1.android布局-ConstraintLayout-约束布局

ConstraintLayout 是什么？

ConstraintLayout

ConstraintLayout 怎么用？

基本用法

layout_constraint[当前控件位置]_[目标控件位置]="[目标控件ID]"

1.上下排列

a  
b  

b:
app:layout_constraintTop_toBottomOf="a"

实例：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/a"
        style="@style/text"
        android:text="@string/a" />

    <TextView
        android:id="@+id/b"
        style="@style/text"
        android:text="@string/b"
        app:layout_constraintTop_toBottomOf="@id/a" />
</android.support.constraint.ConstraintLayout>

2.左右排列

a b
a:
app:layout_constraintRight_toLeftOf="b"
b:
app:layout_constraintLeft_toRightOf="a"

实例：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/a"
        style="@style/text"
        app:layout_constraintRight_toLeftOf="@id/b"
        android:text="@string/a" />

    <TextView
        android:id="@+id/b"
        style="@style/text"
        android:text="@string/b"
        app:layout_constraintLeft_toRightOf="@id/a" />
</android.support.constraint.ConstraintLayout>

左右排列更严谨的写法

a b
b:
app:layout_constraintStart_toEndOf="a"
app:layout_constraintTop_toTopOf="a"
app:layout_constraintBottom_toBottomOf="a"

实例：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/a"
        style="@style/text"
        app:layout_constraintRight_toLeftOf="@id/b"
        app:layout_constraintEnd_toStartOf="@id/b"
        app:layout_constraintTop_toTopOf="@id/b"
        android:text="@string/a" />

    <TextView
        android:id="@+id/b"
        style="@style/text"
        android:text="@string/b"
        app:layout_constraintStart_toEndOf="@id/a"
        app:layout_constraintTop_toTopOf="@id/a"
        app:layout_constraintLeft_toRightOf="@id/a" />
</android.support.constraint.ConstraintLayout>

3.靠最右边

a 靠界面最右边
a：
app:layout_constraiontEnd_toEndOf="parent"

实例：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/a"
        style="@style/text"
        app:layout_constraintEnd_toEndOf="parent"
        android:text="@string/a" />
</android.support.constraint.ConstraintLayout>

constraiontEnd 是自己本身的
toEnd 底部停靠的
parent 是父布局

4.三等分然后停靠最底部

a b c
a:
app:layout_constraiontBottom_toBottomOf="parent"
app:layout_constraiontLeft_toLeftOf="parent"
app:layout_constraiontRight_toLeftOf="b"

b:
app:layout_constraiontBottom_toBottomOf="parent"
app:layout_constraiontLeft_toRightOf="a"
app:layout_constraiontRight_toLeftOf="c"

c:
app:layout_constraiontBottom_toBottomOf="parent"
app:layout_constraiontLeft_toRightOf="b"
app:layout_constraiontRight_toRightOf="parent"

上面就是构成官网所说的链(chain)

实例：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/a"
        style="@style/text"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/b"
        android:text="@string/a" />

    <TextView
        android:id="@+id/b"
        style="@style/text"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toRightOf="@id/a"
        app:layout_constraintRight_toLeftOf="@id/c"
        android:text="@string/b"/>
    <TextView
        android:id="@+id/c"
        style="@style/text"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintLeft_toRightOf="@id/b"
        android:text="@string/c"/>
</android.support.constraint.ConstraintLayout>

延伸两个属性

app:layout_constraiontHorizontal_weight="1" //等分属性

app:layout_constraiontHorizontal_chainstyle="spread_inside" //spread_inside 两端对齐 packed 聚中  spread(默认)控件之间留空

实例：
聚中：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/a"
        style="@style/text"
        app:layout_constraintHorizontal_chainStyle="packed"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/b"
        android:text="@string/a" />

    <TextView
        android:id="@+id/b"
        style="@style/text"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toRightOf="@id/a"
        app:layout_constraintRight_toLeftOf="@id/c"
        android:text="@string/b"/>
    <TextView
        android:id="@+id/c"
        style="@style/text"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintLeft_toRightOf="@id/b"
        android:text="@string/c"/>
</android.support.constraint.ConstraintLayout>

左右分散：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <TextView
        android:id="@+id/a"
        style="@style/text"
        app:layout_constraintHorizontal_chainStyle="spread_inside"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toLeftOf="@id/b"
        android:text="@string/a" />

    <TextView
        android:id="@+id/b"
        style="@style/text"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toRightOf="@id/a"
        app:layout_constraintRight_toLeftOf="@id/c"
        android:text="@string/b"/>
    <TextView
        android:id="@+id/c"
        style="@style/text"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintLeft_toRightOf="@id/b"
        android:text="@string/c"/>
</android.support.constraint.ConstraintLayout>

Guideline （约束线）

实例：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.constraint.Guideline
        android:id="@+id/guideline"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.5" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/guideline"
        app:layout_constraintWidth_default="spread" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintBottom_toBottomOf="@+id/button"
        app:layout_constraintStart_toStartOf="@+id/guideline"
        app:layout_constraintTop_toTopOf="@+id/button" />
</android.support.constraint.ConstraintLayout>



Guideline 是一个约束线（不会画出来）
app:layout_constraintGuide_percent="0.5" 0.5是50%
上面代码是 在视图50%位置 左右两边有两个butthon

实例：

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.constraint.Guideline
        android:id="@+id/guideline"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        app:layout_constraintGuide_begin="40dp"/>
    
    <TextView
        android:id="@+id/a"
        style="@style/text"
        app:layout_constraintTop_toTopOf="@id/guideline"
        android:text="@string/a"/>
    <TextView
        android:id="@+id/b"
        style="@style/text"
        app:layout_constraintTop_toTopOf="@id/guideline"
        app:layout_constraintLeft_toRightOf="@id/a"
        android:text="@string/b"/>
    <TextView
        android:id="@+id/c"
        style="@style/text"
        app:layout_constraintTop_toTopOf="@id/guideline"
        app:layout_constraintLeft_toRightOf="@id/b"
        android:text="@string/c"/>
</android.support.constraint.ConstraintLayout>

在40dp上画一条约束线 
textview以此排列

源码

源码

相关链接

ConstraintLayout详解

Android新特性介绍，ConstraintLayout完全解析
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