Question

I'm banging my head against the barriers of ConstraintLayout (sorry for the pun...)

Here's what I would like to accomplish:

Place a label and an edittext in the "first row". Align their centers vertically. Add a horizontal barrier referencing those two UI elements below them.
Add two buttons in a second row, one left aligned, one right aligned. Have another barrier below those two.
Let a RecyclerView fill all the space below the second barrier.

So here's my attempt at a layout file:

<?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">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        android:layout_marginBottom="8dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/editText"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toTopOf="@id/top_barrier"
        app:layout_constraintVertical_bias=".5"
        />

    <EditText
        android:id="@+id/editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:inputType="textPersonName"
        android:text="Name"
        app:layout_constraintStart_toEndOf="@id/textView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toTopOf="@id/top_barrier"
        app:layout_constraintVertical_bias=".5"
        />

    <android.support.constraint.Barrier
        android:id="@+id/top_barrier"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:barrierDirection="bottom"
        app:constraint_referenced_ids="textView,editText" />

    <!-- Try to cut from here..... -->

    <ImageButton
        android:id="@+id/imageButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/button"
        app:layout_constraintHorizontal_bias="1"
        app:layout_constraintTop_toBottomOf="@+id/top_barrier"
        app:srcCompat="@android:drawable/btn_star" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:text="Button"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/top_barrier"
        />

    <android.support.constraint.Barrier
        android:id="@+id/lowerBarrier"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:barrierDirection="bottom"
        app:constraint_referenced_ids="imageButton,button" />

    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="0dp"

        android:layout_marginTop="8dp"
        app:layout_constraintTop_toTopOf="@+id/lowerBarrier"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        />

    <!-- ..... to here. -->

</android.support.constraint.ConstraintLayout>

Problem is, that the first barrier moves up, as soon as I add something below it. It seems to move to the bottom of the smaller UI element, which seems a bit nonsensical to me.

The layout without the elements between the comments looks like this:

It stops working when I add the elements between the comments:

I'd be very happy, if you could explain what I'm doing wrong.

Cheers

EDIT:

Interestingly enough, I can get a little further by defining the buttons in the second row in reversed order. But adding a second barrier below those two once again destroys the layout...

<?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">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        android:layout_marginBottom="8dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toStartOf="@+id/editText"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toTopOf="@id/top_barrier"
        app:layout_constraintVertical_bias=".5"
        />

    <EditText
        android:id="@+id/editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:inputType="textPersonName"
        android:text="Name"
        app:layout_constraintStart_toEndOf="@id/textView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toTopOf="@id/top_barrier"
        app:layout_constraintVertical_bias=".5"
        />

    <android.support.constraint.Barrier
        android:id="@+id/top_barrier"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:barrierDirection="bottom"
        app:constraint_referenced_ids="textView,editText" />


    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:text="Button"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/top_barrier"
        />

    <ImageButton
        android:id="@+id/imageButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/button"
        app:layout_constraintHorizontal_bias="1"
        app:layout_constraintTop_toBottomOf="@+id/top_barrier"
        app:srcCompat="@android:drawable/btn_star" />

</android.support.constraint.ConstraintLayout>

Answer 1

Imho，我在您的代码中没有发现任何错误。

<?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">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Name:"
        app:layout_constraintBaseline_toBaselineOf="@+id/editText"
        app:layout_constraintStart_toStartOf="parent" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/textView"
        tools:text="John Smith" />

    <android.support.constraint.Barrier
        android:id="@+id/top_barrier"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:barrierDirection="bottom"
        app:constraint_referenced_ids="textView,editText" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/top_barrier" />

    <ImageButton
        android:id="@+id/imageButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/top_barrier"
        app:srcCompat="@android:drawable/btn_star" />

    <android.support.constraint.Barrier
        android:id="@+id/lowerBarrier"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:barrierDirection="bottom"
        app:constraint_referenced_ids="button,imageButton" />

    <android.support.v7.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/lowerBarrier" />

    <!-- ..... to here. -->

</android.support.constraint.ConstraintLayout>

预览：

我仅为constraintVertical_bias更改了constraintBaseline_toBaselineOf。

Problem with multiple horizontal barriers in ConstraintLayout

1 个答案: