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Android

Posted by dlpuxdzztg
dlpuxdzztg
8,243 Points

Initializing my list.

Hello.

So I keep getting this error:

09-30 11:20:06.632 25491-25491/com.x.x E/AndroidRuntime: FATAL EXCEPTION: main
                                                                      Process: com.x.x, PID: 25491
                                                                      java.lang.NullPointerException: Attempt to read from field 'com.x.x.models.ObjectModel$ModelTypes com.x.x.models.ObjectModel.type' on a null object reference
                                                                          at com.x.x.adapters.ListAdapter.getItemViewType(ListAdapter.java:32)
                                                                          at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4664)
                                                                          at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4617)
                                                                          at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:1994)
                                                                          at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1390)
                                                                          at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1353)
                                                                          at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:574)
                                                                          at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3028)
                                                                          at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:2906)
                                                                          at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3283)
                                                                          at android.view.View.layout(View.java:15654)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:4969)
                                                                          at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1077)
                                                                          at android.view.View.layout(View.java:15654)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:4969)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
                                                                          at android.view.View.layout(View.java:15654)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:4969)
                                                                          at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1705)
                                                                          at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1559)
                                                                          at android.widget.LinearLayout.onLayout(LinearLayout.java:1468)
                                                                          at android.view.View.layout(View.java:15654)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:4969)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
                                                                          at android.view.View.layout(View.java:15654)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:4969)
                                                                          at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1705)
                                                                          at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1559)
                                                                          at android.widget.LinearLayout.onLayout(LinearLayout.java:1468)
                                                                          at android.view.View.layout(View.java:15654)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:4969)
                                                                          at android.widget.FrameLayout.layoutChildren(FrameLayout.java:573)
                                                                          at android.widget.FrameLayout.onLayout(FrameLayout.java:508)
                                                                          at android.view.View.layout(View.java:15654)
                                                                          at android.view.ViewGroup.layout(ViewGroup.java:4969)
                                                                          at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2102)
                                                                          at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1859)
                                                                          at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1078)
                                                                          at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5875)
                                                                          at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
                                                                          at android.view.Choreographer.doCallbacks(Choreographer.java:580)
                                                                          at android.view.Choreographer.doFrame(Choreographer.java:550)
                                                                          at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
                                                                          at android.os.Handler.handleCallback(Handler.java:739)
                                                                          at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                          at android.os.Looper.loop(Looper.java:135)
                                                                          at android.app.ActivityThread.main(ActivityThread.java:5351)
                                                                          at java.lang.reflect.Method.invoke(Native Method)
                                                                          at java.lang.reflect.Method.invoke(Method.java:372)
                                                                          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:908)
                                                                          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:703)

This is where it occurs:

public class ListAdapter extends RecyclerView.Adapter<ObjectHolder> {

    private ArrayList<ObjectModel> mList;

    public ListAdapter(ArrayList<ObjectModel> list) {
        mList = list;
    }

    @Override
    public int getItemViewType(int position) {
        return mList.get(position).type.ordinal();
    }

I understand what the problem is, my mList object has nothing in it, in other words it's null. However, I want the objects to be added to the list by the user him/herself (add button). So how would I initialize an intentionally empty list until something gets added to it by the user?

Thank you.

zxqnvomfcr
zxqnvomfcr
17,224 Points

You'll just need to initialize it, by calling the ArrayList constructor: "new ArrayList<ObjectModel>();"

    private ArrayList<ObjectModel> mList;

    public ListAdapter(ArrayList<ObjectModel> list) {
        mList = new ArrayList<ObjectModel>();
        mList = list;
    }