传统的MVP模式中,不可避免要在V中的生命周期中要做很多业务操作,导致actitvity等还是臃肿不堪。因此,谷歌在2017年的IO大会上推出了Lifecycle框架,希望借Lifecycle将activity的生命周期事件传递给Presenter,让Presenter承担部分业务,从而降低了Activity的复杂度。lifecycle本身就是一个依赖注入的框架,具体的原理和源码也比较简单,这里就不做源码分析了,废话不多说,直接上代码
传统的Activity代码:
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
/**
* 没有使用LifeCycle,导致activity要在不同的生命周期处理各种事情,随着需求的迭代,activity将会臃肿不堪
*/
public class NoLifecycleActivity extends AppCompatActivity{
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_scrolling);
register();
}
/**
*注册广播
*/
private void register(){
// context.registerReceiver(null,null);
}
/**
* 注销广播
*/
private void unregister(){
// context.unregisterReceiver(null);
}
@Override
protected void onDestroy() {
super.onDestroy();
unregister();
}
}
使用Lifecycle的Activity
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
/**
* 添加Lifecycle,将activity的生命周期状态传递给Presenter,让presenter来做事情
*/
public class LifecycleActivity extends AppCompatActivity {
Presenter presenter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_scrolling);
presenter = new Presenter(this);
getLifecycle().addObserver(presenter);//为Lifecycle注册生命周期监听器
presenter.doWork();
}
}
IPresenter:
package com.example.helang.lifecycledemo;
import android.arch.lifecycle.Lifecycle;
import android.arch.lifecycle.LifecycleObserver;
import android.arch.lifecycle.LifecycleOwner;
import android.arch.lifecycle.OnLifecycleEvent;
import android.support.annotation.NonNull;
/**
* Created by helang on 2018/6/19.
*/
public interface IPresenter extends LifecycleObserver {
//一共有五个生命周期,按需添加
@OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
void onCreate(@NonNull LifecycleOwner owner);
@OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
void onDestroy(@NonNull LifecycleOwner owner);
}
Presenter:
package com.example.helang.lifecycledemo;
import android.arch.lifecycle.LifecycleOwner;
import android.content.Context;
import android.support.annotation.NonNull;
import android.util.Log;
/**
* Presenter承担更多业务上的操作,但是,也不易把过多的业务转到Presenter中,不然会造成Presenter变成第二个"Activity"
* Created by helang on 2018/6/19.
*/
public class Presenter implements IPresenter {
private static final String TAG = "Presenter";
private Model model = new Model();
private Context context;
public Presenter(Context context) {
this.context = context;
}
public void doWork(){
model.startWork();
}
/**
* 创建资源等
* @param owner
*/
@Override
public void onCreate(@NonNull LifecycleOwner owner) {
Log.e(TAG,"onCreate");
register();
}
/**
* 释放资源等
* @param owner
*/
@Override
public void onDestroy(@NonNull LifecycleOwner owner) {
Log.e(TAG,"onDestroy");
model.endWork();
unregister();
}
/**
* 比如注册动态广播等操作可以转移到Presenter中,进一步降低Activity的复杂性
*/
private void register(){
// context.registerReceiver(null,null);
}
private void unregister(){
// context.unregisterReceiver(null);
}
}
Model:
package com.example.helang.lifecycledemo;
import android.util.Log;
/**
* Created by helang on 2018/6/19.
*/
public class Model {
private static final String TAG = "MODEL";
public void startWork(){
Log.e(TAG,"startWork");
}
public void endWork(){
Log.e(TAG,"endWork");
}
}
Android的Lifecycle代码很简单,更多的像是一个语法糖,但是,也不要把所有业务处理都丢给Presenter,也不要为了解耦而解耦,一定要根据自己项目的实际情况和发展,来决定自己的项目该怎么做,希望能够和大家一起成长
代码地址:https://github.com/helang1991/LifeCycleDemo