com.android.volley.toolbox

Class ImageLoader

java.lang.Object

com.android.volley.toolbox.ImageLoader

public class ImageLoader
extends java.lang.Object

Helper that handles loading and caching images from remote URLs. The simple way to use this class is to call get(String, com.android.volley.toolbox.ImageLoader.ImageListener) and to pass in the default image listener provided by ImageLoader#getImageListener(android.widget.ImageView, int, int). Note that all function calls to this class must be made from the main thead, and all responses will be delivered to the main thread as well.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private class	ImageLoader.BatchedImageRequest Wrapper class used to map a Request to the set of active ImageContainer objects that are interested in its results.
static interface	ImageLoader.ImageCache Simple cache adapter interface.
class	ImageLoader.ImageContainer Container object for all of the data surrounding an image request.
static interface	ImageLoader.ImageListener Interface for the response handlers on image requests.

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.HashMap<java.lang.String,ImageLoader.BatchedImageRequest>	mBatchedResponses HashMap of the currently pending responses (waiting to be delivered).
private int	mBatchResponseDelayMs Amount of time to wait after first response arrives before delivering all responses.
private ImageLoader.ImageCache	mCache The cache implementation to be used as an L1 cache before calling into volley.
private Handler	mHandler Handler to the main thread.
private java.util.HashMap<java.lang.String,ImageLoader.BatchedImageRequest>	mInFlightRequests HashMap of Cache keys -> BatchedImageRequest used to track in-flight requests so that we can coalesce multiple requests to the same URL into a single network request.
private RequestQueue	mRequestQueue RequestQueue for dispatching ImageRequests onto.
private java.lang.Runnable	mRunnable Runnable for in-flight response delivery.

Constructor Summary

Constructors

Constructor and Description
ImageLoader(RequestQueue queue, ImageLoader.ImageCache imageCache) Constructs a new ImageLoader.

Method Summary

Modifier and Type	Method and Description
private void	batchResponse(java.lang.String cacheKey, ImageLoader.BatchedImageRequest request) Starts the runnable for batched delivery of responses if it is not already started.
ImageLoader.ImageContainer	get(java.lang.String requestUrl, ImageLoader.ImageListener listener) Returns an ImageContainer for the requested URL.
ImageLoader.ImageContainer	get(java.lang.String requestUrl, ImageLoader.ImageListener imageListener, int maxWidth, int maxHeight) Issues a bitmap request with the given URL if that image is not available in the cache, and returns a bitmap container that contains all of the data relating to the request (as well as the default image if the requested image is not available).
private static java.lang.String	getCacheKey(java.lang.String url, int maxWidth, int maxHeight) Creates a cache key for use with the L1 cache.
static ImageLoader.ImageListener	getImageListener(ImageView view, int defaultImageResId, int errorImageResId) The default implementation of ImageListener which handles basic functionality of showing a default image until the network response is received, at which point it will switch to either the actual image or the error image.
boolean	isCached(java.lang.String requestUrl, int maxWidth, int maxHeight) Checks if the item is available in the cache.
private void	onGetImageError(java.lang.String cacheKey, VolleyError error) Handler for when an image failed to load.
private void	onGetImageSuccess(java.lang.String cacheKey, Bitmap response) Handler for when an image was successfully loaded.
void	setBatchedResponseDelay(int newBatchedResponseDelayMs) Sets the amount of time to wait after the first response arrives before delivering all responses.
private void	throwIfNotOnMainThread()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

mRequestQueue

private final RequestQueue mRequestQueue

RequestQueue for dispatching ImageRequests onto.

mBatchResponseDelayMs

private int mBatchResponseDelayMs

Amount of time to wait after first response arrives before delivering all responses.

mCache

private final ImageLoader.ImageCache mCache

The cache implementation to be used as an L1 cache before calling into volley.

mInFlightRequests

private final java.util.HashMap<java.lang.String,ImageLoader.BatchedImageRequest> mInFlightRequests

HashMap of Cache keys -> BatchedImageRequest used to track in-flight requests so that we can coalesce multiple requests to the same URL into a single network request.

mBatchedResponses

private final java.util.HashMap<java.lang.String,ImageLoader.BatchedImageRequest> mBatchedResponses

HashMap of the currently pending responses (waiting to be delivered).

mHandler

private final Handler mHandler

Handler to the main thread.

mRunnable

private java.lang.Runnable mRunnable

Runnable for in-flight response delivery.

