Android Open Source - volley Image Request

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The source code is released under:
Apache License
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Java Source Code

/*
 * Copyright (C) 2011 The Android Open Source Project
 *//  w  w  w. j  a v  a 2 s. c  om
 * 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.android.volley.toolbox;

import java.io.InputStream;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.webkit.URLUtil;

import com.android.volley.DefaultRetryPolicy;
import com.android.volley.NetworkResponse;
import com.android.volley.ParseError;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyLog;

/**
 * A canned request for getting an image at a given URL and calling
 * back with a decoded Bitmap.
 */
public class ImageRequest extends Request<Bitmap> {
    /** Socket timeout in milliseconds for image requests */
    private static final int IMAGE_TIMEOUT_MS = 3000;

    /** Default number of retries for image requests */
    private static final int IMAGE_MAX_RETRIES = 2;

    /** Default backoff multiplier for image requests */
    private static final float IMAGE_BACKOFF_MULT = 2f;

    private final Response.Listener<Bitmap> mListener;
    private final Config mDecodeConfig;
    private final int mMaxWidth;
    private final int mMaxHeight;
    
    private Context mContext;

    /** Decoding lock so that we don't decode more than one image at a time (to avoid OOM's) */
    private static final Object sDecodeLock = new Object();

    /**
     * Creates a new image request, decoding to a maximum specified width and
     * height. If both width and height are zero, the image will be decoded to
     * its natural size. If one of the two is nonzero, that dimension will be
     * clamped and the other one will be set to preserve the image's aspect
     * ratio. If both width and height are nonzero, the image will be decoded to
     * be fit in the rectangle of dimensions width x height while keeping its
     * aspect ratio.
     *
     * @param url URL of the image
     * @param listener Listener to receive the decoded bitmap
     * @param maxWidth Maximum width to decode this bitmap to, or zero for none
     * @param maxHeight Maximum height to decode this bitmap to, or zero for
     *            none
     * @param decodeConfig Format to decode the bitmap to
     * @param errorListener Error listener, or null to ignore errors
     */
    public ImageRequest(Context context,String url, Response.Listener<Bitmap> listener, int maxWidth, int maxHeight,
            Config decodeConfig, Response.ErrorListener errorListener) {
        super(Method.GET, url, errorListener);
        setRetryPolicy(
                new DefaultRetryPolicy(IMAGE_TIMEOUT_MS, IMAGE_MAX_RETRIES, IMAGE_BACKOFF_MULT));
        mListener = listener;
        mDecodeConfig = decodeConfig;
        mMaxWidth = maxWidth;
        mMaxHeight = maxHeight;
        mContext = context;
        // ???????????????????????disk-cache???
        if (url.startsWith("http") || url.startsWith("https")) {
            setShouldCache(true);
        } else {
            setShouldCache(false);
        }
    }

    @Override
    public Priority getPriority() {
        return Priority.HIGH;
    }

    /**
     * Scales one side of a rectangle to fit aspect ratio.
     *
     * @param maxPrimary Maximum size of the primary dimension (i.e. width for
     *        max width), or zero to maintain aspect ratio with secondary
     *        dimension
     * @param maxSecondary Maximum size of the secondary dimension, or zero to
     *        maintain aspect ratio with primary dimension
     * @param actualPrimary Actual size of the primary dimension
     * @param actualSecondary Actual size of the secondary dimension
     */
//    private static int getResizedDimension(int maxPrimary, int maxSecondary, int actualPrimary,
//            int actualSecondary) {
//        // If no dominant value at all, just return the actual.
//        if (maxPrimary == 0 && maxSecondary == 0) {
//            return actualPrimary;
//        }
//
//        // If primary is unspecified, scale primary to match secondary's scaling ratio.
//        if (maxPrimary == 0) {
//            double ratio = (double) maxSecondary / (double) actualSecondary;
//            return (int) (actualPrimary * ratio);
//        }
//
//        if (maxSecondary == 0) {
//            return maxPrimary;
//        }
//
//        double ratio = (double) actualSecondary / (double) actualPrimary;
//        int resized = maxPrimary;
//        if (resized * ratio > maxSecondary) {
//            resized = (int) (maxSecondary / ratio);
//        }
//        return resized;
//    }

