androidview更新
1. android view怎樣刷新
兩種方式刷新：
主線程可以直接調用Invalidate()方法刷新
子線程可以直接調用postInvalidate()方法刷新。
API的描述是這樣的 :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().。當Invalidate()被調用的時候，View的OnDraw()就會被調用，Invalidate()必須是在UI線程中被調用，如果在新線程中更新視圖的就調用postInvalidate()。
2. android 為什麼只能在主線程更新View
使用handler:例：{privateTextViewmTextView;//你的textView.newThread(){@Overridepublicvoidrun(){..你的子線程處理邏輯//下面new一個Message用來裝你要傳到UI線程的東西Messagemsg=newMessage();msg.what=;msg.arg1=;msg.obj=;//mHandler見下面定義mHandler.sendMessage(msg);}}//定義一個HandlerHandlermHandler=newHandler(){@(Messagemsg){//這里就可以從msg取出你從線程中傳到UI線程的東西；//例如Stringtxt=(String)msg.obj;mTextView.setText(txt);}}}思路是這樣了，Handler具體用法，你繼續網路吧
3. android viewpager 數據如何刷新 呢
ViewPager的數據是通過PageAdapter來裝載的，刷新數據的方法有以下：
調用adapter.notifyDataSetChanged(); 刷新控制項，但是要覆蓋PagerAdapter的getItemPosition方法，並返回return POSITION_NONE;
利用PagerAdapter的工作機制,就是PagerAdapter的執行順序,PagerAdapter作為ViewPager的適配器，無論ViewPager有多少頁，PagerAdapter在初始化時也只初始化開始的2個View，即調用2次instantiateItem方法。而接下來每當ViewPager滑動時，PagerAdapter都會調用destroyItem方法將距離該頁2個步幅以上的那個View銷毀，以此保證PagerAdapter最多隻管轄3個View，且當前View是3個中的中間一個，如果當前View缺少兩邊的View，那麼就instantiateItem，如里有超過2個步幅的就destroyItem。
每當Adapter調用instantiateItem時，運用View.setTag方法將該View標識。當需要更新這個View的數據時，通過調用ViewPager.findViewWithTag方法找到相應的View，然後更新View中的數據。
4. Android怎麼強制刷新view
步驟就是：
1、調用子View的invalidate（）
2、跳轉到上一層的invalidateChild函數中區
3、在一次調用invalidateChildInParent的函數一次層層刷新
讓我來閱讀源代碼：
首先在View類中：
/**
* 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; //獲得父類View的對象
final AttachInfo ai = mAttachInfo;//獲得匹配
if (p != null && ai != null) {
final Rect r = ai.mTmpInvalRect;
r.set(0, 0, mRight - mLeft, mBottom - mTop);//設置本View的尺寸，其實就是大小沒有設置位置
// Don't call invalidate -- we don't want to internally scroll
// our own bounds
p.invalidateChild(this, r); //調用父類的刷新函數
}
}
}
下面我們來到Viewgroup對象：
在invalidate中，調用父View的invalidateChild，這是一個從第向上回溯的過程，每一層的父View都將自己的顯示區域與傳入的刷新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 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) {
// 由父類的的位置，偏移刷新區域
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()方法不能放在線程中，所以需要把Invalidate()方法放在Handler中。在MyThread中只需要在規定時間內發送一個Message給handler，當Handler接收到消息就調用Invalidate()方法。
postInvalidate()方法就可以放在線程中做處理，就不需要Handler。
而上面的新線程MyThre可以放在OnCreate()中開始，也可以放在OnStart()中開始。
Invalidate()方法和postInvalidate()都可以在主線程中調用而刷新視圖。
Invalidate()方法在SDK中是這樣描述的：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(). 當Invalidate()被調用的時候，View的OnDraw()就會被調用，Invalidate()必須是在UI線程中被調用，如果在新線程中更新視圖的就調用postInvalidate()。
簡言之，如果確定是在main thread中調用調用話， 使用 invaludate()
否則要調用 postInvalidate()
另外，橫豎屏切換使用重新構造 activity的。所以一定會重新刷新view 。
親！希望能幫助到你哦！~~~
5. Android怎麼強制刷新view
關鍵的一句話就是：
在Android的布局體系中，父View負責刷新、布局顯示子View；而當子View需要刷新時，則是通知父View來完成。
步驟就是：
1、調用子View的invalidate（）
2、跳轉到上一層的invalidateChild函數中區
3、在一次調用invalidateChildInParent的函數一次層層刷新
4、具體的刷新後續操作，我就不清楚了，調用invalidate最終在代碼上就在invalidateChild終止了的，所以表示有點點不清晰，求各位大牛介紹一下吧。。。。。？在此謝過了。。
讓我來閱讀源代碼：
首先在View類中：
/**
* 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; //獲得父類View的對象
final AttachInfo ai = mAttachInfo;//獲得匹配
if (p != null && ai != null) {
final Rect r = ai.mTmpInvalRect;
r.set(0, 0, mRight - mLeft, mBottom - mTop);//設置本View的尺寸，其實就是大小沒有設置位置
// Don't call invalidate -- we don't want to internally scroll
// our own bounds
p.invalidateChild(this, r); //調用父類的刷新函數
}
}
}
下面我們來到Viewgroup對象：
在invalidate中，調用父View的invalidateChild，這是一個從第向上回溯的過程，每一層的父View都將自己的顯示區域與傳入的刷新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 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) {
// 由父類的的位置，偏移刷新區域
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()方法不能放在線程中，所以需要把Invalidate()方法放在Handler中。在MyThread中只需要在規定時間內發送一個Message給handler，當Handler接收到消息就調用Invalidate()方法。
postInvalidate()方法就可以放在線程中做處理，就不需要Handler。
而上面的新線程MyThre可以放在OnCreate()中開始，也可以放在OnStart()中開始。
Invalidate()方法和postInvalidate()都可以在主線程中調用而刷新視圖。
Invalidate()方法在SDK中是這樣描述的：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(). 當Invalidate()被調用的時候，View的OnDraw()就會被調用，Invalidate()必須是在UI線程中被調用，如果在新線程中更新視圖的就調用postInvalidate()。
簡言之，如果確定是在main thread中調用調用話， 使用 invaludate()
否則要調用 postInvalidate()
另外，橫豎屏切換使用重新構造 activity的。所以一定會重新刷新view 。
6. android 別的類怎麼提醒view更新
可以採用廣播機制，收到廣播更新界面就可以。也可以先判斷當前界面是否在最上層，未在最上層不做更新，在最上層再做更新。也可以再resume處理
7. Android下ViewPager 中怎麼更新
首先更新綁定的視圖集合，比如List<View> views，然後刷新adapter，這樣就可以了
8. 怎樣在Android下ViewPager 中更新啊
首先更新綁定的視圖集合，比如List<View> views，然後刷新adapter，這樣就可以了。