Displaying a GridView after using a new xml for dimesion

Question

I ran the example program for Gridview. I had set the layout params to 400, 400 which was working fine on the nexus 5. But when I executed the same for a samsung tablet and an emulator with 2.3.3 the image size was a chaos overlapping on each other. In one of the links I came to know that I should use a new dimension.xml file and setLayoutParams should pick the dimension from that file. It worked fine on the tablet and the emulator, the problem is in nexus 5 now. I am not able to see a single picture although application launches. I can see only a grey color page. Thanks in advance.

My ImageAdapter class is as follows

 public class ImageAdapter extends BaseAdapter {

         private Context mContext;

            public ImageAdapter(Context c) {
                mContext = c;
            }

            public int getCount() {
                return mThumbIds.length;
            }

            public Object getItem(int position) {
                return null;
            }

            public long getItemId(int position) {
                return 0;
            }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView imageView;
            if (convertView == null) {  // if it's not recycled, initialize some attributes
                imageView = new ImageView(mContext);
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setPadding(8,8,8,8);
                imageView.setLayoutParams(new GridView.LayoutParams(R.dimen.width,R.dimen.height));
            } else {
                imageView = (ImageView) convertView;
            }

            imageView.setImageResource(mThumbIds[position]);
            return imageView;
        }

        // references to our images
        private Integer[] mThumbIds = {
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_0, R.drawable.sample_1,
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_0, R.drawable.sample_1,
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_7, R.drawable.wallpaper,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_0, R.drawable.sample_1,
                R.drawable.sample_2, R.drawable.sample_3,
                R.drawable.sample_4, R.drawable.sample_5,
                R.drawable.sample_6, R.drawable.sample_7,
                R.drawable.sample_7, R.drawable.wallpaper
        };
    }

My activity_main.xml is as follows

    <?xml version="1.0" encoding="utf-8"?>
    <GridView xmlns:android="http://schemas.android.com/apk/res/android" 
        android:id="@+id/gridview"
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent"
        android:columnWidth="2dp"
        android:numColumns="2"
        android:verticalSpacing="5dp"
        android:horizontalSpacing="1dp"
        android:stretchMode="columnWidth"
        android:drawSelectorOnTop="True"

        android:gravity="center_vertical|center_horizontal"
        android:layout_gravity="center"
    />

My dimens.xml is as follows

    <?xml version="1.0" encoding="utf-8"?>
    <resources>

        <!-- Default screen margins, per the Android Design guidelines. -->

        <dimen name="width">150dp</dimen>
        <dimen name="height">150dp</dimen>
    </resources>

Answer 1

Create dimensions for different screens. Dont use default dimen.xml from values folder.
Kindly create as follows.
values-hdpi
-dimens.xml
values-mdpi
-dimens.xml
values-xhdpi
-dimens.xml
values-xxhdpi
-dimens.xml
values-large-mdpi
-dimens.xml
values-600dp(for 7" Tablet)
-dimens.xml
values-720dp(for 10" Tablet)
-dimens.xml
Set the values according to the screen sizes in the above folders. This will suit all the screen densities in android devices including Tablets and mobiles. for converting dp's and sp's to support different screen resolutions kindly use this link

Answer 2

Don't rely on hard-coded values for your dimensions if you don't have to. Android devices have so many form factors you will drive yourself crazy trying to figure out proper values for every device. Since you are already setting the number of columns in the GridView, why not let that determine the size? If you want, you can vary the number of columns to accommodate larger screens or landscape orientation.

In res/layout/activiy_main.xml:

<GridView xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/gridview"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent"
    android:columnWidth="2dp"
    android:numColumns="@integer/gridview_columns"
    android:verticalSpacing="5dp"
    android:horizontalSpacing="1dp"
    android:stretchMode="columnWidth"
    android:drawSelectorOnTop="True"

    android:gravity="center_vertical|center_horizontal"
    android:layout_gravity="center"
/>

In res/values/dimens.xml:

<integer name="gridview_columns">2</integer>

In res/values-sw600dp/dimens.xml:

<integer name="gridview_columns">3</integer>

In res/values-sw720dp/dimens.xml:

<integer name="gridview_columns">4</integer>