Android ListView滑動時加載卡頓問題

下面是相關代碼（分頁的就沒放）：

Java代碼   

1. /**
2. * list滾動監聽
3. */
4. listView.setOnScrollListener(new OnScrollListener() {
5. @Override
6. public void onScrollStateChanged(AbsListView view, int scrollState) {
7. // TODO Auto-generated method stub
8. // 異步加載圖片
9. if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {//list中止滾動時加載圖片
10. pageImgLoad(_start_index, _end_index);
11. }
12. }
13. @Override
14. public void onScroll(AbsListView view, int firstVisibleItem,
15. int visibleItemCount, int totalItemCount) {
16. // TODO Auto-generated method stub
17. //設置當前屏幕顯示的起始index和結束index
18. _start_index = firstVisibleItem;
19. _end_index = firstVisibleItem + visibleItemCount;
20. if (_end_index >= totalItemCount) {
21. _end_index = totalItemCount - 1;
22. }
23. }
24. });

[java]  view plain copy

1. /** 
2.      * list滾動監聽 
3.      */  
4.     listView.setOnScrollListener(new OnScrollListener() {  
5.         @Override  
6.         public void onScrollStateChanged(AbsListView view, int scrollState) {  
7.             // TODO Auto-generated method stub  
8.             // 異步加載圖片  
9.             if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {//list中止滾動時加載圖片  
10.                 pageImgLoad(_start_index, _end_index);  
11.             }  
12.         }  
13.         @Override  
14.         public void onScroll(AbsListView view, int firstVisibleItem,  
15.                 int visibleItemCount, int totalItemCount) {  
16.             // TODO Auto-generated method stub  
17.             //設置當前屏幕顯示的起始index和結束index  
18.             _start_index = firstVisibleItem;  
19.             _end_index = firstVisibleItem + visibleItemCount;  
20.             if (_end_index >= totalItemCount) {  
21.                 _end_index = totalItemCount - 1;  
22.             }  
23.         }  
24.     });  

Java代碼   

1. /**
2. * 只加載from start_index to end_index 的圖片
3. * @param start_index
4. * @param end_index
5. */
6. private void pageImgLoad(int start_index, int end_index) {
7. for (; start_index < end_index; start_index++) {
8. HashMap<String, Object> curr_item = adapter.getItem(start_index);
9. if (curr_item.get(Constant.NEWS_ICON_URL) != null
10. && curr_item.get(Constant.NEWS_ICON) == null) {
11. loadImage(curr_item);
12. }
13. }
14. }

[java]  view plain copy

1. /** 
2.      * 只加載from start_index to end_index 的圖片  
3.      * @param start_index 
4.      * @param end_index 
5.      */  
6.     private void pageImgLoad(int start_index, int end_index) {  
7.         for (; start_index < end_index; start_index++) {  
8.             HashMap<String, Object> curr_item = adapter.getItem(start_index);  
9.             if (curr_item.get(Constant.NEWS_ICON_URL) != null  
10.                     && curr_item.get(Constant.NEWS_ICON) == null) {  
11.                 loadImage(curr_item);  
12.             }  
13.         }  
14.     }  

