Sampleview.java

private RelativeLayout drawInsideEditor;

@Bind(R.id.dp_main_layout)
RelativeLayout mainLayout;

// oncreate
drawInsideEditor = (RelativeLayout) View.inflate(this, R.layout.dp_text_editor_layout, null);
mainLayout.addView(drawInsideEditor);

RelativeLayout drawText = (RelativeLayout) View.inflate(this, R.layout.dp_item_textview_preview, null);
drawInsideEditor.addview(drawText); //ini sukses
updateView(drawInsideEditor);
//atau
mainLayout.addview(drawText); // ini NPE
updateView(mainLayout);

void updateview(RelativeLayout main){
for (int i = 0; i < main.getChildCount(); i++) {
   View viewLayout = main.getChildAt(i);
    ImageButton edit = (ImageButton) viewLayout.findViewById(R.id.fab_edit); 
    edit.setBackground(....) // ini kena NPE kalo pake mainlayout.
  }
}