如何从片段的另一个布局中访问按钮

Question

i am trying to get a button from another layout in fragment.this fragment have another inflate another layout.i get a java.lang.NullPointerException. how to solve this problem?

public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    final View view = inflater.inflate(R.layout.add_to_cart_display, container, false);


    myAdapter=new MyAdapter(getActivity());

    Button remove=(Button) view.findViewById(R.id.remove_cart_items);
    RecyclerView recyclerView=(RecyclerView)view.findViewById(R.id.recyclerView);
    recyclerView.setHasFixedSize(true);
    ch=new CartHelper(getActivity());
    recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    rc=new RCadapter(getDataset());
    recyclerView.setAdapter(rc);



    return view;


}

from above pgm the remove button not in the add_cart_display xml file. it locate in another layout file. here i am accessing this button.it give the following error.

10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: FATAL EXCEPTION: main 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: Process: com.infizoom.infishopping, PID: 13886 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: java.lang.NullPointerException 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at com.infizoom.infishopping.add_cart_class.onStart(add_cart_class.java:75) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.Fragment.performStart(Fragment.java:1724) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:918) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.BackStackRecord.run(BackStackRecord.java:698) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.os.Handler.handleCallback(Handler.java:808) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.os.Handler.dispatchMessage(Handler.java:103) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at android.os.Looper.loop(Looper.java:193) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at android.app.ActivityThread.main(ActivityThread.java:5341) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at java.lang.reflect.Method.invokeNative(Native Method) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at java.lang.reflect.Method.invoke(Method.java:515) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:825) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:641) 10-31 12:38:20.484 13886-13886/com.infizoom.infishopping E/AndroidRuntime:
at dalvik.system.NativeStart.main(Native Method)

add_to_cart_display.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_marginTop="@dimen/abc_action_bar_default_height_material"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/recyclerView"
    android:layout_width="fill_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    />

Remove Button inside the CardView

Answer 1

   final View view = inflater.inflate(R.layout.add_to_cart_display, container, false);
   Button remove=(Button) view.findViewById(R.id.remove_cart_items);

you are looking for a Button with id remove_cart_items inside add_to_cart_display. But in layout may be there is no Button with id remove_cart_items. That`s way you get null

Answer 2

I got an answer. i can access the button inside the cardview by recyclerAdapter onBindViewHolder(). but i dnot know how to call toast in side this function.

public static class ViewHolder extends RecyclerView.ViewHolder{

    public TextView product_name_at_cart;
    public Button remove;
    public ViewHolder(View layoutview) {
        super(layoutview);
        remove =(Button) layoutview.findViewById(R.id.remove_cart_items);
        product_name_at_cart=(TextView)layoutview.findViewById(R.id.add_cart_item_name);

    }
}

OnBindViewHolder

public void onBindViewHolder(ViewHolder viewholder, int position) {

    viewholder.product_name_at_cart.setText(mDataset.get(position).getProduct_name());

    viewholder.remove.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
                    Log.w("gopal", "Gopal btn click");
            Cursor m=ch.getcurrent_id();
            if(m.moveToFirst()){
                do{
                    int id=m.getInt(5);
                    Toast.makeText(???????, "Gopal id " + id, Toast.LENGTH_SHORT).show();
                }while (m.moveToNext());
            }
        }
    });

}

What function will came in the Toast Msg.????

Answer 3

In RecyclerAdapter , I have defined a private Activity context.

Then, you can call the Toast.makeText(context, "your message", ...) ,