Drawable加入动画机制（二）

来源：互联网发布：时间穿梭机淘宝编辑：程序博客网时间：2024/06/07 15:39

在上篇文章中，我们介绍了一种给Drawable加入动画机制的方法

Drawable加入动画机制（一）

下面来介绍下我根据这个机制写的三段式动画，效果如下图

首先在AnimationScaleState中加入了一个中间Scale参数——mMidScale，

如果在调用前设置了中间Scale，则实现三段式动画

重写start()，如果Mid不为0，则Repeat三次，把Duration变为三段

    @Override    public void start()    {        if(mState.mAnimating){            return;        }        if(mState.mInterpolator == null){            mState.mInterpolator = new LinearInterpolator();        }        if(mState.mTransformation == null){            mState.mTransformation = new Transformation();        }        else{            mState.mTransformation.clear();        }        if(mState.mAnimation == null){            mState.mAnimation = new AlphaAnimation(0.0f, 1.0f);        }        else{            mState.mAnimation.reset();        }        //setup for 3-phased animation        if(mState.mMidScale != 0){            mState.mAnimation.setDuration(mState.mDuration / 3);            mState.mAnimation.setRepeatMode(Animation.RESTART);            mState.mAnimation.setRepeatCount(2);            hasMidScale = true;        }        mState.mAnimation.setDuration(mState.mDuration);        mState.mAnimation.setInterpolator(mState.mInterpolator);        mState.mAnimation.setStartTime(Animation.START_ON_FIRST_FRAME);        mState.mAnimating = true;        invalidateSelf();    }

然后再重写draw

如果MidScale为0，那就实现一段动画

如果不为空，则用animStep标注当前步骤，并逐阶段计算新Scale

同时针对上一篇中提出的问题，加入了动画结束后的stop机制，如果不加入此机制，State中的AlphaAnimation会一直执行下去

    @Override    public void draw(Canvas canvas)    {        final AnimationScaleState st = mState;        if(st.mDrawable == null){            return;        }        final Rect bounds = (st.mUseBounds ? getBounds() : mTmpRect);        int saveCount = canvas.save();        canvas.scale(st.mScale, st.mScale,                bounds.left + bounds.width()  / 2,                bounds.top  + bounds.height() / 2);        st.mDrawable.draw(canvas);        canvas.restoreToCount(saveCount);        if (st.mAnimating) {            long animTime = AnimationUtils.currentAnimationTimeMillis();            st.mAnimation.getTransformation(animTime, st.mTransformation);            float transformation = st.mTransformation.getAlpha();            if (!hasMidScale) {                st.mScale = (st.mMinScale                        + (st.mMaxScale - st.mMinScale) * (st.mInvert ? (1.0f - transformation) : transformation));                invalidateSelf();                if (transformation == 1.0f)                    stop();            }            // An implementation of 3-Phased Animation using AlphaAnimation            else {                if (animStep == 1) {                    st.mScale = (st.mMidScale                            + (st.mMaxScale - st.mMidScale) * (st.mInvert ? (1.0f - transformation) : transformation));                    if (transformation == 1.0f) {                        animStep = 2;                    }                } else if (animStep == 2) {                    st.mScale = (st.mMaxScale                            - (st.mMaxScale - st.mMinScale) * (st.mInvert ? (1.0f - transformation) : transformation));                    if (transformation == 1.0f){                        animStep = 3;                    }                } else if (animStep == 3) {                    st.mScale = (st.mMinScale                            + (st.mMidScale - st.mMinScale) * (st.mInvert ? (1.0f - transformation) : transformation));                    if (transformation == 1.0f) {                        animStep = 1;                        stop();                    }                }                invalidateSelf();            }        }    }

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