XYLibrary笔记六：再理MVP框架

项勇

发布于 2023-03-24 13:22:48

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此文是借鉴于XTLib中的mvp模式上做的讲解,以加强对框架的理解

1.主要代码介绍

抽象MActivity代码

MActivity.class

public abstract class MActivity<P extends BasePresenter> extends Activity {
    public P mPresenter;
    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        initView();
    }
    @Override
    protected void onStart(){
        super.onStart();
    }
    protected void initView(){
        if (mPresenter == null) {
            mPresenter = getPresenter();//获取 mPresenter
            if (this instanceof BaseView){
                mPresenter.add((BaseView) this);//将 view 传递到 mPresenter 中
            }
        }
    }
    /**
     * 获取 Presenter,P 为泛型,返回相对应的Presenter,(RadioPresenter/BTPresenter/MusicPresenter/VideoPresenter/)
     * @return
     */
    public abstract P getPresenter();
    @Override
    protected void onResume() {
       super.onResume();
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
      if(mPresenter != null){
         mPresenter.delete();//将 mPresenter 中的 view 删除，防止内存泄漏
         mPresenter=null;
      }
    }

BaseActivity继承MActivity

BaseActivity.class

public abstract class BaseActivity extends MActivity<Presenter> implements View {
    ...
}

应用的MainActivity继承BaseActivity

MainActivity.class

public class MainActivity extends BaseActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        XService.startService(TestService.class);
        XService.bindService(TestService.class,mConnection, Service.BIND_AUTO_CREATE);
        XLog.i("Acticity持有的P: "+mPresenter);
        mPresenter.onCreate();
    }
    @Override
    public Presenter getPresenter() {
        return new Presenter(this);
    }
    ...
}

抽象MService

MService.class
public abstract class MService< P extends BasePresenter> extends Service {
   private static final String TAG = "XService";
   public P mPresenter;
   protected void initView(){
      if (mPresenter == null) {
         mPresenter = getPresenter();//获取 mPresenter
         if (this instanceof BaseView){
            mPresenter.add((BaseView) this);//将 view 传递到 mPresenter 中
         }
      }
   }
   @Override
   public IBinder onBind(Intent intent) {
      return null;
   }
   @Override
   public void onCreate() {
      super.onCreate();
      initView();
   }
   @Override
   public int onStartCommand(Intent intent, int flags, int startId) {
      return super.onStartCommand(intent, flags, startId);
   }
   /**
    * 获取 Presenter,P 为泛型,返回相对应的Presenter,(RadioPresenter/BTPresenter/MusicPresenter/VideoPresenter/)
    * @return
    */
   public abstract P getPresenter();
   @Override
   public void onDestroy() {
      super.onDestroy();
      mPresenter.delete();//将 mPresenter 中的 view 删除，防止内存泄漏
      mPresenter=null;
   }
}

BaseService继承自MService

BaseService.class

public abstract class BaseService extends MService<Presenter> implements View {
    ...
}

应用的TestService继承BaseService

TestService.class

public class TestService extends BaseService {
    @Override
    public void onCreate() {
        super.onCreate();
        mPresenter.onCreate();
        XLog.i("Service持有的P: "+mPresenter);
        XLog.i(mPresenter);
    }
    @Override
    public Presenter getPresenter() {
        return new Presenter(this);
    }
    ...
}

BasePresenter.class

public abstract class BasePresenter<V extends BaseView, M extends BaseModel> {
    public Context mContext;
    private WeakReference<V> mWeakReference;
    public M mModel;
    public Handler mHandler = new Handler();
    public BasePresenter(Context context) {
        this.mContext=context;
        mModel = getModel();
    }
    /**
     * 获取 model，实现该抽象类的子类必须实现此方法，之后就可以使用 mModel操作Model层业务逻辑
     * @return
     */
    public abstract M getModel();
    /**
     * 将 view 添加到弱引用中
     * @param view
     */
    public void add(V view) {
        mWeakReference = new WeakReference<V>(view);
    }
    /**
     * 获取弱引用中的 view
     * @return
     */
    public V get() {
        return mWeakReference == null ? null : mWeakReference.get();
    }
    /**
     * 删除弱引用中的 view
     */
    public void delete() {
        if (mWeakReference != null) {
            mWeakReference.clear();
            mWeakReference = null;
        }
    }
    public void onDestroy(){
    }
}

Presenter则继承BasePresenter

Presenter.class

public class Presenter extends BasePresenter<View, Model> implements View{
    ...
}

2.启动流程：

2.1MainActivity启动

初始化时会创建并持有一个Presenter

Presenter.class

...   
 protected void initView(){
        if (mPresenter == null) {
            mPresenter = getPresenter();//获取 mPresenter
            if (this instanceof BaseView){
                mPresenter.add((BaseView) this);//将 view 传递到 mPresenter 中
            }
        }
    }
...

resenter构建方法中持有单例model

Presenter.class

...
@Override
public Model getModel() {
    return Model.getInstant();
}
...

