How to prepare a dial-like GridLayout?

Question

Background

I'm trying to create a dial-like GridLayout, similar to this sketch :

The problem

I'm failing to create it correctly.

The idea I had was that all cells would take the same space, spreading the size evenly, except for the backspace button on the right that would span over 3 rows.

What I tried

What I currently have is this:

private TextView generateGridTextButton(final CharSequence textToShowAndAddUponClick) {
    TextView tv = (TextView) LayoutInflater.from(this).inflate(R.layout.grid_text_button, mButtonsGrid, false);
    tv.setText(textToShowAndAddUponClick);
    tv.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(final View view) {
            //...
        }
    });
    return tv;
}

private void initButtonsGrid() {
    for (int i = 1; i <= 3; ++i)
        mButtonsGrid.addView(generateGridTextButton(Integer.toString(i)));
    final ImageView backspaceButton = new ImageView(this);
    backspaceButton.setImageResource(android.R.drawable.sym_def_app_icon);
    final LayoutParams backspaceButtonLayoutParams = new LayoutParams(GridLayout.spec(GridLayout.UNDEFINED, 3, 3), GridLayout.spec(GridLayout.UNDEFINED, 1, 1));
    backspaceButtonLayoutParams.setGravity(Gravity.TOP | Gravity.CENTER_HORIZONTAL);
    backspaceButtonLayoutParams.height = backspaceButtonLayoutParams.width = LayoutParams.WRAP_CONTENT;
    backspaceButton.setLayoutParams(backspaceButtonLayoutParams);
    backspaceButton.setBackground(...));
    mButtonsGrid.addView(backspaceButton);
    for (int i = 4; i <= 9; ++i)
        mButtonsGrid.addView(generateGridTextButton(Integer.toString(i)));
    backspaceButton.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(final View view) {
            //...
        }
    });
    mButtonsGrid.addView(generateGridTextButton("*"));
    mButtonsGrid.addView(generateGridTextButton("0"));
    mButtonsGrid.addView(generateGridTextButton("+"));

    final ImageView actionButton = new ImageView(this);
    actionButton.setImageResource(android.R.drawable.sym_def_app_icon);
    final LayoutParams actionButtonLayoutParams = new LayoutParams(GridLayout.spec(GridLayout.UNDEFINED, 1, 1), GridLayout.spec(GridLayout.UNDEFINED, 1, 1));
    actionButtonLayoutParams.setGravity(Gravity.CENTER);
    actionButtonLayoutParams.height = actionButtonLayoutParams.width = LayoutParams.WRAP_CONTENT;
    actionButton.setLayoutParams(actionButtonLayoutParams);
    actionButton.setBackground(...);
    actionButton.setClickable(true);
    mButtonsGrid.addView(actionButton);
}

res/layout/grid_text_button.xml

<TextView
    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="wrap_content"
    android:layout_height="wrap_content" android:layout_rowWeight="1"
    android:background="@drawable/..." android:clickable="true" android:fontFamily="..."
    android:gravity="center" android:textColor="#2a373e" android:textSize="36sp" app:layout_columnWeight="1"
    app:layout_gravity="fill" tools:text="1"/>

The layout file has this:

    <android.support.v7.widget.GridLayout android:id="@+id/gridLayout"
        ...  app:columnCount="4"
        app:orientation="horizontal" app:rowCount="4">

This almost works but for some reason the 2 top rows of buttons take less height than the 2 bottom rows of buttons:

I tried to play with the values of the gravity, the weight, the span... but nothing I tried helped (even got worse).

The question

What is wrong here? Why do the rows take different heights?

How can I fix this ?

Answer 1

The reason for this was that I used android:layout_rowWeight instead of app:layout_rowWeight , so it didn't work well on old Android versions.

Now it works fine: