LazyImageAdapter.java

/*
 *  Copyright (c) 2012 Daniel Huckaby
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package com.handlerexploit.prime.example.adapters;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.TextView;

import com.handlerexploit.prime.example.R;
import com.handlerexploit.prime.example.utils.Utilities.Image;
import com.handlerexploit.prime.widgets.RemoteImageView;

/**
 * This class uses the basic ViewHolder optimization pattern and is displaying
 * the expected implementation of the {@link RemoteImageView}. If you follow the
 * correct pattern the user experience should be clean and painless.
 */
public class LazyImageAdapter extends ArrayAdapter<Image> {
    
    private int resId;
    
    public LazyImageAdapter(Context context, int resId) {
        super(context, 0);
        this.resId = resId;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        
        ViewHolder holder;
        if (convertView == null) {
            convertView = LayoutInflater.from(getContext()).inflate(resId, null);

            holder = new ViewHolder();
            holder.text = (TextView) convertView.findViewById(R.id.text);
            holder.icon = (RemoteImageView) convertView.findViewById(R.id.icon);
            
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        
        Image image = getItem(position);

        holder.text.setText(image.title);
        
        /*
         * Set the default image, this is required. If you do not set a default
         * image the recycled views will display the incorrect images if/when
         * they are finally loaded. If the image is available in memory this
         * default may not ever be displayed to the user.
         */
        holder.icon.setImageBitmap(null);
        
        /*
         * Make sure to always set something to this attribute if you are using
         * it in an adapter. This is the expected adapter behavior and our
         * recycling optimizations will not work correctly if we do not set this
         * correctly.
         */
        holder.icon.setImageURL(image.imageURL);

        return convertView;
    }

    private static class ViewHolder {
        TextView text;
        RemoteImageView icon;
    }
}