如何转换类型类 <?> 诠释

Question

I am trying to convert this data type to call out the method later on in another class to switch around layouts being made in other methods such as recipe1Layout(); by the index number of a class that has a field of a Class<?> Array.

Here is the getItem() method

public int getItem(){
     int index = 0;
     for(int i = 0; i < 100; i++) {
         try{
           index = recipe.getClass().getField("Classes").get(i);
         } catch(Exception e){

         }
     }
     return index;
 }

Here is the Recipe Class

    public class Recipes {
      public Class<?>[] Classes = {
        ChileConLecheActivity.class,
        ArrozActivity.class,
        EnchiladasActivity.class,
        SopaActivity.class
      };
    }

The type of Class needs to be here because I have other uses for the recipe class.
For example, making a new instance of all classes to later on be called out to make adjustments to all the classes with one method.
The only thing I can think of is converting the type Class to an int so I can call out the method returning the index number I can do something like recipe.

    index = Integer.parseInt(Classes[I].getName().toString());

But this is where I am asking for help I have no idea how to get rid of the error in the logcat.

The error shows up as

IndexOutOfArrayException

Answer 1

First off, stop using reflection. Use a public static array.

public class Recipes {
  public static final Class<?>[] CLASSES = {
    ChileConLecheActivity.class,
    ArrozActivity.class,
    EnchiladasActivity.class,
    SopaActivity.class
  };
}

Then, assuming your recipe instance has a field of what Class<Activity> it is assigned to, then, you would want something like this

 public int getItem(){
     int index = -1;
     for(int i = 0 ; i < Recipe.CLASSES.length; i++) {
        if (recipe.getActivityClass().equals(Recipe.CLASSES[i]) { 
           index = i;
           break; 
        } 
     }
     return index;
 }

However, under certain situations, coupling one Activity class to any single Recipe instance, probably isn't a good idea.

I am trying to convert this data type to call out the method later on in another class to switch around layouts being made in other methods

if I understand what you are trying to do, you want a some mapping structure to some classes which have some pre-defined layouts.

Generally, this can be done with enums and OOP patterns

Have some base classes like this

public interface Layoutable {
    int getLayout();
}

public enum Recipe {
    ChileConLeche(R.layout.chile_con_leche),
    Arroz(R.layout.arroz),
    Enchiladas(R.layout.enchiladas),
    Sopa(R.layout.sopa)

    int layout;
    Recipe(int layout) { this.layout = layout };
}

Ideally, you would want to use Fragments, but here is an example of an Activity structure

public abstract class RecipeActvity extends AppCompatActivity implements Layoutable {
    protected Recipe recipe;
    protected int getLayout() { return recipe.layout; }
}

public class ChileConLecheActivity extends RecipeActvity {
    public ChileConLecheActivity() {
        this.recipe = Recipe.ChileConLeche;
    }

    @Override
    public void onCreate(...) {
        setContentView(getLayout());
    }
}

You can also combine this with a Map<Recipe, Class<RecipeActivity>> , from which you would use map.get(Recipe.ChileConCarne) to get the respective class element, for which you can startActivity() with