Add view to constraintLayout with constraints similar to another child

☆樱花仙子☆ 提交于 2019-12-05 13:30:36
Nicolas Roard

ConstraintLayout.LayoutParams cache its parameters, and is associated to the widget you use it on, so you cannot simply pass one widget's layoutParams to another.

You have to instead generate a new layoutParams for your new object, and copy the corresponding fields.

For example, if you have something like:

<?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:id="@+id/content_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <Button
        android:text="Button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/button"
        android:layout_marginTop="16dp"
        app:layout_constraintTop_toTopOf="parent"
        android:layout_marginStart="16dp"
        app:layout_constraintLeft_toLeftOf="parent"
        android:layout_marginLeft="16dp" />

</android.support.constraint.ConstraintLayout>

Then you could do:

ConstraintLayout layout = (ConstraintLayout) findViewById(R.id.content_main);
ConstraintLayout.LayoutParams params = 
                (ConstraintLayout.LayoutParams) button.getLayoutParams();

Button anotherButton = new Button(this);

ConstraintLayout.LayoutParams newParams = new ConstraintLayout.LayoutParams(
                ConstraintLayout.LayoutParams.WRAP_CONTENT,
                ConstraintLayout.LayoutParams.WRAP_CONTENT);

newParams.leftToLeft = params.leftToLeft;
newParams.topToTop = params.topToTop;
newParams.leftMargin = params.leftMargin;
newParams.topMargin = params.topMargin;

layout.addView(anotherButton, -1, newParams);

This would put the second button exactly in the same place as the one defined in XML.

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