Android折叠抽屉

效果图

折叠抽屉.gif

原理

这里我们把逻辑分成两份
1 抽屉控件
2 折叠控件

抽屉控件

抽屉我们都知道官方为我们提供了一个组件 DrawerLayout
我们自定义一个FoldDrawerLayout 继承自 DrawerLayout 使其用法与DrawerLayout 完全相同
同时复写onAttachedToWindow 方法
循环判断子view 判断子view是不是抽屉控件 如果是
则在子view外层在套上一层 可折叠的容器 在添加该容器

 override fun onAttachedToWindow() {
        super.onAttachedToWindow()
        for (i in 0 until childCount){
            var child = getChildAt(i)
             // 判断是否是抽屉view
            if(isDrawerView(child)){
                var layPar = child.layoutParams as LayoutParams
                var foldlayout = PolyToPolyMenu(context)
                //如果是抽屉类 把它的父类改成可折叠的容器 在添加它
                removeView(child)
                foldlayout.addView(child)
                addView(foldlayout , i , layPar)
            }
        }

        setDrawerListener(object : DrawerListener{
            override fun onDrawerStateChanged(newState: Int) {
            }

            override fun onDrawerSlide(drawerView: View, slideOffset: Float) {
                if(drawerView is PolyToPolyMenu){
                    drawerView.mFactor = slideOffset
                }
            }

            override fun onDrawerClosed(drawerView: View) {
            }

            override fun onDrawerOpened(drawerView: View) {
            }

        })

    }

判断是否是抽屉控件

 fun isDrawerView(child:View):Boolean{
        var gravity = (child.layoutParams as LayoutParams).gravity
        var absGravity = GravityCompat.getAbsoluteGravity(gravity , ViewCompat.getLayoutDirection(child))
        return (absGravity and  (Gravity.LEFT or Gravity.RIGHT)) !=0
    }

监听抽屉的滑动进度 动态改变折叠容器的 缩放值

完整抽屉控件代码

package com.bhb.seniorcustomview.matrix

import android.content.Context
import android.util.AttributeSet
import android.view.Gravity
import android.view.View
import android.view.ViewGroup
import androidx.core.view.GravityCompat
import androidx.core.view.ViewCompat
import androidx.drawerlayout.widget.DrawerLayout

/**
 *  create by BHB on 9/1/21
 */

class FoldDrawerLayout : DrawerLayout{

    constructor(context: Context, attributes: AttributeSet):super(context , attributes){
    }
    constructor(context: Context, attributes: AttributeSet, defStyle : Int):super(context , attributes , defStyle){
    }

    override fun onAttachedToWindow() {
        super.onAttachedToWindow()
        for (i in 0 until childCount){
            var child = getChildAt(i)
             // 判断是否是抽屉view
            if(isDrawerView(child)){
                var layPar = child.layoutParams as LayoutParams
                var foldlayout = PolyToPolyMenu(context)
                //如果是抽屉类 把它的父类改成可折叠的容器 在添加它
                removeView(child)
                foldlayout.addView(child)
                addView(foldlayout , i , layPar)
            }
        }

        setDrawerListener(object : DrawerListener{
            override fun onDrawerStateChanged(newState: Int) {
            }

            override fun onDrawerSlide(drawerView: View, slideOffset: Float) {
                if(drawerView is PolyToPolyMenu){
                    drawerView.mFactor = slideOffset
                }
            }

            override fun onDrawerClosed(drawerView: View) {
            }

            override fun onDrawerOpened(drawerView: View) {
            }

        })

    }

    fun isDrawerView(child:View):Boolean{
        var gravity = (child.layoutParams as LayoutParams).gravity
        var absGravity = GravityCompat.getAbsoluteGravity(gravity , ViewCompat.getLayoutDirection(child))
        return (absGravity and  (Gravity.LEFT or Gravity.RIGHT)) !=0
    }

