What is meaning of margin in constraint set connect

Question

The official documentation of the constraint set connect says: https://developer.android.com/reference/android/support/constraint/ConstraintSet.html#connect(int, int, int, int, int)

void connect (int startID, 
                int startSide, 
                int endID, 
                int endSide, 
                int margin)

the margin to constrain (margin must be postive)

For my understanding if I want to connect two views with the left to right of then this margin is left margin.

//left to right of

constraintset.connect(textView.id,ConstraintSet.LEFT,previousTextViewId,ConstraintSet.RIGHT,10)

then 10 is the left margin. Am I right? I have implemented this concept but no margin is set even no right or left. What am I missing?

Answer 1

Update: It looks like this issue has been fixed, but I haven't checked it out. See the bug report.

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Your understanding is also how I understand things. Here is a quick way to check how things are working.

In the layout below, the top left corner of textRight lines up with the lower right corner of textLeft. When MainActivity runs, textRight should move 1,000px down and 1,000px to the right. It moves 1,000 px down but does not move to the right at all.

I believe that this is an outstanding issue. See this issue report.

I don't know a work-around and I am surprised that this could even be a bug. I am willing to stand corrected if anyone sees the error.

two_text_views.xml

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

    <TextView
        android:id="@+id/textLeft"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:text="TextView1"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        android:layout_marginStart="8dp" />

    <TextView
        android:id="@+id/textRight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView2"
        android:layout_marginTop="0dp"
        app:layout_constraintTop_toBottomOf="@+id/textLeft"
        app:layout_constraintStart_toEndOf="@+id/textLeft"
        android:layout_marginStart="0dp" />
</android.support.constraint.ConstraintLayout>

**MainActivity.java**

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ConstraintLayout layout;
        super.onCreate(savedInstanceState);
        setContentView(R.layout.two_text_views);

        ConstraintSet constraints = new ConstraintSet();
        constraints.clone(layout);
        constraints.connect(R.id.textRight, ConstraintSet.LEFT, R.id.textLeft, ConstraintSet.RIGHT, 1000);
        constraints.connect(R.id.textRight, ConstraintSet.TOP, R.id.textLeft, ConstraintSet.BOTTOM, 1000);
        constraints.applyTo(layout);
    }
}

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EDIT So, here is a fix. Use ConstraintSet.START and ConstraintSet.END instead of ConstraintSet.LEFT and ConstraintSet.RIGHT. I just tried it and it works OK. I can't say why left and right don't work.