Android: Keep ratio for a full-width and undefined height ImageView in a ConstraintLayout?

问题

In a ConstraintLayout, an ImageView is bound to its parent in such a way that:

1. Its left side is bound to the screen's left side

2. Its right side is bound to the screen's right side

3. Its top side is bound to a widget's bottom side

4. Its bottom side is bound to the screen's bottom side

Thus my ImageView appears to be full-width, and its height is the distance between a widget and the bottom of the screen.

<ImageView
    android:id="@+id/imageView16"
    android:layout_width="0dp"
    android:layout_height="0dp"
    android:orientation="horizontal"
    android:background="@drawable/ic_background_stars"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toBottomOf="@id/linearLayout4"
    app:layout_constraintBottom_toBottomOf="parent"
    />

The problem is that the SVG it contains is also full-width, but the ratio has been destroyed: it's not big enough, in terms of height. So the SVG is distorded.

Question

How could I show the SVG in full-width (from the left screen's side to the right one), keeping its ratio (so that its height would be sufficiently great)?

回答1:

In addition to the last answer, the reason your image is not being scaled properly is because you are using it as the background.

Your code..

android:background="@drawable/ic_background_stars"

Instead, use it as image resource.

app:srcCompat="@drawable/ic_background_stars"

And the default scale type of ImageView should do the work for you. Else, you can even experiment with various scale types.

回答2:

I think that you can use app:layout_constraintDimensionRatio="your ratio" to keep the aspect ratio if your image

For example, if you want square you need the same width and height so use - app:layout_constraintDimensionRatio="1:1"

来源：https://stackoverflow.com/questions/55562638/android-keep-ratio-for-a-full-width-and-undefined-height-imageview-in-a-constra