@Override
public void onClick(View v) {
    if(v.getId() == R.id.action_reading) {
        PopupMenu popup = new PopupMenu(context, v);
        popup.setOnMenuItemClickListener(new OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem arg0) {
                System.out.println("------ click menu");
                return false;
            }
        });
        popup.getMenuInflater().inflate(R.menu.action_reading_menu, popup.getMenu());
        popup.show();
    }
}

<Button android:id="@+id/action_reading"
        android:layout_width="30dp"
        android:layout_height="35dp"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"/>

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >
    <item android:id="@+id/delete_item_reading"
        android:title="Delete"
        android:visible="true"></item>
</menu>

java.lang.RuntimeException: Binary XML file line #17: You must supply a layout_height attribute.