我需要将 Shimmer effect 添加到图像视图中，如我的 ImageView 链接中给出的那样。动画应该是从下到上，而不是示例图片中的从左到右。我已经尝试过facebook shimmer libraby，但它仅支持上面的 API 16。如果从以上 14 开始，我需要支持。我也尝试过this library，但它不支持 ImageViews 以及从下到上的动画。是否有任何库可以实现 Imageview 的微光效果（具有从下到上的动画）？或者有什么方法可以使用 ImageView 来实现这个功能？
【问题讨论】：
标签： android android-animation android-imageview
您可以创建自己的自定义视图！
class ShimmerView : View, ValueAnimator.AnimatorUpdateListener{
constructor(context: Context)
: super(context) { init() }
constructor(context: Context, attrs: AttributeSet)
: super(context, attrs) { init() }
constructor(context: Context, attrs: AttributeSet, defStyleAttr: Int)
: super(context, attrs, defStyleAttr) { init() }
companion object {
const val EDGE_ALPHA = 12
const val SHADER_COLOR_R = 170
const val SHADER_COLOR_G = 170
const val SHADER_COLOR_B = 170
const val CENTER_ALPHA = 100
const val ITEM_BG_COLOR = Color.WHITE
val EDGE_COLOR = Color.argb(EDGE_ALPHA, SHADER_COLOR_R, SHADER_COLOR_G, SHADER_COLOR_B)
val CENTER_COLOR = Color.argb(CENTER_ALPHA, SHADER_COLOR_R, SHADER_COLOR_G, SHADER_COLOR_B)
const val LIST_ITEM_LINES = 3
const val CORNER_RADIUS = 2
const val LINE_HEIGHT = 15
const val H_SPACING = 12
const val W_SPACING = 16
const val IMAGE_SIZE = 50
const val ANIMATION_DURATION = 1500L
}
private var listItems: Bitmap? = null
private var animator: ValueAnimator? = null
private var paint: Paint? = null
private var shaderPaint: Paint? = null
private var shaderColors: IntArray? = null
private var lineHeight: Float = 0F
private var hSpacing: Float = 0F
private var wSpacing: Float = 0F
private var imageSize: Float = 0F
private var cornerRadius: Float = 0F
// 1. Инициализируем переменные.
// 1. Initialize variables.
fun init() {
val metric = context.resources.displayMetrics
cornerRadius = dpToPixels(metric, CORNER_RADIUS)
hSpacing = dpToPixels(metric, H_SPACING)
wSpacing = dpToPixels(metric, W_SPACING)
lineHeight = spToPixels(metric, LINE_HEIGHT)
imageSize = dpToPixels(metric, IMAGE_SIZE)
animator = ValueAnimator.ofFloat(-1F, 2F)
animator?.duration = ANIMATION_DURATION
animator?.interpolator = LinearInterpolator()
animator?.repeatCount = ValueAnimator.INFINITE
animator?.addUpdateListener(this)
paint = Paint()
shaderPaint = Paint()
shaderPaint?.isAntiAlias = true
shaderColors = intArrayOf(EDGE_COLOR, CENTER_COLOR, EDGE_COLOR)
}
// 2. Когда View отобразилась на экране, запускаем анимацию.
// 2. When View is displayed on the screen, run the animation.
override fun onVisibilityChanged(changedView: View?, visibility: Int) {
super.onVisibilityChanged(changedView, visibility)
when(visibility) {
VISIBLE -> animator?.start()
INVISIBLE, GONE -> animator?.cancel()
}
}
// 3. При выполнении анимации, изменяем положение шейдера и перерисовываем View.
// 3. When the animation, change the position of the shader and redraw View.
override fun onAnimationUpdate(valueAnimator: ValueAnimator) {
if(isAttachedToWindow) {
val factor: Float = valueAnimator.animatedValue as Float
updateShader(width = width.toFloat(), factor = factor)
invalidate()
}
}
// 4. Одновременно со стартом анимации, рисуем элементы.
