画像を重ねて表示する ref: http://qiita.com/kuchinashi_r/items/eca7107914e00262d241

file3.java

Context appContext = getApplicationContext();
ImageView image = new ImageView(appContext);
BitmapDrawable newIcon = (BitmapDrawable) getResources().getDrawable(R.drawable.new_icon);
newIcon.setGravity(Gravity.LEFT | Gravity.TOP);
Drawable[] drawables = {
        getResources().getDrawable(R.drawable.twitter),
        newIcon
};
LayerDrawable ld = new LayerDrawable(drawables);
image.setImageDrawable(ld);
RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(WC, WC);
lp.addRule(RelativeLayout.ALIGN_TOP | RelativeLayout.ALIGN_LEFT);
mRootLayout.addView(image, lp);

twitter_merge.xml

<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >

    <item android:id="@+id/twitter">
        <bitmap android:src="@drawable/twitter" />
    </item>
    <item
        android:id="@+id/new_icon"
        android:left="50dp">
        <bitmap
            android:gravity="top|left"
            android:src="@drawable/new_icon" >
        </bitmap>
    </item>

</layer-list>