    @Override
    protected Response<Bitmap> parseNetworkResponse(NetworkResponse response) {
        // Serialize all decode on a global lock to reduce concurrent heap usage.
        synchronized (sDecodeLock) {
            try {
                return doParse(response);
            } catch (OutOfMemoryError e) {
                VolleyLog.e("Caught OOM for %d byte image, url=%s", response.data.length, getUrl());
                return Response.error(new ParseError(e));
            }
        }
    }

    /**
     * The real guts of parseNetworkResponse. Broken out for readability.
     */
    private Response<Bitmap> doParse(NetworkResponse response) {
        Bitmap bitmap = null;
        if (URLUtil.isNetworkUrl(getUrl())) {
            byte[] data = response.data;
            bitmap = BitmapDecoder.bytes2Bitmap(data, mDecodeConfig, mMaxWidth, mMaxHeight);
        } else {
            InputStream is = BitmapDecoder.getInputStream(mContext, getUrl());
            bitmap = BitmapDecoder.inputStream2Bitmap(mContext, getUrl(),is, mDecodeConfig, mMaxWidth, mMaxHeight);
        }
//        BitmapFactory.Options decodeOptions = new BitmapFactory.Options();
//        Bitmap bitmap = null;
//        if (mMaxWidth == 0 && mMaxHeight == 0) {
//            decodeOptions.inPreferredConfig = mDecodeConfig;
//            bitmap = BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
//        } else {
//            // If we have to resize this image, first get the natural bounds.
//            decodeOptions.inJustDecodeBounds = true;
//            BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
//            int actualWidth = decodeOptions.outWidth;
//            int actualHeight = decodeOptions.outHeight;
//
//            // Then compute the dimensions we would ideally like to decode to.
//            int desiredWidth = getResizedDimension(mMaxWidth, mMaxHeight,
//                    actualWidth, actualHeight);
//            int desiredHeight = getResizedDimension(mMaxHeight, mMaxWidth,
//                    actualHeight, actualWidth);
//
//            // Decode to the nearest power of two scaling factor.
//            decodeOptions.inJustDecodeBounds = false;
//            // TODO(ficus): Do we need this or is it okay since API 8 doesn't support it?
//            // decodeOptions.inPreferQualityOverSpeed = PREFER_QUALITY_OVER_SPEED;
//            decodeOptions.inSampleSize =
//                findBestSampleSize(actualWidth, actualHeight, desiredWidth, desiredHeight);
//            Bitmap tempBitmap =
//                BitmapFactory.decodeByteArray(data, 0, data.length, decodeOptions);
//
//            // If necessary, scale down to the maximal acceptable size.
//            if (tempBitmap != null && (tempBitmap.getWidth() > desiredWidth ||
//                    tempBitmap.getHeight() > desiredHeight)) {
//                bitmap = Bitmap.createScaledBitmap(tempBitmap,
//                        desiredWidth, desiredHeight, true);
//                tempBitmap.recycle();
//            } else {
//                bitmap = tempBitmap;
//            }
//        }

        if (bitmap == null) {
            return Response.error(new ParseError(response));
        } else {
            return Response.success(bitmap, HttpHeaderParser.parseCacheHeaders(response));
        }
    }

    @Override
    protected void deliverResponse(Bitmap response) {
        mListener.onResponse(response);
    }

    /**
     * Returns the largest power-of-two divisor for use in downscaling a bitmap
     * that will not result in the scaling past the desired dimensions.
     *
     * @param actualWidth Actual width of the bitmap
     * @param actualHeight Actual height of the bitmap
     * @param desiredWidth Desired width of the bitmap
     * @param desiredHeight Desired height of the bitmap
     */
    // Visible for testing.
//    static int findBestSampleSize(
//            int actualWidth, int actualHeight, int desiredWidth, int desiredHeight) {
//        double wr = (double) actualWidth / desiredWidth;
//        double hr = (double) actualHeight / desiredHeight;
//        double ratio = Math.min(wr, hr);
//        float n = 1.0f;
//        while ((n * 2) <= ratio) {
//            n *= 2;
//        }
//
//        return (int) n;
//    }
}
Java Source Code List