異步加載圖片代碼，這裏我以前使用的是AsyncTask，可是繼承AsyncTask後不能被執行屢次，因此我改用了線程呼叫handler更新UI：

Java代碼   

2. /**
3. * 異步加載圖片
4. * @param curr_item
5. */
6. private void loadImage(final HashMap<String, Object> curr_item) {
7. executorService.submit(new Runnable() {
8. public void run() {
9. try {
10. Drawable curr_icon = null;
11. String icon_URL = (String) curr_item
12. .get(Constant.NEWS_ICON_URL);
13. String newsId = (String) curr_item.get(Constant.NEWS_ID);
15. if (imageCache.containsKey(icon_URL)) {//軟引用
16. SoftReference<Drawable> softReference = imageCache
17. .get(icon_URL);
18. curr_icon = softReference.get();
19. System.out.println("CASE USING SoftReference!!!!!!!!!!!!!!!!!!!!");
20. }
21. if (curr_icon == null) {
22. HttpUtils hu = new HttpUtils();
23. FileUtils fu = new FileUtils();
24. if (hu.is_Intent(Home_Activity.this)) {
25. fu.write2LocalFromIS(Home_Activity.this, newsId
26. + Constant.SAVE_NEWS_ICON_NAME
27. + Constant.SAVE_IMG_SUFFIX,
28. hu.getISFromURL(icon_URL));
29. }
30. // 從本地加載圖片 若是沒網則直接加載本地圖片
31. curr_icon = fu.readDrawableFromLocal(
32. Home_Activity.this, newsId
33. + Constant.SAVE_NEWS_ICON_NAME
34. + Constant.SAVE_IMG_SUFFIX);
35. imageCache.put(icon_URL, new SoftReference<Drawable>(
36. curr_icon));
37. }
38. curr_item.put(Constant.NEWS_ICON, curr_icon);
39. // UI交給handler更新
40. Message msg = _viewHandler.obtainMessage();
41. msg.arg1 = Constant.MSG_LIST_IMG_OK;
42. msg.sendToTarget();
43. } catch (Exception e) {
44. throw new RuntimeException(e);
45. }
46. }
47. });
48. }

[java]  view plain copy

1. /** 
2.      * 異步加載圖片 
3.      * @param curr_item 
4.      */  
5.     private void loadImage(final HashMap<String, Object> curr_item) {  
6.         executorService.submit(new Runnable() {  
7.             public void run() {  
8.                 try {  
9.                     Drawable curr_icon = null;  
10.                     String icon_URL = (String) curr_item  
11.                             .get(Constant.NEWS_ICON_URL);  
12.                     String newsId = (String) curr_item.get(Constant.NEWS_ID);  
13.   
14.                     if (imageCache.containsKey(icon_URL)) {//軟引用  
15.                         SoftReference<Drawable> softReference = imageCache  
16.                                 .get(icon_URL);  
17.                         curr_icon = softReference.get();  
18.                         System.out.println("CASE USING SoftReference!!!!!!!!!!!!!!!!!!!!");  
19.                     }  
20.                     if (curr_icon == null) {  
21.                         HttpUtils hu = new HttpUtils();  
22.                         FileUtils fu = new FileUtils();  
23.                         if (hu.is_Intent(Home_Activity.this)) {  
24.                             fu.write2LocalFromIS(Home_Activity.this, newsId  
25.                                     + Constant.SAVE_NEWS_ICON_NAME  
26.                                     + Constant.SAVE_IMG_SUFFIX,  
27.                                     hu.getISFromURL(icon_URL));  
28.                         }  
29.                         // 從本地加載圖片 若是沒網則直接加載本地圖片  
30.                         curr_icon = fu.readDrawableFromLocal(  
31.                                 Home_Activity.this, newsId  
32.                                         + Constant.SAVE_NEWS_ICON_NAME  
33.                                         + Constant.SAVE_IMG_SUFFIX);  
34.                         imageCache.put(icon_URL, new SoftReference<Drawable>(  
35.                                 curr_icon));  
36.                     }  
37.                     curr_item.put(Constant.NEWS_ICON, curr_icon);  
38.                     // UI交給handler更新  
39.                     Message msg = _viewHandler.obtainMessage();  
40.                     msg.arg1 = Constant.MSG_LIST_IMG_OK;  
41.                     msg.sendToTarget();  
42.                 } catch (Exception e) {  
43.                     throw new RuntimeException(e);  
44.                 }  
45.             }  
46.         });  
47.     }  

Java代碼   

1. handler代碼：

[java]  view plain copy

1. handler代碼：  

Java代碼   

1. Handler _viewHandler = new Handler() {

[java]  view plain copy

1. Handler _viewHandler = new Handler() {  

Java代碼   

1. @Override
2. public void handleMessage(Message msg) {
3. switch (msg.arg1) {
4. case Constant.MSG_LIST_IMG_OK:
5. // 更新UI
6. adapter.notifyDataSetChanged();
7. break;
8. }
9. super.handleMessage(msg);
10. }
11. };

[java]  view plain copy

1. @Override  
2.     public void handleMessage(Message msg) {  
3.         switch (msg.arg1) {  
4.         case Constant.MSG_LIST_IMG_OK:  
5.             // 更新UI  
6.             adapter.notifyDataSetChanged();  
7.             break;  
8.         }  
9.         super.handleMessage(msg);  
10.     }  
11. };  

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