Recyclerview on item click set image to another imageview in activity

问题

I'm working on Recyclerview, and I want to set an image to center imageview from Recyclerview's selected item

Error : You must pass in a non null View

here I'm trying to set an image to imageview located in activity_set_back.xml from Onclick method of Recyclerview's

I have: moviesList(ArrayList) that hold all URL and I'm getting position on click only thing I need to do is set that image to img_back(Imageview) Shown in this code

MoviesAdapter.class

this is my adapter

    public class MoviesAdapter extends RecyclerView.Adapter<MoviesAdapter.MyViewHolder> {

    String string_url;
    String clicked_url;
    private ArrayList<Image> moviesList;

    public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        public ImageView img_backimage;
        public ImageView img_back;

        public MyViewHolder(View itemView) {
            super(itemView);
            img_backimage = (ImageView) itemView.findViewById(R.id.img_backimage);
            img_back =(ImageView) itemView.findViewById(R.id.img_edit_this);
            itemView.setOnClickListener(this);


        }

        @Override
        public void onClick(View view) {
            int position = getLayoutPosition(); // gets item position
            clicked_url= moviesList.get(position).getPath();
            Toast.makeText(view.getContext(),position+"",Toast.LENGTH_LONG).show();
            Glide.with(view.getContext()).load(clicked_url)
                    .diskCacheStrategy(DiskCacheStrategy.ALL)
                    .fitCenter()
                    .crossFade()
                    .into(img_back);
        }

    }

    public MoviesAdapter(ArrayList<Image> moviesList) {
        this.moviesList = moviesList;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        View rootView = inflater.inflate(R.layout.image_list_row, parent, false);
        return new MyViewHolder(rootView);
    }

    @Override
    public void onBindViewHolder(final MyViewHolder holder, int position) {
        string_url= moviesList.get(position).getPath();
        Glide.with(holder.img_backimage.getContext()).load(string_url)
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .fitCenter()
                .crossFade()
                .into(holder.img_backimage);
    }
    @Override
    public int getItemCount() {
        return moviesList.size();
    }
}

image_list_row.xml

<?xml version="1.0" encoding="utf-8"?>


 <RelativeLayout
        android:id="@+id/rl_single_item"
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="?android:attr/selectableItemBackground"
        android:clickable="true"
        android:focusable="true"
        android:orientation="horizontal"
        android:paddingBottom="8dp"
        android:paddingLeft="4dp"
        android:paddingRight="4dp"
        android:paddingTop="6dp">


        <ImageView
            android:id="@+id/img_backimage"
            android:layout_width="wrap_content"
            android:layout_height="100dp"
            android:layout_centerInParent="true"
            android:scaleType="fitCenter"
            android:src="@drawable/background"/>

    </RelativeLayout>

activity_set_back.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.weblogicindia.paint.SetBackActivity">

    <RelativeLayout
        android:id="@+id/rl_Paint_Area_container"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/grid_view_container">

        <RelativeLayout
            android:id="@+id/rl_Paint_Area2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_centerInParent="true"
            android:gravity="center"
            >

            <ImageView
                android:id="@+id/img_edit_this"
                android:layout_centerInParent="true"
                android:layout_width="fill_parent"
                android:layout_height="wrap_content"
                android:adjustViewBounds="true"
                android:scaleType="fitCenter"
                android:src="@drawable/background"/>


        </RelativeLayout>

    </RelativeLayout>

    <RelativeLayout
        android:id="@+id/grid_view_container"
        android:layout_width="match_parent"
        android:layout_alignParentBottom="true"
        android:layout_height="wrap_content"
        android:background="@color/colorAccent">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler_view"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"/>

    </RelativeLayout>
</RelativeLayout>

回答1:

Here your imageview- img_edit_this is inside your activity and not inside the itemview. Inorder to access the imageview in your activity from adapter, you first need to pass a listner from your activity to adapter during adapter initilalisation. Then use this listener in your adapter to change the imageview in activity.

First create an interface like this

public interface RecyclerImageClick {
void onCenterImageChange(String imagePath);
}

Make your activity implement this, for egs

public class MembersList extends AppCompatActivity implements RecyclerImageClick

Now implement the method onCenterImageChange(String imagePath) in activity

Now when initialising adapter, pass this listner into it along with arraylist like this

data= new MoviesAdapter(ArrayList<Image> moviesList,this);

Now change your adapter constructor like this

private RecyclerImageClick listener;
public MoviesAdapter(ArrayList<Image> moviesList,RecyclerImageClick listener) {
        this.moviesList = moviesList;
        this.listener=listener;
    }

Now inside the adapter's imageview click listener call listener.onCenterImageChange(imagePath)

Now inside your activity, declare your imageview and set it to the image path passed from adapter

回答2:

Don't use onclick method of RecyclerView to detect child click instead use ClickListener on child view in bind method as in

@Override
    public void onBindViewHolder(final MyViewHolder holder, int position) {
        string_url= moviesList.get(position).getPath();
        Glide.with(holder.img_backimage.getContext()).load(string_url)
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .fitCenter()
                .crossFade()
                .into(holder.img_backimage);
        holder.itemView.setonClickListener(new View.OnClickListener(){          
            Glide.with(view.getContext()).load(string_url)
                    .diskCacheStrategy(DiskCacheStrategy.ALL)
                    .fitCenter()
                    .crossFade()
                    .into(img_back);
        });
    }

来源：https://stackoverflow.com/questions/49397689/recyclerview-on-item-click-set-image-to-another-imageview-in-activity