get parent's view from a layout

Question

I have a FragmentActivity with this layout:

<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" >  <TextView     android:id="@+id/textView1"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="@string/menulabel"     android:textSize="24sp" />  <EditText     android:id="@+id/editText1"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:ems="10"     android:inputType="text"     android:layout_below="@+id/textView1"     android:hint="@string/search_title_hint" />  <TextView     android:id="@+id/textView2"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="@string/spinnersearch"     android:layout_below="@+id/editText1" />  <LinearLayout     android:id="@+id/layout1"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:layout_below="@+id/textView2" >      <Spinner         android:id="@+id/spinner_search"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:prompt="@string/spinnersearch" />      <Button         android:id="@+id/button1"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:text="@string/reset_search" />  </LinearLayout>  <Button     android:id="@+id/button2"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="@string/buttonnewcat"     android:layout_below="@+id/layout1" />  <Button     android:id="@+id/button3"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="@string/buttondelcat"      android:layout_below="@+id/button2" />  <Button     android:id="@+id/button4"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="@string/buttoneditcat"     android:layout_below="@+id/button3" />  <Button     android:id="@+id/button5"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="@string/buttonnewtext"     android:layout_below="@+id/button4" />  <Button     android:id="@+id/button6"     android:layout_width="wrap_content"     android:layout_height="wrap_content"     android:text="@string/buttondeltext"     android:layout_below="@+id/button5" />  <RelativeLayout     android:layout_width="match_parent"     android:layout_height="match_parent" >      <side.menu.scroll.ScrollerLinearLayout         android:id="@+id/menu_content_side_slide_layout"         android:layout_width="match_parent"         android:layout_height="match_parent"         android:orientation="vertical" >          <LinearLayout             android:layout_width="match_parent"             android:layout_height="45dp"             android:background="@drawable/ab_solid_example"             android:orientation="horizontal" >              <ImageView                 android:id="@+id/main_tmp_button"                 android:layout_width="wrap_content"                 android:layout_height="wrap_content"                 android:background="@drawable/actionbar_background"                 android:src="@drawable/download" />          </LinearLayout>         <FrameLayout             android:id="@+id/fragment_container"             android:layout_width="match_parent"             android:layout_height="match_parent"             android:background="@drawable/bg_groud" />      </side.menu.scroll.ScrollerLinearLayout> </RelativeLayout> 

and the ScrollerLinearLayout class is something like this:

public class ScrollerLinearLayout extends LinearLayout {     // code of the class } 

How to access from ScrollerLinearLayout to the parent layout to get - for example - the editetxt? FragmentActivity and ScrollerLineraLayout are in different packages of the same projects. I tried to use the getParent() function in this way within the ScrollerLinearLayout but it doesn't work.

RelativeLayout r = (RelativeLayout) this.getParent().getParent(); int w = r.findViewById(R.id.editText1).getLayoutParams().width; 

Someone help me? Thanks!

Answer 1

The getParent method returns a ViewParent, not a View. You need to cast the first call to getParent() also:

RelativeLayout r = (RelativeLayout) ((ViewGroup) this.getParent()).getParent(); 

As stated in the comments by the OP, this is causing a NPE. To debug, split this up into multiple parts:

ViewParent parent = this.getParent(); RelativeLayout r; if (parent == null) {     Log.d("TEST", "this.getParent() is null"); } else {     if (parent instanceof ViewGroup) {         ViewParent grandparent = ((ViewGroup) parent).getParent();         if (grandparent == null) {             Log.d("TEST", "((ViewGroup) this.getParent()).getParent() is null");         }         else {             if (parent instanceof RelativeLayout) {                 r = (RelativeLayout) grandparent;             }             else {                 Log.d("TEST", "((ViewGroup) this.getParent()).getParent() is not a RelativeLayout");             }         }     }     else {         Log.d("TEST", "this.getParent() is not a ViewGroup");     } }  //now r is set to the desired RelativeLayout.