// 4. Simultaneously with the start of the animation, draw the elements.
override fun onSizeChanged(w: Int, h: Int, oldw: Int, oldh: Int) {
super.onSizeChanged(w, h, oldw, oldh)
updateShader(width = w.toFloat())
if (h > 0 && w > 0) {
drawListItems(w, h)
} else {
listItems = null
animator?.cancel()
}
}
private fun updateShader(width: Float, factor: Float = -1F) {
val left = width * factor
val shader = LinearGradient(
left, 0F, left+width, 0F, shaderColors, floatArrayOf(0f, 0.5f, 1f), Shader.TileMode.CLAMP)
shaderPaint?.shader = shader
}
override fun onDraw(canvas: Canvas) {
canvas.drawColor(EDGE_COLOR)
canvas.drawRect(0F, 0F, canvas.width.toFloat(), canvas.height.toFloat(), shaderPaint)
if (listItems != null) { canvas.drawBitmap(listItems, 0F, 0F, paint) }
}
private fun drawListItems(w: Int, h: Int) {
listItems = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888)
val canvas = Canvas(listItems)
val item = getItemBitmap(w)
var top = 0
do {
canvas.drawBitmap(item, 0F, top.toFloat(), paint)
top += item.height
} while (top < canvas.height)
canvas.drawColor(ITEM_BG_COLOR, PorterDuff.Mode.SRC_IN)
}
private fun getItemBitmap(w: Int): Bitmap {
val h = calculateListItemHeight(LIST_ITEM_LINES)
val item = Bitmap.createBitmap(w, h, Bitmap.Config.ALPHA_8)
val canvas = Canvas(item)
canvas.drawColor(Color.argb(255, 0, 0, 0))
val itemPaint = Paint()
itemPaint.isAntiAlias = true
itemPaint.color = Color.argb(0, 0, 0, 0)
itemPaint.xfermode = PorterDuffXfermode(PorterDuff.Mode.DST_IN)
//Avatar
val rectF = RectF(wSpacing, hSpacing, wSpacing+imageSize, hSpacing+imageSize)
canvas.drawOval(rectF, itemPaint)
val textLeft = rectF.right + hSpacing
val textRight = canvas.width - wSpacing
//Title line
val titleWidth = (textRight - textLeft)*0.5F
rectF.set(textLeft, hSpacing, textLeft+titleWidth, hSpacing+lineHeight)
canvas.drawRoundRect(rectF, cornerRadius, cornerRadius, itemPaint)
//Time stamp
val timeWidth = (textRight - textLeft)*0.2F
rectF.set(textRight-timeWidth, hSpacing, textRight, hSpacing+lineHeight)
canvas.drawRoundRect(rectF, cornerRadius, cornerRadius, itemPaint)
//Text lines
for (i in 0..LIST_ITEM_LINES-1) {
val lineTop = rectF.bottom + hSpacing
rectF.set(textLeft, lineTop, textRight, lineTop+lineHeight)
canvas.drawRoundRect(rectF, cornerRadius, cornerRadius, itemPaint)
}
return item
}
private fun calculateListItemHeight(lines: Int): Int {
return ((lines*lineHeight) + (hSpacing*(lines+1))).toInt()
}
private fun dpToPixels(metrics: DisplayMetrics, dp: Int): Float {
return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp.toFloat(), metrics)
}
private fun spToPixels(metrics: DisplayMetrics, sp: Int): Float {
return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, sp.toFloat(), metrics)
}
override fun onDetachedFromWindow() {
super.onDetachedFromWindow()
animator?.removeAllUpdateListeners()
animator = null
listItems = null
}
}
【讨论】：
Facebook Shimmer 库确实支持 API 级别 14。我在具有以下设置的项目中使用它：
defaultConfig {
....
minSdkVersion 14
targetSdkVersion 23
....
}
有了这个依赖：
dependencies {
....
compile 'com.facebook.shimmer:shimmer:0.1.0'
}
【讨论】：