Java tutorial
/* * Copyright 2012 Google Inc. * * 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.vinay.volley.lazyload; import java.util.ArrayList; import android.animation.Animator; import android.animation.AnimatorListenerAdapter; import android.annotation.TargetApi; import android.content.Context; import android.content.res.Resources; import android.graphics.Bitmap; import android.graphics.drawable.BitmapDrawable; import android.graphics.drawable.ColorDrawable; import android.graphics.drawable.Drawable; import android.graphics.drawable.TransitionDrawable; import android.net.http.AndroidHttpClient; import android.os.Build; import android.support.v4.app.FragmentActivity; import android.widget.ImageView; import com.android.volley.Cache; import com.android.volley.Network; import com.android.volley.RequestQueue; import com.android.volley.VolleyError; import com.android.volley.toolbox.BasicNetwork; import com.android.volley.toolbox.DiskBasedCache; import com.android.volley.toolbox.HttpClientStack; import com.android.volley.toolbox.HurlStack; /** * A class that wraps up remote image loading requests using the Volley library combined with a memory cache. An single * instance of this class should be created once when your Activity or Fragment is created, then use * {@link #get(String, android.widget.ImageView)} or one of the variations to queue the image to be fetched and loaded * from the network. Loading images in a {@link android.widget.ListView} or {@link android.widget.GridView} is also * supported but you must store the {@link com.android.volley.Request} in your ViewHolder type class and pass it into * loadImage to ensure the request is canceled as views are recycled. */ public class ImageLoader extends com.android.volley.toolbox.ImageLoader { private static final int ANIMATION_FADE_IN_TIME = 250; private static final ColorDrawable transparentDrawable = new ColorDrawable(android.R.color.transparent); private static final int HALF_FADE_IN_TIME = ANIMATION_FADE_IN_TIME / 2; private static final String CACHE_DIR = "images"; private Resources mResources; private ArrayList<Drawable> mPlaceHolderDrawables; private boolean mFadeInImage = true; private int mMaxImageHeight = 0; private int mMaxImageWidth = 0; private static RequestQueue queue = null; /** * Creates an ImageLoader with Bitmap memory cache. No default placeholder image will be shown while the image is * being fetched and loaded. */ public ImageLoader(FragmentActivity activity) { super(newRequestQueue(activity), BitmapCache.getInstance(activity.getSupportFragmentManager())); mResources = activity.getResources(); } /** * Creates an ImageLoader with Bitmap memory cache and a default placeholder image while the image is being fetched * and loaded. */ public ImageLoader(FragmentActivity activity, int defaultPlaceHolderResId) { super(newRequestQueue(activity), BitmapCache.getInstance(activity.getSupportFragmentManager())); mResources = activity.getResources(); mPlaceHolderDrawables = new ArrayList<Drawable>(1); mPlaceHolderDrawables .add(defaultPlaceHolderResId == -1 ? null : mResources.getDrawable(defaultPlaceHolderResId)); } /** * Creates an ImageLoader with Bitmap memory cache and a list of default placeholder drawables. */ public ImageLoader(FragmentActivity activity, ArrayList<Drawable> placeHolderDrawables) { super(newRequestQueue(activity), BitmapCache.getInstance(activity.getSupportFragmentManager())); mResources = activity.getResources(); mPlaceHolderDrawables = placeHolderDrawables; } private RequestQueue getRequestQueue() { return queue; } /** * Starts processing requests on the {@link RequestQueue}. */ public void startProcessingQueue() { getRequestQueue().start(); } /** * Stops processing requests on the {@link RequestQueue}. */ public void stopProcessingQueue() { getRequestQueue().stop(); } public ImageLoader setFadeInImage(boolean fadeInImage) { mFadeInImage = fadeInImage; return this; } public ImageLoader setMaxImageSize(int maxImageWidth, int maxImageHeight) { mMaxImageWidth = maxImageWidth; mMaxImageHeight = maxImageHeight; return this; } public ImageLoader setMaxImageSize(int maxImageSize) { return setMaxImageSize(maxImageSize, maxImageSize); } public ImageContainer get(String requestUrl, ImageView imageView) { return get(requestUrl, imageView, 0); } public ImageContainer get(String requestUrl, ImageView imageView, int placeHolderIndex) { return get(requestUrl, imageView, mPlaceHolderDrawables.get(placeHolderIndex), mMaxImageWidth, mMaxImageHeight); } public