属性动画05-ObjectAnimator的高级使用

如果看了objectanimator(真正的劳动者)和TypeEvaluator的使用那么你对自定义TypeEvaluator和对任意属性做动画这两个概念就应该很熟悉了.下面这个例子就是对二者的综合使用.

我们知道补间动画的效果很局限于移动,缩放,旋转,和淡入淡出这四种效果.通过ObjectAnimator我们可以完成对任意属性设置动画效果,通过TypeEvaluator我们可以改变动画的效果显示状态.

需求:移动小球,并改变小球颜色.

blic class MyView extends View {    private Paint mPaint;    private Point mPoint;    private String color;    public String getColor() {        return color;    }    public void setColor(String color) {        this.color = color;        mPaint.setColor(Color.parseColor(color));        invalidate();    }    public MyView(Context context) {        super(context);        init();    }    public MyView(Context context, AttributeSet attrs) {        super(context, attrs);        init();    }    public MyView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    private void init() {        mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mPaint.setColor(Color.BLUE);    }    @Override    protected void onDraw(Canvas canvas) {        super.onDraw(canvas);        if (mPoint == null) {            mPoint = new Point(50, 50);            drawCircle(canvas);            startAnimation();        } else {            drawCircle(canvas);        }    }    private void drawCircle(Canvas canvas) {        canvas.drawCircle(mPoint.getX(), mPoint.getY(), 50, mPaint);    }    private void startAnimation() {        Point startPoint = new Point(50, 50);        Point endPoint = new Point(getWidth() - 50, getHeight() - 50);        ValueAnimator animator = ValueAnimator                .ofObject(new PointEvaluator(), startPoint, endPoint);        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {            @Override            public void onAnimationUpdate(ValueAnimator animation) {                mPoint = ((Point) animation.getAnimatedValue());                LogUtil.i(mPoint.getX() + "------" + mPoint.getY());                invalidate();            }        });        ObjectAnimator colorAnimator = ObjectAnimator.ofObject(this, "color", new ColorEvaluator(),                "#0000ff", "#ff0000");        AnimatorSet animatorSet = new AnimatorSet();        animatorSet.play(animator).with(colorAnimator);        animatorSet.setDuration(5000);        animatorSet.start();    }}

颜色的控制

public class ColorEvaluator implements TypeEvaluator<String> {    private int currentRed = -1;    private int currentGreen = -1;    private int currentBlue = -1;    @Override    public String evaluate(float fraction, String startValue, String endValue) {        int startRed = Integer.parseInt(startValue.substring(1, 3), 16);        int startGreen = Integer.parseInt(startValue.substring(3, 5), 16);        int startBlue = Integer.parseInt(startValue.substring(5, 7), 16);        int endRed = Integer.parseInt(endValue.substring(1, 3), 16);        int endGreen = Integer.parseInt(endValue.substring(3, 5), 16);        int endBlue = Integer.parseInt(endValue.substring(5, 7), 16);        if (currentRed == -1) {            currentRed = startRed;        }        if (currentBlue == -1) {            currentBlue = startBlue;        }        if (currentGreen == -1) {            currentGreen = startGreen;        }        int diffRed = Math.abs(startRed - endRed);        int diffGreen = Math.abs(startGreen - endGreen);        int diffBlue = Math.abs(startBlue - endBlue);        if (currentRed != endRed) {            currentRed = getCurrentColor(startRed, endRed, diffRed, 0, fraction);        } else if (currentGreen != endGreen) {            currentGreen = getCurrentColor(startGreen, endGreen, diffGreen, diffRed, fraction);        } else if (currentBlue != endBlue) {            currentBlue = getCurrentColor(startBlue, endBlue, diffBlue, diffRed + diffGreen, fraction);        }        String currentColor = "#" + getHexString(currentRed) +                getHexString(currentGreen) +                getHexString(currentBlue);        LogUtil.i(currentColor);        return currentColor;    }    private int getCurrentColor(int startColor, int endColor,                                int diffColor, int offset, float fraction) {        int currentColor = 0;        if (startColor > endColor) {            currentColor = (int) (startColor - (fraction * diffColor - offset));            if (currentColor < endColor) {                currentColor = endColor;            }        } else {            currentColor = (int) (startColor + (fraction * diffColor - offset));            if (currentColor > endColor) {                currentColor = endColor;            }        }        return currentColor;    }    private String getHexString(int value) {        String hexString = Integer.toHexString(value);        if (hexString.length() == 1) {            hexString = "0" + hexString;        }        return hexString;    }}

效果: