Android下拉刷新功能实现过程详解

[plain] view plaincopyprint?

1. package net.oschina.app.widget;  
2.   
3. import net.oschina.app.R;  
4. import android.content.Context;  
5. import android.util.AttributeSet;  
6. import android.view.LayoutInflater;  
7. import android.view.MotionEvent;  
8. import android.view.View;  
9. import android.view.ViewGroup;  
10. import android.view.animation.LinearInterpolator;  
11. import android.view.animation.RotateAnimation;  
12. import android.widget.AbsListView;  
13. import android.widget.AbsListView.OnScrollListener;  
14. import android.widget.ImageView;  
15. import android.widget.LinearLayout;  
16. import android.widget.ListView;  
17. import android.widget.ProgressBar;  
18. import android.widget.TextView;  
19.   
20. /**  
21.  * 下拉刷新控件  
22.  * @author liux (http://my.oschina.net/liux)  
23.  * @version 1.0  
24.  * @created 2012-3-21  
25.  */  
26. public class PullToRefreshListView extends ListView implements OnScrollListener {    
27.          
28.     private final static String TAG = "PullToRefreshListView";    
29.       
30.     // 下拉刷新标志     
31.     private final static int PULL_To_REFRESH = 0;   
32.     // 松开刷新标志     
33.     private final static int RELEASE_To_REFRESH = 1;   
34.     // 正在刷新标志     
35.     private final static int REFRESHING = 2;    
36.     // 刷新完成标志     
37.     private final static int DONE = 3;    
38.     
39.     private LayoutInflater inflater;    
40.     
41.     private LinearLayout headView;    
42.     private TextView tipsTextview;    
43.     private TextView lastUpdatedTextView;    
44.     private ImageView arrowImageView;    
45.     private ProgressBar progressBar;    
46.     // 用来设置箭头图标动画效果     
47.     private RotateAnimation animation;    
48.     private RotateAnimation reverseAnimation;    
49.     
50.     // 用于保证startY的值在一个完整的touch事件中只被记录一次     
51.     private boolean isRecored;    
52.     
53.     private int headContentWidth;    
54.     private int headContentHeight;    
55.     private int headContentOriginalTopPadding;  
56.     
57.     private int startY;    
58.     private int firstItemIndex;    
59.     private int currentScrollState;  
60.     
61.     private int state;    
62.     
63.     private boolean isBack;    
64.     
65.     public OnRefreshListener refreshListener;    
66.       
67.     public PullToRefreshListView(Context context, AttributeSet attrs) {    
68.         super(context, attrs);    
69.         init(context);    
70.     }    
71.       
72.     public PullToRefreshListView(Context context, AttributeSet attrs, int defStyle) {    
73.         super(context, attrs, defStyle);    
74.         init(context);    
75.     }    
76.     
77.     private void init(Context context) {     
78.         //设置滑动效果  
79.         animation = new RotateAnimation(0, -180,    
80.                 RotateAnimation.RELATIVE_TO_SELF, 0.5f,    
81.                 RotateAnimation.RELATIVE_TO_SELF, 0.5f);    
82.         animation.setInterpolator(new LinearInterpolator());    
83.         animation.setDuration(100);    
84.         animation.setFillAfter(true);    
85.     
86.         reverseAnimation = new RotateAnimation(-180, 0,    
87.                 RotateAnimation.RELATIVE_TO_SELF, 0.5f,    
88.                 RotateAnimation.RELATIVE_TO_SELF, 0.5f);    
89.         reverseAnimation.setInterpolator(new LinearInterpolator());    
90.         reverseAnimation.setDuration(100);    
91.         reverseAnimation.setFillAfter(true);    
92.           
93.         inflater = LayoutInflater.from(context);    
94.         headView = (LinearLayout) inflater.inflate(R.layout.pull_to_refresh_head, null);    
95.     
96.         arrowImageView = (ImageView) headView.findViewById(R.id.head_arrowImageView);    
97.         arrowImageView.setMinimumWidth(50);    
98.         arrowImageView.setMinimumHeight(50);    
99.         progressBar = (ProgressBar) headView.findViewById(R.id.head_progressBar);    
100.         tipsTextview = (TextView) headView.findViewById(R.id.head_tipsTextView);    
101.         lastUpdatedTextView = (TextView) headView.findViewById(R.id.head_lastUpdatedTextView);    
102.           