}

折叠控件

我们把一个完整的控件平均分割成n份
计算每一份的实际长度 mFoldWidth = mWidth/ sFoldNums.toFloat()
和缩放之后 每一份的宽度 var foldedItemWidth = mWidth * mFactor / sFoldNums
此时 y轴偏移量 实际长度 和 宽度 可以组成一个直角三角形

y轴偏移量.png

根据勾股定理可得 y轴偏移量
var depth = Math.sqrt(mFoldWidth.toDouble() * mFoldWidth - foldedItemWidth * foldedItemWidth).toFloat()

第一份在y轴上向上偏移 第二份在y轴上向下偏移 第三份在y轴上向上偏移 第四份在y轴上向下偏移
以此类推 实现折叠的效果

循环计算每一份的矩阵值

for (i in 0 until sFoldNums){
            //表示第几份 i==0 时 ， 表示第一份
            var isEven = i % 2 == 0
            var sLeft = mFoldWidth * i
            var sRight = mFoldWidth * (i + 1)


            var src = floatArrayOf(sLeft , 0f ,
                sRight , 0f ,
                sRight ,mHeight.toFloat() ,
                sLeft , mHeight.toFloat())


            var dst = floatArrayOf(foldedItemWidth * i + transWidth  , if(isEven) 0f else depth,
                foldedItemWidth*(i + 1)+ transWidth ,if(isEven) depth else 0f
                ,foldedItemWidth*(i + 1)+ transWidth  , if(isEven) mHeight.toFloat() + depth else mHeight.toFloat(),
                foldedItemWidth * i+ transWidth , if(isEven) mHeight.toFloat()  else mHeight.toFloat() + depth)


            mMatrices[i]!!.setPolyToPoly(src , 0 , dst , 0 , src.size shr  1 )
        }

Matrix setPolyToPoly(float[] src, int srcIndex,float[] dst, int dstIndex,int pointCount)
把原图像的节点 src 按对应的顺序修改为dst 的值
srcIndex src开始计算的位置 dstIndex dst开始计算的位置 pointCount计算的位数

此处的transWidth 是用来向右对齐的 折叠缩放之后默认靠左 我们对每一个节点x轴加上多余的距离 使最终效果靠右
var transWidth = mWidth *(1-mFactor)

复写dispatchDraw方法
循环绘制 每一份裁剪出自己的范围

override fun dispatchDraw(canvas: Canvas?) {
        for (i in 0 until sFoldNums){
            canvas!!.save()
            var rect = Rect(mFoldWidth.toInt() * i ,0 , mFoldWidth.toInt()*(i + 1) , mHeight)
            canvas.setMatrix(mMatrices[i])
            canvas.clipRect(rect)
            super.dispatchDraw(canvas)
            canvas.translate(mFoldWidth*i , 0f)

            if(i % 2 == 0){
                canvas.drawRect(mFoldWidth*i , 0f , mFoldWidth * (i+1) , mHeight.toFloat() , mSolidPaint)
            }else{
                canvas.drawRect(mFoldWidth*i , 0f , mFoldWidth * (i+1) , mHeight.toFloat() , mShadowPaint)
            }

            canvas.restore()
        }
    }

完整折叠控件代码

package com.bhb.seniorcustomview.matrix

import android.content.Context
import android.graphics.*
import android.util.AttributeSet
import android.util.Log
import android.view.View
import android.widget.LinearLayout
import com.bhb.seniorcustomview.R
import java.util.jar.Attributes

/**
 *  create by BHB on 8/29/21
 *   图片折叠
 */

class PolyToPolyMenu : LinearLayout{


    // 每一份所占的 宽度
    var mFoldWidth = 0f
    // 折叠之后所占完整控件宽度的比例
    var mFactor = 0.8f
    set(value) {
        field = value
        updateFold()
        invalidate()
    }
    var mMatrices = arrayOfNulls<Matrix>(sFoldNums)

    var mSolidPaint = Paint()
    var mShadowPaint = Paint()
    lateinit var mShadowGradientShader  : LinearGradient


