Draggable

图层可以被垂直拖放，也可以被水平拖放，或者同时垂直水平拖放。在拖放时还可以模拟因惯性晃来晃去的效果。如果想让拖放在某个位置停止，你还可以限定拖放的区域范围。虽然限定了拖放范围，但还是可以允许其被拖拽出去，但是默认地它会被弹回来。

layer.draggable.enabled <布尔值>

让图层可已以被拖放。

layerA = new Layer
layerA.draggable.enabled = true

layer.draggable.horizontal <布尔值>

开启或者关闭水平方向的拖放。

layerA = new Layer
layerA.draggable.enabled = true
#Disable horizontal dragging 
layerA.draggable.horizontal = false

layer.draggable.vertical <布尔值>

开启或者关闭垂直方向的拖放。

layerA = new Layer
layerA.draggable.enabled = true
#Disable vertical dragging 
layerA.draggable.vertical = false

layer.draggable.speedX <数字>

改变水平方向拖动的速度。它的值是鼠标每移动一像素被拖动元素所移动的像素值，默认值是1。当设置的值小于1时，拖动时元素移动距离将会小于鼠标移动距离。当其值为0时，水平方向拖拽就被禁止了。

layerA = new Layer
layerA.draggable.enabled = true
# Make horizontal dragging slow 
layerA.draggable.speedX = 0.1
# Make horizontal dragging fast 
layerA.draggable.speedX = 10

layer.draggable.speedY <数字>

改变垂直方向拖动的速度。它的值是鼠标每移动一像素被拖动元素所移动的像素值，默认值是1。当设置的值小于1时，拖动时元素移动距离将会小于鼠标移动距离。当其值为0时，垂直方向拖拽就被禁止了。

layerA = new Layer
layerA.draggable.enabled = true
# Make vertical dragging slow 
layerA.draggable.speedY = 0.1
# Make vertical dragging fast 
layerA.draggable.speedY = 10

layer.draggable.constraints <对象>

拖拽区域，即限制图层可以被拖动的范围。如果你给constraints设置了x和y属性，那么图层在DragStart（开始拖动）时会自动定位到这个坐标点，在你点击时它就会以过渡动画的形式移动过去。

layerA = new Layer
layerA.draggable.enabled = true
# Set dragging constraints 
layerA.draggable.constraints =
    x: 0
    y: 0
    width: 200
    height: 200

layer.draggable.constraintsOffset <对象>

获取可拖动图层相对于其拖动范围的位置偏移。如果你将constraints设置为{ x: 100, y: 100 }，而图层默认的初始位置在坐标原点（0,0），此时就可以通过constraintsOffset来计算他当前相对于拖拽区域的偏移，结果是{ x:-100, y:-100 } 。当你拖动它时他就会立即被弹回到拖拽区域。

layerA = new Layer
layerA.draggable.enabled = true
# Set dragging constraints 
layerA.draggable.constraints =
    x: 100
    y: 100
    width: 200
    height: 200
# Get the constraintsOffset 
print layerA.draggable.constraintsOffset
# Returns { x:-100, y:-100 } 

layer.draggable.isBeyondConstraints <布尔值>

查看当前可拖拽图层是否超出了拖拽区域（只读）。

layerA = new Layer
layerA.draggable.enabled = true
# Set dragging constraints 
layerA.draggable.constraints =
    x: 100
    y: 100
    width: 400
    height: 400
# On move, see if the layer is beyond constraints or not 
layerA.on Events.Move, ->
    print layerA.draggable.isBeyondConstraints

layer.draggable.overdrag <布尔值>

启用或禁用是否允许超出拖拽区域。

layerA = new Layer
layerA.draggable.enabled = true
layerA.draggable.constraints =
    x: 0
    y: 0
    width: 200
    height: 200
# Disable dragging beyond constraints 
layerA.draggable.overdrag = false

layer.draggable.overdragScale <数字>

设置超出拖拽区域时的拖拽阻力。其值是一个0到1的数字，默认为0.5。

layerA = new Layer
layerA.draggable.enabled = true
layerA.draggable.constraints =
    x: 0
    y: 0
    width: 200
    height: 200
# Increase resistance when dragging beyond constraints 
layerA.draggable.overdragScale = 0.25

layer.draggable.momentum <布尔值>

开启或禁用拖拽时的动量/惯性模拟，默认是开启的。

layerA = new Layer
layerA.draggable.enabled = true
# Disable momentum 
layerA.draggable.momentum = false

layer.draggable.momentumOptions <对象>

拖拽后动量模拟的详细设置。

layerA = new Layer
layerA.draggable.enabled = true
# Define friction and tolerance of momentum 
layerA.draggable.momentumOptions =
    friction: 2.1
    tolerance: 0.1

layer.draggable.bounce <布尔值>

当拖动超出拖拽区域时，动量模拟是否启用弹性动画。

layerA = new Layer
layerA.draggable.enabled = true
layerA.draggable.constraints =
    x: 0
    y: 0
    width: 200
    height: 200
# Snap back after dragging beyond constraints 
layerA.draggable.bounce = false

layer.draggable.bounceOptions <对象>

当拖动超出拖拽区域时，动量模拟的弹性动画详细设置。

layerA = new Layer
layerA.draggable.enabled = true
layerA.draggable.constraints =
    x: 0
    y: 0
    width: 200
    height: 200
# Define friction, tension and tolerance of bounce 
layerA.draggable.bounceOptions =
    friction: 40,
    tension: 200,
    tolerance: 0.0001

