Android Gallery first item not displaying: parent.getWidth returns 0

I have a Gallery displaying TextViews. When it's shown, the 1st item is not displayed. This is because parent.getWidth() returns 0 at the first call.

So how can I set the item's width to be a fraction of its parent gallery's width?

Here is the code:

public class GalleryActivity extends Activity {
  private Gallery gallery;
  public void onCreate (Bundle savedInstanceState) {
    super.onCreate (savedInstanceState);
    setContentView (R.layout.gallery);
    gallery = (Gallery) findViewById (R.id.gallery);
    gallery.setAdapter (new Adapter ());
  }

  private class Adapter extends BaseAdapter {
    private String[] items = {"A", "B", "C", "D", "E", "F"};
    public int getCount () {
      return items.length;
    }
    public Object getItem (int position) {
      return items[position];
    }
    public long getItemId (int position) {
      return position;
    }
    public View getView (int position, View convertView, ViewGroup parent) {
      TextView view = new TextV开发者_Go百科iew (GalleryActivity.this);
      view.setText (getItem (position).toString ());
      view.setBackgroundColor (Color.GRAY);
      view.setGravity (Gravity.CENTER);
      view.setLayoutParams (new Gallery.LayoutParams (parent.getWidth () / 3,
      LayoutParams.FILL_PARENT));
      return view;
    }
  }
}

layout/gallery.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical" android:layout_width="fill_parent"
  android:layout_height="fill_parent">
  <Gallery android:id="@+id/gallery" android:layout_width="fill_parent"
    android:layout_height="wrap_content" android:layout_weight="1"
    android:scrollbars="horizontal" android:spacing="1dp"></Gallery>
  <TextView android:layout_width="fill_parent" android:layout_height="wrap_content"
    android:layout_weight="3"></TextView>
</LinearLayout>

OK don't quote me on this but I believe the width won't actually get set until some contents have been drawn, so getWidth will always return 0 before that. If so, and you know what width and height you want anyway you can manually set width and height ahead of time with setWidth() and setHeight()...

If all you want is the width and height of the actually display screen, you can use...

                Display display = windowManager.getDefaultDisplay();
                if (display != null) {
                    this.setHeight(display.getHeight());
                    this.setWidth(display.getWidth());
                }

And disclaimer: I've never worked with Galleries before and wouldn't be surprised if there's a better, "best practice" way to do what you're trying...

I've found what's wrong: in the last line, parent.getWidth() returns 0 at the first call (because layout is not finished) so the first item is not displayed...

So the question now becomes: How can I set a gallery item's width as a fraction of its parent's width? The difficulty is that Gallery only accepts Gallery.LayoutParams.

I've now reformulated the original question.

I recently ran into this same problem. I managed to solve this by calling notifyDataSetChanged() on the galleries adapter immediately after I set the adapter. It would seem that the view is updated before the gallery is even visible so I don't see any glitches from suddenly changing the width.

Something like this in the onCreate() callback:

Adapter adapter = new Adapter();
gallery.setAdapter(adapter);
adapter.notifyDataSetChanged()