Android view中invalidate方法学习小节
/**
* Invalidate the whole view. If the view is visible,
* {@link #onDraw(android.graphics.Canvas)} will be called at some point in
* the future. This must be called from a UI thread. To call from a non-UI thread,
* call {@link #postInvalidate()}.
*/
public void invalidate() {
invalidate(true);
}
view中的invalidate方法会调用invalidate（true）;
/**
* This is where the invalidate() work actually happens. A full invalidate()
* causes the drawing cache to be invalidated, but this function can be called with
* invalidateCache set to false to skip that invalidation step for cases that do not
* need it (for example, a component that remains at the same dimensions with the same
* content).
*
* @param invalidateCache Whether the drawing cache for this view should be invalidated as
* well. This is usually true for a full invalidate, but may be set to false if the
* View's contents or dimensions have not changed.
*/
void invalidate(boolean invalidateCache) {
if (skipInvalidate()) {
return;
}
if ((mPrivateFlags & (PFLAG_DRAWN | PFLAG_HAS_BOUNDS)) == (PFLAG_DRAWN | PFLAG_HAS_BOUNDS) ||
(invalidateCache && (mPrivateFlags & PFLAG_DRAWING_CACHE_VALID) == PFLAG_DRAWING_CACHE_VALID) ||
(mPrivateFlags & PFLAG_INVALIDATED) != PFLAG_INVALIDATED || isOpaque() != mLastIsOpaque) {
mLastIsOpaque = isOpaque();
mPrivateFlags &= ~PFLAG_DRAWN;
mPrivateFlags |= PFLAG_DIRTY;
if (invalidateCache) {
mPrivateFlags |= PFLAG_INVALIDATED;
mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
}
final AttachInfo ai = mAttachInfo;
final ViewParent p = mParent;
//noinspection PointlessBooleanExpression,ConstantConditions
if (!HardwareRenderer.RENDER_DIRTY_REGIONS) {
if (p != null && ai != null && ai.mHardwareAccelerated) {
// fast-track for GL-enabled applications; just invalidate the whole hierarchy
// with a null dirty rect, which tells the ViewAncestor to redraw everything
p.invalidateChild(this, null);
return;
}
}
if (p != null && ai != null) {
final Rect r = ai.mTmpInvalRect;
r.set(0, 0, mRight - mLeft, mBottom - mTop);
// Don't call invalidate -- we don't want to internally scroll
// our own bounds
p.invalidateChild(this, r);
}
}
}
最终都会执行mParent的invalidateChild(this, r);如果开启硬件加速的话，r=null，即重绘整个View，r代表需要绘制的区域，r.set方法的调用设置了需要绘制区域的长和高。
下面看一下invalidateChild()方法
/**
* Don't call or override this method. It is used for the implementation of
* the view hierarchy.
*/
public final void invalidateChild(View child, final Rect dirty) {
ViewParent parent = this;
final AttachInfo attachInfo = mAttachInfo;
if (attachInfo != null) {
// If the child is drawing an animation, we want to copy this flag onto
// ourselves and the parent to make sure the invalidate request goes
// through
final boolean drawAnimation = (child.mPrivateFlags & PFLAG_DRAW_ANIMATION)
== PFLAG_DRAW_ANIMATION;
// Check whether the child that requests the invalidate is fully opaque
// Views being animated or transformed are not considered opaque because we may
// be invalidating their old position and need the parent to paint behind them.
Matrix childMatrix = child.getMatrix();
final boolean isOpaque = child.isOpaque() && !drawAnimation &&
child.getAnimation() == null && childMatrix.isIdentity();
// Mark the child as dirty, using the appropriate flag
// Make sure we do not set both flags at the same time
int opaqueFlag = isOpaque ? PFLAG_DIRTY_OPAQUE : PFLAG_DIRTY;
if (child.mLayerType != LAYER_TYPE_NONE) {
mPrivateFlags |= PFLAG_INVALIDATED;
mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
child.mLocalDirtyRect.union(dirty);
}
final int[] location = attachInfo.mInvalidateChildLocation;
location[CHILD_LEFT_INDEX] = child.mLeft;
location[CHILD_TOP_INDEX] = child.mTop;
if (!childMatrix.isIdentity() ||
(mGroupFlags & ViewGroup.FLAG_SUPPORT_STATIC_TRANSFORMATIONS) != 0) {
RectF boundingRect = attachInfo.mTmpTransformRect;
boundingRect.set(dirty);
Matrix transformMatrix;
if ((mGroupFlags & ViewGroup.FLAG_SUPPORT_STATIC_TRANSFORMATIONS) != 0) {
Transformation t = attachInfo.mTmpTransformation;
boolean transformed = getChildStaticTransformation(child, t);
if (transformed) {
transformMatrix = attachInfo.mTmpMatrix;
transformMatrix.set(t.getMatrix());
if (!childMatrix.isIdentity()) {
transformMatrix.preConcat(childMatrix);
}
} else {
transformMatrix = childMatrix;
}
} else {
transformMatrix = childMatrix;
}
transformMatrix.mapRect(boundingRect);
dirty.set((int) (boundingRect.left - 0.5f),
(int) (boundingRect.top - 0.5f),
(int) (boundingRect.right + 0.5f),
(int) (boundingRect.bottom + 0.5f));
}
do {
View view = null;
if (parent instanceof View) {
view = (View) parent;
}
if (drawAnimation) {
if (view != null) {
view.mPrivateFlags |= PFLAG_DRAW_ANIMATION;
} else if (parent instanceof ViewRootImpl) {
((ViewRootImpl) parent).mIsAnimating = true;
}
}
// If the parent is dirty opaque or not dirty, mark it dirty with the opaque
// flag coming from the child that initiated the invalidate
if (view != null) {
if ((view.mViewFlags & FADING_EDGE_MASK) != 0 &&
view.getSolidColor() == 0) {
opaqueFlag = PFLAG_DIRTY;
}
if ((view.mPrivateFlags & PFLAG_DIRTY_MASK) != PFLAG_DIRTY) {
view.mPrivateFlags = (view.mPrivateFlags & ~PFLAG_DIRTY_MASK) | opaqueFlag;
}
}
parent = parent.invalidateChildInParent(location, dirty);
if (view != null) {
// Account for transform on current parent
Matrix m = view.getMatrix();
if (!m.isIdentity()) {
RectF boundingRect = attachInfo.mTmpTransformRect;
boundingRect.set(dirty);
m.mapRect(boundingRect);
dirty.set((int) (boundingRect.left - 0.5f),
(int) (boundingRect.top - 0.5f),
(int) (boundingRect.right + 0.5f),
(int) (boundingRect.bottom + 0.5f));
}
}
} while (parent != null);
}
}location数组设置了要绘制区域（dirty）的距离当前视图的左边界和上边界的距离，然后重点在do，while循环。parent = parent.invalidateChildInParent(location, dirty);
/**
* Don't call or override this method. It is used for the implementation of
* the view hierarchy.
