android View onMeasure

基于4.4 code:

View.java:

    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),                getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));    }............................................................................. protected final void setMeasuredDimension(int measuredWidth, int measuredHeight) { ..................................................................... mMeasuredWidth = measuredWidth; mMeasuredHeight = measuredHeight; mPrivateFlags |= PFLAG_MEASURED_DIMENSION_SET; }............................................................................../** * Like {@link #getMeasuredWidthAndState()}, but only returns the * raw width component (that is the result is masked by * {@link #MEASURED_SIZE_MASK}). * * @return The raw measured width of this view. */ public final int getMeasuredWidth() { return mMeasuredWidth & MEASURED_SIZE_MASK; }

之前光顾看基类ViewGroup了，结果发现 View的onMeasure中通过setMeasuredDimension()设置的View的mMeasuredWidth/Height 在 ViewGroup中根本

没有被用到，很是疑惑，感觉measure的意义没了，后来看了细化出来的FrameLayout等layout类，才发现，在这些真正的按照某种规则排布子View的类中

在onMeasure和onLayout中都是会用到子view的getMeasuredWidth/height()的，其实看到ViewGroup的onLayout是抽象函数时，应该有所察觉的。

而MeasuredWidth/Height 也基本只有在父View onMeasure/onLayout的情况下有用。

在子view的layout被调用时，会调到setFrame(l, t, r, b)，这个函数才是真正的设置了View的尺寸，不一定就是之前measure时的MeasuredHeight。

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