MVP實操

理論：

　　Presenter負責邏輯的處理，Model提供數據，View負責顯示

　　MVP架構模式對於MVC模式主要特色是View 和 Model的徹底分離，全部的交互都經過Presenter這個中間者。

優勢：

1. model 和 view徹底分離，能夠修改視圖而不影響模型

2. 易於解決內存泄露問題

3. 能夠更方便的單元測試

練習：

1,定義一個接口Iview;

public interface Iview {
    void showToast();
    void showList(List<String> list);
}

2,寫一個model類以獲取數據

public class DemoModel {

    public List getData(){
        List<String> list = new ArrayList();
        list.add("one");
        list.add("two");
        list.add("three");
        list.add("four");
        list.add("five");
        return list;
    }
}

3，presenter類獲得view和model的引用

public class DemoPresenter {

    Iview view;
    DemoModel model;

    public DemoPresenter(DemoModel demoModel){
        model = demoModel;
    }

    public void attach(Iview view){
        this.view = view;
    }

    public void detache(){
        this.view = null;
    }

    public void fetch(){
        List data = model.getData();
        view.showList(data);
        view.showToast();
    }
}

4.Activity實現Iview

class MainActivity : AppCompatActivity(), Iview {

    lateinit var mListView:ListView
    var mDemoPresenter:DemoPresenter? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        mDemoPresenter = DemoPresenter(DemoModel())
        mDemoPresenter?.attach(this)
        initView()
        mDemoPresenter?.fetch()

    }

    private fun initView() {
       mListView = findViewById<ListView>(R.id.mListView)
    }

    override fun showToast() {
        Toast.makeText(this,"ok",Toast.LENGTH_SHORT).show()
    }

    override fun showList(list: MutableList<String>?) {
        mListView.adapter = ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,list)
    }

    override fun onDestroy() {
        mDemoPresenter?.detache()
        mDemoPresenter = null
        super.onDestroy()
    }
}

5,在Activity中實例一個Presenter與之綁定，綁定後經過presenter對象調用fetch（）來獲取數據並顯示。