*
* This implementation returns null if this ViewGroup does not have a parent,
* if this ViewGroup is already fully invalidated or if the dirty rectangle
* does not intersect with this ViewGroup's bounds.
*/
public ViewParent invalidateChildInParent(final int[] location, final Rect dirty) {
if ((mPrivateFlags & PFLAG_DRAWN) == PFLAG_DRAWN ||
(mPrivateFlags & PFLAG_DRAWING_CACHE_VALID) == PFLAG_DRAWING_CACHE_VALID) {
if ((mGroupFlags & (FLAG_OPTIMIZE_INVALIDATE | FLAG_ANIMATION_DONE)) !=
FLAG_OPTIMIZE_INVALIDATE) {
dirty.offset(location[CHILD_LEFT_INDEX] - mScrollX,
location[CHILD_TOP_INDEX] - mScrollY);
if ((mGroupFlags & FLAG_CLIP_CHILDREN) == 0) {
dirty.union(0, 0, mRight - mLeft, mBottom - mTop);
}
final int left = mLeft;
final int top = mTop;
if ((mGroupFlags & FLAG_CLIP_CHILDREN) == FLAG_CLIP_CHILDREN) {
if (!dirty.intersect(0, 0, mRight - left, mBottom - top)) {
dirty.setEmpty();
}
}
mPrivateFlags &= ~PFLAG_DRAWING_CACHE_VALID;
location[CHILD_LEFT_INDEX] = left;
location[CHILD_TOP_INDEX] = top;
if (mLayerType != LAYER_TYPE_NONE) {
mPrivateFlags |= PFLAG_INVALIDATED;
mLocalDirtyRect.union(dirty);
}
return mParent;
} else {
mPrivateFlags &= ~PFLAG_DRAWN & ~PFLAG_DRAWING_CACHE_VALID;
location[CHILD_LEFT_INDEX] = mLeft;
location[CHILD_TOP_INDEX] = mTop;
if ((mGroupFlags & FLAG_CLIP_CHILDREN) == FLAG_CLIP_CHILDREN) {
dirty.set(0, 0, mRight - mLeft, mBottom - mTop);
} else {
// in case the dirty rect extends outside the bounds of this container
dirty.union(0, 0, mRight - mLeft, mBottom - mTop);
}
if (mLayerType != LAYER_TYPE_NONE) {
mPrivateFlags |= PFLAG_INVALIDATED;
mLocalDirtyRect.union(dirty);
}
return mParent;
}
}
return null;
}
逻辑有点复杂，大概的思想就是循环计算dirty区域相对于俯视图的坐标，即先得到子视图的dirty的大小然后在父视图中根据子视图和子视图的dirty的大小计算这块dirty相对于父视图的位置，这里做了计算dirty.offset(location[CHILD_LEFT_INDEX] - mScrollX, location[CHILD_TOP_INDEX] - mScrollY);通过之前的do while循环，最终的到整块dirty区域相对于最外层view的位置。循环的最上层是ViewRoot。下面是ViewRoot的invalidateChildInParent
public ViewParent invalidateChildInParent(final int[] location, final Rect dirty) {
invalidateChild(null, dirty);
return null;
}最终会return null
public void invalidateChild(View child, Rect dirty) {
checkThread();
if (DEBUG_DRAW) Log.v(TAG, "Invalidate child: " + dirty);
if (mCurScrollY != 0 || mTranslator != null) {
mTempRect.set(dirty);
dirty = mTempRect;
if (mCurScrollY != 0) {
dirty.offset(0, -mCurScrollY);
}
if (mTranslator != null) {
mTranslator.translateRectInAppWindowToScreen(dirty);
}
if (mAttachInfo.mScalingRequired) {
dirty.inset(-1, -1);
}
}
mDirty.union(dirty);
if (!mWillDrawSoon) {
scheduleTraversals();
}
}
checkTread检查是不是UI线程。不是UI线程则报异常。最后执行sheduleTraversals， scheduleTraversals会发送一个异步消息，最终调用performTraversals()执行重绘。