ConstraintLayout

1.相对布局

layout_constraintLeft_toLeftOf
layout_constraintLeft_toRightOf
layout_constraintRight_toLeftOf
layout_constraintRight_toRightOf
layout_constraintTop_toTopOf
layout_constraintTop_toBottomOf
layout_constraintBottom_toTopOf
layout_constraintBottom_toBottomOf
layout_constraintBaseline_toBaselineOf
layout_constraintStart_toEndOf
layout_constraintStart_toStartOf
layout_constraintEnd_toStartOf
layout_constraintEnd_toEndOf

2.居中

 app:layout_constraintLeft_toLeftOf="parent"
 app:layout_constraintRight_toRightOf="parent"

3.居中以后有偏向

layout_constraintHorizontal_bias=“float<1.0”
layout_constraintVertical_bias="float<1.0"

4.圆形布局

layout_constraintCircle : references another widget id
layout_constraintCircleRadius : the distance to the other widget center
layout_constraintCircleAngle : which angle the widget should be at (in degrees, from 0 to 360)

5.最大，最小限制（设置为wrap_content生效）

android:minWidth set the minimum width for the layout
android:minHeight set the minimum height for the layout
android:maxWidth set the maximum width for the layout
android:maxHeight set the maximum height for the layout

6.ratio

7.chain
8.group
分组控制空间行为，属性（visibility）