How to add an icon before each item in alert dialog?

You need custom ListAdapter to add your image. One way is to subclass the ArrayAdapter (used by default by the AlertDialog). Here is an example:

final Item[] items = {
    new Item("Email", android.R.drawable.ic_menu_add),
    new Item("Facebook", android.R.drawable.ic_menu_delete),
    new Item("...", 0),//no icon for this one
};

ListAdapter adapter = new ArrayAdapter<Item>(
    this,
    android.R.layout.select_dialog_item,
    android.R.id.text1,
    items){
        public View getView(int position, View convertView, ViewGroup parent) {
            //Use super class to create the View
            View v = super.getView(position, convertView, parent);
            TextView tv = (TextView)v.findViewById(android.R.id.text1);

            //Put the image on the TextView
            tv.setCompoundDrawablesWithIntrinsicBounds(items[position].icon, 0, 0, 0);

            //Add margin between image and text (support various screen densities)
            int dp5 = (int) (5 * getResources().getDisplayMetrics().density + 0.5f);
            tv.setCompoundDrawablePadding(dp5);

            return v;
        }
    };


new AlertDialog.Builder(this)
    .setTitle("Share Appliction")
    .setAdapter(adapter, new DialogInterface.OnClickListener() {
        public void onClick(DialogInterface dialog, int item) {
            //...
        }
    }).show();

Here is the Item class

public static class Item{
    public final String text;
    public final int icon;
    public Item(String text, Integer icon) {
        this.text = text;
        this.icon = icon;
    }
    @Override
    public String toString() {
        return text;
    }
}