android-constraintlayout - 如何在指南中将 View 居中？

Question

假设我有一个水平 GuideLine在父级的 30% 和一个 View (假设一个按钮)处，如何使该 View 以指南为中心？

像这样:



更新:

我在这里使用的 View 具有基于比率的高度，并且答案的解决方案不起作用。

这是当前的布局:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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">

    <ImageView
        android:id="@+id/imgLogo"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="@id/guideline_30"
        app:layout_constraintDimensionRatio="H,1:1"
        app:layout_constraintEnd_toStartOf="@+id/guidelineV_75"
        app:layout_constraintStart_toEndOf="@+id/guidelineV_25"
        app:layout_constraintTop_toTopOf="@+id/guideline_30"
        app:srcCompat="@drawable/ic_launcher_background" />

    <android.support.constraint.Guideline
        android:id="@+id/guideline_30"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_percent="0.3" />

    <android.support.constraint.Guideline
        android:id="@+id/guidelineV_25"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.25" />

    <android.support.constraint.Guideline
        android:id="@+id/guidelineV_75"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        app:layout_constraintGuide_percent="0.75" />

</android.support.constraint.ConstraintLayout>

Answer 1

Using fix width or height

需要使用相同的 Guideline对于顶部和底部约束，如:

app:layout_constraintTop_toTopOf="@id/guideline_30"
app:layout_constraintBottom_toBottomOf="@id/guideline_30"

xml:

<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">

    <ImageView
        android:id="@+id/imgLogo"
        android:layout_width="150dp"
        android:layout_height="150dp"
        app:layout_constraintTop_toTopOf="@id/guideline_30"
        app:layout_constraintBottom_toBottomOf="@id/guideline_30"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        android:src="@drawable/splash_logo" />

    <android.support.constraint.Guideline
        android:id="@+id/guideline_30"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_percent="0.30" />

</android.support.constraint.ConstraintLayout>

输出:

Using width and height based on ratio

当您根据比率使用宽度和高度时，它不会居中。

但是为了得到你想要的结果，你也可以设置 Guideline = 0.15 (0.3/2) 并修改 constraintTop和 constraintBotttom

xml:

<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">

    <ImageView
    android:id="@+id/imgLogo"
    android:layout_width="0dp"
    android:layout_height="0dp"
    app:layout_constraintDimensionRatio="H,1:1"
    app:layout_constraintEnd_toStartOf="@+id/guidelineV_75"
    app:layout_constraintStart_toEndOf="@+id/guidelineV_25"
    app:layout_constraintTop_toTopOf="@+id/guideline_15"
    app:srcCompat="@drawable/ic_launcher_background" />

<android.support.constraint.Guideline
    android:id="@+id/guideline_15"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    app:layout_constraintGuide_percent="0.15" />

<android.support.constraint.Guideline
    android:id="@+id/guidelineV_25"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    app:layout_constraintGuide_percent="0.25" />

<android.support.constraint.Guideline
    android:id="@+id/guidelineV_75"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    app:layout_constraintGuide_percent="0.75" />

</android.support.constraint.ConstraintLayout>

输出: