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本篇模拟三个角色：Android 架构师-小福、Android 控件开发工程师-小黑、 Android 开发工程师-小白，下面按照三个角色不同角度分析measure过程。
小福负责分享：
小黑负责分享：
java.lang.IllegalStateException: onMeasure() did not set the measured dimension by calling setMeasuredDimension()
public class View implements Drawable.Callback, Drawable.Callback2, KeyEvent.Callback,
AccessibilityEventSource {
/**
* 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() {
// 直接返回mMeasuredWidth与后者相与清理掉其他开关获取真是measure大小
return mMeasuredWidth & MEASURED_SIZE_MASK;
}
/**
* <p>This mehod must be called by {@link #onMeasure(int, int)} to store the
* measured width and measured height. Failing to do so will trigger an
* exception at measurement time.</p>
*
* @param measuredWidth The measured width of this view. May be a complex
* bit mask as defined by {@link #MEASURED_SIZE_MASK} and
* {@link #MEASURED_STATE_TOO_SMALL}.
* @param measuredHeight The measured height of this view. May be a complex
* bit mask as defined by {@link #MEASURED_SIZE_MASK} and
* {@link #MEASURED_STATE_TOO_SMALL}.
*/
protected final void setMeasuredDimension(int measuredWidth, int measuredHeight) {
// 通常在onMeasure中调用，传入测量过的视图宽度与高度
mMeasuredWidth = measuredWidth;
mMeasuredHeight = measuredHeight;
mPrivateFlags |= MEASURED_DIMENSION_SET;
}
/**
* Bits of {@link #getMeasuredWidthAndState()} and
* {@link #getMeasuredWidthAndState()} that provide the actual measured size.
*/
// MeasureSpec中的Mode或占用int类型中前几位
public static final int MEASURED_SIZE_MASK = 0x00ffffff;
}public class View implements Drawable.Callback, Drawable.Callback2, KeyEvent.Callback,
AccessibilityEventSource {
/**
* Return the width of the your view.
*
* @return The width of your view, in pixels.
*/
@ViewDebug.ExportedProperty(category = "layout")
public final int getWidth() {
// 视图的右侧减去左侧的值
return mRight - mLeft;
}
/**
* Assign a size and position to this view.
*
* This is called from layout.
*
* @param left Left position, relative to parent
* @param top Top position, relative to parent
* @param right Right position, relative to parent
* @param bottom Bottom position, relative to parent
* @return true if the new size and position are different than the
* previous ones
* {@hide}
*/
protected boolean setFrame(int left, int top, int right, int bottom) {
boolean changed = false;
......
// 四个值中任意一个发生改变就行
if (mLeft != left || mRight != right || mTop != top || mBottom != bottom) {
changed = true;
......
mLeft = left;
mTop = top;
mRight = right;
mBottom = bottom;
......
}
return changed;
}
public void layout(int l, int t, int r, int b) {
......
// 当前视图布局时执行，传入当前视图的上下左右边界值
boolean changed = setFrame(l, t, r, b);
if (changed || (mPrivateFlags & LAYOUT_REQUIRED) == LAYOUT_REQUIRED) {
......
// 上面执行完成后才会触发onLayout
onLayout(changed, l, t, r, b);
......
}
......
mPrivateFlags &= ~FORCE_LAYOUT;
}
}Android View measure （二） 自定义UI控件measure相关
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原文地址：http://blog.csdn.net/androiddevelop/article/details/44263757
