android view怎样刷新

Posted 2023-04-05

两种方式刷新：

主线程可以直接调用Invalidate()方法刷新

子线程可以直接调用postInvalidate()方法刷新。

API的描述是这样的 : Invalidatethe whole view. If the view is visible, onDraw(Canvas) will be called at somepoint in the future. This must be called from a UI thread. To call from anon-UI thread, call postInvalidate().。当Invalidate()被调用的时候，View的OnDraw()就会被调用，Invalidate()必须是在UI线程中被调用，如果在新线程中更新视图的就调用postInvalidate()。

参考技术A 调用invalidate()方法

Android怎么强制刷新view

步骤就是：
1、调用子View的invalidate（）
2、跳转到上一层的invalidateChild函数中区
3、在一次调用invalidateChildInParent的函数一次层层刷新

让我来阅读源代码：
首先在View类中：
/**
* Invalidate the whole view. If the view is visible, @link #onDraw 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()
if (ViewDebug.TRACE_HIERARCHY)
ViewDebug.trace(this, ViewDebug.HierarchyTraceType.INVALIDATE);

if ((mPrivateFlags & (DRAWN | HAS_BOUNDS)) == (DRAWN | HAS_BOUNDS))
mPrivateFlags &= ~DRAWN & ~DRAWING_CACHE_VALID;
final ViewParent p = mParent; //获得父类View的对象
final AttachInfo ai = mAttachInfo;//获得匹配
if (p != null && ai != null)
final Rect r = ai.mTmpInvalRect;
r.set(0, 0, mRight - mLeft, mBottom - mTop);//设置本View的尺寸，其实就是大小没有设置位置
// Don't call invalidate -- we don't want to internally scroll
// our own bounds
p.invalidateChild(this, r); //调用父类的刷新函数



下面我们来到Viewgroup对象：

在invalidate中，调用父View的invalidateChild，这是一个从第向上回溯的过程，每一层的父View都将自己的显示区域与传入的刷新Rect做交集。
/**
* 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)
if (ViewDebug.TRACE_HIERARCHY)
ViewDebug.trace(this, ViewDebug.HierarchyTraceType.INVALIDATE_CHILD);

ViewParent parent = this;
final AttachInfo attachInfo = mAttachInfo;
if (attachInfo != null)
final int[] location = attachInfo.mInvalidateChildLocation;
// 刷新子View的位置
location[CHILD_LEFT_INDEX] = child.mLeft;
location[CHILD_TOP_INDEX] = child.mTop;
// 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 & DRAW_ANIMATION) == DRAW_ANIMATION;
// Check whether the child that requests the invalidate is fully opaque
final boolean isOpaque = child.isOpaque() && !drawAnimation &&
child.getAnimation() != null;
// Mark the child as dirty, using the appropriate flag
// Make sure we do not set both flags at the same time
final int opaqueFlag = isOpaque ? DIRTY_OPAQUE : DIRTY;
do
View view = null;
if (parent instanceof View)
view = (View) parent;

if (drawAnimation)
if (view != null)
view.mPrivateFlags |= DRAW_ANIMATION;
else if (parent instanceof ViewRoot)
((ViewRoot) 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 && (view.mPrivateFlags & DIRTY_MASK) != DIRTY)
view.mPrivateFlags = (view.mPrivateFlags & ~DIRTY_MASK) | opaqueFlag;

parent = parent.invalidateChildInParent(location, dirty);
while (parent != null);

/**
* 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 (ViewDebug.TRACE_HIERARCHY)
ViewDebug.trace(this, ViewDebug.HierarchyTraceType.INVALIDATE_CHILD_IN_PARENT);

if ((mPrivateFlags & DRAWN) == DRAWN)
if ((mGroupFlags & (FLAG_OPTIMIZE_INVALIDATE | FLAG_ANIMATION_DONE)) !=
FLAG_OPTIMIZE_INVALIDATE)
// 由父类的的位置，偏移刷新区域
dirty.offset(location[CHILD_LEFT_INDEX] - mScrollX,
location[CHILD_TOP_INDEX] - mScrollY);
final int left = mLeft;
final int top = mTop;
if (dirty.intersect(0, 0, mRight - left, mBottom - top) ||
(mPrivateFlags & DRAW_ANIMATION) == DRAW_ANIMATION)
mPrivateFlags &= ~DRAWING_CACHE_VALID;
location[CHILD_LEFT_INDEX] = left;
location[CHILD_TOP_INDEX] = top;
return mParent;

else
mPrivateFlags &= ~DRAWN & ~DRAWING_CACHE_VALID;
location[CHILD_LEFT_INDEX] = mLeft;
location[CHILD_TOP_INDEX] = mTop;
dirty.set(0, 0, mRight - location[CHILD_LEFT_INDEX],
mBottom - location[CHILD_TOP_INDEX]);
return mParent;


return null;

另外：
Invalidate()方法不能放在线程中，所以需要把Invalidate()方法放在Handler中。在MyThread中只需要在规定时间内发送一个Message给handler，当Handler接收到消息就调用Invalidate()方法。
postInvalidate()方法就可以放在线程中做处理，就不需要Handler。

而上面的新线程MyThre可以放在OnCreate()中开始，也可以放在OnStart()中开始。
Invalidate()方法和postInvalidate()都可以在主线程中调用而刷新视图。
Invalidate()方法在SDK中是这样描述的：Invalidate the whole view. If the view is visible, onDraw(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 postInvalidate(). 当Invalidate()被调用的时候，View的OnDraw()就会被调用，Invalidate()必须是在UI线程中被调用，如果在新线程中更新视图的就调用postInvalidate()。
简言之，如果确定是在main thread中调用调用话， 使用 invaludate()

否则要调用 postInvalidate()

另外，横竖屏切换使用重新构造 activity的。所以一定会重新刷新view 。

亲！希望能帮助到你哦！~~~ 参考技术A postinvalidate 和 invalidate 就可以强制刷新本回答被提问者和网友采纳