android 圆角边框边框渐变,支持边框、圆角、渐变色、透明度的GradientButton

最近在项目中发现好多Button背景颜色相同，但圆角大小不等的Button，这样就得写一大堆的shape或者selector，不便于管理及后期维护，于是乎变想能不能写一个支持边框、圆角、渐变色、透明度的万用Button呢。为了能够兼容button自带的属性，当然继承自AppCompatButton是最好的，剩下的就需要考虑selector各状态在我们自定义Button中怎么获取与渲染了。最开始想到，自己draw？不过这样有点low，需要我们处理一大堆的状态，譬如：state_pressed、state_enabled...

那有没有更好的实现方式呢？我们把这些状态交由系统管理呢？在一顿寻找后，发现还真有呢，真是踏破铁鞋无觅处，得来全不费工夫--------GradientDrawable，没错就是它，一个Drawable的子类。我们看看它的描叙：

A Drawable with a color gradient for buttons, backgrounds, etc.

并且通过查看它提供的相应方法，它不仅能替我们管理好各种state，也支持边框绘制、圆角设置，渐变色当然更不用说了，看它的名字就知道啦。好了废话就不多说了，下面就是GradientButton的代码实现过程：

const val TOP_BOTTOM = 0

const val TR_BL = 1

const val RIGHT_LEFT = 2

const val BR_TL = 3

const val BOTTOM_TOP = 4

const val BL_TR = 5

const val LEFT_RIGHT = 6

const val TL_BR = 7

class GradientButton(context: Context, attrs: AttributeSet? = null) :

AppCompatButton(context, attrs, android.R.attr.borderlessButtonStyle) {

@IntDef(TOP_BOTTOM, TR_BL, RIGHT_LEFT, BR_TL, BOTTOM_TOP, BL_TR, LEFT_RIGHT, TL_BR)

@kotlin.annotation.Retention(AnnotationRetention.SOURCE)

annotation class Orientation

private val radii by lazy { FloatArray(8) }

private var mBackgroundDrawable: GradientButtonDrawable? = null

private var mPaddingLeft = 0.0f

private var mPaddingTop = 0.0f

private var mPaddingRight = 0.0f

private var mPaddingBottom = 0.0f

private var mMinWidth = 0

private var mMinHeight = 0

init {

val stateListDrawable = StateListDrawable()

attrs?.also { it ->

context.obtainStyledAttributes(it, R.styleable.GradientButton).apply {

val borderColorStateList = getColorStateList(R.styleable.GradientButton_border_color)

val borderWidth = getDimension(R.styleable.GradientButton_border_width, 0.0f)

val isRadiusAdjustBounds = getBoolean(R.styleable.GradientButton_is_radius_adjust_bounds, false)

val radius = getDimension(R.styleable.GradientButton_all_radius, 0.0f)

val topLeftRadius = getDimension(R.styleable.GradientButton_top_left_radius, 0.0f)

val topRightRadius = getDimension(R.styleable.GradientButton_top_right_radius, 0.0f)

val bottomLeftRadius = getDimension(R.styleable.GradientButton_bottom_left_radius, 0.0f)

val bottomRightRadius = getDimension(R.styleable.GradientButton_bottom_right_radius, 0.0f)

val backgroundColorStateList = getColorStateList(R.styleable.GradientButton_background_color)

val orientation = getInt(R.styleable.GradientButton_orientation, LEFT_RIGHT)

val startBackgroundColorStateList =

getColorStateList(R.styleable.GradientButton_start_background_color)

val centerBackgroundColorStateList =

getColorStateList(R.styleable.GradientButton_center_background_color)

val endBackgroundColorStateList = getColorStateList(R.styleable.GradientButton_end_background_color)

val backgroundAlpha = getFraction(R.styleable.GradientButton_background_alpha, 1, 1, 0.0f)

val padding = getDimension(R.styleable.GradientButton_padding, -1.0f)

mPaddingLeft = (if (padding != -1.0f) {

padding

} else {

getDimension(R.styleable.GradientButton_padding_left, mPaddingLeft)

})

mPaddingTop = (if (padding != -1.0f) {

padding

} else {

getDimension(R.styleable.GradientButton_padding_top, mPaddingTop)

})

mPaddingRight = (if (padding != -1.0f) {

padding

} else {

getDimension(R.styleable.GradientButton_padding_right, mPaddingRight)

})

mPaddingBottom = (if (padding != -1.0f) {

padding

} else {

getDimension(R.styleable.GradientButton_padding_bottom, mPaddingBottom)

})

mMinWidth = getDimensionPixelSize(R.styleable.GradientButton_min_width, 0)

mMinHeight = getDimensionPixelSize(R.styleable.GradientButton_min_height, 0)

mBackgroundDrawable = createBackgroundDrawable(getOrientation(orientation))

if (borderWidth > 0.0f || backgroundColorStateList != null || (startBackgroundColorStateList != null && endBackgroundColorStateList != null)) {

setTopLeftRadius(topLeftRadius)

setTopRightRadius(topRightRadius)

setBottomLeftRadius(bottomLeftRadius)

setBottomRightRadius(bottomRightRadius)

setRadius(radius)

setBorder(borderWidth, borderColorStateList)

setBackgroundColorStateList(backgroundColorStateList)

setGradientBackgroundColorStateList(

startBackgroundColorStateList,

centerBackgroundColorStateList,

endBackgroundColorStateList

)

setBackgroundAlpha(backgroundAlpha)

mBackgroundDrawable?.setRadius(isRadiusAdjustBounds, radii)

