android动画之view动画

前言：

android动画中可以分为2种动画，view动画（补间动画）和属性动画（Animator）
本文大概分析一下View动画，作为笔记。

正文：

View动画其实现的类是Animation子类，包名：package android.view.animation
其中包括ScaleAnimation，RotationAnimation等

分别实现下面方法。

    /**
     * Helper for getTransformation. Subclasses should implement this to apply
     * their transforms given an interpolation value.  Implementations of this
     * method should always replace the specified Transformation or document
     * they are doing otherwise.
     * 
     * @param interpolatedTime The value of the normalized time (0.0 to 1.0)
     *        after it has been run through the interpolation function.
     * @param t The Transformation object to fill in with the current
     *        transforms.
     */
    protected void applyTransformation(float interpolatedTime, Transformation t) {
    }

view通过startAnimation开启动画：

    /**
     * Start the specified animation now.
     *
     * @param animation the animation to start now
     */
    public void startAnimation(Animation animation) {
        animation.setStartTime(Animation.START_ON_FIRST_FRAME);
        setAnimation(animation);
        invalidateParentCaches();
        invalidate(true);
    }

熟悉View更新机制可以知道，调用invalidate(true);会更新整个view的视图树，View会依次调用：

onMeasure()
onLayout()
onDraw();

除了onDraw方法，另外两个方法都没有跟Animation相关的操作

final Animation a = getAnimation();
        if (a != null) {
            more = applyLegacyAnimation(parent, drawingTime, a, scalingRequired);
            concatMatrix = a.willChangeTransformationMatrix();
            if (concatMatrix) {
                mPrivateFlags3 |= PFLAG3_VIEW_IS_ANIMATING_TRANSFORM;
            }
            transformToApply = parent.getChildTransformation();
        }


....


        if (more && hardwareAcceleratedCanvas) {
            if (a.hasAlpha() && (mPrivateFlags & PFLAG_ALPHA_SET) == PFLAG_ALPHA_SET) {
                // alpha animations should cause the child to recreate its display list
                invalidate(true);
            }
        }

从上面代码可以知道，如果more为true的话，会一直invalidate

其中 more = applyLegacyAnimation

    private boolean applyLegacyAnimation(ViewGroup parent, long drawingTime,
            Animation a, boolean scalingRequired) 
{
        Transformation invalidationTransform;
        final int flags = parent.mGroupFlags;
        final boolean initialized = a.isInitialized();
        if (!initialized) {
            a.initialize(mRight - mLeft, mBottom - mTop, parent.getWidth(), parent.getHeight());
            a.initializeInvalidateRegion(0, 0, mRight - mLeft, mBottom - mTop);
            if (mAttachInfo != null) a.setListenerHandler(mAttachInfo.mHandler);
            onAnimationStart();
        }

        final Transformation t = parent.getChildTransformation();
        boolean more = a.getTransformation(drawingTime, t, 1f);
        if (scalingRequired && mAttachInfo.mApplicationScale != 1f) {
            if (parent.mInvalidationTransformation == null) {
                parent.mInvalidationTransformation = new Transformation();
            }
            invalidationTransform = parent.mInvalidationTransformation;
            a.getTransformation(drawingTime, invalidationTransform, 1f);
        } else {
            invalidationTransform = t;
        }

        if (more) {
            if (!a.willChangeBounds()) {
                if ((flags & (ViewGroup.FLAG_OPTIMIZE_INVALIDATE | ViewGroup.FLAG_ANIMATION_DONE)) ==
                        ViewGroup.FLAG_OPTIMIZE_INVALIDATE) {
                    parent.mGroupFlags |= ViewGroup.FLAG_INVALIDATE_REQUIRED;
                } else if ((flags & ViewGroup.FLAG_INVALIDATE_REQUIRED) == 0) {
                    // The child need to draw an animation, potentially offscreen, so
                    // make sure we do not cancel invalidate requests
                    parent.mPrivateFlags |= PFLAG_DRAW_ANIMATION;
                    parent.invalidate(mLeft, mTop, mRight, mBottom);
                }
            } else {
                if (parent.mInvalidateRegion == null) {
                    parent.mInvalidateRegion = new RectF();
                }
                final RectF region = parent.mInvalidateRegion;
                a.getInvalidateRegion(0, 0, mRight - mLeft, mBottom - mTop, region,
                        invalidationTransform);

