Android 自定义ViewGroup
step:
重写onMeasure 、遍历测量子VIew，得到尺寸后保存，有些子VIew可能需要重新测量，然后得出所有子VIew位置和尺寸后，计算出自己的尺寸，然后使用setMeasuredDimension(w,h)保存结果
step2:
遍历每个子VIew，调用layout方法来将位置和尺寸传给子VIew
code:
package com.example.myapplication.view
import android.content.Context
import android.util.AttributeSet
import android.view.ViewGroup
import androidx.core.view.children
class TagLayout(context: Context,attributeSet: AttributeSet):ViewGroup(context,attributeSet) {
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
for (child in children){
}
}
override fun onLayout(p0: Boolean, l: Int, t: Int, r: Int, b: Int) {
for (child in children){
if (children.indexOf(child) == 0){
child.layout(0,0,(r-l) /2,(b-t) /2 )
}else{
child.layout((r-l) /2,(b-t) /2,r-l,b-t )
}
}
}
}
//计算子View模式以及父View的模式范围
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
val witchSpecMode = MeasureSpec.getMode(widthMeasureSpec) //模式
val witchSpecSize = MeasureSpec.getSize(widthMeasureSpec) //大小
for ((index, child) in children.withIndex()) {
var childParams = child.layoutParams
var childWitchSpecMode = 0
var childWitchSpecSize = 0
when (layoutParams.width) {
LayoutParams.MATCH_PARENT -> {
when (witchSpecMode) { //计算ViewGroup取值
MeasureSpec.EXACTLY -> {
childWitchSpecMode = MeasureSpec.EXACTLY //精确值
childWitchSpecSize - usedSpecSize
}
MeasureSpec.AT_MOST -> {
childWitchSpecMode = MeasureSpec.AT_MOST // 200dp.... 或者填充
childWitchSpecSize - usedSpecSize
}
MeasureSpec.UNSPECIFIED -> {
//父VIew没限制 可用空间无限,子View填满
childWitchSpecMode = MeasureSpec.UNSPECIFIED
childWitchSpecSize =
0 //早期Android witchSpecSize 默认时0,现在Android 写不写0会影响计算结果
}
}
}
LayoutParams.WRAP_CONTENT -> {
when (witchSpecMode) {
//有精确空间,不要超过大小}
MeasureSpec.EXACTLY, MeasureSpec.AT_MOST -> {
childWitchSpecMode = MeasureSpec.AT_MOST
childWitchSpecSize - usedSpecSize
}
MeasureSpec.UNSPECIFIED -> {
//父VIew没限制 可用空间无限,子View填满
childWitchSpecMode = MeasureSpec.UNSPECIFIED
childWitchSpecSize =
0 //早期Android witchSpecSize 默认时0,现在Android 写不写0会影响计算结果
}
}
}
else -> {
//精确要求大小
childWitchSpecMode = MeasureSpec.EXACTLY
childWitchSpecSize - layoutParams.width
}
}
child.measure()
val childBounds = childrenBounds[index]
childBounds.set()
}
val selfWidth
val selfHeight
setMeasuredDimension(selfWidth, selfHeight)
}
以上计算方法Android给出一个方法 ->
measureChildWithMargins(view,measureW,useW,measureH,useH)
这个方法的child.getLayourParams 会转成MarginLayoutParams 需要我们重写generateLayoutParams方法进行转换
override fun generateLayoutParams(attrs: AttributeSet?): LayoutParams {
return MarginLayoutParams(context,attrs)
}
具体算法跟layout 相关
package com.example.myapplication.view
import android.content.Context
import android.graphics.Rect
import android.util.AttributeSet
import android.view.ViewGroup
import androidx.core.view.children
import kotlin.math.max
class TagLayout(context: Context, attributeSet: AttributeSet) : ViewGroup(context, attributeSet) {
private val childrenBounds = mutableListOf()
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
var witchUse = 0
var lineWitchUse = 0
var heightUse = 0
var lineMaxheigh = 0
val specSize = MeasureSpec.getSize(widthMeasureSpec)
val specMode = MeasureSpec.getMode(widthMeasureSpec)
for ((index, child) in children.withIndex()) {
measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, heightUse)
if ((specMode != MeasureSpec.UNSPECIFIED) && (lineWitchUse + child.measuredWidth > specSize)){
//如果时不限制大小,则 specSize 就没有用了,然后计算已用和自身超过最大值 换行
lineWitchUse = 0
heightUse += lineMaxheigh
lineMaxheigh = 0
measureChildWithMargins(child, widthMeasureSpec, 0, heightMeasureSpec, heightUse)
}
if (index >= childrenBounds.size) {
childrenBounds.add(Rect())
}
val childBounds = childrenBounds[index]
childBounds.set(lineWitchUse, heightUse, lineWitchUse + child.measuredWidth, heightUse + child.measuredHeight) //测量阶段用measureWitch...
