如何获得完成回调的setImageUrl与排球图书馆和NetworkImageView？

问题描述

我尝试了谷歌的新排球图书馆和它看起来锐利和负荷影像很快，当我用这个方法 setImageUrl ：

I'm trying out the Google's new Volley library and it's looking sharp and loads images quickly when I use this method setImageUrl:

holder.image.setImageUrl(url, ImageCacheManager.getInstance().getImageLoader());

我想给它添加一个回调/监听器方法，当加载完成后，将火起来，这样我就可以删除进度视图，并显示图像。这是存在于选项通用图像装载机和毕加索库，但由于某种原因，我无法找到一个方法来做到这一点的排球，试图谷歌不同的选择但到目前为止，还没有发现任何引用。

I want to add to it a call back/listener method that will fire up when loading is finished,so I can remove the progressBar view and show the image.It's an option that exists in Universal Image Loader and Picasso libraries, butfor some reason I can't find a way to do that in Volley, tried to Google different optionsbut so far haven't found any reference.

做一些具有code示例来说明如何做？

Does some has a code sample to illustrate how it's done?

在此先感谢。

推荐答案

您可以使用此视图，而不是谷歌的观点（我已经复制从它的来源，并做了一些改动）：

You can use this View instead of Google's View (I've copied sources from it and made some changes):

public class VolleyImageView extends ImageView {

    public interface ResponseObserver
    {
        public void onError();
        public void onSuccess();
    }

    private ResponseObserver mObserver;

    public void setResponseObserver(ResponseObserver observer) {
        mObserver = observer;
    }

    /**
     * The URL of the network image to load
     */
    private String mUrl;

    /**
     * Resource ID of the image to be used as a placeholder until the network image is loaded.
     */
    private int mDefaultImageId;

    /**
     * Resource ID of the image to be used if the network response fails.
     */
    private int mErrorImageId;

    /**
     * Local copy of the ImageLoader.
     */
    private ImageLoader mImageLoader;

    /**
     * Current ImageContainer. (either in-flight or finished)
     */
    private ImageContainer mImageContainer;

    public VolleyImageView(Context context) {
        this(context, null);
    }

    public VolleyImageView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public VolleyImageView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    /**
     * Sets URL of the image that should be loaded into this view. Note that calling this will
     * immediately either set the cached image (if available) or the default image specified by
     * {@link VolleyImageView#setDefaultImageResId(int)} on the view.
     *
     * NOTE: If applicable, {@link VolleyImageView#setDefaultImageResId(int)} and {@link
     * VolleyImageView#setErrorImageResId(int)} should be called prior to calling this function.
     *
     * @param url         The URL that should be loaded into this ImageView.
     * @param imageLoader ImageLoader that will be used to make the request.
     */
    public void setImageUrl(String url, ImageLoader imageLoader) {
        mUrl = url;
        mImageLoader = imageLoader;
        // The URL has potentially changed. See if we need to load it.
        loadImageIfNecessary(false);
    }

    /**
     * Sets the default image resource ID to be used for this view until the attempt to load it
     * completes.
     */
    public void setDefaultImageResId(int defaultImage) {
        mDefaultImageId = defaultImage;
    }

    /**
     * Sets the error image resource ID to be used for this view in the event that the image
     * requested fails to load.
     */
    public void setErrorImageResId(int errorImage) {
        mErrorImageId = errorImage;
    }

    /**
     * Loads the image for the view if it isn't already loaded.
     *
     * @param isInLayoutPass True if this was invoked from a layout pass, false otherwise.
     */
    private void loadImageIfNecessary(final boolean isInLayoutPass) {
        int width = getWidth();
        int height = getHeight();

        boolean isFullyWrapContent = getLayoutParams() != null
                && getLayoutParams().height == LayoutParams.WRAP_CONTENT
                && getLayoutParams().width == LayoutParams.WRAP_CONTENT;
        // if the view's bounds aren't known yet, and this is not a wrap-content/wrap-content
        // view, hold off on loading the image.
        if (width == 0 && height == 0 && !isFullyWrapContent) {
            return;
        }

        // if the URL to be loaded in this view is empty, cancel any old requests and clear the
        // currently loaded image.
        if (TextUtils.isEmpty(mUrl)) {
            if (mImageContainer != null) {
                mImageContainer.cancelRequest();
                mImageContainer = null;
            }
            setDefaultImageOrNull();
            return;
        }

        // if there was an old request in this view, check if it needs to be canceled.
        if (mImageContainer != null && mImageContainer.getRequestUrl() != null) {
            if (mImageContainer.getRequestUrl().equals(mUrl)) {
                // if the request is from the same URL, return.
                return;
            } else {
                // if there is a pre-existing request, cancel it if it's fetching a different URL.
                mImageContainer.cancelRequest();
                setDefaultImageOrNull();
            }
        }

        // The pre-existing content of this view didn't match the current URL. Load the new image
        // from the network.
        ImageContainer newContainer = mImageLoader.get(mUrl,
                new ImageListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        if (mErrorImageId != 0) {
                            setImageResource(mErrorImageId);
                        }

                        if(mObserver!=null)
                        {
                            mObserver.onError();
                        }
                    }

                    @Override
                    public void onResponse(final ImageContainer response, boolean isImmediate) {
                        // If this was an immediate response that was delivered inside of a layout
                        // pass do not set the image immediately as it will trigger a requestLayout
                        // inside of a layout. Instead, defer setting the image by posting back to
                        // the main thread.
                        if (isImmediate && isInLayoutPass) {
                            post(new Runnable() {
                                @Override
                                public void run() {
                                    onResponse(response, false);
                                }
                            });
                            return;
                        }

                        if (response.getBitmap() != null) {
                            setImageBitmap(response.getBitmap());
                        } else if (mDefaultImageId != 0) {
                            setImageResource(mDefaultImageId);
                        }

                        if(mObserver!=null)
                        {
                            mObserver.onSuccess();
                        }
                    }
                });

        // update the ImageContainer to be the new bitmap container.
        mImageContainer = newContainer;
    }

    private void setDefaultImageOrNull() {
        if (mDefaultImageId != 0) {
            setImageResource(mDefaultImageId);
        } else {
            setImageBitmap(null);
        }
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        loadImageIfNecessary(true);
    }

    @Override
    protected void onDetachedFromWindow() {
        if (mImageContainer != null) {
            // If the view was bound to an image request, cancel it and clear
            // out the image from the view.
            mImageContainer.cancelRequest();
            setImageBitmap(null);
            // also clear out the container so we can reload the image if necessary.
            mImageContainer = null;
        }
        super.onDetachedFromWindow();
    }

    @Override
    protected void drawableStateChanged() {
        super.drawableStateChanged();
        invalidate();
    }
}

用例：

 //set observer to view
 holder.image.setResponseObserver(new VolleyImageView.ResponseObserver() {
     @Override
     public void onError() {

     }

     @Override
     public void onSuccess() {

     }
 });

//and then load image
holder.image.setImageUrl(url, ImageCacheManager.getInstance().getImageLoader());

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