PropertyValuesHolder的使用

参考：
PropertyValuesHolder的使用

【HenCoder Android 开发进阶】自定义 View 1-7：属性动画（进阶篇）

《Animation动画详解》

Android 属性动画：这是一篇很详细的 属性动画 总结&攻略

属性动画需要了解的知识点：
ValueAnimator extends Animator implements AnimationHandler.AnimationFrameCallback 
ObjectAnimator extends ValueAnimator
AnimatorSet extends Animator 
View的anim

public static Keyframe ofFloat(float fraction, float value)  

fraction：表示当前的显示进度，即从加速器中getInterpolation()函数的返回值；
value：表示当前应该在的位置 

第一步：生成Keyframe对象；
第二步：利用PropertyValuesHolder.ofKeyframe()生成PropertyValuesHolder对象
第三步：ObjectAnimator.ofPropertyValuesHolder()生成对应的Animator

同一个动画中改变多个属性：多个动画同时执行

方式一：ViewPropertyAnimator

view.animate()
        .scaleX(1)
        .scaleY(1)
        .alpha(1);

方式二：PropertyValuesHolder

PropertyValuesHolder holder1 = PropertyValuesHolder.ofFloat("scaleX", 1);
PropertyValuesHolder holder2 = PropertyValuesHolder.ofFloat("scaleY", 1);
PropertyValuesHolder holder3 = PropertyValuesHolder.ofFloat("alpha", 1);

ObjectAnimator animator = ObjectAnimator.ofPropertyValuesHolder(view, holder1, holder2, holder3)
animator.start();

方式三：AnimatorSet （可指定动画顺序）

ObjectAnimator animator1 = ObjectAnimator.ofFloat(...);
animator1.setInterpolator(new LinearInterpolator());
ObjectAnimator animator2 = ObjectAnimator.ofInt(...);
animator2.setInterpolator(new DecelerateInterpolator());

AnimatorSet animatorSet = new AnimatorSet();
// 两个动画依次执行
animatorSet.playSequentially(animator1, animator2);

// 两个动画同时执行
animatorSet.playTogether(animator1, animator2);

// 使用 AnimatorSet.play(animatorA).with/before/after(animatorB)
// 的方式来精确配置各个 Animator 之间的关系
animatorSet.play(animator1).with(animator2);
animatorSet.play(animator1).before(animator2);
animatorSet.play(animator1).after(animator2);

animatorSet.start();

PropertyValuesHolder的使用

通过设置 Keyframe （关键帧），把同一个动画属性拆分成多个阶段。

//1、设置关键帧
//参数：动画进度百分比，动画属性值
Keyframe.ofFloat(float fraction, float value)
Keyframe.ofInt(float fraction, int value)
Keyframe.ofObject(float fraction, Object value)

//2、将关键帧添加到PropertyValuesHolder
//参数：属性名（需要set/get方法），关键帧Keyframe
PropertyValuesHolder.ofKeyframe(String propertyName, Keyframe... values)
//参数：属性值、属性值
PropertyValuesHolder.ofFloat(String propertyName, float... values)
//参数：属性值、属性值
PropertyValuesHolder.ofInt(Property<?, Integer> property, int... values);
//参数：属性值、TypeEvaluator、属性值
PropertyValuesHolder.ofObject(String propertyName, TypeEvaluator evaluator, Object... values);

//3、添加到ObjectAnimator
//参数：执行动画的对象，属性值Holder
ObjectAnimator.ofPropertyValuesHolder(Object target,PropertyValuesHolder... values)

PropertyValuesHolder使用示例：

KeyframeView

public class KeyframeView extends View {
    final float radius = dpToPixel(80);

    float progress = 0;
    RectF arcRectF = new RectF();

    Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);

    public KeyframeView(Context context) {
        super(context);
    }

    public KeyframeView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public KeyframeView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    {
        paint.setTextSize(dpToPixel(40));
        paint.setTextAlign(Paint.Align.CENTER);
    }

    public float getProgress() {
        return progress;
    }

    public void setProgress(float progress) {
        this.progress = progress;
        invalidate();
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        float centerX = getWidth() / 2;
        float centerY = getHeight() / 2;

        paint.setColor(Color.parseColor("#E91E63"));
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeCap(Paint.Cap.ROUND);
        paint.setStrokeWidth(dpToPixel(15));
        arcRectF.set(centerX - radius, centerY - radius, centerX + radius, centerY + radius);
        canvas.drawArc(arcRectF, 135, progress * 2.7f, false, paint);

        paint.setColor(Color.WHITE);
        paint.setStyle(Paint.Style.FILL);
        canvas.drawText((int) progress + "%", centerX, centerY - (paint.ascent() + paint.descent()) / 2, paint);
    }
}

Utils

public class Utils {

    public static float dpToPixel(float dp) {
        DisplayMetrics metrics = Resources.getSystem().getDisplayMetrics();
        return dp * metrics.density;
    }

}

布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <Button
        android:id="@+id/btn"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="执行动画" />

    <Button
        android:id="@+id/firstview"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:text="我是一个view" />

    <com.joanzapata.android.KeyframeView
        android:id="@+id/secondview"
        android:layout_width="200dp"
        android:layout_height="200dp"
        android:layout_below="@+id/firstview"
        android:layout_marginTop="20dp" />
</LinearLayout>

代码：

public class MyActivityI extends AppCompatActivity implements View.OnClickListener {

    private Button mButton;
    private Button view1;
    private KeyframeView view2;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_anim);

        mButton = (Button) findViewById(R.id.btn);
        view1 = (Button) findViewById(R.id.firstview);
        view2 = (KeyframeView) findViewById(R.id.secondview);
        mButton.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        anim1();
        anim2();
    }

    private void anim2() {
        // 在 0% 处开始
        Keyframe keyframe1 = Keyframe.ofFloat(0, 0);
        // 时间经过 50% 的时候，动画完成度 100%
        Keyframe keyframe2 = Keyframe.ofFloat(0.5f, 100);
        // 时间见过 100% 的时候，动画完成度倒退到 80%，即反弹 20%
        Keyframe keyframe3 = Keyframe.ofFloat(1, 80);
        PropertyValuesHolder holder = PropertyValuesHolder.ofKeyframe("progress", keyframe1, keyframe2, keyframe3);

        ObjectAnimator animator = ObjectAnimator.ofPropertyValuesHolder(view2, holder);
        animator.setDuration(5000);
        animator.start();
    }

    /**
     * PropertyValuesHolder这个类可以先将动画属性和值暂时的存储起来，后一起执行，在有些时候可以使用替换掉AnimatorSet，减少代码量
     */
    private void anim1() {

        //keyframe
        Keyframe keyframe1 = Keyframe.ofFloat(0.0f, 0);
        Keyframe keyframe2 = Keyframe.ofFloat(0.25f, -30);
        Keyframe keyframe3 = Keyframe.ofFloat(0.5f, 30);
        Keyframe keyframe4 = Keyframe.ofFloat(1.0f, 0);
        PropertyValuesHolder rotation = PropertyValuesHolder.ofKeyframe(View.ROTATION, keyframe1, keyframe2, keyframe3, keyframe4);

        PropertyValuesHolder alpha = PropertyValuesHolder.ofFloat("alpha", 1.0f, 0.2f, 1.0f);
        PropertyValuesHolder scaleX = PropertyValuesHolder.ofFloat("scaleX", 1.0f, 0.2f, 1.0f);
        PropertyValuesHolder scaleY = PropertyValuesHolder.ofFloat("scaleY", 1.0f, 0.2f, 1.0f);

        ObjectAnimator animator = ObjectAnimator.ofPropertyValuesHolder(view1, alpha, scaleX, scaleY, rotation);
        animator.setInterpolator(new OvershootInterpolator());
        animator.setDuration(5000).start();
    }
}