相对布局和约束布局的等效属性

(1)相对布局:

android:layout_centerInParent="true"    

(1)约束布局等效:

app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintTop_toTopOf="parent"

---

(2)相对布局:

android:layout_centerHorizontal="true"

(2)约束布局等效:

app:layout_constraintLeft_toLeftOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintRight_toRightOf="parent"
app:layout_constraintEnd_toEndOf="parent"

---

(3)相对布局:

android:layout_centerVertical="true"    

(3)约束布局等效:

app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintTop_toTopOf="parent"

---

(4)相对布局:

android:layout_alignParentLeft="true"   

(4)约束布局等效:

app:layout_constraintLeft_toLeftOf="parent"

---

(5)相对布局:

android:layout_alignParentStart="true"

(5)约束布局等效:

app:layout_constraintStart_toStartOf="parent"

---

(6)相对布局:

android:layout_alignParentRight="true"

(6)约束布局等效:

app:layout_constraintRight_toRightOf="parent"

---

(7)相对布局:

android:layout_alignParentEnd="true"    

(7)约束布局等效:

app:layout_constraintEnd_toEndOf="parent"

---

(8)相对布局:

android:layout_alignParentTop="true"

(8)约束布局等效:

app:layout_constraintTop_toTopOf="parent"

---

(9)相对布局:

android:layout_alignParentBottom="true" 

(9)约束布局等效:

app:layout_constraintBottom_toBottomOf="parent"

---

(10)相对布局:

android:layout_alignStart="@id/view"

(10)约束布局等效:

app:layout_constraintStart_toStartOf="@id/view"

---

(11)相对布局:

android:layout_alignLeft="@id/view" 

(11)约束布局等效:

app:layout_constraintLeft_toLeftOf="@id/view"

---

(12)相对布局:

android:layout_alignEnd="@id/view"  

(12)约束布局等效:

app:layout_constraintEnd_toEndOf="@id/view"

---

(13)相对布局:

android:layout_alignRight="@id/view"

(13)约束布局等效:

app:layout_constraintRight_toRightOf="@id/view"

---

(14)相对布局:

android:layout_alignTop="@id/view"  

(14)约束布局等效:

app:layout_constraintTop_toTopOf="@id/view"

---

(15)相对布局:

android:layout_alignBaseline="@id/view" 

(15)约束布局等效:

app:layout_constraintBaseline_toBaselineOf="@id/view"

---

(16)相对布局:

android:layout_alignBottom="@id/view"

(16)约束布局等效:

app:layout_constraintBottom_toBottomOf="@id/view"

---

(17)相对布局:

android:layout_toStartOf="@id/view"

(17)约束布局等效:

app:layout_constraintEnd_toStartOf="@id/view"

---

(18)相对布局:

android:layout_toLeftOf="@id/view"  

(18)约束布局等效:

app:layout_constraintRight_toLeftOf="@id/view"

---

(19)相对布局:

android:layout_toEndOf="@id/view"

(19)约束布局等效:

app:layout_constraintStart_toEndOf="@id/view"

---

(20)相对布局:

android:layout_toRightOf="@id/view"

(20)约束布局等效:

app:layout_constraintLeft_toRightOf="@id/view"

---

(21)相对布局:

android:layout_above="@id/view" 

(21)约束布局等效:

app:layout_constraintBottom_toTopOf="@id/view"

---

(22)相对布局:

android:layout_below="@id/view" 

(22)约束布局等效:

app:layout_constraintTop_toBottomOf="@id/view"

---

ConstraintLayout的目的是通过对每个视图应用一些规则来避免嵌套，从而优化和平抑布局的视图层次结构。

规则类似于RelativeLayout，例如将底边设置为其他视图的底部。

app:layout_constraintBottom_toBottomOf="@+id/view1"

与RelativeLayout不同的是，ConstraintLayout提供了一个偏置值，用于相对于手柄(用红圈标记)的0%和100%水平和垂直偏移来定位视图。这些百分比(和分数)提供了视图在不同屏幕密度和大小之间的无缝定位。

app:layout_constraintHorizontal_bias="0.33" <!-- from 0.0 to 1.0 -->
app:layout_constraintVertical_bias="0.53" <!-- from 0.0 to 1.0 -->

Baseline句柄(圆角的长管道，在圆句柄的下面)用于将视图的内容与另一个视图引用对齐。

正方形句柄(在视图的每个角落)用于在dps中调整视图的大小。

这完全是基于个人观点和我对ConstraintLayout的印象

一个很大的区别是，即使视图消失了，ConstraintLayout仍然尊重约束。所以它不会破坏布局如果你有一个链你想让一个视图消失在中间。

正式来说，ConstraintLayout要快得多

在Android N版本中，ConstraintLayout类提供了与RelativeLayout类似的功能，但成本要低得多。

The only difference i've noted is that things set in a relative layout via drag and drop automatically have their dimensions relative to other elements inferred, so when you run the app what you see is what you get. However in the constraint layout even if you drag and drop an element in the design view, when you run the app things may be shifted around. This can easily be fixed by manually setting the constraints or, a more risky move being to right click the element in the component tree, selecting the constraint layout sub menu, then clicking 'infer constraints'. Hope this helps

由@davidpbr ConstraintLayout性能报告

我做了两个类似的7个子布局，每个都有一个父ConstraintLayout和RelativeLayout。 基于Android Studio方法跟踪工具，它似乎ConstraintLayout花更多的时间在onMeasure和执行额外的工作在onfinishinflation。

使用的库(support-v4, appcompat-v7…):

com.android.support.constraint: constraint-layout: 1.0.0-alpha1

设备/Android版本转载于: 三星Galaxy S6 (SM-G920A;对不起，没有Nexus atm)。Android 5.0.2

快速方法跟踪比较:

示例Github回购:https://github.com/OnlyInAmerica/ConstraintLayoutPerf