                // The child need to draw an animation, potentially offscreen, so
                // make sure we do not cancel invalidate requests
                parent.mPrivateFlags |= PFLAG_DRAW_ANIMATION;

                final int left = mLeft + (int) region.left;
                final int top = mTop + (int) region.top;
                parent.invalidate(left, top, left + (int) (region.width() + .5f),
                        top + (int) (region.height() + .5f));
            }
        }
        return more;
    }

        final Transformation t = parent.getChildTransformation();
        boolean more = a.getTransformation(drawingTime, t, 1f);

从父亲拿到对应的Transformation

/**
 * Defines the transformation to be applied at
 * one point in time of an Animation.
 *
 */
public class Transformation



    protected Matrix mMatrix;
    protected float mAlpha;
    protected int mTransformationType;

其中Transformation里面定义了几个参数.

    Transformation getChildTransformation() {
        if (mChildTransformation == null) {
            mChildTransformation = new Transformation();
        }
        return mChildTransformation;
    }

该类用于保存view中当前动画的一些相关的参数，然后再调用
a.getTransformation(drawingTime, t, 1f);

getTransformation ：

if (duration != 0) {
            normalizedTime = ((float) (currentTime - (mStartTime + startOffset))) /
                    (float) duration;
        } else {
            // time is a step-change with a zero duration
            normalizedTime = currentTime < mStartTime ? 0.0f : 1.0f;
        }

        final boolean expired = normalizedTime >= 1.0f || isCanceled();
        mMore = !expired;

        if (!mFillEnabled) normalizedTime = Math.max(Math.min(normalizedTime, 1.0f), 0.0f);

        if ((normalizedTime >= 0.0f || mFillBefore) && (normalizedTime <= 1.0f || mFillAfter)) {
            if (!mStarted) {
                fireAnimationStart();
                mStarted = true;
                if (NoImagePreloadHolder.USE_CLOSEGUARD) {
                    guard.open("cancel or detach or getTransformation");
                }
            }

            if (mFillEnabled) normalizedTime = Math.max(Math.min(normalizedTime, 1.0f), 0.0f);

            if (mCycleFlip) {
                normalizedTime = 1.0f - normalizedTime;
            }

            final float interpolatedTime = mInterpolator.getInterpolation(normalizedTime);
            applyTransformation(interpolatedTime, outTransformation);
        }

如果当前进度再0和1之间 more = true：

final float interpolatedTime = mInterpolator.getInterpolation(normalizedTime);
            applyTransformation(interpolatedTime, outTransformation);

其中applyTransformation是一个空方法，用于给子类定义,如RotateAnimation：

    @Override
    protected void applyTransformation(float interpolatedTime, Transformation t) {
        float degrees = mFromDegrees + ((mToDegrees - mFromDegrees) * interpolatedTime);
        float scale = getScaleFactor();
        
        if (mPivotX == 0.0f && mPivotY == 0.0f) {
            t.getMatrix().setRotate(degrees);
        } else {
            t.getMatrix().setRotate(degrees, mPivotX * scale, mPivotY * scale);
        }
    }

其中t就是保存再parent的

final Transformation t = parent.getChildTransformation();

more为true的情况下:

if (parent.mInvalidateRegion == null) {
                    parent.mInvalidateRegion = new RectF();
                }
                final RectF region = parent.mInvalidateRegion;
                a.getInvalidateRegion(0, 0, mRight - mLeft, mBottom - mTop, region,
                        invalidationTransform);//代码1

                // The child need to draw an animation, potentially offscreen, so
                // make sure we do not cancel invalidate requests
                parent.mPrivateFlags |= PFLAG_DRAW_ANIMATION;

                final int left = mLeft + (int) region.left;
                final int top = mTop + (int) region.top;
                parent.invalidate(left, top, left + (int) (region.width() + .5f),
                        top + (int) (region.height() + .5f));

