Get child location in HorizontalScrollView and scroll to it

Question

Looks like I can't get or set any position or scrolling amount in my simple layout:

// Relative layout - main_layout
<HorizontalScrollView
    android:id="@+id/MenuScroll"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:fillViewport="true"
    android:scrollbars="none" >

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="48dp"
        android:orientation="horizontal"
        android:layout_gravity="center"
        android:padding="0dp" >

        <Button
            android:id="@+id/button1"
            android:layout_width="150dp"
            android:layout_height="fill_parent" />

        <Button
            android:id="@+id/button2"
            android:layout_width="150dp"
            android:layout_height="fill_parent" />

        <Button
            android:id="@+id/button3"
            android:layout_width="150dp"
            android:layout_height="fill_parent" />

        <Button
            android:id="@+id/button4"
            android:layout_width="150dp"
            android:layout_height="fill_parent" />

        <Button
            android:id="@+id/button5"
            android:layout_width="150dp"
            android:layout_height="fill_parent" />

    </LinearLayout>
</HorizontalScrollView>
// End of RelativeLayout - main_layout

What I want in my MainActivity is to get the position of any button inside the HorizontalScrollView and scroll to that position. At the moment I can't get the left value (it's always 0) and if I try to scrollTo the HorizontalScrollView it just doesn't, regardless of what the value for x or y is.

// imports
public class MainActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.main_layout);

        final Button button3 = (Button)findViewById(R.id.button3);
        Rect rectf = new Rect();
        button3.getLocalVisibleRect(rectf);
        Log.i("Left: ", String.valueOf(rectf.left)); // it is always 0

        HorizontalScrollView MenuScroll = (HorizontalScrollView)findViewById(R.id.MenuScroll);
        // Trying to scroll to X=100 but it doesn't
        MenuScroll.scrollTo(100, MenuScroll.getBottom());
    }
}

So, as I said, I can't get the left position for my button and either can scroll to some X position in my HorizontalScrollView. Is this possible?

Solution 1

(it's always 0)

Keep in mind that the views don't have dimensions in the onCreate method as they are placed on the screen after the onCreate callback returns.

What I want in my MainActivity is to get the position of any button inside the HorizontalScrollView and scroll to that position.

Have a look at the code below(placed in the onCreate method):

    final HorizontalScrollView MenuScroll = (HorizontalScrollView) findViewById(R.id.MenuScroll);

    MenuScroll.post(new Runnable() {

        @Override
        public void run() {
            final Button button3 = (Button) findViewById(R.id.button3);
            int scrollTo = 0;
            final int count = ((LinearLayout) MenuScroll.getChildAt(0))
                    .getChildCount();
            for (int i = 0; i < count; i++) {
                final View child = ((LinearLayout) MenuScroll.getChildAt(0))
                        .getChildAt(i);                 
                if (child != button3) {
                    scrollTo += child.getWidth();
                } else {
                    break;
                }
            }
            MenuScroll.scrollTo(scrollTo, 0);
        }

    });

Also be careful with the attributes you use in the layout(I'm referring to the layout_gravity which could cause problems if I'm not mistaken).

Solution 2

It can be done directly like:

scrollTo = button3.getLeft();

Comments

[camelCaseCoder]

No need to iterate over all the child views and adding up their widths to get the scroll value. Simply set scrollTo = button3.getLeft()