Java tutorial
/* * Copyright (C) 2012 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.tangjd.displayingbitmaps.util; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.net.ConnectivityManager; import android.net.NetworkInfo; import android.os.Build; import android.support.v4.BuildConfig; import android.widget.Toast; import com.tangjd.common.utils.Log; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileDescriptor; import java.io.FileInputStream; import java.io.IOException; import java.io.OutputStream; import java.net.HttpURLConnection; import java.net.URL; /** * A simple subclass of {@link ImageResizer} that fetches and resizes images fetched from a URL. */ public class ImageFetcher extends ImageResizer { private static final String TAG = "ImageFetcher"; private static final int HTTP_CACHE_SIZE = 10 * 1024 * 1024; // 10MB private static final String HTTP_CACHE_DIR = "http"; private static final int IO_BUFFER_SIZE = 8 * 1024; private DiskLruCache mHttpDiskCache; private File mHttpCacheDir; private boolean mHttpDiskCacheStarting = true; private final Object mHttpDiskCacheLock = new Object(); private static final int DISK_CACHE_INDEX = 0; /** * Initialize providing a target image width and height for the processing images. * * @param context * @param imageWidth * @param imageHeight */ public ImageFetcher(Activity context, int imageWidth, int imageHeight) { super(context, imageWidth, imageHeight); init(context); } /** * Initialize providing a single target image size (used for both width and height); * * @param context * @param imageSize */ public ImageFetcher(Activity context, int imageSize) { super(context, imageSize); init(context); } private void init(Activity context) { checkConnection(context); mHttpCacheDir = ImageCache.getDiskCacheDir(context, HTTP_CACHE_DIR); } @Override protected void initDiskCacheInternal() { super.initDiskCacheInternal(); initHttpDiskCache(); } private void initHttpDiskCache() { if (!mHttpCacheDir.exists()) { mHttpCacheDir.mkdirs(); } synchronized (mHttpDiskCacheLock) { if (ImageCache.getUsableSpace(mHttpCacheDir) > HTTP_CACHE_SIZE) { try { mHttpDiskCache = DiskLruCache.open(mHttpCacheDir, 1, 1, HTTP_CACHE_SIZE); if (BuildConfig.DEBUG) { Log.d(TAG, "HTTP cache initialized"); } } catch (IOException e) { mHttpDiskCache = null; } } mHttpDiskCacheStarting = false; mHttpDiskCacheLock.notifyAll(); } } @Override protected void clearCacheInternal() { super.clearCacheInternal(); synchronized (mHttpDiskCacheLock) { if (mHttpDiskCache != null && !mHttpDiskCache.isClosed()) { try { mHttpDiskCache.delete(); if (BuildConfig.DEBUG) { Log.d(TAG, "HTTP cache cleared"); } } catch (IOException e) { Log.e(TAG, "clearCacheInternal - " + e); } mHttpDiskCache = null; mHttpDiskCacheStarting = true; initHttpDiskCache(); } } } @Override protected void flushCacheInternal() { super.flushCacheInternal(); synchronized (mHttpDiskCacheLock) { if (mHttpDiskCache != null) { try { mHttpDiskCache.flush(); if (BuildConfig.DEBUG) { Log.d(TAG, "HTTP cache flushed"); } } catch (IOException e) { Log.e(TAG, "flush - " + e); } } } } @Override protected void closeCacheInternal() { super.closeCacheInternal(); synchronized (mHttpDiskCacheLock) { if (mHttpDiskCache != null) { try { if (!mHttpDiskCache.isClosed()) { mHttpDiskCache.close(); mHttpDiskCache = null; if (BuildConfig.DEBUG) { Log.d(TAG, "HTTP cache closed"); } } } catch (IOException e) { Log.e(TAG, "closeCacheInternal - " + e); } } } } /** * Simple network connection check. * * @param context */ private void checkConnection(Context context) { final ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); final NetworkInfo networkInfo = cm.getActiveNetworkInfo(); if (networkInfo == null || !networkInfo.isConnectedOrConnecting()) { Toast.makeText(context, "!", Toast.LENGTH_LONG).show(); Log.e(TAG, "checkConnection - no connection found"); } } /** * The main process method, which will be called by the ImageWorker in the AsyncTask background * thread. * * @param url The url to load the bitmap, in this case, a regular http URL * @return The downloaded and resized bitmap */ private Bitmap processBitmap(String url) { if (BuildConfig.DEBUG) { Log.d(TAG, "processBitmap - " + url); } final String key = ImageCache.hashKeyForDisk(url); FileDescriptor fileDescriptor = null; FileInputStream fileInputStream = null; DiskLruCache.Snapshot snapshot; synchronized (mHttpDiskCacheLock) { // Wait for disk cache to initialize while (mHttpDiskCacheStarting) { try { mHttpDiskCacheLock.wait(); } catch (InterruptedException e) { } } if (mHttpDiskCache != null) { try { snapshot = mHttpDiskCache.get(key); if (snapshot == null) { Log.e(TAG, "doInBackground - not found in http cache, downloading..."); DiskLruCache.Editor editor = mHttpDiskCache.edit(key); if (editor != null) { if (downloadUrlToStream(url, editor.newOutputStream(DISK_CACHE_INDEX))) { editor.commit(); } else { editor.abort(); } } snapshot = mHttpDiskCache.get(key); } else { Log.e(TAG, "doInBackground - http disk cache hit"); } if (snapshot != null) { fileInputStream = (FileInputStream) snapshot.getInputStream(DISK_CACHE_INDEX); fileDescriptor = fileInputStream.getFD(); } } catch (IOException e) { Log.e(TAG, "processBitmap - " + e); } catch (IllegalStateException e) { Log.e(TAG, "processBitmap - " + e); } finally { if (fileDescriptor == null && fileInputStream != null) { try { fileInputStream.close(); } catch (IOException e) { } } } } } Bitmap bitmap = null; if (fileDescriptor != null) { bitmap = decodeSampledBitmapFromDescriptor(fileDescriptor, mImageWidth, mImageHeight, getImageCache()); } if (fileInputStream != null) { try { fileInputStream.close(); } catch (IOException e) { } } return bitmap; } @Override protected Bitmap processBitmap(Object data) { return processBitmap(String.valueOf(data)); } /** * Download a bitmap from a URL and write the content to an output stream. * * @param urlString The URL to fetch * @return true if successful, false otherwise */ public boolean downloadUrlToStream(String urlString, OutputStream outputStream) { disableConnectionReuseIfNecessary(); HttpURLConnection urlConnection = null; BufferedOutputStream out = null; BufferedInputStream in = null; try { final URL url = new URL(urlString); urlConnection = (HttpURLConnection) url.openConnection(); in = new BufferedInputStream(urlConnection.getInputStream(), IO_BUFFER_SIZE); out = new BufferedOutputStream(outputStream, IO_BUFFER_SIZE); int b; while ((b = in.read()) != -1) { out.write(b); } return true; } catch (final IOException e) { Log.e(TAG, "Error in downloadBitmap - " + e + " Url: " + urlString); } finally { if (urlConnection != null) { urlConnection.disconnect(); } try { if (out != null) { out.close(); } if (in != null) { in.close(); } } catch (final IOException e) { } } return false; } /** * Workaround for bug pre-Froyo, see here for more info: * http://android-developers.blogspot.com/2011/09/androids-http-clients.html */ public static void disableConnectionReuseIfNecessary() { // HTTP connection reuse which was buggy pre-froyo if (Build.VERSION.SDK_INT < Build.VERSION_CODES.FROYO) { System.setProperty("http.keepAlive", "false"); } } }