Android - Constraint layout - How to align a view centered over edge of other view?

问题

I want to build a layout like this:

Inside the constraint layout there is an Image View which acts like a banner, then there is a Card that is center aligned with the bottom edge of the banner and then there is another Image View that is center aligned with the top edge of the card.

The problem I am facing is that the second Image View (GREEN one) when aligned with the card goes in the background instead of staying in the foreground.

Here is the xml,

<android.support.constraint.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:fitsSystemWindows="true"
            app:layout_collapseMode="parallax"
            android:paddingBottom="@dimen/padding_10">

            <ImageView
                android:id="@+id/imageView_jobBackdrop_jobDetails"
                android:layout_width="match_parent"
                android:layout_height="175dp"
                android:fitsSystemWindows="true"
                android:scaleType="centerCrop"
                android:src="@drawable/backdrop_job_details"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_collapseMode="parallax"/>

            <ImageView
                android:id="@+id/imageView_companyLogo_jobDetails"
                android:layout_width="75dp"
                android:layout_height="75dp"
                android:fitsSystemWindows="true"
                app:layout_collapseMode="parallax"
                app:layout_constraintBottom_toTopOf="@+id/cardView_jobHeader_jobDetails"
                app:layout_constraintEnd_toEndOf="@id/cardView_jobHeader_jobDetails"
                app:layout_constraintStart_toStartOf="@id/cardView_jobHeader_jobDetails"
                app:layout_constraintTop_toTopOf="@+id/cardView_jobHeader_jobDetails" />

            <android.support.v7.widget.CardView
                android:id="@+id/cardView_jobHeader_jobDetails"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginBottom="24dp"
                android:layout_marginEnd="16dp"
                android:layout_marginStart="16dp"
                app:layout_constraintBottom_toBottomOf="@+id/imageView_jobBackdrop_jobDetails"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/imageView_jobBackdrop_jobDetails"
                app:layout_constraintVertical_bias="0.5">

                <android.support.constraint.ConstraintLayout
                    android:id="@+id/parent"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content">

                    <TextView
                        android:id="@+id/textView_jobTitle_jobDetails"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:layout_marginEnd="16dp"
                        android:layout_marginStart="16dp"
                        android:layout_marginTop="32dp"
                        android:gravity="center"
                        android:text="Fresher Software Developer Job. Urgent Openning. Angular Js, HTML, JavaScript, CSS"
                        app:layout_constraintEnd_toEndOf="parent"
                        app:layout_constraintStart_toStartOf="parent"
                        app:layout_constraintTop_toTopOf="parent" />

                </android.support.constraint.ConstraintLayout>
            </android.support.v7.widget.CardView>
        </android.support.constraint.ConstraintLayout>

回答1:

Try this:

<?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"
    android:orientation="vertical"
    android:padding="20dp">

    <android.support.v7.widget.CardView
        android:id="@+id/card_1"
        android:layout_width="0dp"
        android:layout_height="200dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="8dp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <android.support.v7.widget.CardView
        android:id="@+id/card_2"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginBottom="8dp"
        android:layout_marginLeft="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginTop="0dp"
        app:cardBackgroundColor="#69F"
        app:layout_constraintBottom_toBottomOf="@+id/card_1"
        app:layout_constraintLeft_toLeftOf="@+id/card_1"
        app:layout_constraintRight_toRightOf="@+id/card_1"
        app:layout_constraintTop_toBottomOf="@+id/card_1" />

</android.support.constraint.ConstraintLayout>

Explanation :- This works because of these four lines

Following lines sets the blue CardView centered on the bottom edge of White CardView.

<!-- top constraint is set to bottom of White CardView -->
app:layout_constraintTop_toBottomOf="@+id/card_1"

<!-- bottom constraint is set to bottom of White CardView -->
app:layout_constraintBottom_toBottomOf="@+id/card_1"

Following lines set the blue CardView centered horizontally

<!-- left constraint is set to left of White CardView -->
app:layout_constraintLeft_toLeftOf="@+id/card_1"

<!-- right constraint is set to right of White CardView -->
app:layout_constraintRight_toRightOf="@+id/card_1"

回答2:

try below:

<?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"
    android:fitsSystemWindows="true"
    app:layout_collapseMode="parallax">


    <ImageView
        android:id="@+id/imageView_jobBackdrop_jobDetails"
        android:layout_width="match_parent"
        android:layout_height="175dp"
        android:fitsSystemWindows="true"
        android:scaleType="centerCrop"
        android:background="@android:color/white"
        app:layout_collapseMode="parallax"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="match_parent"
        android:layout_height="60dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:background="@android:color/black"
        app:layout_constraintBottom_toBottomOf="@+id/imageView_jobBackdrop_jobDetails"
        app:layout_constraintEnd_toEndOf="@+id/imageView_jobBackdrop_jobDetails"
        app:layout_constraintStart_toStartOf="@+id/imageView_jobBackdrop_jobDetails"
        app:layout_constraintTop_toBottomOf="@+id/imageView_jobBackdrop_jobDetails"  />

    <ImageView
        android:id="@+id/imageView3"
        android:layout_width="75dp"
        android:layout_height="75dp"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:background="@android:color/darker_gray"
        app:layout_constraintBottom_toTopOf="@+id/imageView2"
        app:layout_constraintEnd_toEndOf="@+id/imageView2"
        app:layout_constraintStart_toStartOf="@+id/imageView2"
        app:layout_constraintTop_toTopOf="@+id/imageView2"  />


</android.support.constraint.ConstraintLayout>

来源：https://stackoverflow.com/questions/46645517/android-constraint-layout-how-to-align-a-view-centered-over-edge-of-other-vi