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android – How to make ConstraintLayout work with percentage values?

Posted by: admin March 10, 2020 Leave a comment

Questions:

With a Preview 1 of Android Studio 2.2 Google released a new layout in its support library: ConstraintLayout. With ConstraintLayout it is easier to use a Design tool in Android Studio, but I didn’t find a way to use relative sizes (percents or ‘weights’ like in LinearLayout). Is there a way to define the constraints based on percents? E.g. make a View take 40% of a screen, create 20% margin between views, set a View’s width to 50% of another View’s width?

How to&Answers:

You can currently do this in a couple of ways.

One is to create guidelines (right-click the design area, then click add vertical/horizontal guideline). You can then click the guideline’s “header” to change the positioning to be percentage based. Finally, you can constrain views to guidelines.

Another way is to position a view using bias (percentage) and to then anchor other views to that view.

That said, we have been thinking about how to offer percentage based dimensions. I can’t make any promise but it’s something we would like to add.

Answer:

It may be useful to have a quick reference here.

Placement of views

Use a guideline with app:layout_constraintGuide_percent like this:

<androidx.constraintlayout.widget.Guideline
    android:id="@+id/guideline"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    app:layout_constraintGuide_percent="0.5"/>

And then you can use this guideline as anchor points for other views.

or

Use bias with app:layout_constraintHorizontal_bias and/or app:layout_constraintVertical_bias to modify view location when the available space allows

<Button
    ...
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintHorizontal_bias="0.25"
    ...
    />

Size of views

Another percent based value is height and/or width of elements, with app:layout_constraintHeight_percent and/or app:layout_constraintWidth_percent:

<Button
    ...
    android:layout_width="0dp"
    app:layout_constraintWidth_percent="0.5"
    ...
    />

Answer:

As of “ConstraintLayout1.1.0-beta1” you can use percent to define widths & heights.

android:layout_width="0dp"
app:layout_constraintWidth_default="percent"
app:layout_constraintWidth_percent=".4"

This will define the width to be 40% of the width of the screen.
A combination of this and guidelines in percent allows you to create any percent-based layout you want.

Answer:

With the new release of ConstraintLayout v1.1 you can now do the following:

<Button
android:layout_width="0dp"
android:layout_height="0dp"
app:layout_constraintHeight_percent="0.2"
app:layout_constraintWidth_percent="0.65" />

This will constrain the button to be 20% the height and 65% of the width of the parent view.

Answer:

How to use Guidelines

The accepted answer is a little unclear about how to use guidelines and what the “header” is.

Steps

First add a Guideline.

enter image description here

Select the Guidline or move it a little bit to make the constraints visible.

enter image description here

Then click the round circle (the “header”) until it becomes a percent. You can then drag this percentage down to 50% or whatever you want.

enter image description here

After that you can constrain your view to the Guideline to make it some percentage of the parent (using match_constraint on the view).

enter image description here

Answer:

The Guideline is invaluable – and the app:layout_constraintGuide_percent is a great friend… However sometimes we want percentages without guidelines. Now it’s possible to use weights:

android:layout_width="0dp"
app:layout_constraintHorizontal_weight="1"

Here is a more complete example that uses a guideline with additional weights:

<?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:padding="16dp"
    tools:context="android.itomerbu.layoutdemo.MainActivity">

    <android.support.constraint.Guideline
        android:id="@+id/guideline"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        app:layout_constraintGuide_percent="0.44"/>

    <Button
        android:id="@+id/btnThird"
        android:layout_width="0dp"
        app:layout_constraintHorizontal_weight="1"
        android:layout_height="wrap_content"
        android:text="@string/btnThird"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginBottom="8dp"
        app:layout_constraintRight_toLeftOf="@+id/btnTwoThirds"
        app:layout_constraintBottom_toTopOf="@+id/guideline"
        android:layout_marginStart="8dp"
        android:layout_marginLeft="8dp"/>

    <Button
        android:id="@+id/btnTwoThirds"
        app:layout_constraintHorizontal_weight="2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/btnTwoThirds"
        app:layout_constraintBottom_toBottomOf="@+id/btnThird"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintLeft_toRightOf="@+id/btnThird"/>
</android.support.constraint.ConstraintLayout>