}

recycle()

}

} ?: also {

mBackgroundDrawable = createBackgroundDrawable(getOrientation(LEFT_RIGHT))

}

mBackgroundDrawable?.also {

stateListDrawable.addState(it.state, mBackgroundDrawable)

setGradientDrawable(stateListDrawable)

}

setPadding(mPaddingLeft.toInt(), mPaddingTop.toInt(), mPaddingRight.toInt(), mPaddingBottom.toInt())

minWidth = mMinWidth

minimumWidth = mMinWidth

minHeight = mMinHeight

minimumHeight = mMinHeight

}

private fun setGradientDrawable(stateListDrawable: StateListDrawable) {

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {

background = stateListDrawable

} else {

setBackgroundDrawable(stateListDrawable)

}

/**

* 设置渐变色方向

fun setOrientation(@Orientation orientation: Int) {

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {

mBackgroundDrawable?.orientation = getOrientation(orientation)

}

fun setBackgroundAlpha(@FloatRange(from = 0.0, to = MAX_VALUE) alpha: Float) {

mBackgroundDrawable?.alpha = ((1.0f - alpha) * 255).toInt()

}

/**

* 渐变色设置

fun setGradientBackgroundColorStateList(

startBackgroundColorStateList: ColorStateList?,

centerBackgroundColorStateList: ColorStateList? = null,

endBackgroundColorStateList: ColorStateList?

) {

mBackgroundDrawable?.setGradientBackgroundColorStateList(

startBackgroundColorStateList,

centerBackgroundColorStateList,

endBackgroundColorStateList

)

}

fun setBackgroundColorStateList(backgroundColorStateList: ColorStateList?) {

mBackgroundDrawable?.setBackgroundColorStateList(backgroundColorStateList)

}

fun setBackgroundColorRes(@ColorRes backgroundColor: Int) {

setBackgroundColorRes(backgroundColor, backgroundColor, backgroundColor)

}

fun setBackgroundColorRes(@ColorRes startBackgroundColor: Int, @ColorRes centerBackgroundColor: Int?, @ColorRes endBackgroundColor: Int) {

val centerBackgroundColorStateList = centerBackgroundColor?.let {

ColorStateList(arrayOf(intArrayOf(android.R.attr.state_enabled)), intArrayOf(context.resources.getColor(it)))

}

mBackgroundDrawable?.setGradientBackgroundColorStateList(ColorStateList(arrayOf(intArrayOf(android.R.attr.state_enabled)),

intArrayOf(context.resources.getColor(startBackgroundColor))),

centerBackgroundColorStateList,

ColorStateList(arrayOf(intArrayOf(android.R.attr.state_enabled)),

intArrayOf(context.resources.getColor(endBackgroundColor))))

}

private fun getOrientation(@Orientation orientation: Int): GradientDrawable.Orientation {

return when (orientation) {

TOP_BOTTOM -> GradientDrawable.Orientation.TOP_BOTTOM

TR_BL -> GradientDrawable.Orientation.TR_BL

RIGHT_LEFT -> GradientDrawable.Orientation.RIGHT_LEFT

BR_TL -> GradientDrawable.Orientation.BR_TL

BOTTOM_TOP -> GradientDrawable.Orientation.BOTTOM_TOP

BL_TR -> GradientDrawable.Orientation.BL_TR

TL_BR -> GradientDrawable.Orientation.TL_BR

else -> GradientDrawable.Orientation.LEFT_RIGHT

}

private fun createBackgroundDrawable(orientation: GradientDrawable.Orientation) =

GradientButtonDrawable(orientation, null)

fun setBorder(@FloatRange(from = 0.0, to = MAX_VALUE) borderWidth: Float, borderColorStateList: ColorStateList?) {

mBackgroundDrawable?.setBorder(borderWidth, borderColorStateList)

}

fun setBorder(@FloatRange(from = 0.0, to = MAX_VALUE) borderWidth: Float, @ColorRes borderColorRes: Int){

setBorder(borderWidth, ColorStateList(arrayOf(intArrayOf(android.R.attr.state_enabled)),

intArrayOf(context.resources.getColor(borderColorRes))))

}

/**

* 设置圆角自适应最小边

fun setRadiusAdjustBounds(isRadiusAdjustBounds: Boolean) {

mBackgroundDrawable?.setRadius(isRadiusAdjustBounds, null)

}

fun setRadius(@FloatRange(from = 0.0, to = MAX_VALUE) radius: Float) {

if (radius > 0.0f) {

for (index in radii.indices) {

radii[index] = radius

}