    companion object{
        // 整个控件分割的数量
        val sFoldNums = 8
    }

    constructor(context: Context ):super(context ){
        init()
    }
    constructor(context: Context , attributes: AttributeSet):super(context , attributes){
        init()
    }
    constructor(context: Context , attributes: AttributeSet , defStyle : Int):super(context , attributes , defStyle){
        init()
    }



    var mWidth :Int = 0
    var mHeight :Int = 0
    fun updateFold(){
        mWidth = measuredWidth
        mHeight = measuredHeight

        mFoldWidth = mWidth/ sFoldNums.toFloat()
        var alpha = 255 * (1-mFactor) .toInt()
        mSolidPaint.setColor(Color.argb(alpha * 0.8f.toInt() , 0 , 0 , 0))
        mShadowPaint.alpha = alpha


        var foldedItemWidth = mWidth * mFactor / sFoldNums

        // 计算y轴上的偏移量
        var depth = Math.sqrt(mFoldWidth.toDouble() * mFoldWidth - foldedItemWidth * foldedItemWidth).toFloat()


        var transWidth = mWidth *(1-mFactor)

        for (i in 0 until sFoldNums){
            //表示第几份 i==0 时 ， 表示第一份
            var isEven = i % 2 == 0
            var sLeft = mFoldWidth * i
            var sRight = mFoldWidth * (i + 1)


            var src = floatArrayOf(sLeft , 0f ,
                sRight , 0f ,
                sRight ,mHeight.toFloat() ,
                sLeft , mHeight.toFloat())


            var dst = floatArrayOf(foldedItemWidth * i + transWidth  , if(isEven) 0f else depth,
                foldedItemWidth*(i + 1)+ transWidth ,if(isEven) depth else 0f
                ,foldedItemWidth*(i + 1)+ transWidth  , if(isEven) mHeight.toFloat() + depth else mHeight.toFloat(),
                foldedItemWidth * i+ transWidth , if(isEven) mHeight.toFloat()  else mHeight.toFloat() + depth)


            mMatrices[i]!!.setPolyToPoly(src , 0 , dst , 0 , src.size shr  1 )
        }
    }

    fun init(){

        for (i in 0 until sFoldNums){
            mMatrices[i] = Matrix()
        }
        mShadowGradientShader = LinearGradient(0f, 0f , mFoldWidth ,
            0f , Color.BLACK , Color.TRANSPARENT , Shader.TileMode.CLAMP)
        mShadowPaint.setShader(mShadowGradientShader)

    }

    override fun onLayout(changed: Boolean, l: Int, t: Int, r: Int, b: Int) {
        super.onLayout(changed, l, t, r, b)
        updateFold()
    }

    override fun dispatchDraw(canvas: Canvas?) {
        for (i in 0 until sFoldNums){
            canvas!!.save()
            var rect = Rect(mFoldWidth.toInt() * i ,0 , mFoldWidth.toInt()*(i + 1) , mHeight)
            canvas.setMatrix(mMatrices[i])
            canvas.clipRect(rect)
            super.dispatchDraw(canvas)
            canvas.translate(mFoldWidth*i , 0f)

            if(i % 2 == 0){
                canvas.drawRect(mFoldWidth*i , 0f , mFoldWidth * (i+1) , mHeight.toFloat() , mSolidPaint)
            }else{
                canvas.drawRect(mFoldWidth*i , 0f , mFoldWidth * (i+1) , mHeight.toFloat() , mShadowPaint)
            }

            canvas.restore()
        }
    }


}

布局文件代码

<?xml version="1.0" encoding="utf-8"?>
<com.bhb.seniorcustomview.matrix.FoldDrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".matrix.TestScaleActivity">

    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@mipmap/bg_book3"
        android:scaleType="fitXY"/>

    <LinearLayout
        android:layout_gravity="left"
        android:background="#eee"
        android:layout_width="200dp"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:text="这里是菜单啊啊啊啊啊"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:text="这里是菜单"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:text="这里是菜单"/>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:gravity="center_horizontal"
            android:text="这里是菜单"/>

    </LinearLayout>




</com.bhb.seniorcustomview.matrix.FoldDrawerLayout>