layer.draggable.velocity <对象>

当前拖拽图层的速度，它是只读的。

layerA = new Layer
layerA.draggable.enabled = true
# On DragMove, print the x and y velocity 
layerA.draggable.on Events.DragMove, ->
    print layerA.draggable.velocity

layer.draggable.direction

当前拖拽的方向，会返回”up”, “down”, “left” 或 “right”中的一个，它也是只读的。

layerA = new Layer
layerA.draggable.enabled = true
# Print the current direction 
layerA.on Events.DragMove, ->
    print layerA.draggable.direction

layer.draggable.angle <数字>

当前拖动的角度（角度制），它是只读的。

layerA = new Layer
layerA.draggable.enabled = true
# Print the current angle 
layerA.on Events.DragMove, ->
    print layerA.draggable.angle

layer.draggable.updatePosition(point)

这个方法可以让你覆盖之前设置的最终值。你可以给拖动添加自定义行为，让该图层在固定的距离范围内迅速移动。

参数

• point — An object with x and y properties.

layerA = new Layer
layerA.draggable.enabled = true
# Round numbers to a set amount 
round = (number, nearest) ->
    Math.round(number / nearest) * nearest
# Drag in increments of 20px 
layerA.draggable.updatePosition = (point) ->
    point.x = round(point.x, 20)
    point.y = round(point.y, 20)
    return point

layer.draggable.directionLock <布尔值>

在拖动距离超过某一上限之后，限定你只能在垂直和水平中的一个方向进行拖动。

layerA = new Layer
layerA.draggable.enabled = true
# Allow dragging only in one direction at a time 
layerA.draggable.directionLock = true

layer.draggable.directionLockThreshold <对象>

锁定方向的上限。x和y的值代表在它锁定方向之前你可以在两个方向上拖动的距离。

layerA = new Layer
layerA.draggable.enabled = true
# Snap horizontally after dragging 50px 
# Snap vertically instantly 
layerA.draggable.directionLock = true
layerA.draggable.directionLockThreshold =
    x: 50
    y: 0

layer.draggable.pixelAlign <布尔值>

在拖动时是否对齐像素，用以取消子像素抗锯齿。

layerA = new Layer
layerA.draggable.enabled = true
# Snap to pixel while dragging 
layerA.draggable.pixelAlign = true

layer.draggable.isDragging <布尔值>

判断现在某个图层是否正在被拖动（松开后动画时返回的是false），它是只读的。

layerA = new Layer
layerA.draggable.enabled = true
# Check if the layer is being dragged 
layerA.on Events.DragMove, ->
    print layerA.draggable.isDragging

layer.draggable.isAnimating <布尔值>

判断当前图层是否正在进行模拟动量或弹性动画，它是只读的。

layerA = new Layer
layerA.draggable.enabled = true
# Check if the layer is animating 
layerA.on Events.DragMove, ->
    print layerA.draggable.isAnimating

layer.draggable.isMoving <布尔值>

判断当前图层是否在移动，无论是因为拖动移动还是因为模拟动量或弹性动画，它是只读的。

layerA = new Layer
layerA.draggable.enabled = true
# Check if the layer is moving 
layerA.on Events.DragMove, ->
    print layerA.draggable.isMoving

layer.draggable.offset <对象>

获取当前可拖动图层相对于屏幕的位置信息（x和y坐标），它是只读的。

layerA = new Layer
layerA.draggable.enabled = true
# Get the x and y position of the layer 
layerA.on Events.DragMove, ->
    print layerA.draggable.offset

layer.draggable.layerStartPoint <对象>

获取开始拖动时该图层的位置信息（只读）。

layerA = new Layer
layerA.draggable.enabled = true
# On DragStart, get the current x and y position  
layerA.on Events.DragStart, ->
    print layerA.draggable.layerStartPoint

layer.draggable.cursorStartPoint <对象>

获取开始拖动时光标相对于画布的位置信息（只读）。

layerA = new Layer
layerA.draggable.enabled = true
# On DragStart, get x and y position of the cursor 
layerA.on Events.DragStart, ->
    print layerA.draggable.cursorStartPoint

layer.draggable.layerCursorOffset <对象>

获取光标相对于该可拖动图层的位置偏移。如果你拖动该图层的左上角，将会返回{ x: 0, y: 0 }（只读）。

layerA = new Layer
layerA.draggable.enabled = true
# Get the cursor position within the layer 
layerA.on Events.DragStart, ->
    print layerA.draggable.layerCursorOffset

layer.draggable.propagateEvents <布尔值>

设置可拖动图层的事件传播属性，默认为true。当你在ScrollComponents和PageComponents等嵌套组件里面添加可拖动图层时，该属性就会派上用场。

比如说你想在scroll.content图层中添加一个可拖动图层。默认情况下，拖动该图层时scroll.content图层也会跟着被拖动，这是因为他们都监听到拖动事件了。

想要在拖动可拖动图层时让scroll.content保持不动，即阻止某个子图层的拖动事件传播到它的父图层，把propagateEvents设置为false就可以了，它对于所有嵌套图层都是有效的。

scroll = new ScrollComponent
    width: Screen.width,
    height: Screen.height
scroll.content.backgroundColor = "#28affa"
layerA = new Layer
    parent: scroll.content,
    backgroundColor: "#fff"
layerA.draggable.enabled = true
# Setting propagateEvents to false allows you to drag layerA 
# without also scrolling within the ScrollComponent 
layerA.draggable.propagateEvents = false