使用Layout、offset、layoutParam实现位移动画

Android中常见的实现位移滑动效果的方式有：

• layoutParam
• offsetTopAndBottom\offsetLeftAndRight
• layout
• scrollTo/scrollBy
• scroller
• viewDragHelper

对于常见滑动效果通过两篇文章说明。本节将说明layout \ offset \ layoutParam。

1、layout()方式实现位移滑动

public void layout(int l, int t, int r, int b)

看一下实现随手指移动核心代码

bindView {
var layoutLastX = 0
var layoutLastY = 0
var originLeft = 0
var originTop = 0
var originRight = 0
var originBottom = 0
vLayoutMove.setOnTouchListener { v, event ->
    when (event.action) {
        MotionEvent.ACTION_DOWN -> {
            layoutLastX = event.x.toInt()
            layoutLastY = event.y.toInt()
            originLeft = v.left
            originTop = v.top
            originRight = v.right
            originBottom = v.bottom
        }
        MotionEvent.ACTION_MOVE -> {
            val offsetX = event.x - layoutLastX
            val offsetY = event.y - layoutLastY
            v.layout(
                (originLeft + offsetX).toInt(),
                (originTop + offsetY).toInt(),
                (originRight + offsetX).toInt(),
                (originBottom + offsetY).toInt()
            )
        }
        MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
        	//将位置恢复到初始位置
            v.layout(
                originLeft, originTop, originRight, originBottom
            )
        }
    }
    true
}

2、offset方式实现位移滑动

public void offsetLeftAndRight(int offset)
public void offsetTopAndBottom(int offset)

由于比较简单，直接看核心代码实现

var offsetLastX = 0F
var offsetLastY = 0F
var offsetOriginX = 0F
var offsetOriginY = 0F
vOffsetMove.setOnTouchListener { v, event ->
    when (event.action) {
        MotionEvent.ACTION_DOWN -> {
            offsetLastX = event.x
            offsetLastY = event.y
            offsetOriginX = v.left.toFloat()
            offsetOriginY = v.top.toFloat()
        }
        MotionEvent.ACTION_MOVE -> {
            val offsetX = event.x - offsetLastX
            val offsetY = event.y - offsetLastY
            v.offsetLeftAndRight(offsetX.toInt())
            v.offsetTopAndBottom(offsetY.toInt())
        }
        MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
            v.layout(
                offsetOriginX.toInt(),
                offsetOriginY.toInt(),
                offsetOriginX.toInt() + v.width,
                offsetOriginY.toInt() + v.height
            )
        }
    }
    true
}

3、layoutParam方式实现位移滑动

v.layoutParams = layoutParam

直接看核心代码

var paramLastX = 0F
  var paramLastY = 0F
  var paramOriginX = 0F
  var paramOriginY = 0F
  vLayoutParamMove.setOnTouchListener { v, event ->
      val layoutParam: ViewGroup.MarginLayoutParams =
          v.layoutParams as ViewGroup.MarginLayoutParams
      when (event.action) {
          MotionEvent.ACTION_DOWN -> {
              paramLastX = event.x
              paramLastY = event.y
              paramOriginX = layoutParam.leftMargin.toFloat()
              paramOriginY = layoutParam.topMargin.toFloat()
          }
          MotionEvent.ACTION_MOVE -> {
              val offsetX = event.x - paramLastX
              val offsetY = event.y - paramLastY
              layoutParam.leftMargin = (layoutParam.leftMargin + offsetX).toInt()
              layoutParam.topMargin = (layoutParam.topMargin + offsetY).toInt()
              v.layoutParams = layoutParam
          }
          MotionEvent.ACTION_UP, MotionEvent.ACTION_CANCEL -> {
              layoutParam.leftMargin = paramOriginX.toInt()
              layoutParam.topMargin = paramOriginY.toInt()
              v.layoutParams = layoutParam
          }
      }
      true
  }
}