content: /**
   * Copyright (C) 2013 The Android Open Source Project
   *
   * 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.cjj.volley.toolbox;
  
  import android.content.Context;
  import android.text.TextUtils;
  import android.util.AttributeSet;
  import android.view.ViewGroup.LayoutParams;
  import android.widget.ImageView;
  
  import com.cjj.volley.VolleyError;
  import com.cjj.volley.toolbox.ImageLoader.ImageContainer;
  import com.cjj.volley.toolbox.ImageLoader.ImageListener;
  
  /**
   * Handles fetching an image from a URL as well as the life-cycle of the
   * associated request.
   */
  public class NetworkImageView extends ImageView {
      /** 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 NetworkImageView(Context context) {
          this(context, null);
      }
  
      public NetworkImageView(Context context, AttributeSet attrs) {
          this(context, attrs, 0);
      }
  
      public NetworkImageView(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 NetworkImageView#setDefaultImageResId(int)} on the view.
       *
       * NOTE: If applicable, {@link NetworkImageView#setDefaultImageResId(int)} and
       * {@link NetworkImageView#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.
       */
      void loadImageIfNecessary(final boolean isInLayoutPass) {
          int width = getWidth();
          int height = getHeight();
  
          boolean wrapWidth = false, wrapHeight = false;
          if (getLayoutParams() != null) {
              wrapWidth = getLayoutParams().width == LayoutParams.WRAP_CONTENT;
              wrapHeight = getLayoutParams().height == 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.
          boolean isFullyWrapContent = wrapWidth && wrapHeight;
          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();
              }
          }
  
          // Calculate the max image width / height to use while ignoring WRAP_CONTENT dimens.
          int maxWidth = wrapWidth ? 0 : width;
          int maxHeight = wrapHeight ? 0 : height;
  
          // 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);
                          }
                      }
  
                      @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);
                          }
                      }
                  }, maxWidth, maxHeight);
  
          // 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();
      }
  }
  