lineWitchUse += child.measuredWidth
witchUse = max(witchUse,lineWitchUse) //计算比较最大宽度 确保时最大宽度
lineMaxheigh = max(lineMaxheigh, child.measuredHeight)
}
val selfWidth = witchUse
val selfHeight = heightUse + lineMaxheigh
setMeasuredDimension(selfWidth, selfHeight)
}
override fun onLayout(p0: Boolean, l: Int, t: Int, r: Int, b: Int) {
for ((index, child) in children.withIndex()) {
val childBounds = childrenBounds[index]
child.layout(
childBounds.left,
childBounds.top,
childBounds.right,
childBounds.bottom
)
}
}
override fun generateLayoutParams(attrs: AttributeSet?): LayoutParams {
return MarginLayoutParams(context,attrs)
}
}
/*
package com.example.myapplication.view
import android.content.Context
import android.graphics.Rect
import android.util.AttributeSet
import android.view.ViewGroup
import androidx.core.view.children
class TagLayout(context: Context, attributeSet: AttributeSet) : ViewGroup(context, attributeSet) {
private val childrenBounds = listOf()
override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
val witchSpecMode = MeasureSpec.getMode(widthMeasureSpec) //模式
val witchSpecSize = MeasureSpec.getSize(widthMeasureSpec) //大小
for ((index, child) in children.withIndex()) {
measureChildWithMargins(child,widthMeasureSpec,,heightMeasureSpec,heightUse)
val childBounds = childrenBounds[index]
childBounds.set()
var childParams = child.layoutParams
var childWitchSpecMode = 0
var childWitchSpecSize = 0
when (layoutParams.width) {
LayoutParams.MATCH_PARENT -> {
when (witchSpecMode) { //计算ViewGroup取值
MeasureSpec.EXACTLY -> {
childWitchSpecMode = MeasureSpec.EXACTLY //精确值 200dp.... 或者填充
childWitchSpecSize - usedSpecSize
}
MeasureSpec.AT_MOST -> {
childWitchSpecMode = MeasureSpec.AT_MOST //精确值 200dp.... 或者填充
childWitchSpecSize - usedSpecSize
}
MeasureSpec.UNSPECIFIED -> {
//父VIew没限制 可用空间无限,子View填满
childWitchSpecMode = MeasureSpec.UNSPECIFIED
childWitchSpecSize =
0 //早期Android witchSpecSize 默认时0,现在Android 写不写0会影响计算结果
}
}
}
LayoutParams.WRAP_CONTENT -> {
when (witchSpecMode) {
//有精确空间,不要超过大小}
MeasureSpec.EXACTLY, MeasureSpec.AT_MOST -> {
childWitchSpecMode = MeasureSpec.AT_MOST
childWitchSpecSize - usedSpecSize
}
MeasureSpec.UNSPECIFIED -> {
//父VIew没限制 可用空间无限,子View填满
childWitchSpecMode = MeasureSpec.UNSPECIFIED
childWitchSpecSize =
0 //早期Android witchSpecSize 默认时0,现在Android 写不写0会影响计算结果
}
}
}
else -> {
//精确要求大小
childWitchSpecMode = MeasureSpec.EXACTLY
childWitchSpecSize - layoutParams.width
}
}
}
val selfWidth
val selfHeight
setMeasuredDimension(selfWidth, selfHeight)
}
override fun onLayout(p0: Boolean, l: Int, t: Int, r: Int, b: Int) {
for ((index, child) in children.withIndex()) {
val childBounds = childrenBounds[index]
child.layout(
childBounds.left,
childBounds.top,
childBounds.right,
childBounds.bottom
)
}
}
}
*/