103.         headContentOriginalTopPadding = headView.getPaddingTop();    
104.           
105.           
106.         measureView(headView);    
107.         headContentHeight = headView.getMeasuredHeight();    
108.         headContentWidth = headView.getMeasuredWidth();   
109.           
110.         headView.setPadding(headView.getPaddingLeft(), -1 * headContentHeight, headView.getPaddingRight(), headView.getPaddingBottom());    
111.         headView.invalidate();    
112.   
113. //        System.out.println("初始高度："+headContentHeight);   
114. //        System.out.println("初始width："+headContentWidth);  
115. //        System.out.println("初始TopPad："+headContentOriginalTopPadding);  
116. //        System.out.println("headContentOriginalTopPadding:"+headContentOriginalTopPadding);  
117. //        System.out.println("PaddingLeft:"+headView.getPaddingLeft());  
118. //        System.out.println("PaddingRight:"+headView.getPaddingRight());  
119. //        System.out.println("PaddingBottom:"+headView.getPaddingBottom());  
120. //        System.out.println("headContentHeight:"+headContentHeight);  
121.           
122.         addHeaderView(headView);          
123.         setOnScrollListener(this);   
124.     }    
125.     
126.     public void onScroll(AbsListView view, int firstVisiableItem, int visibleItemCount,  int totalItemCount) {    
127.         firstItemIndex = firstVisiableItem;    
128.     }    
129.     
130.     public void onScrollStateChanged(AbsListView view, int scrollState) {    
131.         currentScrollState = scrollState;  
132.     }    
133.     
134.     public boolean onTouchEvent(MotionEvent event) {    
135.         switch (event.getAction()) {    
136.         case MotionEvent.ACTION_DOWN:    
137.             if (firstItemIndex == 0 && !isRecored) {    
138.                 startY = (int) event.getY();    
139.                 isRecored = true;    
140.                 //System.out.println("当前-按下高度-ACTION_DOWN-Y："+startY);  
141.             }    
142.             break;    
143.           
144.         case MotionEvent.ACTION_CANCEL://失去焦点&取消动作  
145.         case MotionEvent.ACTION_UP:    
146.     
147.             if (state != REFRESHING) {    
148.                 if (state == DONE) {    
149.                     //System.out.println("当前-抬起-ACTION_UP：DONE什么都不做");  
150.                 }    
151.                 else if (state == PULL_To_REFRESH) {    
152.                     state = DONE;    
153.                     changeHeaderViewByState();                        
154.                     //System.out.println("当前-抬起-ACTION_UP：PULL_To_REFRESH-->DONE-由下拉刷新状态到刷新完成状态");  
155.                 }    
156.                 else if (state == RELEASE_To_REFRESH) {    
157.                     state = REFRESHING;    
158.                     changeHeaderViewByState();    
159.                     onRefresh();                        
160.                     //System.out.println("当前-抬起-ACTION_UP：RELEASE_To_REFRESH-->REFRESHING-由松开刷新状态，到刷新完成状态");  
161.                 }    
162.             }    
163.     
164.             isRecored = false;    
165.             isBack = false;    
166.     
167.             break;    
168.     
