MihaiDamian:

I have the fallowing problem: my Grid is null. I dont know why i have this problem :( I have the fallowing structure :

Activity Courses :

            layout="@layout/app_bar_courses"
        android:id="@+id/app_bar_coursesID"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

app bar courses

    android:id="@+id/content_coursesID"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    />

and final layout content courses ( just the start of it )

     xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/mainGrid"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:layout_alignParentBottom="true"
    android:alignmentMode="alignMargins"
    android:columnCount="1"
    android:columnOrderPreserved="false"
    android:padding="14dp"
    android:rowCount="3"
    >

The code in courses java file

View myLayout=findViewById(R.id.app_bar_coursesID);
    View mySecondLayout=myLayout.findViewById(R.id.content_coursesID);

    GridView grid;
    String web[]={"TV"};
    int[] tvid ={};
    CourseCustomAdapter adapter = new CourseCustomAdapter(Courses.this, web, tvid);
    //TODO:why grid is null
    grid=(GridView)mySecondLayout.findViewById(R.id.mainGrid);
    grid.setAdapter(adapter);

Ty in advance, hope this isnt a repost :D