着调用Presenter的onCreate会将View传入Model

Presenter.class

...
public void onCreate(){
    mModel.onCreate();
    addView();
}
public void addView(){
    mModel.setViews(this);
}
...

添加到Model的Views集合

Model.class

private static ArrayList<View> mViews=new ArrayList<View>();
...
public void setViews(View mPV){
    XLog.i("Model中增加P"+mPV);
    mViews.add(mPV);
}
...

打印如下

45.831  I/MainActivity.java: [ (MainActivity.java:23)#onCreate ] Acticity持有的P_id: @26f08e
45.832  I/Model.java: [ (Model.java:27)#onCreate ] execute
45.847  I/Model.java: [ (Model.java:36)#onResume ] execute
45.849  I/Model.java: [ (Model.java:15)#setViews ] Model中增加P@26f08e

此时单例Model和Activity的Presenter就创建起来，Model中的生产出的值就会通过接口传出到Activity中

然后Activity启动并绑定Service

2.2 Service启动

同理过程中也会创建一个Service的Presenter，接着Presenter也会把View添加到单例model的Views中

45.900  I/TestService.java: [ (TestService.java:21)#onCreate ] Service持有的P_id: @1a5879a
45.901  I/TestService.java: [ (TestService.java:22)#onCreate ] @1a5879a
45.903  I/Model.java: [ (Model.java:15)#setViews ] Model中增加P@1a5879a

时MVP框架的应用就创建完成，此时存活着一个Activity和对应的Presenter，一个Service和对应的Presenter，一个Model

3.运行

Model中生产的值通过遍历View分别传出

我简单创建了一个Handler，每秒+1，并值传出来

Model.class

...
private mHandler handler;
private int i = 0;
private class mHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        handler.removeMessages(0x01);
        handler.sendEmptyMessageDelayed(0x01,1000);
        ++i;
        for (View mView : mViews) {
            XLog.i(mView+" 发送传出处理的值："+i);
            mView.onTime(i);
        }
    }
}
...

该值首先会通过View传到对应的Presenter，紧接着传出到实现了View方法的Activity和Service

@Override
public void onTime(int position) {
    get().onTime(position);
}

Activity和Service都会收到来自单例Model传过来的数据

MVP的特性才展现出来

打印如下

45.915  I/Model.java: [ (Model.java:68)#handleMessage ] @26f08e 发值：1
45.918  I/MainActivity.java: [ (MainActivity.java:81)#onTime ] @26f08e收值：1
45.920  I/Model.java: [ (Model.java:68)#handleMessage ] @1a5879a 发值：1
45.924  I/TestService.java: [ (TestService.java:47)#onTime ] @1a5879a收值：1
46.918  I/Model.java: [ (Model.java:68)#handleMessage ] @26f08e 发值：2
46.920  I/MainActivity.java: [ (MainActivity.java:81)#onTime ] @26f08e收值：2
46.925  I/Model.java: [ (Model.java:68)#handleMessage ] @1a5879a 发值：2
46.926  I/TestService.java: [ (TestService.java:47)#onTime ] @1a5879a收值：2
47.922  I/Model.java: [ (Model.java:68)#handleMessage ] @26f08e 发值：3
47.923  I/MainActivity.java: [ (MainActivity.java:81)#onTime ] @26f08e收值：3
47.927  I/Model.java: [ (Model.java:68)#handleMessage ] @1a5879a 发值：3
47.928  I/TestService.java: [ (TestService.java:47)#onTime ] @1a5879a收值：3

4.灵活添加和移除View

4.1 移除

当Activity销毁时，通过onDestroy的方法除Model中对应Presenter的View，防止泄漏

Model.class

...
public void onDestroy(View mPV) {
    XLog.i("Model中去除P"+mPV);
    mViews.remove(mPV);
    ...
}
...

打印如下：

52:03.088  I/Model.java: [ (Model.java:49)#onDestroy ] Model中去除P_id: @170acea

4.2 添加

当Activity再次创建时，model中会再增加其新的对应Presenter的View

52:07.186  I/MainActivity.java: [ (MainActivity.java:23)#onCreate ] Acticity持有的P_id: @b79a950
52:07.207  I/Model.java: [ (Model.java:15)#setViews ] Model中增加P_id: @b79a950

当不再有Presenter持有Model时，Model会被释放

Model.class

...
public void onDestroy(View mPV) {
    XLog.i("Model中去除P"+mPV);
    mViews.remove(mPV);
    if (mViews.size()==0){
        clear();
    }
}
public final void clear() {
    handler.removeMessages(0x01);
    handler = null;
    mModel = null;
}
...

5.补充BaseActivity和BaseService

是归与逻辑层的两个方法，用于逻辑与界面分离时，当逻辑层添加了新的接口时，界面并不需要，或者没来得及实现时，在逻辑层的BaseActivity和BaseService中添加了接口，界面层就不需要去实现。

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原始发表：2021-01-27，如有侵权请联系 cloudcommunity@tencent.com 删除

mvp