属性动画 - 简书

属性动画

ViewPropertyAnimator

 imageView.animate()
            .translationX(200.dp)
            .translationY(100.dp)
            .scaleX(2f)
            .scaleY(2f)
            .alpha(0.5f)
            .setStartDelay(1000)

缺点：

有局限性，只能改变其中的几个属性，横向纵向渐变旋转
比如需要更改圆半径大小的动画，对于这种自定义的属性不能实现

优点：

使用方便

ObjectAnimator

class CircleView @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : View(context, attrs, defStyleAttr) {

    var radius = 50.dp
    set(value) {
        field = value
        invalidate()
    }

    private val paint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        color = Color.GREEN
    }

    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        canvas.drawCircle(width/2f,height/2f,radius,paint)
    }
}

val animtor = ObjectAnimator.ofFloat(imageView, "radius", 150.dp)
animtor.startDelay = 1000
animtor.start()

优点：

支持自定义的属性值

缺点：

一次只支持一个属性值，如果操作多个属性值的话，需要设置多个，然后一起执行。

AnimatorSet 动画集(对多个动画进行合成)

animtor,animtor1,animtor2 三个ObjectAnimator动画顺序执行

val animatorSet = AnimatorSet()
animatorSet.playSequentially(animtor,animtor1,animtor2)
animatorSet.start()

PropertyValuesHolder

用法

val propertyValuesHolder = PropertyValuesHolder.ofFloat("radius", 150.dp)

        val objectAnimator = ObjectAnimator.ofPropertyValuesHolder(imageView,propertyValuesHolder)
        objectAnimator.startDelay = 1000
        objectAnimator.duration = 2000
        objectAnimator.start()

优点

支持更精细的动画控制，可以支持多个自定义属性值（ObjectAnimator.ofPropertyValuesHolder此方法支持多个holder）

和AnimatorSet区别

不支持多个属性值动画按顺序执行

Keyframe

使用方式

val distance = 200.dp
val keyframe = Keyframe.ofFloat(0f, 0f * distance)
val keyframe1 = Keyframe.ofFloat(0.2f, 0.4f * distance)
val keyframe2 = Keyframe.ofFloat(0.8f, 0.6f * distance)
val keyframe3 = Keyframe.ofFloat(1f, 1f * distance)
val holder = PropertyValuesHolder.ofKeyframe(
            "translationX",
            keyframe,
            keyframe1,
            keyframe2,
            keyframe3
        )
val animator = ObjectAnimator.ofPropertyValuesHolder(imageView,holder)
animator.startDelay = 2000
animator.start()

优点

更加精准的控制动画执行的快慢进度，实现特殊的动画效果

Interpolator 插值器

使用方式

val animator = ObjectAnimator.ofFloat(imageView,"translationX",200.dp)
animator.interpolator = LinearInterpolator()
animator.startDelay = 2000
animator.start()

总结

适用于场景内的动画AccelerateDecelerateInterpolator()
适用于出场动画 AccelerateInterpolator
适用于入场动画 DecelerateInterpolator

TypeEvaluator

使用方式

 val animtor =
            ObjectAnimator.ofObject(imageView, "point", PointFEvaluator(), PointF(100.dp, 200.dp))
animtor.startDelay = 1000
animtor.start()

private class PointFEvaluator :TypeEvaluator<PointF>{
        override fun evaluate(fraction: Float, startValue: PointF, endValue: PointF): PointF {

            val startX = startValue.x
            val startY = startValue.y
            val endX = endValue.x
            val endY = endValue.y
            val currentX = startX + (endX-startX)*fraction
            val currentY = startY + (endY-startY)*fraction
            return PointF(currentX,currentY)
        }

    }

class PointFView @JvmOverloads constructor(
    context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0
) : View(context, attrs, defStyleAttr) {

    private val mPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
        strokeWidth = 20.dp
        strokeCap = Paint.Cap.ROUND
    }

    var point = PointF(0f,0f)
    set(value) {
        field = value
        invalidate()
    }

    override fun onDraw(canvas: Canvas) {
        super.onDraw(canvas)
        canvas.drawPoint(point.x,point.y,mPaint)
    }
}

Listeners

各种动画的监听器，监听动画开始啦结束啦等

ValueAnimator

不常用

硬件加速

利用GPU提高视图渲染的速度？没搞明白