Constraintlayout layout

• stay API9 The above Android Used in the operating system , It is mainly to solve the problem of too many nested layouts , Position and adjust widgets in a flexible way .
• from Android2.3 rise , The official template uses constraint layout by default
• constraintLayout and RelaiveLaout similar , Adopt the layout mode of relative positioning .
• More flexibility in constrained layout , And the spatial position and size can be constrained according to the scale , It can better adapt to models with different screen sizes

Baseline positioning

Text baseline , Text alignment

Two textview If the space height is inconsistent, you can use baseline positioning to align the text

Angular positioning

Margin positioning

stay ConstraintLayout Inside to achieve margin positioning , You must first constrain the position of the corresponding control in the constrained layout , Otherwise it will not take effect （margin The layout is only applicable to the view Work ）

Chain positioning

The controls in the constraint layout are arranged like a chain , Each link in the chain is a control .