前言
有時候做項目的時候,遇到滾動的RecyclerView或者ScrollView滾動到邊緣要展示漸入漸出效果,如果是使用圖片設置的話,圖片的背景色可能與當前整個視圖的背景顏色衝突,並且圖片也會增大Apk體積。有沒有什麼好的方法可以使用代碼去設置呢?其實系統View裏面已經存在在滾動到View邊緣設置漸入漸出效果,接下來直接貼出一份自定義的ScrollView代碼。
代碼部分
/**
* 邊緣陰影效果的view
*/
class FadeScrollView @JvmOverloads constructor(
context: Context,
attrs: AttributeSet? = null,
defStyleAttr: Int = 0,
) : NestedScrollView(context, attrs, defStyleAttr) {
companion object {
//漸變從0-1.0
private const val DEFAULT_FADING_EDGE_ENABLED = false
private const val DEFAULT_FADING_EDGE_STRENGTH = 0.9f
}
private var horizontalFadeEdgeEnabled = DEFAULT_FADING_EDGE_ENABLED
private var verticalFadeEdgeEnabled = DEFAULT_FADING_EDGE_ENABLED
private var topFadeEdgeStrength = DEFAULT_FADING_EDGE_STRENGTH
private var bottomFadeEdgeStrength = DEFAULT_FADING_EDGE_STRENGTH
private var leftFadeEdgeStrength = DEFAULT_FADING_EDGE_STRENGTH
private var rightFadeEdgeStrength = DEFAULT_FADING_EDGE_STRENGTH
init {
val array = context.obtainStyledAttributes(attrs, R.styleable.FadeScrollView, defStyleAttr, 0)
horizontalFadeEdgeEnabled = array.getBoolean(R.styleable.FadeScrollView_horizontalFadingEdgeEnabled, horizontalFadeEdgeEnabled)
verticalFadeEdgeEnabled = array.getBoolean(R.styleable.FadeScrollView_verticalFadingEdgeEnabled, verticalFadeEdgeEnabled)
topFadeEdgeStrength = array.getFloat(R.styleable.FadeScrollView_topFadingEdgeStrength, topFadingEdgeStrength)
bottomFadeEdgeStrength = array.getFloat(R.styleable.FadeScrollView_bottomFadingEdgeStrength, bottomFadeEdgeStrength)
leftFadeEdgeStrength = array.getFloat(R.styleable.FadeScrollView_leftFadingEdgeStrength, leftFadeEdgeStrength)
rightFadeEdgeStrength = array.getFloat(R.styleable.FadeScrollView_rightFadingEdgeStrength, rightFadeEdgeStrength)
array.recycle()
isHorizontalFadingEdgeEnabled = horizontalFadeEdgeEnabled
isVerticalFadingEdgeEnabled = verticalFadeEdgeEnabled
}
override fun getTopFadingEdgeStrength(): Float {
return getFadingEdgeStrength(verticalFadeEdgeEnabled, topFadeEdgeStrength)
}
override fun getBottomFadingEdgeStrength(): Float {
return getFadingEdgeStrength(verticalFadeEdgeEnabled, bottomFadeEdgeStrength)
}
override fun getLeftFadingEdgeStrength(): Float {
return getFadingEdgeStrength(horizontalFadeEdgeEnabled, leftFadeEdgeStrength)
}
override fun getRightFadingEdgeStrength(): Float {
return getFadingEdgeStrength(horizontalFadeEdgeEnabled, rightFadeEdgeStrength)
}
private fun getFadingEdgeStrength(fadeEdgeEnabled: Boolean, fadeEdgeStrength: Float): Float {
return if (fadeEdgeEnabled) {
when {
fadeEdgeStrength <= 0 -> {
0f
}
fadeEdgeStrength >= 1 -> {
1f
}
else -> {
fadeEdgeStrength
}
}
} else {
0f
}
}
}
屬性
<declare-styleable name="FadeScrollView">
<attr name="horizontalFadingEdgeEnabled" format="boolean" />
<attr name="verticalFadingEdgeEnabled" format="boolean" />
<attr name="topFadingEdgeStrength" format="float" />
<attr name="bottomFadingEdgeStrength" format="float" />
<attr name="leftFadingEdgeStrength" format="float" />
<attr name="rightFadingEdgeStrength" format="float" />
</declare-styleable>