Constructor Detail

ImageLoader

public ImageLoader(RequestQueue queue,
                   ImageLoader.ImageCache imageCache)

Constructs a new ImageLoader.

Parameters:

queue - The RequestQueue to use for making image requests.

imageCache - The cache to use as an L1 cache.

Method Detail

getImageListener

public static ImageLoader.ImageListener getImageListener(ImageView view,
                                                         int defaultImageResId,
                                                         int errorImageResId)

The default implementation of ImageListener which handles basic functionality of showing a default image until the network response is received, at which point it will switch to either the actual image or the error image.

Parameters:

view - The imageView that the listener is associated with.

defaultImageResId - Default image resource ID to use, or 0 if it doesn't exist.

errorImageResId - Error image resource ID to use, or 0 if it doesn't exist.

isCached

public boolean isCached(java.lang.String requestUrl,
                        int maxWidth,
                        int maxHeight)

Checks if the item is available in the cache.

Parameters:

requestUrl - The url of the remote image

maxWidth - The maximum width of the returned image.

maxHeight - The maximum height of the returned image.

Returns:

True if the item exists in cache, false otherwise.

get

public ImageLoader.ImageContainer get(java.lang.String requestUrl,
                                      ImageLoader.ImageListener listener)

Returns an ImageContainer for the requested URL. The ImageContainer will contain either the specified default bitmap or the loaded bitmap. If the default was returned, the ImageLoader will be invoked when the request is fulfilled.

Parameters:

requestUrl - The URL of the image to be loaded.

get

public ImageLoader.ImageContainer get(java.lang.String requestUrl,
                                      ImageLoader.ImageListener imageListener,
                                      int maxWidth,
                                      int maxHeight)

Issues a bitmap request with the given URL if that image is not available in the cache, and returns a bitmap container that contains all of the data relating to the request (as well as the default image if the requested image is not available).

Parameters:

requestUrl - The url of the remote image

imageListener - The listener to call when the remote image is loaded

maxWidth - The maximum width of the returned image.

maxHeight - The maximum height of the returned image.

Returns:

A container object that contains all of the properties of the request, as well as the currently available image (default if remote is not loaded).

setBatchedResponseDelay

public void setBatchedResponseDelay(int newBatchedResponseDelayMs)

Sets the amount of time to wait after the first response arrives before delivering all responses. Batching can be disabled entirely by passing in 0.

Parameters:

newBatchedResponseDelayMs - The time in milliseconds to wait.

onGetImageSuccess

private void onGetImageSuccess(java.lang.String cacheKey,
                               Bitmap response)

Handler for when an image was successfully loaded.

Parameters:

cacheKey - The cache key that is associated with the image request.

response - The bitmap that was returned from the network.

onGetImageError

private void onGetImageError(java.lang.String cacheKey,
                             VolleyError error)

Handler for when an image failed to load.

Parameters:

cacheKey - The cache key that is associated with the image request.

batchResponse

private void batchResponse(java.lang.String cacheKey,
                           ImageLoader.BatchedImageRequest request)

Starts the runnable for batched delivery of responses if it is not already started.

Parameters:

cacheKey - The cacheKey of the response being delivered.

request - The BatchedImageRequest to be delivered.

throwIfNotOnMainThread

private void throwIfNotOnMainThread()

getCacheKey

private static java.lang.String getCacheKey(java.lang.String url,
                                            int maxWidth,
                                            int maxHeight)

Creates a cache key for use with the L1 cache.

Parameters:

url - The URL of the request.

maxWidth - The max-width of the output.

maxHeight - The max-height of the output.