1. 引言：

為了提高ListView的效率和應用程序的性能，在Android應用程序中不應該一次性載入ListView所要顯示的全部信息，而是採取分批載入策略，隨著用戶的滑動，動態的從後臺載入所需的數據，並渲染到ListView組件中，這樣可以極大的改善應用程序的性能和用戶體驗。2. 交互：

進入ListView組件，首先預載入N條記錄，當用戶滑動到最後一條記錄顯示載入提示信息，並從後臺載入N條數據，接著渲染UI界面。3. 效果圖：

4. 程序實現： view plaincopy to clipboard

1. packagecom.focus.loading;
2. importandroid.app.ListActivity;
3. importandroid.os.Bundle;
4. importandroid.os.Handler;
5. importandroid.view.Gravity;
6. importandroid.view.View;
7. importandroid.view.ViewGroup;
8. importandroid.widget.AbsListView;
9. importandroid.widget.BaseAdapter;
10. importandroid.widget.LinearLayout;
11. importandroid.widget.ListView;
12. importandroid.widget.ProgressBar;
13. importandroid.widget.TextView;
14. importandroid.widget.AbsListView.OnScrollListener;
15. importandroid.widget.LinearLayout.LayoutParams;
16. publicclassListViewLoadingActivityextendsListActivityimplements
17. OnScrollListener{
18. @Override
19. publicvoidonCreate(BundlesavedInstanceState){
20. super.onCreate(savedInstanceState);
21. /**
22. *"載入項"佈局，此佈局被添加到ListView的Footer中。
23. */
24. mLoadLayout=newLinearLayout(this);
25. mLoadLayout.setMinimumHeight(60);
26. mLoadLayout.setGravity(Gravity.CENTER);
27. mLoadLayout.setOrientation(LinearLayout.HORIZONTAL);
28. /**
29. *向"載入項"佈局中添加一個圓型進度條。
30. */
31. ProgressBarmProgressBar=newProgressBar(this);
32. mProgressBar.setPadding(0,0,15,0);
33. mLoadLayout.addView(mProgressBar,mProgressBarLayoutParams);
34. /**
35. *向"載入項"佈局中添加提示信息。
36. */
37. TextViewmTipContent=newTextView(this);
38. mTipContent.setText("載入中...");
39. mLoadLayout.addView(mTipContent,mTipContentLayoutParams);
40. /**
41. *獲取ListView組件，並將"載入項"佈局添加到ListView組件的Footer中。
42. */
43. mListView=getListView();
44. mListView.addFooterView(mLoadLayout);
45. /**
46. *組ListView組件設置Adapter,並設置滑動監聽事件。
47. */
48. setListAdapter(mListViewAdapter);
49. mListView.setOnScrollListener(this);
50. }
51. publicvoidonScroll(AbsListViewview,intmFirstVisibleItem,
52. intmVisibleItemCount,intmTotalItemCount){
53. mLastItem=mFirstVisibleItem+mVisibleItemCount-1;
54. if(mListViewAdapter.count>mCount){
55. mListView.removeFooterView(mLoadLayout);
56. }
57. }
58. publicvoidonScrollStateChanged(AbsListViewview,intmScrollState){
60. /**
61. *當ListView滑動到最後一條記錄時這時，我們會看到已經被添加到ListView的"載入項"佈局，這時應該載入剩餘數據。
62. */
63. if(mLastItem==mListViewAdapter.count
64. &&mScrollState==OnScrollListener.SCROLL_STATE_IDLE){
65. if(mListViewAdapter.count<=mCount){
66. mHandler.postDelayed(newRunnable(){
67. @Override
68. publicvoidrun(){
69. mListViewAdapter.count+=10;
70. mListViewAdapter.notifyDataSetChanged();
71. mListView.setSelection(mLastItem);
72. }
73. },1000);
74. }
75. }
76. }
77. classListViewAdapterextendsBaseAdapter{
78. intcount=10;
79. publicintgetCount(){
80. returncount;
81. }
82. publicObjectgetItem(intposition){
83. returnposition;
84. }
85. publiclonggetItemId(intposition){
86. returnposition;
87. }
88. publicViewgetView(intposition,Viewview,ViewGroupparent){
89. TextViewmTextView;
90. if(view==null){
91. mTextView=newTextView(ListViewLoadingActivity.this);
92. }else{
93. mTextView=(TextView)view;
94. }
95. mTextView.setText("Item"+position);
96. mTextView.setTextSize(20f);
97. mTextView.setGravity(Gravity.CENTER);
98. mTextView.setHeight(60);
99. returnmTextView;
100. }
101. }
102. privateLinearLayoutmLoadLayout;
103. privateListViewmListView;
104. privateListViewAdaptermListViewAdapter=newListViewAdapter();
105. privateintmLastItem=0;
106. privateintmCount=41;
107. privatefinalHandlermHandler=newHandler();
108. privatefinalLayoutParamsmProgressBarLayoutParams=newLinearLayout.LayoutParams(
109. LinearLayout.LayoutParams.WRAP_CONTENT,
110. LinearLayout.LayoutParams.WRAP_CONTENT);
111. privatefinalLayoutParamsmTipContentLayoutParams=newLinearLayout.LayoutParams(
112. LinearLayout.LayoutParams.WRAP_CONTENT,
113. LinearLayout.LayoutParams.WRAP_CONTENT);
114. }

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