具有2种不同类型的对象数据

Question

I have the following:

public class Notifier{
    CustomPlayer mCustomPlayer;
    CurrentPlayer mCurrentPlayer;
}

public class MainActivity extends Activity{

    public void onCreate(){
        Notifier ntf = new Notifier();
        if( index == 0){
            ntf.mCustomPlayer = new CustomPlayer(this);
        }
        else{
            ntf.mCustomPlayer = new CurrentPlayer(this); // having problem here
        }
    }
}

In Notifier class, I just want to have one object mCustomPlayer to switch between CustomPlayer and CurrentPlayer in MainActivity class.

I tried adding the following in Notifier class,

public class Notifier{
    CustomPlayer mCustomPlayer;
    CurrentPlayer mCurrentPlayer;

    public Object getType(int index) {
        if (index == 1) {
            return CurrentPlayer.class;
        }
        else {
            return CustomPlayer.class;
        }
    }
}

With that I am having a problem when trying to initialize mCustomPlayer in MainActivity class.

ntf.mCustomPlayer = new (ntf.mCustomPlayer)getType(0); // compile error

Is there a way to realize this?
It has been a day since I am trying to configure out the correct implementation.
Should I use Interface in this case?

Answer 1

To use the new keyword you must supply a class (ie new MyClass() ).

You could use reflection for this... but wouldn't it be much simpler to just have a common superclass (or interface) for CustomPlayer and CurrentPlayer ?

For example, suppose both CustomPlayer and CurrentPlayer have the playOne() and playTwo() methods. You could then define:

public interface Player {
    void playOne();
    void playTwo();
}

public class CurrentPlayer implements Player {
    @Override
    public void playOne() { 
        // code
    }

    @Override
    public void playTwo() {
        // code
    }
}

private class CustomPlayer implements Player {
    @Override
    public void playOne() {
        // code
    }

    @Override
    public void playTwo() {
        // code
    }
}

public class Notifier {
    Player mPlayer;
 }

And then assign mPlayer with new CurrentPlayer() or new CustomPlayer() You can then call any methods on the interface.

Answer 2

You could using Reflection:

public class Notifier{

    public CommonInterface getInstance(int index, Class<Activity> activity){
      Class<?> claz = getType(0);
      Constructor<?> cons = claz.getConstructor(activity);
      return (CommonInterface) cons.newInstance(this);
      //or you could just type cast it manually if you do not wish to use CommonInterface
}

But having a common interface is the right way to go. You dont have to worry about reflection then.

Answer 3

Since you have same function for both the classes so use interface and access the object -

public class MainActivity extends Activity{
    interface CurrentPlayer  { void game(); }
    interface CustomPlayer   { void game(); }

    interface Player extends CurrentPlayer, CustomPlayer { }

     public void onCreate(){
        Player swan = new Player() {
            @Override 
            public void game() {
                System.out.println("Swan Player");  //Swan Player
            }
        };
     }
}