Similar to launcher desktop sliding effect

This example involves the following knowledge points:
1) Use of the attrs. xml file
2) gesturedetector. ongesturelistener listens for gestures
3) Use of onlayout (), onmeasure (), and ontouchevent ()
Next, let's talk about my Implementation ideas:
1) each desktop is a large component and horizontally arranged in a linear layout file. Each desktop is suitable for the same screen size. Therefore, we need to expand linearlayout and rewrite the onmeasure () and onlayout () methods.
2) To slide with gestures, you only need to implement the ondown () and onscroll () methods in the gesturedetector. ongesturelistener interface.
3) To receive touch-screen events, you must implement ontouchevent ()
Let's take a look at the Code:

1. Public class scrolllayout extends linearlayout implements gesturedetector. ongesturelistener {
2. Private int offset; // relative distance
3. Private gesturedetector; // gesture event
4. Private int childwidth; // The width of the sub-View
5. Private int childcount; // Number of subviews
6. Private int defaultwindow; // default window
8. Private Boolean setsharewindowflag = false; // ensure that the default window settings are executed only once.
10. Public scrolllayout (context ){
11. Super (context );
12. Init ();
13. }
15. Public scrolllayout (context, attributeset attrs ){
16. Super (context, attrs );
17. Init ();
18. // Obtain the defined defaultwindow Value
19. Typedarray = context. obtainstyledattributes (attrs, R. styleable. myscrollwindow );
20. Defaultwindow = typedarray. getinteger (R. styleable. myscrollwindow_defaultwindow, 0 );
21. }
23. Private void Init (){
24. Gesturedetector = new gesturedetector (this. getcontext (), this );
25. }
27. // A gesture event can be triggered only when the returned value is true.
28. Public Boolean ondown (motionevent e ){
29. Return true;
30. }
32. Public void onshowpress (motionevent e ){}
34. Public Boolean onsingletapup (motionevent e ){
35. Return false;
36. }
37. // Slide along the gesture
38. Public Boolean onscroll (motionevent E1, motionevent E2, float distancex, float distancey ){
39. // Obtain the sliding distance
40. Offset = (INT) (offset-distancex );
41. // Prevents sliding out of the Boundary
42. If (Offset> 0 ){
43. Offset = 0;
44. } Else if (offset <-1 * childwidth * (childCount-1 )){
45. Offset =-1 * childwidth * (childCount-1 );
46. }
47. // Redraw the Layout
48. Requestlayout ();
49. Return true;
50. }
52. Public void onlongpress (motionevent e ){
54. }
56. Public Boolean onfling (motionevent E1, motionevent E2, float velocityx, float velocityy ){
57. Return false;
58. }
60. // Set the layout file width and height to the width and height of each desktop
61. @ Override
62. Protected void onmeasure (INT widthmeasurespec, int heightmeasurespec ){
63. Super. onmeasure (widthmeasurespec, heightmeasurespec );
65. // Set the same width and height for each desktop and Screen
66. Int childcount = getchildcount ();
67. For (INT I = 0; I <childcount; I ++ ){
68. Getchildat (I). Measure (widthmeasurespec, heightmeasurespec );
69. }
71. }
73. // Set the Layout
74. @ Override
75. Protected void onlayout (Boolean changed, int L, int T, int R, int B ){
77. Childcount = getchildcount (); // gets the number of child views
78. Childwidth = childcount> 0? Getchildat (0). getmeasuredwidth (): 0; // get the byte point width
79. If (! Setsharewindowflag & defaultwindow> = 0 & defaultwindow <= childCount-1 ){
80. // Set the left end distance of the default window
81. Offset =-1 * defaultwindow * childwidth;
82. Setmediawindowflag = true;
83. }
84. // Set the initial distance from (0, 0) to the X axis.
85. Int left = 0 + offset;
86. For (INT I = 0; I <childcount; I ++ ){
87. // Set the position of each subview in the layout
88. View child = getchildat (I );
89. If (child. getvisibility ()! = View. Gone ){
90. Child. layout (left, 0, childwidth + left, child. getmeasuredheight ());
91. Left = left + childwidth;
92. }
93. }
94. }
96. // Touch screen events
97. @ Override
98. Public Boolean ontouchevent (motionevent event ){
99. Boolean result = gesturedetector. ontouchevent (event );
100. If (event. getaction () = motionevent. action_up ){
101. // When the finger is raised, the entire sub-view is displayed based on the sliding distance.
102. Showonedesktop ();
103. }
104. Return result;
105. }
107. // Determine the desktop that is displayed when your finger is raised
108. Private void showonedesktop (){
109. Int Index = math. Abs (offset)/childwidth;
110. If (math. Abs (offset)-Index * childwidth> childwidth/2 ){
111. Index ++;
112. }
113. Offset = offset> 0? Index * childwidth:-1 * Index * childwidth;
114. Requestlayout ();
115. }
116. }

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The attrs. xml file used in this Code:

1. <Resources>
2. <Declare-styleable name = "myscrollwindow">
3. <ATTR name = "defaultwindow" format = "integer"/>
4. </Declare-styleable>
5. </Resources>

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It can be used the same as the layout file provided by the system.

1. <? XML version = "1.0" encoding = "UTF-8"?>
2. <Com. WXG. scroll_1_view.scrolllayout
3. Xmlns: Android = "http://schemas.android.com/apk/res/android"
4. Xmlns: Demo = "http://schemas.android.com/apk/res/com.wxg.scroll_window"
5. Android: Id = "@ + ID/testlayout"
6. Android: layout_width = "fill_parent"
7. Android: layout_height = "fill_parent"
8. Demo: defaultwindow = "1"
9. >
10. <Framelayout
11. Android: layout_height = "fill_parent"
12. Android: layout_width = "fill_parent"
13. Android: Background = "# cccccc">
15. <Button
16. Android: layout_height = "wrap_content"
17. Android: layout_width = "wrap_content"
18. Android: text = "1"/>
19. </Framelayout>
20. <Framelayout
21. Android: layout_height = "fill_parent"
22. Android: layout_width = "fill_parent"
23. Android: Background = "# ffffff">
25. <Button
26. Android: layout_height = "wrap_content"
27. Android: layout_width = "wrap_content"
28. Android: text = "2"/>
29. </Framelayout>
30. <Framelayout
31. Android: layout_height = "fill_parent"
32. Android: layout_width = "fill_parent"
33. Android: Background = "# bcbcbc">
35. <Button
36. Android: layout_height = "wrap_content"
37. Android: layout_width = "wrap_content"
38. Android: text = "3"/>
39. </Framelayout>
42. </COM. WXG. scroll_1_view.scrolllayout>