Drag を実装する その1 : GestureDetector なし

Drag and scale | Android Developers （MotionEventCompat を使ってたりちょっと古い）を参考に変えたもの

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1. class SimpleDragView : FrameLayout {  
2.   
3.     constructor(context: Context) : super(context)  
4.     constructor(context: Context, attrs: AttributeSet?) : super(context, attrs)  
5.     constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(  
6.         context,  
7.         attrs,  
8.         defStyleAttr  
9.     )  
10.   
11.     private var activePointerId = INVALID_POINTER_ID  
12.     private var lastTouchX = 0f  
13.     private var lastTouchY = 0f  
14.   
15.     private val targetView: View  
16.   
17.     init {  
18.         val size = (100 * resources.displayMetrics.density).toInt()  
19.         targetView = View(context).apply {  
20.             layoutParams = LayoutParams(size, size)  
21.             setBackgroundColor(Color.RED)  
22.         }  
23.         addView(targetView)  
24.     }  
25.   
26.     override fun onTouchEvent(ev: MotionEvent): Boolean {  
27.         when (ev.actionMasked) {  
28.             MotionEvent.ACTION_DOWN -> {  
29.                 val pointerIndex = ev.actionIndex  
30.                 val x = ev.getX(pointerIndex)  
31.                 val y = ev.getY(pointerIndex)  
32.   
33.                 if (!(x.toInt() in 0..width && y.toInt() in 0..height)) {  
34.                     return false  
35.                 }  
36.   
37.                 val left = targetView.translationX  
38.                 val right = left + targetView.width  
39.                 val top = targetView.translationY  
40.                 val bottom = top + targetView.height  
41.   
42.                 if (!(x in left..right && y in top..bottom)) {  
43.                     return false  
44.                 }  
45.   
46.                 lastTouchX = x  
47.                 lastTouchY = y  
48.   
49.                 activePointerId = ev.getPointerId(0)  
50.             }  
51.             MotionEvent.ACTION_MOVE -> {  
52.                 if (activePointerId == INVALID_POINTER_ID) {  
53.                     return false  
54.                 }  
55.   
56.                 val pointerIndex = ev.findPointerIndex(activePointerId)  
57.                 val x = ev.getX(pointerIndex)  
58.                 val y = ev.getY(pointerIndex)  
59.   
60.                 if (!(x.toInt() in 0..width && y.toInt() in 0..height)) {  
61.                     return false  
62.                 }  
63.   
64.                 val diffX = x - lastTouchX  
65.                 val diffY = y - lastTouchY  
66.   
67.                 targetView.translationX += diffX  
68.                 targetView.translationY += diffY  
69.   
70.                 lastTouchX = x  
71.                 lastTouchY = y  
72.             }  
73.             MotionEvent.ACTION_UP,  
74.             MotionEvent.ACTION_CANCEL -> {  
75.                 activePointerId = INVALID_POINTER_ID  
76.             }  
77.             MotionEvent.ACTION_POINTER_UP -> {  
78.                 if (activePointerId == INVALID_POINTER_ID) {  
79.                     return false  
80.                 }  
81.   
82.                 val pointerIndex = ev.actionIndex  
83.                 if (ev.getPointerId(pointerIndex) != activePointerId) {  
84.                     return false  
85.                 }  
86.   
87.                 val newPointerIndex = if (pointerIndex == 0) 1 else 0  
88.                 val x = ev.getX(newPointerIndex)  
89.                 val y = ev.getY(newPointerIndex)  
90.   
91.                 if (!(x.toInt() in 0..width && y.toInt() in 0..height)) {  
92.                     activePointerId = INVALID_POINTER_ID  
93.                     return false  
94.                 }  
95.   
96.                 lastTouchX = x  
97.                 lastTouchY = y  
98.   
99.                 activePointerId = ev.getPointerId(newPointerIndex)  
100.             }  
101.         }  
102.   
103.         return true  
104.     }  
105. }  

class SimpleDragView : FrameLayout { constructor(context: Context) : super(context) constructor(context: Context, attrs: AttributeSet?) : super(context, attrs) constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super( context, attrs, defStyleAttr ) private var activePointerId = INVALID_POINTER_ID private var lastTouchX = 0f private var lastTouchY = 0f private val targetView: View init { val size = (100 * resources.displayMetrics.density).toInt() targetView = View(context).apply { layoutParams = LayoutParams(size, size) setBackgroundColor(Color.RED) } addView(targetView) } override fun onTouchEvent(ev: MotionEvent): Boolean { when (ev.actionMasked) { MotionEvent.ACTION_DOWN -> { val pointerIndex = ev.actionIndex val x = ev.getX(pointerIndex) val y = ev.getY(pointerIndex) if (!(x.toInt() in 0..width && y.toInt() in 0..height)) { return false } val left = targetView.translationX val right = left + targetView.width val top = targetView.translationY val bottom = top + targetView.height if (!(x in left..right && y in top..bottom)) { return false } lastTouchX = x lastTouchY = y activePointerId = ev.getPointerId(0) } MotionEvent.ACTION_MOVE -> { if (activePointerId == INVALID_POINTER_ID) { return false } val pointerIndex = ev.findPointerIndex(activePointerId) val x = ev.getX(pointerIndex) val y = ev.getY(pointerIndex) if (!(x.toInt() in 0..width && y.toInt() in 0..height)) { return false } val diffX = x - lastTouchX val diffY = y - lastTouchY targetView.translationX += diffX targetView.translationY += diffY lastTouchX = x lastTouchY = y } MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> { activePointerId = INVALID_POINTER_ID } MotionEvent.ACTION_POINTER_UP -> { if (activePointerId == INVALID_POINTER_ID) { return false } val pointerIndex = ev.actionIndex if (ev.getPointerId(pointerIndex) != activePointerId) { return false } val newPointerIndex = if (pointerIndex == 0) 1 else 0 val x = ev.getX(newPointerIndex) val y = ev.getY(newPointerIndex) if (!(x.toInt() in 0..width && y.toInt() in 0..height)) { activePointerId = INVALID_POINTER_ID return false } lastTouchX = x lastTouchY = y activePointerId = ev.getPointerId(newPointerIndex) } } return true } }