package com.itbird.design.principle.mvp.google; import android.os.Bundle; import android.util.Log; import android.widget.TextView; import androidx.appcompat.app.AppCompatActivity; import com.itbird.design.R; public class TaskGoogleActivity extends AppCompatActivity implements TaskDetailContract.View { private static final String TAG = TaskGoogleActivity.class.getSimpleName(); private TaskDetailContract.Presenter mPresenter; private TextView mTextView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); findViewById(R.id.textview); Log.e(TAG, TAG + " onCreate"); new TaskGooglePresenter(this); } @Override public void setPresenter(TaskDetailContract.Presenter presenter) { mPresenter = presenter; } @Override public void updateTextView(String s) { mTextView.setText(s); } }
TaskGooglePresenter
package com.itbird.design.principle.mvp.google; public class TaskGooglePresenter implements TaskDetailContract.Presenter { private static final String TAG = TaskGooglePresenter.class.getSimpleName(); TaskDetailContract.View mView; public TaskGooglePresenter(TaskDetailContract.View view) { mView = view; mView.setPresenter(this); } @Override public void loadDataFromModel() { //TODO :loaddata,此处可以用model、或者进行业务操作 //调用界面方法,进行数据刷新 mView.updateTextView("loaddata success!!!"); } }
小结 我们单从设计来说, Google MVP Demo的确向我们展示了MVP的优点:
但是,但是对于我们实际开发使用来说,依然有以下几点问题:
基于上面提出的三点,我们去优化Google的MVP框架。 我们首先将第一点和第二点通过抽象来解决一下。 IPresenter
package com.itbird.design.principle.mvp.v1; /** * 自定义MVP框架,BasePresenter * Created by itbird on 2022/2/25 */ public interface IPresenter { /** * 与view班定 * * @param view */ void onAttach(IView view); /** * 与view解绑 */ void onDetach(); /** * 是否与view已经班定成功 * * @return */ boolean isViewAttached(); /** * 获取view * @return */ IView getView(); }
IView
package com.itbird.design.principle.mvp.v1; /** * 自定义MVP框架,BaseView * Created by itbird on 2022/2/25 */ public interface IView { }
接下来是借助activity生命周期,对presenter的初始化进行封装 BaseActivity
package com.itbird.design.principle.mvp.v1; import android.app.Activity; import android.os.Bundle; import androidx.annotation.Nullable; /** * Created by itbird on 2022/3/29 */ public abstract class BaseActivity extends Activity implements IView { IPresenter mPresenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); mPresenter = createPresenter(); if (mPresenter != null) { mPresenter.onAttach(this); } } @Override protected void onDestroy() { super.onDestroy(); if (mPresenter != null) { mPresenter.onDetach(); mPresenter = null; } } abstract IPresenter createPresenter(); }
BasePresenter
package com.itbird.design.principle.mvp.v1; import java.lang.ref.WeakReference; /** * Created by itbird on 2022/3/29 */ public class BasePresenter<V extends IView> implements IPresenter { WeakReference<V> mIView; @Override public void onAttach(IView iView) { mIView = new WeakReference<>((V) iView); } @Override public void onDetach() { mIView = null; } @Override public V getView() { if (mIView != null) { mIView.get(); } return null; } @Override public boolean isViewAttached() { return mIView != null && mIView.get() != null; } }
看上图类图,我们依然发现有一些不满足的点:
1)activity中,依然需要初始化mPresenter
@Override IPresenter createPresenter() { mTaskPresenter = new TaskMyPresenter(); return mTaskPresenter; }
是否可以做到在activity中,自己像presenter中调用view一样,自己一句话getView就可以搞定
2)观察类图,其实IView、IPresenter没有必要存在,因为毕竟只是baseActivity、basePresenter的行为
所以改造如下: BasePresenter
package com.itbird.design.principle.mvp.v2; import java.lang.ref.WeakReference; /** * Created by itbird on 2022/3/29 */ public abstract class BasePresenter<V> { WeakReference<V> mIView; public void onAttach(V iView) { mIView = new WeakReference<>(iView); } public void onDetach() { mIView = null; } public V getView() { if (mIView != null) { mIView.get(); } return null; } public boolean isViewAttached() { return mIView != null && mIView.get() != null; } }
BaseActivity
package com.itbird.design.principle.mvp.v2; import android.app.Activity; import android.os.Bundle; import androidx.annotation.Nullable; /** * Created by itbird on 2022/3/29 */ public abstract class BaseActivity<V, T extends BasePresenter<V>> extends Activity { T mPresenter; @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); mPresenter = initPresenter(); if (mPresenter != null) { mPresenter.onAttach((V) this); } } @Override protected void onDestroy() { super.onDestroy(); if (mPresenter != null) { mPresenter.onDetach(); mPresenter = null; } } public T getPresenter() { return mPresenter; } abstract T initPresenter(); }
此时,契约类,不再需要依赖BasePresenter/BaseView相关接口,而且View中也可以自己获取到presenter的引用了。
package com.itbird.design.principle.mvp.v2; /** * my Demo * Created by itbird on 2022/2/25 */ public interface TaskMyContract { interface View { //界面UI刷新方法 void updateTextView(String s); } interface Presenter { void loadDataFromModel(); } }
package com.itbird.design.principle.mvp.v2; import android.os.Bundle; import android.util.Log; import android.widget.TextView; import com.itbird.design.R; public class TaskMyActivity extends BaseActivity<TaskMyContract.View, TaskMyPresenter> implements TaskMyContract.View { private static final String TAG = TaskMyActivity.class.getSimpleName(); TextView mTextView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mTextView = findViewById(R.id.textview); Log.e(TAG, TAG + " onCreate"); mPresenter.loadDataFromModel(); } @Override TaskMyPresenter initPresenter() { return new TaskMyPresenter(); } @Override public void updateTextView(String s) { mTextView.setText(s); } }
此时的类图,是否更加明确,而且上面各个问题都已经得到了解决。