android下载网络图片并缓存

android下载网络图片并缓存

分类：图片缓存加载2014-02-12 10:58 2320人阅读评论(0) 收藏举报

异步下载网络图片，并提供是否缓存至内存或外部文件的功能

异步加载类AsyncImageLoader

public void downloadImage(final String url, final ImageCallback callback);

public void downloadImage(final String url, final boolean cache2Memory, final ImageCallback callback);

public void setCache2File(boolean flag);

public void setCachedDir(String dir);

图片下载和缓存实现类LoaderImpl

1.AsyncImageLoader.java

[java]view plaincopy

1.package com.imagecache;

2.

3.import https://www.360docs.net/doc/47237543.html,ng.ref.SoftReference;

4.import java.util.HashMap;

5.import java.util.HashSet;

6.import java.util.Map;

7.import java.util.concurrent.ExecutorService;

8.import java.util.concurrent.Executors;

9.

10.import android.content.Context;

11.import android.graphics.Bitmap;

12.import android.os.Handler;

13.import android.util.Log;

14.

15.public class AsyncImageLoader {

16.//保存正在下载的图片URL集合，避免重复下载用

17.private static HashSet sDownloadingSet;

18.//软引用内存缓存

19.private static Map> sImageCache;

20.//图片三种获取方式管理者，网络URL获取、内存缓存获取、外部文件缓存获取

21.private static LoaderImpl impl;

22.//线程池相关

23.private static ExecutorService sExecutorService;

24.

25.//通知UI线程图片获取ok时使用

26.private Handler handler;

27.

28.

29./**

30. * 异步加载图片完毕的回调接口

31. */

32.public interface ImageCallback{

33./**

34. * 回调函数

35. * @param bitmap: may be null!

36. * @param imageUrl

37. */

38.public void onImageLoaded(Bitmap bitmap, String imageUrl);

39. }

40.

41.static{

42. sDownloadingSet = new HashSet();

43. sImageCache = new HashMap>();

44. impl = new LoaderImpl(sImageCache);

45. }

46.

47.public AsyncImageLoader(Context context){

48. handler = new Handler();

49. startThreadPoolIfNecessary();

50.

51. String defaultDir = context.getCacheDir().getAbsolutePath();

52. setCachedDir(defaultDir);

53. }

54.

55./**

56. * 是否缓存图片至/data/data/package/cache/目录

57. * 默认不缓存

58. */

59.public void setCache2File(boolean flag){

60. impl.setCache2File(flag);

61. }

62.

63./**

64. * 设置缓存路径，setCache2File(true)时有效

65. */

66.public void setCachedDir(String dir){

67. impl.setCachedDir(dir);

68. }

69.

70./**开启线程池*/

71.public static void startThreadPoolIfNecessary(){

72.if(sExecutorService == null || sExecutorService.isShutdown() || sExe

cutorService.isTerminated()){

73. sExecutorService = Executors.newFixedThreadPool(3);

74.//sExecutorService = Executors.newSingleThreadExecutor();

75. }

76. }

77.

78./**

79. * 异步下载图片，并缓存到memory中

80. * @param url

81. * @param callback see ImageCallback interface

82. */

83.public void downloadImage(final String url, final ImageCallback callback

){

84. downloadImage(url, true, callback);

85. }

86.

87./**

88. *

89. * @param url

90. * @param cache2Memory 是否缓存至memory中

91. * @param callback

92. */

93.public void downloadImage(final String url, final boolean cache2Memory,

final ImageCallback callback){

94.if(sDownloadingSet.contains(url)){

95. Log.i("AsyncImageLoader", "###该图片正在下载，不能重复下载！");

96.return;

97. }

98.