169.         case MotionEvent.ACTION_MOVE:    
170.             int tempY = (int) event.getY();   
171.             //System.out.println("当前-滑动-ACTION_MOVE Y："+tempY);  
172.             if (!isRecored && firstItemIndex == 0) {    
173.                 //System.out.println("当前-滑动-记录拖拽时的位置 Y："+tempY);  
174.                 isRecored = true;    
175.                 startY = tempY;    
176.             }    
177.             if (state != REFRESHING && isRecored) {    
178.                 // 可以松开刷新了     
179.                 if (state == RELEASE_To_REFRESH) {    
180.                     // 往上推，推到屏幕足够掩盖head的程度，但还没有全部掩盖     
181.                     if ((tempY - startY < headContentHeight+20)    
182.                             && (tempY - startY) > 0) {    
183.                         state = PULL_To_REFRESH;    
184.                         changeHeaderViewByState();                            
185.                         //System.out.println("当前-滑动-ACTION_MOVE：RELEASE_To_REFRESH--》PULL_To_REFRESH-由松开刷新状态转变到下拉刷新状态");  
186.                     }    
187.                     // 一下子推到顶     
188.                     else if (tempY - startY <= 0) {    
189.                         state = DONE;    
190.                         changeHeaderViewByState();                           
191.                         //System.out.println("当前-滑动-ACTION_MOVE：RELEASE_To_REFRESH--》DONE-由松开刷新状态转变到done状态");  
192.                     }    
193.                     // 往下拉，或者还没有上推到屏幕顶部掩盖head     
194.                     else {    
195.                         // 不用进行特别的操作，只用更新paddingTop的值就行了     
196.                     }    
197.                 }    
198.                 // 还没有到达显示松开刷新的时候,DONE或者是PULL_To_REFRESH状态     
199.                 else if (state == PULL_To_REFRESH) {    
200.                     // 下拉到可以进入RELEASE_TO_REFRESH的状态     
201.                     if (tempY - startY >= headContentHeight+20 && currentScrollState == SCROLL_STATE_TOUCH_SCROLL) {    
202.                         state = RELEASE_To_REFRESH;    
203.                         isBack = true;    
204.                         changeHeaderViewByState();    
205.                         //System.out.println("当前-滑动-PULL_To_REFRESH--》RELEASE_To_REFRESH-由done或者下拉刷新状态转变到松开刷新");  
206.                     }    
207.                     // 上推到顶了     
208.                     else if (tempY - startY <= 0) {    
209.                         state = DONE;    
210.                         changeHeaderViewByState();     
211.                         //System.out.println("当前-滑动-PULL_To_REFRESH--》DONE-由Done或者下拉刷新状态转变到done状态");  
212.                     }    
213.                 }    
214.                 // done状态下     
215.                 else if (state == DONE) {    
216.                     if (tempY - startY > 0) {    
217.                         state = PULL_To_REFRESH;    
218.                         changeHeaderViewByState();   
219.                         //System.out.println("当前-滑动-DONE--》PULL_To_REFRESH-由done状态转变到下拉刷新状态");  
220.                     }    
221.                 }    
222.                   
223.                 // 更新headView的size     
224.                 if (state == PULL_To_REFRESH) {   
225.                     int topPadding = (int)((-1 * headContentHeight + (tempY - startY)));  
226.                     headView.setPadding(headView.getPaddingLeft(), topPadding, headView.getPaddingRight(), headView.getPaddingBottom());     
227.                     headView.invalidate();    
228.                     //System.out.println("当前-下拉刷新PULL_To_REFRESH-TopPad："+topPadding);  
229.                 }    
230.     
231.                 // 更新headView的paddingTop     
232.                 if (state == RELEASE_To_REFRESH) {    
233.                     int topPadding = (int)((tempY - startY - headContentHeight));  
234.                     headView.setPadding(headView.getPaddingLeft(), topPadding, headView.getPaddingRight(), headView.getPaddingBottom());      
235.                     headView.invalidate();    
236.                     //System.out.println("当前-释放刷新RELEASE_To_REFRESH-TopPad："+topPadding);  
237.                 }    
238.             }    
239.             break;    
240.         }    
241.         return super.onTouchEvent(event);    
242.     }    
243.     
244.     // 当状态改变时候，调用该方法，以更新界面     
245.     private void changeHeaderViewByState() {    
246.         switch (state) {    
247.         case RELEASE_To_REFRESH:    
248.               
249.             arrowImageView.setVisibility(View.VISIBLE);    
250.             progressBar.setVisibility(View.GONE);    
251.             tipsTextview.setVisibility(View.VISIBLE);    
252.             lastUpdatedTextView.setVisibility(View.VISIBLE);    
253.     
254.             arrowImageView.clearAnimation();    
255.             arrowImageView.startAnimation(animation);    
256.     
257.             tipsTextview.setText(R.string.pull_to_refresh_release_label);    
258.     
259.             //Log.v(TAG, "当前状态，松开刷新");    
260.             break;    
261.         case PULL_To_REFRESH:  
262.               
