Here is my RadioGroup/RadioButton extension (SoftRadioGroup/SoftRadioButton).
RadioGroup is no more needed in the layout XML. You can group the RadioButtons with a property called group.
SoftRadioButton:
import java.util.HashMap;
import java.util.Random;
import android.content.Context;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.RadioButton;
public class SoftRadioButton extends RadioButton {
    private static HashMap<String, SoftRadioGroup> GROUP_MAPPINGS = new HashMap<String, SoftRadioGroup>();
    private String mGroupName;
    public SoftRadioButton(Context context, AttributeSet attrs) {
        super(context, attrs);
        addToGroup(attrs);
    }
    public SoftRadioGroup getRadioGroup() {
        return GROUP_MAPPINGS.get(mGroupName);
    }
    private void addToGroup(AttributeSet attrs) {
        for (int i = 0; i < attrs.getAttributeCount(); i++) {
            if (attrs.getAttributeName(i).equals("group")) {
                String groupName = attrs.getAttributeValue(i);
                SoftRadioGroup group;
                if ((group = GROUP_MAPPINGS.get(groupName)) != null) {
                    // RadioGroup already exists
                    group.addView(this);
                    setOnClickListener(group);
                    mGroupName = groupName;
                } else {
                    // this is the first RadioButton in the RadioGroup
                    group = new SoftRadioGroup();
                    group.addView(this);
                    mGroupName = groupName;
                    setOnClickListener(group);
                    GROUP_MAPPINGS.put(groupName, group);
                }
                return;
            }
        }
        // group is not specified in the layout xml. Let's generate a random
        // RadioGroup
        SoftRadioGroup group = new SoftRadioGroup();
        group.addView(this);
        Random rn = new Random();
        String groupName;
        do {
            groupName = Integer.toString(rn.nextInt());
        } while (GROUP_MAPPINGS.containsKey(groupName));
        GROUP_MAPPINGS.put(groupName, group);
        mGroupName = groupName;
        setOnClickListener(group);
    }
}
SoftRadioGroup:
import java.util.ArrayList;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.RadioButton;
public class SoftRadioGroup implements OnClickListener {
    private ArrayList<RadioButton> buttons = new ArrayList<RadioButton>();
    public void addView(RadioButton button) {
        buttons.add(button);
    }
    @Override
    public void onClick(View v) {
        for (RadioButton button : buttons) {
            button.setChecked(false);
        }
        RadioButton button = (RadioButton) v;
        button.setChecked(true);
    }
    public RadioButton getCheckedRadioButton() {
        for (RadioButton button : buttons) {
            if (button.isSelected())
                return button;
        }
        return null;
    }
    public int getChildCount() {
        return buttons.size();
    }
    public RadioButton getChildAt(int i) {
        return buttons.get(i);
    }
    public void check(SoftRadioButton button) {
        if (buttons.contains(button)) {
            for (RadioButton b : buttons) {
                b.setChecked(false);
            }
        }
    }
}
Usage in XML layout embedded in a table (2 groups with 2 buttons per group):
<TableLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:stretchColumns="1" >
            <TableRow
                android:id="@+id/tableRow1"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content" >
                <Your.Package.SoftRadioButton
                    android:id="@+id/filterActivity_RadioButton_byDate"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:checked="true"
                    android:contentDescription="date"
                    android:text="@string/filterActivity_RadioButton_byDate"
                    fake:group="orderBy" />
                <Your.Package.SoftRadioButton
                    android:id="@+id/filterActivity_RadioButton_byPrice"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:contentDescription="price"
                    android:text="@string/filterActivity_RadioButton_byPrice"
                    fake:group="orderBy" />
            </TableRow>
            <TableRow
                android:id="@+id/tableRow2"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content" >
                <Your.Package.SoftRadioButton
                    android:id="@+id/filterActivity_RadioButton_asc"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:contentDescription="down"
                    android:text="@string/filterActivity_RadioButton_asc"
                    fake:group="direction" />
                <Your.Package.SoftRadioButton
                    android:id="@+id/filterActivity_RadioButton_desc"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:checked="true"
                    android:contentDescription="up"
                    android:text="@string/filterActivity_RadioButton_desc"
                    fake:group="direction" />
            </TableRow>
        </TableLayout>