Answer:

With the ConstraintLayout v1.1.2, the dimension should be set to 0dp and then set the layout_constraintWidth_percent or layout_constraintHeight_percent attributes to a value between 0 and 1 like :

<!-- 50% width centered Button -->
<Button
    android:id="@+id/button"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintWidth_percent=".5" />

(You don’t need to set app:layout_constraintWidth_default="percent" or app:layout_constraintHeight_default="percent" with ConstraintLayout 1.1.2 and following versions)

Answer:

Try this code. You can change the height and width percentages with app:layout_constraintHeight_percent and app:layout_constraintWidth_percent.

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:background="#FF00FF"
        android:orientation="vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintHeight_percent=".6"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintWidth_percent=".4"></LinearLayout>

</android.support.constraint.ConstraintLayout>

Gradle:

dependencies {
...
    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
}

enter image description here

Answer:

you can use app:layout_constraintVertical_weight it same as layout_weight in linearlayout

<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">

<Button
    android:id="@+id/button4"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:text="Button"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toLeftOf="@+id/button5"
    app:layout_constraintVertical_weight="1"/>

<Button
    android:id="@+id/button5"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:text="Button"
    app:layout_constraintLeft_toRightOf="@+id/button4"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintVertical_weight="1"/>
</android.support.constraint.ConstraintLayout>

NOTE: app:layout_constraintVertical_weight(app:layout_constraintHorizontal_weight) will work with android:layout_width="0dp" (android:layout_height="0dp"

Answer:

For someone that might find useful, you can use layout_constraintDimensionRatio im any child view inside a ConstraintLayout and we can define the Height or Width a ratio of the other dimension( at least one must be 0dp either width or heigh) example

 <ImageView
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:src="@drawable/top_image"
        app:layout_constraintDimensionRatio="16:9"        
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

in this case the aspect ratio it’s 16:9 app:layout_constraintDimensionRatio="16:9" you can find more info HERE

Answer:

I know this isn’t directly what OP was originally asking for but this helped me a lot in this situation when I had a similar question.. Adding this for people looking to change the layout window size (which i use regularly), via code. Add this to your onCreate in the activity of question. (Changes it to 80%)

DisplayMetrics dm = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(dm);

int width = dm.widthPixels;
int height = dm.heightPixels;

getWindow().setLayout((int)(width * 0.8), (int)(height * 0.8));

Answer:

Simply, just replace , in your guideline tag

app:layout_constraintGuide_begin="291dp"

with

app:layout_constraintGuide_percent="0.7"

where 0.7 means 70%.

Also if you now try to drag guidelines, the dragged value will now show up in %age.

Answer:

Using Guidelines you can change the positioning to be percentage based

<android.support.constraint.Guideline
android:id="@+id/guideline"
android:layout_width="1dp"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.5"/>

You can also use this way

android:layout_width="0dp"
app:layout_constraintWidth_default="percent"
app:layout_constraintWidth_percent="0.4"

Answer:

Constraint Layout 1.0 making a view take up a percentage of the screen required making two guidelines. In Constraint Layout 1.1 it’s been made simpler by allowing you to easily constrain any view to a percentage width or height.

enter image description here

Isn’t this fantastic? All views support layout_constraintWidth_percent and layout_constraintHeight_percent attributes. These will cause the constraint to be fixed at a percentage of the available space. So making a Button or a TextView expand to fill a percent of the screen can be done with a few lines of XML.

For example, if you want to set the width of the button to 70% of screen, you can do it like this:

<Button
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_constraintWidth_percent="0.7" />

Please note that you will have to put the dimension should be used as percentage to 0dp as we have specified android:layout_width to 0dp above.

Similarly, if you want to set the height of the button to 20% of screen, you can do it like this:

<Button
android:layout_width="wrap_content"
android:layout_height="0dp"
android:layout_constraintWidth_percent="0.2" />

See! we have specified android:layout_height to 0dp this time as we want button to use height as percentage.