263.             progressBar.setVisibility(View.GONE);    
264.             tipsTextview.setVisibility(View.VISIBLE);    
265.             lastUpdatedTextView.setVisibility(View.VISIBLE);    
266.             arrowImageView.clearAnimation();    
267.             arrowImageView.setVisibility(View.VISIBLE);    
268.             if (isBack) {    
269.                 isBack = false;    
270.                 arrowImageView.clearAnimation();    
271.                 arrowImageView.startAnimation(reverseAnimation);    
272.             }   
273.             tipsTextview.setText(R.string.pull_to_refresh_pull_label);    
274.   
275.             //Log.v(TAG, "当前状态，下拉刷新");    
276.             break;    
277.     
278.         case REFRESHING:     
279.             //System.out.println("刷新REFRESHING-TopPad："+headContentOriginalTopPadding);  
280.             headView.setPadding(headView.getPaddingLeft(), headContentOriginalTopPadding, headView.getPaddingRight(), headView.getPaddingBottom());     
281.             headView.invalidate();    
282.     
283.             progressBar.setVisibility(View.VISIBLE);    
284.             arrowImageView.clearAnimation();    
285.             arrowImageView.setVisibility(View.GONE);    
286.             tipsTextview.setText(R.string.pull_to_refresh_refreshing_label);    
287.             lastUpdatedTextView.setVisibility(View.GONE);    
288.     
289.             //Log.v(TAG, "当前状态,正在刷新...");    
290.             break;    
291.         case DONE:    
292.             //System.out.println("完成DONE-TopPad："+(-1 * headContentHeight));  
293.             headView.setPadding(headView.getPaddingLeft(), -1 * headContentHeight, headView.getPaddingRight(), headView.getPaddingBottom());    
294.             headView.invalidate();    
295.     
296.             progressBar.setVisibility(View.GONE);    
297.             arrowImageView.clearAnimation();    
298.             // 此处更换图标     
299.             arrowImageView.setImageResource(R.drawable.ic_pulltorefresh_arrow);    
300.     
301.             tipsTextview.setText(R.string.pull_to_refresh_pull_label);    
302.             lastUpdatedTextView.setVisibility(View.VISIBLE);    
303.     
304.             //Log.v(TAG, "当前状态，done");    
305.             break;    
306.         }    
307.     }    
308.     
309.     //点击刷新  
310.     public void clickRefresh() {  
311.         setSelection(0);  
312.         state = REFRESHING;    
313.         changeHeaderViewByState();    
314.         onRefresh();   
315.     }  
316.       
317.     public void setOnRefreshListener(OnRefreshListener refreshListener) {    
318.         this.refreshListener = refreshListener;    
319.     }    
320.     
321.     public interface OnRefreshListener {    
322.         public void onRefresh();    
323.     }    
324.     
325.     public void onRefreshComplete(String update) {    
326.         lastUpdatedTextView.setText(update);    
327.         onRefreshComplete();  
328.     }   
329.       
330.     public void onRefreshComplete() {    
331.         state = DONE;    
332.         changeHeaderViewByState();    
333.     }    
334.     
335.     private void onRefresh() {    
336.         if (refreshListener != null) {    
337.             refreshListener.onRefresh();    
338.         }    
339.     }    
340.     
341.     // 计算headView的width及height值    
342.     private void measureView(View child) {    
343.         ViewGroup.LayoutParams p = child.getLayoutParams();    
344.         if (p == null) {    
345.             p = new ViewGroup.LayoutParams(ViewGroup.LayoutParams.FILL_PARENT,    
346.                     ViewGroup.LayoutParams.WRAP_CONTENT);    
347.         }    
348.         int childWidthSpec = ViewGroup.getChildMeasureSpec(0, 0 + 0, p.width);    
349.         int lpHeight = p.height;    
350.         int childHeightSpec;    
351.         if (lpHeight > 0) {    
352.             childHeightSpec = MeasureSpec.makeMeasureSpec(lpHeight,    
353.                     MeasureSpec.EXACTLY);    
354.         } else {    
355.             childHeightSpec = MeasureSpec.makeMeasureSpec(0,    
356.                     MeasureSpec.UNSPECIFIED);    
357.         }    
358.         child.measure(childWidthSpec, childHeightSpec);    
359.     }    
360.         
361. }  

另外一种实现方式：

http://blog.csdn.net/sinyu890807/article/details/9255575