View向上滑動指定距離進行指定操做

1. 此view是自定義view，用戶能夠修改其繼承的父類

package com.koolearn.android.view

import android.content.Context
import android.support.constraint.ConstraintLayout
import android.util.AttributeSet
import android.view.MotionEvent

class SlideTopView(context: Context,attr: AttributeSet):ConstraintLayout(context,attr){
//    private var lastX = 0
    private var lastY = 0;
    private lateinit var onSlideTopListener:(Int)->Unit
    override fun onTouchEvent(event: MotionEvent): Boolean {
//        val x = event.rawX.toInt()
        val y = event.rawY.toInt()

        when (event.action) {
            MotionEvent.ACTION_DOWN -> {
//                lastX = x
                lastY = y
            }
            MotionEvent.ACTION_MOVE -> {
//                val offsetX = x - lastX
                var offsetY = y - lastY
                if(top+offsetY>0){//只能向上滑動
                    offsetY=0
                }
                layout(left,top + offsetY,right,bottom + offsetY)
                onSlideTopListener(top+offsetY)
//                lastX = x
                lastY = y
            }
            MotionEvent.ACTION_UP -> {
            }
        }
        return true
    }

    fun setOnSlideTop(onSlideTopListener:(currentTop:Int)->Unit){
        this.onSlideTopListener = onSlideTopListener;
    }
}
複製代碼