NetworkImageView.java revision da703141dabd9cae3f71e15a4b9cbb79f6d5d4b8 
1/**
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16package com.android.volley.toolbox;
17
18import android.content.Context;
19import android.text.TextUtils;
20import android.util.AttributeSet;
21import android.widget.ImageView;
22
23import com.android.volley.toolbox.ImageLoader.ImageContainer;
24
25/**
26 * Handles fetching an image from a URL as well as the life-cycle of the
27 * associated request.
28 */
29public class NetworkImageView extends ImageView {
30    /** The URL of the network image to load */
31    private String mUrl;
32
33    /**
34     * Resource ID of the image to be used as a placeholder until the network image is loaded.
35     */
36    private int mDefaultImageId;
37
38    /**
39     * Resource ID of the image to be used if the network response fails.
40     */
41    private int mErrorImageId;
42
43    /** Local copy of the ImageLoader. */
44    private ImageLoader mImageLoader;
45
46    /** Current ImageContainer. (either in-flight or finished) */
47    private ImageContainer mImageContainer;
48
49    public NetworkImageView(Context context) {
50        this(context, null);
51    }
52
53    public NetworkImageView(Context context, AttributeSet attrs) {
54        this(context, attrs, 0);
55    }
56
57    public NetworkImageView(Context context, AttributeSet attrs, int defStyle) {
58        super(context, attrs, defStyle);
59    }
60
61    /**
62     * Sets URL of the image that should be loaded into this view. Note that calling this will
63     * immediately either set the cached image (if available) or the default image specified by
64     * {@link NetworkImageView#setDefaultImageResId(int)} on the view.
65     *
66     * NOTE: If applicable, {@link NetworkImageView#setDefaultImageResId(int)} and
67     * {@link NetworkImageView#setErrorImageResId(int)} should be called prior to calling
68     * this function.
69     *
70     * @param url The URL that should be loaded into this ImageView.
71     * @param imageLoader ImageLoader that will be used to make the request.
72     */
73    public void setImageUrl(String url, ImageLoader imageLoader) {
74        mUrl = url;
75        mImageLoader = imageLoader;
76        // The URL has potentially changed. See if we need to load it.
77        loadImageIfNecessary();
78    }
79
80    /**
81     * Sets the default image resource ID to be used for this view until the attempt to load it
82     * completes.
83     */
84    public void setDefaultImageResId(int defaultImage) {
85        mDefaultImageId = defaultImage;
86    }
87
88    /**
89     * Sets the error image resource ID to be used for this view in the event that the image
90     * requested fails to load.
91     */
92    public void setErrorImageResId(int errorImage) {
93        mErrorImageId = errorImage;
94    }
95
96    /**
97     * Loads the image for the view if it isn't already loaded.
98     */
99    private void loadImageIfNecessary() {
100        int width = getWidth();
101        int height = getHeight();
102
103        // if the view's bounds aren't known yet, hold off on loading the image.
104        if (width == 0 && height == 0) {
105            return;
106        }
107
108        // if the URL to be loaded in this view is empty, cancel any old requests and clear the
109        // currently loaded image.
110        if (TextUtils.isEmpty(mUrl)) {
111            if (mImageContainer != null) {
112                mImageContainer.cancelRequest();
113                mImageContainer = null;
114            }
115            setImageBitmap(null);
116            return;
117        }
118
119        // if there was an old request in this view, check if it needs to be canceled.
120        if (mImageContainer != null && mImageContainer.getRequestUrl() != null) {
121            if (mImageContainer.getRequestUrl().equals(mUrl)) {
122                // if the request is from the same URL, return.
123                return;
124            } else {
125                // if there is a pre-existing request, cancel it if it's fetching a different URL.
126                mImageContainer.cancelRequest();
127                setImageBitmap(null);
128            }
129        }
130
131        // The pre-existing content of this view didn't match the current URL. Load the new image
132        // from the network.
133        ImageContainer newContainer = mImageLoader.get(mUrl,
134                ImageLoader.getImageListener(this, mDefaultImageId, mErrorImageId));
135
136        // update the ImageContainer to be the new bitmap container.
137        mImageContainer = newContainer;
138    }
139
140    @Override
141    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
142        super.onLayout(changed, left, top, right, bottom);
143        loadImageIfNecessary();
144    }
145
146    @Override
147    protected void onDetachedFromWindow() {
148        if (mImageContainer != null) {
149            // If the view was bound to an image request, cancel it and clear
150            // out the image from the view.
151            mImageContainer.cancelRequest();
152            setImageBitmap(null);
153            // also clear out the container so we can reload the image if necessary.
154            mImageContainer = null;
155        }
156        super.onDetachedFromWindow();
157    }
158
159    @Override
160    protected void drawableStateChanged() {
161        super.drawableStateChanged();
162        invalidate();
163    }
164}
165