99. Bitmap bitmap = impl.getBitmapFromMemory(url);

100.if(bitmap != null){

101.if(callback != null){

102. callback.onImageLoaded(bitmap, url);

103. }

104. }else{

105.//从网络端下载图片

106. sDownloadingSet.add(url);

107. sExecutorService.submit(new Runnable(){

108.@Override

109.public void run() {

110.final Bitmap bitmap = impl.getBitmapFromUrl(url, cache2 Memory);

111. handler.post(new Runnable(){

112.@Override

113.public void run(){

114.if(callback != null)

115. callback.onImageLoaded(bitmap, url);

116. sDownloadingSet.remove(url);

117. }

118. });

119. }

120. });

121. }

122. }

123.

124./**

125. * 预加载下一张图片，缓存至memory中

126. * @param url

127. */

128.public void preLoadNextImage(final String url){

129.//将callback置为空，只将bitmap缓存到memory即可。

130. downloadImage(url, null);

131. }

132.

133.}

2.LoaderImpl.java

[java]view plaincopy

1.package com.imagecache;

2.

3.import java.io.FileInputStream;

4.import java.io.FileNotFoundException;

5.import java.io.FileOutputStream;

6.import java.io.IOException;

7.import java.io.InputStream;

8.import java.io.UnsupportedEncodingException;

9.import https://www.360docs.net/doc/47237543.html,ng.ref.SoftReference;

10.import https://www.360docs.net/doc/47237543.html,.HttpURLConnection;

11.import https://www.360docs.net/doc/47237543.html,.URL;

12.import java.security.MessageDigest;

13.import java.security.NoSuchAlgorithmException;

14.import java.util.Map;

15.

16.import android.graphics.Bitmap;

17.import android.graphics.BitmapFactory;

18.

19./**

20. *

21. * @author Administrator

22. * @desc 异步加载图片管理器

23. *

24. */

25.public class LoaderImpl {

26.//内存中的软应用缓存

27.private Map> imageCache;

28.

29.//是否缓存图片至本地文件

30.private boolean cache2FileFlag = false;

31.

32.//缓存目录,默认是/data/data/package/cache/目录

33.private String cachedDir;

34.

35.public LoaderImpl(Map> imageCache){

36.this.imageCache = imageCache;

37. }

38.

39./**

40. * 是否缓存图片至外部文件

41. * @param flag

42. */

43.public void setCache2File(boolean flag){

44. cache2FileFlag = flag;

45. }

47./**

48. * 设置缓存图片到外部文件的路径

49. * @param cacheDir

50. */

51.public void setCachedDir(String cacheDir){

52.this.cachedDir = cacheDir;

53. }

54.

55./**

56. * 从网络端下载图片

57. * @param url 网络图片的URL地址

58. * @param cache2Memory 是否缓存(缓存在内存中)

59. * @return bitmap 图片bitmap结构

60. *

61. */

62.public Bitmap getBitmapFromUrl(String url, boolean cache2Memory){

63. Bitmap bitmap = null;

64.try{

65. URL u = new URL(url);

66. HttpURLConnection conn = (HttpURLConnection)u.openConnection();

67. InputStream is = conn.getInputStream();

68. bitmap = BitmapFactory.decodeStream(is);

69.

70.if(cache2Memory){

71.//1.缓存bitmap至内存软引用中

72. imageCache.put(url, new SoftReference(bitmap));

73.if(cache2FileFlag){

74.//2.缓存bitmap至/data/data/packageName/cache/文件夹中

75. String fileName = getMD5Str(url);

76. String filePath = this.cachedDir + "/" +fileName;

77. FileOutputStream fos = new FileOutputStream(filePath);

78. https://www.360docs.net/doc/47237543.html,press(https://www.360docs.net/doc/47237543.html,pressFormat.PNG, 100, fos);

79. }

80. }

81.

82. is.close();

83. conn.disconnect();

84.return bitmap;

85. }catch(IOException e){

86. e.printStackTrace();

87.return null;

88. }

90.

91./**

92. * 从内存缓存中获取bitmap

93. * @param url

94. * @return bitmap or null.

