Android invalidate requestLayout forceLayout

Invalidate

只是讓draw失效，不涉及measure、layout

forceLayout requestLayout

• forceLayout只是標記view，下次遍歷一定measure，但是不發起遍歷。
• requestLayout 標記一定measure後，還想父佈局傳遞，發起一次遍歷

public void forceLayout() {
    if (mMeasureCache != null) mMeasureCache.clear();
    mPrivateFlags |= PFLAG_FORCE_LAYOUT;
    mPrivateFlags |= PFLAG_INVALIDATED;
}

public void requestLayout() {
    if (mMeasureCache != null) mMeasureCache.clear();
    ...
    mPrivateFlags |= PFLAG_FORCE_LAYOUT;
    mPrivateFlags |= PFLAG_INVALIDATED;

    if (mParent != null && !mParent.isLayoutRequested()) {
        mParent.requestLayout();
    }
    ...
}

總計

• invalidate 針對draw
• forceLayout 強制下一次遍歷時，measure該view，但不知道什麼時候遍歷
• requestLayout，強制measure，併發起一次遍歷