1Description.md

## 1Description.md

      
        

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    Make your multiple type view adapter with annotations!
Gist for Making a Multiple View Types Adapter With Annotations
Pretty easy to use.

Create your delegate adapters, implementing DelegateAdapter, and with the annotation DelegateAdapterType.
e.g:

@DelegateAdapterType(itemType = 0)
public class SimpleTextDelegateAdapter implements DelegateAdapter { ... getView() ... }

Your main adapter have to extend the DispatcherAdapter. You will have to override getItemViewType add your delegateAdapters in the DelegateAdaptersAnnotation just like this:

@DelegateAdapters(delegateAdapters = {
  	SimpleTextDelegateAdapter.class,
		HtmliTextDelegateAdapter.class,
		GalleryDelegateAdapter.class
}) 
public class MyAdapter extends DispatcherAdapter{ ... }

You're done!

You can improve this gist/lib. We can imagine for example a wrapper class containing all the delegates, and an annotation DelegateAdapterWrapper(Class) for  the DispatcherAdapter, so we only pass one the wrapper as parameter. Then if you have to add a new view type for your list, the only thing you have to do is add it in the wrapper class! Pretty handy no?

  

  

## DelegateAdapter.java
/**
 * You have to implement this interface for your delegates.
 */
public interface DelegateAdapter {
  public View getView(int position, View convertView, ViewGroup parent, LayoutInflater inflater, Object item);
}

## DelegateAdaptersAnnotation.java
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
public @interface DelegateAdaptersAnnotation {
  Class<? extends DelegateAdapter>[] delegateAdapters();
}

## DelegateAdapterType.java
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface DelegateAdapterType {
  long itemType();
}

## DispatcherAdapter.java
/**
 * Your custom adapter should extends this class
 */
public abstract class DispatcherAdapter extends BaseAdapter {
  private   LongSparseArray<DelegateAdapter> mDelegateAdapterSparseArray;
  protected Context mContext;
  protected LayoutInflater mLayoutInflater;

  public DispatcherAdapter(Context context) {
    mContext = context;
    mLayoutInflater = LayoutInflater.from(context);

    initDelegates();
  }

  /**
   *  Init the delegates here, with reflection
   */
  private void initDelegates() {
    mDelegateAdapterSparseArray = new LongSparseArray<DelegateAdapter>();

    DelegateAdaptersAnnotation annotation = getClass().getAnnotation(DelegateAdaptersAnnotation.class);
    if (annotation != null) {
      Class[] clazzs = annotation.delegateAdapters();
      if (clazzs != null) {
        for (Class<?> clazz : clazzs) {
          if (!DelegateAdapter.class.isAssignableFrom(clazz)) {
            throw new RuntimeException("The class " + clazz.getName() + " is not a subclass of " + DelegateAdapter.class.getName());
          }
          DelegateAdapterType delegateAdapterType = clazz.getAnnotation(DelegateAdapterType.class);
          if(delegateAdapterType == null){
            throw new RuntimeException("The class "+clazz.getName()+" should have the annotation DelegateAdapterField");
          }

          long itemtype = delegateAdapterType.itemType();

          if(mDelegateAdapterSparseArray.get(itemtype) != null){
            throw new RuntimeException("The item type "+itemtype+" is already defined!");
          }

          DelegateAdapter adapter = null;
          try {
            adapter = (DelegateAdapter) clazz.newInstance();
          } catch (Exception e) {
            throw new RuntimeException("Error while instanciating "+clazz.getName()+" with default constructor: "+e.getMessage(), e);
          }

          mDelegateAdapterSparseArray.put(itemtype, adapter);
        }
      }
    }
  }

  @Override
  public View getView(int position, View convertView, ViewGroup parent) {
    long itemtype = getItemViewType(position);
    DelegateAdapter delegateAdapter = mDelegateAdapterSparseArray.get(itemtype);
    if(delegateAdapter == null){
      throw new RuntimeException("Unknown type "+itemtype+" called");
    }
    return mDelegateAdapterSparseArray.get(itemtype).getView(position, convertView, parent, mLayoutInflater, getItem(position));
  }

  @Override
  public int getViewTypeCount() {
    return mDelegateAdapterSparseArray.size();
  }
}