95. */

96.public Bitmap getBitmapFromMemory(String url){

97. Bitmap bitmap = null;

98.if(imageCache.containsKey(url)){

99.synchronized(imageCache){

100. SoftReference bitmapRef = imageCache.get(url); 101.if(bitmapRef != null){

102. bitmap = bitmapRef.get();

103.return bitmap;

104. }

105. }

106. }

107.//从外部缓存文件读取

108.if(cache2FileFlag){

109. bitmap = getBitmapFromFile(url);

110.if(bitmap != null)

111. imageCache.put(url, new SoftReference(bitmap)); 112. }

113.

114.return bitmap;

115. }

116.

117./**

118. * 从外部文件缓存中获取bitmap

119. * @param url

120. * @return

121. */

122.private Bitmap getBitmapFromFile(String url){

123. Bitmap bitmap = null;

124. String fileName = getMD5Str(url);

125.if(fileName == null)

126.return null;

127.

128. String filePath = cachedDir + "/" + fileName;

129.

130.try {

131. FileInputStream fis = new FileInputStream(filePath); 132. bitmap = BitmapFactory.decodeStream(fis);

133. } catch (FileNotFoundException e) {

134. e.printStackTrace();

135. bitmap = null;

136. }

137.return bitmap;

138. }

139.

140.

141./**

142. * MD5 加密

143. */

144.private static String getMD5Str(String str) {

145. MessageDigest messageDigest = null;

146.try {

147. messageDigest = MessageDigest.getInstance("MD5");

148. messageDigest.reset();

149. messageDigest.update(str.getBytes("UTF-8"));

150. } catch (NoSuchAlgorithmException e) {

151. System.out.println("NoSuchAlgorithmException caught!"); 152.return null;

153. } catch (UnsupportedEncodingException e) {

154. e.printStackTrace();

155.return null;

156. }

157.

158.byte[] byteArray = messageDigest.digest();

159. StringBuffer md5StrBuff = new StringBuffer();

160.for (int i = 0; i < byteArray.length; i++) { 161.if (Integer.toHexString(0xFF & byteArray[i]).length() == 1) 162. md5StrBuff.append("0").append(Integer.toHexString(0xFF & by teArray[i]));

163.else

164. md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i])) ;

165. }

166.

167.return md5StrBuff.toString();

168. }

169.

170./**

171. * MD5 加密

172. private static String getMD5Str(Object...objects){

173. StringBuilder stringBuilder=new StringBuilder();

174. for (Object object : objects) {

175. stringBuilder.append(object.toString());

176. }

177. return getMD5Str(stringBuilder.toString());

178. }*/

179.}

3.测试Activity

[java]view plaincopy

1.package com.imagecache;

2.

3.import android.app.Activity;

4.import android.graphics.Bitmap;

5.import android.os.Bundle;

6.import android.widget.ImageView;

7.

8.public class MainActivity extends Activity {

9./** Called when the activity is first created. */

10.@Override

11.public void onCreate(Bundle savedInstanceState) {

12.super.onCreate(savedInstanceState);

13. setContentView(https://www.360docs.net/doc/47237543.html,yout.main);

14.

15.final ImageView iv = (ImageView)findViewById(R.id.iv);

16.//网络图片地址

17. String imgUrl = "http://...";

18.

19.//for test

20. AsyncImageLoader loader = new AsyncImageLoader(getApplicationContext

());

21.

22.//将图片缓存至外部文件中

23. loader.setCache2File(true); //false

24.//设置外部缓存文件夹

25. loader.setCachedDir(this.getCacheDir().getAbsolutePath());

26.

27.//下载图片，第二个参数是否缓存至内存中

28. loader.downloadImage(imgUrl, true/*false*/, new AsyncImageLoader.Ima

geCallback() {

29.@Override

30.public void onImageLoaded(Bitmap bitmap, String imageUrl) {

31.if(bitmap != null){

32. iv.setImageBitmap(bitmap);

33. }else{

34.//下载失败，设置默认图片

35. }

36. }

37. });

38. }

39.

40.}