最后一行代码通过调用parent.invalidate更新子类，其中region：

final RectF region = parent.mInvalidateRegion;
                a.getInvalidateRegion(0, 0, mRight - mLeft, mBottom - mTop, region,
                        invalidationTransform);


 public void getInvalidateRegion(int left, int top, int right, int bottom,
            RectF invalidate, Transformation transformation) {

        final RectF tempRegion = mRegion;
        final RectF previousRegion = mPreviousRegion;

        invalidate.set(left, top, right, bottom);
        transformation.getMatrix().mapRect(invalidate);
        // Enlarge the invalidate region to account for rounding errors
        invalidate.inset(-1.0f, -1.0f);
        tempRegion.set(invalidate);
        invalidate.union(previousRegion);

        previousRegion.set(tempRegion);

        final Transformation tempTransformation = mTransformation;
        final Transformation previousTransformation = mPreviousTransformation;

        tempTransformation.set(transformation);
        transformation.set(previousTransformation);
        previousTransformation.set(tempTransformation);
    }

后面就是继续调用view的绘制流程

动画最终都是通过draw方法，再每一次的绘制脉冲到来的时候绘制，再在view的draw方法里面，
只是通过当前的位置，移动，或者放大，改变画布的位置等数据达到效果.

if (offsetForScroll) {
            canvas.translate(mLeft - sx, mTop - sy);
        } else {
            if (!drawingWithRenderNode) {
                canvas.translate(mLeft, mTop);
            }
            if (scalingRequired) {
                if (drawingWithRenderNode) {
                    // TODO: Might not need this if we put everything inside the DL
                    restoreTo = canvas.save();
                }
                // mAttachInfo cannot be null, otherwise scalingRequired == false
                final float scale = 1.0f / mAttachInfo.mApplicationScale;
                canvas.scale(scale, scale);
            }
        }

        float alpha = drawingWithRenderNode ? 1 : (getAlpha() * getTransitionAlpha());
        if (transformToApply != null
                || alpha < 1
                || !hasIdentityMatrix()
                || (mPrivateFlags3 & PFLAG3_VIEW_IS_ANIMATING_ALPHA) != 0) {
            if (transformToApply != null || !childHasIdentityMatrix) {
                int transX = 0;
                int transY = 0;

                if (offsetForScroll) {
                    transX = -sx;
                    transY = -sy;
                }

                if (transformToApply != null) {
                    if (concatMatrix) {
                        if (drawingWithRenderNode) {
                            renderNode.setAnimationMatrix(transformToApply.getMatrix());
                        } else {
                            // Undo the scroll translation, apply the transformation matrix,
                            // then redo the scroll translate to get the correct result.
                            canvas.translate(-transX, -transY);
                            canvas.concat(transformToApply.getMatrix());
                            canvas.translate(transX, transY);
                        }
                        parent.mGroupFlags |= ViewGroup.FLAG_CLEAR_TRANSFORMATION;
                    }

                    float transformAlpha = transformToApply.getAlpha();
                    if (transformAlpha < 1) {
                        alpha *= transformAlpha;
                        parent.mGroupFlags |= ViewGroup.FLAG_CLEAR_TRANSFORMATION;
                    }
                }

                if (!childHasIdentityMatrix && !drawingWithRenderNode) {
                    canvas.translate(-transX, -transY);
                    canvas.concat(getMatrix());
                    canvas.translate(transX, transY);
                }
            }

而上面的动画，并没有调用onlayout相应的方法，也就是说，view里面的动画并没有改变view本身的位置
而改变的只是画布canvas的位置等.

可以看View里面的判断当前点是否按下当前的view：

    /**
     * Utility method to determine whether the given point, in local coordinates,
     * is inside the view, where the area of the view is expanded by the slop factor.
     * This method is called while processing touch-move events to determine if the event
     * is still within the view.
     *
     * @hide
     */
    public boolean pointInView(float localX, float localY, float slop) {
        return localX >= -slop && localY >= -slop && localX < ((mRight - mLeft) + slop) &&
                localY < ((mBottom - mTop) + slop);
    }

由于view动画并没有修改mRight ,mLeft等值，所以即使view移动到其他地方，点击原来view还是有事件

完

转载于:https://www.jianshu.com/p/e516b04dca2e