Android GridLayout- cover whole screen programmatically

Question

I want grid layout to cover whole screen and I want to do it programmatically. When I do it in static xml by adding app:layout_columnWeight attribute, it looks exactly which I want to have as follows:

But when I tried to create same layout programmatically, it looks like this:

I want it to look same as first image. Here is my code:

public class MainActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    android.support.v7.widget.GridLayout gridLayout = new android.support.v7.widget.GridLayout(this);
    gridLayout.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT));
    gridLayout.setColumnCount(3);
    for (int i = 0; i < 9; i++) {
        Button button = new Button(MainActivity.this);
        GridLayout.LayoutParams lp = (GridLayout.LayoutParams) button.getLayoutParams();

        if (lp == null) {
            lp = new GridLayout.LayoutParams();
        }
        lp.columnSpec = GridLayout.spec(GridLayout.UNDEFINED, 1, 1f);
        button.setLayoutParams(lp);
        button.setText("Button " + (i + 1));
        gridLayout.addView(button);
    }
    LinearLayout linearLayout = new LinearLayout(this);
    linearLayout.addView(gridLayout);
    setContentView(linearLayout);
}
}

Please help me. Note- I am using min sdk as 21.

Update- Here is my xml code

<LinearLayout

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">

<android.support.v7.widget.GridLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    app:columnCount="3">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 1" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 2" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 3" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 4" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 5" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 6" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 7" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 8" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_columnWeight="1"
        app:layout_gravity="fill"
        android:text="Button 9" />
</android.support.v7.widget.GridLayout>
</LinearLayout>

Answer 1

Replace your activity with:

 public class MainActivity extends AppCompatActivity {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.YOUR_LAYOUT_NAME);

}
}