view 的繪製和重新整理
阿新 • • 發佈：2019-01-10
view繪製
流程
view重新整理
invalidate()
在UI執行緒中呼叫，重繪當前UI
父view負責重新整理，佈局顯示子view，而當子view需要重新整理時，則是通知父view來完成的。
呼叫view的invalidate函式中，會呼叫到invalidateInternal函式，接著呼叫到 viewGroup. invalidateChild方法 do{}while()迴圈查詢parent，最後走到ViewRootImpl.呼叫到viewRootImpl的scheduleTraversals()方法
public class View implements PostInvalidate()
在非UI執行緒中呼叫，通知UI執行緒重繪。利用Handler 從子執行緒給主執行緒發訊息 重新整理介面
/**
* <p>Cause an invalidate to happen on a subsequent cycle through the event loop.
* Use this to invalidate the View from a non-UI thread.</p>
*
* <p>This method can be invoked from outside of the UI thread
* only when this View is attached to a window.</p>
*
* @see #invalidate()
* @see #postInvalidateDelayed(long)
*/
public void postInvalidate() {
postInvalidateDelayed(0);
}
/**
* <p>Cause an invalidate to happen on a subsequent cycle through the event
* loop. Waits for the specified amount of time.</p>
*
* <p>This method can be invoked from outside of the UI thread
* only when this View is attached to a window.</p>
*
* @param delayMilliseconds the duration in milliseconds to delay the
* invalidation by
*
* @see #invalidate()
* @see #postInvalidate()
*/
public void postInvalidateDelayed(long delayMilliseconds) {
// We try only with the AttachInfo because there's no point in invalidating
// if we are not attached to our window
final AttachInfo attachInfo = mAttachInfo;
if (attachInfo != null) {
//呼叫根view 的dispatchInvalidateDelayed()方法
attachInfo.mViewRootImpl.dispatchInvalidateDelayed(this, delayMilliseconds);
}
}
public final class ViewRootImpl implements ViewParent,
View.AttachInfo.Callbacks, HardwareRenderer.HardwareDrawCallbacks {
// 根view 的dispatchInvalidateDelayed()方法
public void dispatchInvalidateDelayed(View view, long delayMilliseconds) {
//通過handler 給主執行緒發訊息 重新整理view 再呼叫view的invalidate()方法
Message msg = mHandler.obtainMessage(MSG_INVALIDATE, view);
mHandler.sendMessageDelayed(msg, delayMilliseconds);
}
final class ViewRootHandler extends Handler {
@Override
public void handleMessage(Message msg) {
switch (msg.what) {
case MSG_INVALIDATE:
((View) msg.obj).invalidate();
break;
}
}
}requestLayout()
位置沒有變化不會呼叫 draw 方法
/**
* Call this when something has changed which has invalidated the
* layout of this view. This will schedule a layout pass of the view
* tree. This should not be called while the view hierarchy is currently in a layout
* pass ({@link #isInLayout()}. If layout is happening, the request may be honored at the
* end of the current layout pass (and then layout will run again) or after the current
* frame is drawn and the next layout occurs.
*
* <p>Subclasses which override this method should call the superclass method to
* handle possible request-during-layout errors correctly.</p>
*/
public void requestLayout() {
if (mMeasureCache != null) mMeasureCache.clear();
if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == null) {
// Only trigger request-during-layout logic if this is the view requesting it,
// not the views in its parent hierarchy
ViewRootImpl viewRoot = getViewRootImpl();
if (viewRoot != null && viewRoot.isInLayout()) {
if (!viewRoot.requestLayoutDuringLayout(this)) {
return;
}
}
mAttachInfo.mViewRequestingLayout = this;
}
mPrivateFlags |= PFLAG_FORCE_LAYOUT;
mPrivateFlags |= PFLAG_INVALIDATED;
if (mParent != null && !mParent.isLayoutRequested()) {
//找到父控制元件的requestLayout()
mParent.requestLayout();
}
if (mAttachInfo != null && mAttachInfo.mViewRequestingLayout == this) {
mAttachInfo.mViewRequestingLayout = null;
}
}
//根view
public final class ViewRootImpl implements ViewParent,
View.AttachInfo.Callbacks, HardwareRenderer.HardwareDrawCallbacks {
@Override
public void requestLayout() {
if (!mHandlingLayoutInLayoutRequest) {
checkThread();
mLayoutRequested = true;
scheduleTraversals();
}
}
}