1. MeasureSpec.EXACTLY
The parent has determined an exact size for the child. The child is going to be given those bounds regardless of how big it wants to be.
2. MeasureSpec.AT_MOST
The child can be as large as it wants up to the specified size.
3. MeasureSpec.UNSPECIFIED
The parent has not imposed any constraint on the child. It can be whatever size it wants.
4. MeasureSpec創(chuàng)建規(guī)則
5. 調用關系
5.1 ViewGroup調用：onMeasure -> forEachChild(measureChildWithMargins -> getChildMeasureSpec -> View.measure -> View.onMeasure)
5.2 View調用：onMeasure -> setMeasuredDimension -> getDefaultSize -> getSuggestedMinimunWidth/getSuggestedMinimunHeight -> determinMeasureWidthorHeight
5.3 ViewGroup會重寫View的onMeasure方法柒凉，父類View.onMeasure基本只是通過MeasureSpec確定大小而已，TextView等具體view會重寫onMeasure方法蔑穴。
5.4 ViewGroup會對包含的子View進行遍歷測量跋核，具體的子View的MeasureSpec數(shù)據(jù)由子View的onMeasure方法完成叼风。
6. MeasureSpec影響因素
父容器的MeasureSpec和子View的LayoutParams共同決定了子View的MeasureSpec荣月。在measure階段View的寬和高由其measureSpec中的specSize決定
7. 擴展
clipToPadding:是否讓子View裁剪以適應父View的padding秃臣，默認false
clipChildren：是否讓子View裁剪當超過父View的邊界，默認false
getLeft/getX：不要莫名其妙的將兩個不同應用場景存在的方法進行對比區(qū)分淮蜈，根據(jù)場景不就區(qū)分了嗎斋攀。getLeft等于相對父View的距離，getX等于相對父View的左邊距left+移動TranslationX礁芦。
