Android 遠程圖片擷取和本機快取（三）

   從緩衝中擷取資料：

java代碼：

1. /**
2. * 從緩衝中擷取圖片
3. */
4. private Bitmap getBitmapFromCache(Stringurl) {
5. // 先從mHardBitmapCache緩衝中擷取
6. synchronized (mHardBitmapCache) {
7. final Bitmap bitmap =mHardBitmapCache.get(url);
8. if (bitmap != null) {
9. //如果找到的話，把元素移到linkedhashmap的最前面，從而保證在LRU演算法中是最後被刪除
10. mHardBitmapCache.remove(url);
11. mHardBitmapCache.put(url,bitmap);
12. return bitmap;
13. }
14. }
15. //如果mHardBitmapCache中找不到，到mSoftBitmapCache中找
16. SoftReference<Bitmap>bitmapReference = mSoftBitmapCache.get(url);
17. if (bitmapReference != null) {
18. final Bitmap bitmap =bitmapReference.get();
19. if (bitmap != null) {
20. return bitmap;
21. } else {
22. mSoftBitmapCache.remove(url);
23. }
24. }
25. return null;
26. }

複製代碼

       如果緩衝中不存在，那麼就只能去伺服器端去下載：

java代碼：

1. /**
2. * 非同步下載圖片
3. */
4. class ImageDownloaderTask extendsAsyncTask<String, Void, Bitmap> {
5. private static final int IO_BUFFER_SIZE= 4 * 1024;
6. private String url;
7. private finalWeakReference<ImageView> imageViewReference;
8. public ImageDownloaderTask(ImageViewimageView) {
9. imageViewReference = newWeakReference<ImageView>(imageView);
10. }
12. @Override
13. protected BitmapdoInBackground(String... params) {
14. final AndroidHttpClient client =AndroidHttpClient.newInstance("Android");
15. url = params[0];
16. final HttpGet getRequest = newHttpGet(url);
17. try {
18. HttpResponse response =client.execute(getRequest);
19. final int statusCode =response.getStatusLine().getStatusCode();
20. if (statusCode !=HttpStatus.SC_OK) {
21. Log.w(TAG, "從" +url + "中下載圖片時出錯!,錯誤碼:" + statusCode);
22. return null;
23. }
24. final HttpEntity entity =response.getEntity();
25. if (entity != null) {
26. InputStream inputStream =null;
27. OutputStream outputStream =null;
28. try {
29. inputStream =entity.getContent();
30. finalByteArrayOutputStream dataStream = new ByteArrayOutputStream();
31. outputStream = newBufferedOutputStream(dataStream, IO_BUFFER_SIZE);
32. copy(inputStream,outputStream);
33. outputStream.flush();
34. final byte[] data =dataStream.toByteArray();
35. final Bitmap bitmap =BitmapFactory.decodeByteArray(data, 0, data.length);
36. return bitmap;
37. } finally {
38. if (inputStream !=null) {
39. inputStream.close();
40. }
41. if (outputStream !=null) {
42. outputStream.close();
43. }
44. entity.consumeContent();
45. }
46. }
47. } catch (IOException e) {
48. getRequest.abort();
49. Log.w(TAG, "I/O errorwhile retrieving bitmap from " + url, e);
50. } catch (IllegalStateException e) {
51. getRequest.abort();
52. Log.w(TAG, "Incorrect URL:" + url);
53. } catch (Exception e) {
54. getRequest.abort();
55. Log.w(TAG, "Error whileretrieving bitmap from " + url, e);
56. } finally {
57. if (client != null) {
58. client.close();
59. }
60. }
61. return null;
62. }

複製代碼

系列之Android 遠程圖片擷取和本機快取（一）的文章連結http://www.eoeandroid.com/thread-98446-1-1.html
系列之Android 遠程圖片擷取和本機快取（二）的文章連結http://www.eoeandroid.com/thread-98449-1-1.html