ImageContainer get(String requestUrl, ImageView imageView, Drawable placeHolder) { return get(requestUrl, imageView, placeHolder, mMaxImageWidth, mMaxImageHeight); } public ImageContainer get(String requestUrl, ImageView imageView, Drawable placeHolder, int maxWidth, int maxHeight) { // Find any old image load request pending on this ImageView (in case this view was // recycled) ImageContainer imageContainer = imageView.getTag() != null && imageView.getTag() instanceof ImageContainer ? (ImageContainer) imageView.getTag() : null; // Find image url from prior request String recycledImageUrl = imageContainer != null ? imageContainer.getRequestUrl() : null; // If the new requestUrl is null or the new requestUrl is different to the previous // recycled requestUrl if (requestUrl == null || !requestUrl.equals(recycledImageUrl)) { if (imageContainer != null) { // Cancel previous image request imageContainer.cancelRequest(); imageView.setTag(null); } if (requestUrl != null) { // Queue new request to fetch image imageContainer = get(requestUrl, getImageListener(mResources, imageView, placeHolder, mFadeInImage), maxWidth, maxHeight); // Store request in ImageView tag imageView.setTag(imageContainer); } else { imageView.setImageDrawable(placeHolder); imageView.setTag(null); } } return imageContainer; } private static ImageListener getImageListener(final Resources resources, final ImageView imageView, final Drawable placeHolder, final boolean fadeInImage) { return new ImageListener() { @Override public void onResponse(ImageContainer response, boolean isImmediate) { imageView.setTag(null); if (response.getBitmap() != null) { setImageBitmap(imageView, response.getBitmap(), resources, fadeInImage && !isImmediate); } else { imageView.setImageDrawable(placeHolder); } } @Override public void onErrorResponse(VolleyError volleyError) { } }; } private static RequestQueue newRequestQueue(Context context) { // On HC+ use HurlStack which is based on HttpURLConnection. Otherwise fall back on // AndroidHttpClient (based on Apache DefaultHttpClient) which should no longer be used // on newer platform versions where HttpURLConnection is simply better. Network network = new BasicNetwork(hasHoneycomb() ? new HurlStack() : new HttpClientStack(AndroidHttpClient.newInstance(NetUtils.getUserAgent(context)))); Cache cache = new DiskBasedCache(CacheDirectory.getDiskCacheDir(context, CACHE_DIR)); queue = new RequestQueue(cache, network); queue.start(); return queue; } /** * Sets a {@link android.graphics.Bitmap} to an {@link android.widget.ImageView} using a fade-in animation. If there * is a {@link android.graphics.drawable.Drawable} already set on the ImageView then use that as the image to fade * from. Otherwise fade in from a transparent Drawable. */ @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR1) private static void setImageBitmap(final ImageView imageView, final Bitmap bitmap, Resources resources, boolean fadeIn) { // If we're fading in and on HC MR1+ if (fadeIn && hasHoneycombMR1()) { // Use ViewPropertyAnimator to run a simple fade in + fade out animation to update the // ImageView imageView.animate().scaleY(0.95f).scaleX(0.95f).alpha(0f) .setDuration(imageView.getDrawable() == null ? 0 : HALF_FADE_IN_TIME) .setListener(new AnimatorListenerAdapter() { @Override public void onAnimationEnd(Animator animation) { imageView.setImageBitmap(bitmap); imageView.animate().alpha(1f).scaleY(1f).scaleX(1f).setDuration(HALF_FADE_IN_TIME) .setListener(null); } }); } else if (fadeIn) { // Otherwise use a TransitionDrawable to fade in Drawable initialDrawable; if (imageView.getDrawable() != null) { initialDrawable = imageView.getDrawable(); } else { initialDrawable = transparentDrawable; } BitmapDrawable bitmapDrawable = new BitmapDrawable(resources, bitmap); // Use TransitionDrawable to fade in final TransitionDrawable td = new TransitionDrawable( new Drawable[] { initialDrawable, bitmapDrawable }); imageView.setImageDrawable(td); td.startTransition(ANIMATION_FADE_IN_TIME); } else { // No fade in, just set bitmap directly imageView.setImageBitmap(bitmap); } } /** * Interface an activity can implement to provide an ImageLoader to its children fragments. */ public interface ImageLoaderProvider { public ImageLoader getImageLoaderInstance(); } public static boolean hasHoneycomb() { return Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB; } public static boolean hasHoneycombMR1() { return Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR1; } }