ViewPagerExample.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.activities;

import java.util.ArrayList;
import java.util.List;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.app.LoaderManager.LoaderCallbacks;
import android.support.v4.content.AsyncTaskLoader;
import android.support.v4.content.Loader;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView.ScaleType;

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

/**
 * This class implements and displays the {@link LazyImageAdapter} in the form
 * of a {@link ViewPager}. This example uses a {@link AsyncTaskLoader} internally
 * for generating our list of image urls.
 */
public class ViewPagerExample extends FragmentActivity implements LoaderCallbacks<List<Image>> {
    
    private PagerAdapter mPagerAdapter;
    
    private View mEmptyView;
    
    private ViewPager mViewPager;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.viewpager_content);
        
        mPagerAdapter = new PagerAdapter(this);
        
        mEmptyView = findViewById(R.id.progressContainer);
        mEmptyView.setVisibility(View.VISIBLE);
        
        mViewPager = (ViewPager) findViewById(android.R.id.list);
        mViewPager.setVisibility(View.GONE);
        mViewPager.setOffscreenPageLimit(5);
        mViewPager.setAdapter(mPagerAdapter);
        
        getSupportLoaderManager().initLoader(0, null, this);
    }
    
    @Override
    public Loader<List<Image>> onCreateLoader(int id, Bundle args) {
        return new WrappedAsyncTaskLoader<List<Image>>(this) {

            @Override
            public List<Image> loadInBackground() {
                return Utilities.getRandomLargeImages(ViewPagerExample.this);
            }
        };
    }

    @Override
    public void onLoadFinished(Loader<List<Image>> loader, List<Image> images) {
        for (Image image : images) {
            Bundle bundle = new Bundle();
            bundle.putString(ImageFragment.EXTRA_TITLE, image.title);
            bundle.putString(ImageFragment.EXTRA_URL, image.imageURL);
            mPagerAdapter.add(ImageFragment.class, bundle);
        }
        mEmptyView.setVisibility(View.GONE);
        mViewPager.setVisibility(View.VISIBLE);
    }

    @Override
    public void onLoaderReset(Loader<List<Image>> loader) {
        mPagerAdapter.clear();
        mEmptyView.setVisibility(View.VISIBLE);
        mViewPager.setVisibility(View.GONE);
    }
    
    public static class ImageFragment extends Fragment {
        
        public static final String EXTRA_TITLE = "title";
        public static final String EXTRA_URL = "url";
        
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            
            Bundle arguments = getArguments();
            
            Image image = new Image();
            image.title = arguments.getString(EXTRA_TITLE);
            image.imageURL = arguments.getString(EXTRA_URL);
            
            RemoteImageView remoteImageView = new RemoteImageView(inflater.getContext());
            remoteImageView.setScaleType(ScaleType.CENTER_CROP);
            remoteImageView.setImageURL(image.imageURL);
            
            return remoteImageView;
        }
    }
    
    public static class PagerAdapter extends FragmentStatePagerAdapter {

        private List<Holder> holderList = new ArrayList<Holder>();
        private FragmentActivity fragmentActivity;

        public PagerAdapter(FragmentActivity fragmentActivity) {
            super(fragmentActivity.getSupportFragmentManager());
            this.fragmentActivity = fragmentActivity;
        }

        public void clear() {
            holderList.clear();
            notifyDataSetChanged();
        }

        public void add(Class<? extends Fragment> className, Bundle params) {
            Holder holder = new Holder();
            holder.className = className.getName();
            holder.params = params;

            int position = holderList.size();
            holderList.add(position, holder);
            notifyDataSetChanged();
        }

        public Fragment getFragment(ViewPager viewPager, int position) {
            return (Fragment) instantiateItem(viewPager, position);
        }

        @Override
        public Fragment getItem(int position) {
            Holder currentHolder = holderList.get(position);
            return Fragment.instantiate(fragmentActivity, currentHolder.className, currentHolder.params);
        }

        @Override
        public int getCount() {
            return holderList.size();
        }

        private class Holder {
            String className;
            Bundle params;
        }
    }
}