Java tutorial
package com.azcltd.android.test.kolesov; //http://stackoverflow.com/questions/541966/how-do-i-do-a-lazy-load-of-images-in-listview/3068012#3068012 /* Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you 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. */ import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.drawable.BitmapDrawable; import android.graphics.drawable.Drawable; import android.os.Handler; import android.os.Message; import android.util.Log; import android.widget.ImageView; import org.apache.http.HttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.DefaultHttpClient; import java.io.IOException; import java.io.InputStream; import java.net.MalformedURLException; import java.net.URL; import java.util.HashMap; import java.util.Map; //http://stackoverflow.com/questions/541966/how-do-i-do-a-lazy-load-of-images-in-listview/3068012#3068012 public class DrawableManager { private static final Map<String, Drawable> drawableMap = new HashMap<String, Drawable>(); public static final Map<String, Drawable> GetDrawableMap() { return drawableMap; } public DrawableManager() { // drawableMap = new HashMap<String, Drawable>(); } public Drawable fetchDrawable(String urlString, boolean isForceUpdate) { if (drawableMap.containsKey(urlString) && (!isForceUpdate)) { return drawableMap.get(urlString); } //Log.d(this.getClass().getSimpleName(), "image url:" + urlString); Drawable drawable = null; try { InputStream is = fetch(urlString); drawable = Drawable.createFromStream(is, "src"); is.close(); if (drawable != null) { drawableMap.put(urlString, drawable); // Log.d(this.getClass().getSimpleName(), "got a thumbnail drawable: " + drawable.getBounds() + ", " // + drawable.getIntrinsicHeight() + "," + drawable.getIntrinsicWidth() + ", " // + drawable.getMinimumHeight() + "," + drawable.getMinimumWidth()); } else { drawable = getAsBitmap(urlString); // else // Log.w(urlString, "could not get thumbnail"); } return drawable; } catch (MalformedURLException e) { //Log.e(this.getClass().getSimpleName(), "fetchDrawable failed", e); return null; } catch (IOException e) { //Log.e(this.getClass().getSimpleName(), "fetchDrawable failed", e); return null; } catch (Exception e) { drawable = getAsBitmap(urlString); } return drawable; } private Drawable getAsBitmap(String urlString) { try { InputStream is1 = (InputStream) new URL(urlString).getContent(); Bitmap d = BitmapFactory.decodeStream(is1); is1.close(); Drawable drawable = new BitmapDrawable(d); if (d != null) drawableMap.put(urlString, drawable); return drawable; } catch (Exception e1) { int i = 1; } return null; } private Drawable getThumbnail(Drawable image) { if (image != null) { Bitmap b = ((BitmapDrawable) image).getBitmap(); float coef = (float) b.getWidth() / (float) b.getHeight(); Bitmap bitmapResized = Bitmap.createScaledBitmap(b, (int) (100 * coef), 100, false); return new BitmapDrawable(bitmapResized); } return null; } public void fetchDrawableOnThreadWithNoImage(final String urlString, final ImageView imageView, final boolean isThumbnail) { fetchDrawableOnThread(urlString, imageView, false, false); if (imageView.getDrawable() == null) { //fetchDrawableOnThread(urlString, imageView, false, true); //if(imageView.getDrawable() == null) { if (imageView.getTag(0) != isErrorImageKey) { fetchDrawableOnThread("http://www.wildcatpad.com/images/wutu.jpg", imageView, false, false); imageView.setTag(0, isErrorImageKey); } // else // { // fetchDrawableOnThread(urlString, imageView, false, true); // imageView.setTag(0, ""); // } } } } public static final String isErrorImageKey = "isErrorImage"; public void fetchDrawableOnThread(final String urlString, final ImageView imageView, final boolean isThumbnail, final boolean forceUpdate) { if (drawableMap.containsKey(urlString) && !forceUpdate) { Drawable image = drawableMap.get(urlString); SetDrawableToImageView(image, imageView, isThumbnail); return; } final Handler handler = new Handler() { @Override public void handleMessage(Message message) { DrawableWithFlag obj = (DrawableWithFlag) message.obj; Drawable image = obj.image; boolean flag = obj.isNeedThumbnailed; SetDrawableToImageView(image, imageView, flag); } }; Thread thread = new Thread() { @Override public void run() { //setPriority(3); Drawable drawable = fetchDrawable(urlString, forceUpdate); if (drawable != null) { Message message = handler.obtainMessage(1, new DrawableWithFlag(drawable, isThumbnail)); handler.sendMessage(message); // try{ // //sleep(100); // } // catch(Exception ex) { // int i =0; // } } } }; thread.start(); } private void SetDrawableToImageView(Drawable image, ImageView imageView, boolean isNeedThumbnailed) { if (isNeedThumbnailed && (image != null)) { image = getThumbnail(image); } if (image != null) { imageView.setImageDrawable(image); } } class DrawableWithFlag { Drawable image; boolean isNeedThumbnailed; public DrawableWithFlag(Drawable mImage, boolean mIsNeedThumbnailed) { image = mImage; isNeedThumbnailed = mIsNeedThumbnailed; } } private InputStream fetch(String urlString) throws MalformedURLException, IOException { DefaultHttpClient httpClient = new DefaultHttpClient(); HttpGet request = new HttpGet(urlString); HttpResponse response = httpClient.execute(request); return response.getEntity().getContent(); } }