背景：

通过约束布局完成常见布局的替换

目标：

1. 组件基于父容器居中对齐
2. 组件和组件的基线对齐
3. 百分比偏移

实战：

1. 组件基于父容器居中对齐

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

     <TextView
         android:id="@+id/tv1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="100"
         android:textColor="@color/black"
         android:textSize="50sp"
         android:textStyle="bold"
         app:layout_constraintRight_toRightOf="parent"
         app:layout_constraintLeft_toLeftOf="parent"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintTop_toTopOf="parent" />
     

</androidx.constraintlayout.widget.ConstraintLayout>

 

2. 组件和组件的基线对齐

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

     <TextView
         android:id="@+id/tv1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="100"
         android:textColor="@color/black"
         android:textSize="50sp"
         android:textStyle="bold"
         app:layout_constraintRight_toRightOf="parent"
         app:layout_constraintLeft_toLeftOf="parent"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintTop_toTopOf="parent" />

     <TextView
         android:id="@+id/tv2"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:text="¥"
         android:textColor="@color/black"
         android:textSize="20sp"
         app:layout_constraintBaseline_toBaselineOf="@id/tv1"
         app:layout_constraintStart_toEndOf="@+id/tv1"
        />

</androidx.constraintlayout.widget.ConstraintLayout>

 3. 百分比偏移，不使用margin

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    tools:ignore="HardcodedText">

     <TextView
         android:layout_width="100dp"
         android:layout_height="60dp"
         android:gravity="center"
         android:text="A"
         android:textColor="@color/black"
         android:textSize="25sp"
         android:textStyle="bold"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintHorizontal_bias="0.3"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toTopOf="parent"
         app:layout_constraintVertical_bias="0.8" />

</androidx.constraintlayout.widget.ConstraintLayout>