Android 动画

属性动画: ViewPropertyAnimator

ViewPropertyAnimator  = view.animate() 

示例:

imageView.animate()
            .translationX(200.dp)
            .translationY(200.dp)
            .startDelay = 1000

改变view的属性值,大小 位置 偏移等,限制比较多

ObjectAnimator 

ofFloat(target ,name,values):  

java则需要在view类中声明name值的方法 不然会报错,kotlin则自动生成

kotlin:

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

java

public void setRadius(float value){
 
    radius = value;
    invalidate();
}

如果此view改变需要进行invalidate 或者postinvalidate

canvas.withSave{} 保存变更

前后台切换时,每次进入页面可能会被重新绘制,也就是调用onDraw ,需要在应用前 save , 比如

camera.save()

//

camera.restore()

AnimatorSet 可以操作多个属性动画进行合成

示例1:

val animateSet = AnimatorSet()
animateSet.playSequentially(bottomAnima,flipAnima,topAnima)
animateSet.start()

PropertyValuesHolder:将多个属性拼接在一起
示例:

val bottomHolder = PropertyValuesHolder.ofFloat("bottomFlip",60f)

 KeyFrame: 关键帧

用法:

val keyFra = Keyframe.ofFloat(0f,0f)
        val keyFra2 = Keyframe.ofFloat(0.2f,1.5f * LENGTH)
        val keyFra3 = Keyframe.ofFloat(0.8f,0.6f * LENGTH)
        val keyFra4 = Keyframe.ofFloat(1f,1f * LENGTH)
 
        val keyFrameHolder = PropertyValuesHolder.ofKeyframe("translationX",keyFra,keyFra2,keyFra3,keyFra4)
        val objectAni = ObjectAnimator.ofPropertyValuesHolder(imageView,keyFrameHolder)
        objectAni.startDelay = 1000
        objectAni.duration = 2000
        objectAni.start()

Interpolator 从时间完成度到动画完成度

示例

val objectAni = ObjectAnimator.ofFloat()
objectAni.interpolator = AccelerateInterpolator()

常用差值器:

AccelerateInterpolator 加速差值器

AccelerateDecelerateInterpolator 加减速差值器

LinearInterpolator 匀速差值器

TypeEvaluator:

源码:

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package android.animation;
 
/**
 * This evaluator can be used to perform type interpolation between float values.
 */
public class FloatEvaluator implements TypeEvaluator<Number> {
 
    /**
     * This function returns the result of linearly interpolating the start and end values, with
     * fraction representing the proportion between the start and end values. The
     * calculation is a simple parametric calculation: result = x0 + t * (x1 - x0),
     * where x0 is startValue, x1 is endValue,
     * and t is fraction.
     *
     * @param fraction   The fraction from the starting to the ending values
     * @param startValue The start value; should be of type float or
     *                   Float
     * @param endValue   The end value; should be of type float or Float
     * @return A linear interpolation between the start and end values, given the
     *         fraction parameter.
     */
    public Float evaluate(float fraction, Number startValue, Number endValue) {
        float startFloat = startValue.floatValue();
        return startFloat + fraction * (endValue.floatValue() - startFloat);
    }
}

TypeEvaluator

示例:

class ProVinceEvaluator : TypeEvaluator<String> {
    override fun evaluate(fraction: Float, startValue: String, endValue: String): String {
        val startIndex = proVince.indexOf(startValue)
        val endIndex = proVince.indexOf(endValue)
        val currentIndex = startIndex + ((endIndex - startIndex) * fraction).toInt()
        return proVince[currentIndex]
 
    }

  val proVinceView = findViewById<ProVince>(R.id.province)
        val animator = ObjectAnimator.ofObject(proVinceView,"current", ProVinceEvaluator(),"台湾省")
        animator.startDelay = 1000
        animator.duration = 10000
        animator.start()

Listeners: 动画监听器

ValueAnimator : 最基本的动画

硬件加速:

软件绘制: CPU------->View

硬件绘制:CPU-------->GPU

硬件加速缺点:兼容性不如软件绘制

离屏缓冲:例如:canvas.savelayer 可以用hard layer代替        ,setLayerType设置View的离屏缓冲

,不可写在onDraw方法中 

setLayerType()

LAYER_TYPE_HARDWARE 开启View离屏缓冲,使用硬件绘制

LAYER_TYPE_SOFTWARE 开启View的离屏缓冲,使用软件绘制

LAYER_TYPE_NONE 不使用离屏缓冲

view.withLayer 硬件绘制    需要开启离屏缓冲  ps:需要view自带的属性才有效果