So I've checked all of the other threads on this topic repeatedly but none have yielded the solution. Here's the code:
The XML
<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"
tools:context=".MainActivity">
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent" />
<com.turingtechnologies.materialscrollbar.DragScrollBar
android:layout_width="wrap_content"
android:id="@+id/dragScrollBar"
android:layout_height="match_parent"/>
</RelativeLayout>
The Activity
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Stuff
recyclerView = (RecylerView)findViewById(R.id.recyclerView); //I've verified that this works properly.
DragScrollBar dragScrollBar = (DragScrollBar)findViewById(R.id.dragScrollBar);
if (dragScrollBar == null) { Log.d("d", "fail"); }
dragScrollBar.bindRecyclerView(recyclerView);
}
DragScrollBar.java
public class DragScrollBar extends MaterialScrollBar<DragScrollBar>{
public DragScrollBar(Context context, AttributeSet attrs){
super(context, attrs);
}
}
MaterialScrollBar.java
abstract class MaterialScrollBar<T> extends RelativeLayout {
MaterialScrollBar(Context context, AttributeSet attrs){
super(context, attrs);
initialise(context);
}
//Stuff
}
It draws correctly on the preview but returns a nullPointerException
when dragScrollBar
is used and 'fail' is printed to the console.
I've omitted the other normal constructors but when included they don't make a difference.
EDIT: Here's the stack trace
fail
Shutting down VM
FATAL EXCEPTION: main
Process: com.turingtechnologies.materialscrollbardemo, PID: 31890 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.turingtechnologies.materialscrollbardemo/com.turingtechnologies.materialscrollbardemo.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object com.turingtechnologies.materialscrollbar.DragScrollBar.bindRecyclerView(android.support.v7.widget.RecyclerView)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object com.turingtechnologies.materialscrollbar.DragScrollBar.bindRecyclerView(android.support.v7.widget.RecyclerView)' on a null object reference
at com.turingtechnologies.materialscrollbardemo.MainActivity.onCreate(MainActivity.java:26)
at android.app.Activity.performCreate(Activity.java:6251)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
at android.app.ActivityThread.-wrap11(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
I had run setID() inside of initalise as part of an earlier scheme and hadn't thought to remove it during refactoring.