Java方法中的嵌套泛型？

Question

我正在創建自己的MVP框架，而且我遇到了仿製藥的麻煩。

我的演講是這樣定義的，具有子元素這也是通用主持人的內部類持有引用：

public abstract class Presenter<TView extends View, TKey extends Key> 
{ 
    protected final HashMap<String, StageInstances<?, ?>> _stages; 

    public <TChildView extends View, TChildKey extends Key> void addStage(Class<Presenter<TChildView, TChildKey>> stage, String name) 
    { 
     _stages.put(name, new StageInstances<TChildView, TChildKey>(stage)); 
    } 

    // ... 

    protected class StageInstances<TChildView extends View, TChildKey extends Key> 
    { 
     protected Class<Presenter<TChildView, TChildKey>>  _presenter; 
     protected HashMap<Key, Presenter<TChildView, TChildKey>> _instances; 

     public StageInstances(Class<Presenter<TChildView, TChildKey>> presenter) 
     { 
      _presenter = presenter; 
      _instances = new HashMap<Key, Presenter<TChildView, TChildKey>>(); 
     } 

     public Presenter<?, ?> getInstance(Key key) 
     { 
      if (!_instances.containsKey(key)) 
      { 
       try 
       { 
        _instances.put(key, _presenter.newInstance()); 
       } catch (Exception e) 
       { 
        e.printStackTrace(); 

        return null; 
       } 
      } 

      return _instances.get(key); 
     } 
    } 
} 

，我有這個

public class ResultsPresenter extends Presenter<ResultsView, Results> 

和

一個具體的實現

public class SearchPresenter extends Presenter<SearchView, StringKey> 
{ 
    // ... 

    public void bind() 
    { 
     addStage(ResultsPresenter.class, "results"); 
    } 
} 

where ResultsView，SearchView extend View and Results，St ringKey實施重點

的方法addStage（...）拋出以下編譯時錯誤：

**The method addStage(Class<Presenter<TChildView,TChildKey>>, String) in the type 
Presenter<SearchView,StringKey> is not applicable for the arguments 
(Class<ResultsPresenter>, String)** 

任何幫助，或者更好的做法，將不勝感激

Answer 1

試圖改變方法原型：我變Class<Presenter<TChildView, TChildKey>>到Class<? extends Presenter<TChildView, TChildKey>>

public <TChildView extends View, TChildKey extends Key> void addStage(Class<? extends Presenter<TChildView, TChildKey>> stage, String name) 

講究。這將允許您傳遞Presenter類的子類而不是Presenter本身。

Answer 2

我沒有嘗試過自己，而是出於一種預感，我會說，

addStage(Class<Presenter<TChildView, TChildKey>> stage, String name) 

應該

addStage(Class<Presenter<? extends TChildView,? extends TChildKey>> stage, String name) 

首先嚐試亞歷克斯建議。保持代碼更易讀，比我的更有意義。如果兩者都失敗，請合併它們。