Question

所以在我的应用程序中，我希望有一个新闻提要的东西。在这个列表视图中，我有一个自定义适配器，它具有这样的行布局。

正如您所看到的，每当用户点击“阅读更多”时，我希望黑屏变为透明。所以我尝试了这段代码

public class CustomAdapter extends ArrayAdapter<GEvent> {

private Context mContext;

private Uri eventImage;

final  Holder holder = new Holder();

private View rowView;

public void setEventImage(Uri eventImage) {
    this.eventImage = eventImage;
}

public CustomAdapter(Context context, GEvent[] resource) {
    super(context, R.layout.custom_row , resource);

    this.mContext = context;
}

@NonNull
@Override
public View getView(int position, View convertView, ViewGroup parent) {

    LayoutInflater inflater = LayoutInflater.from(getContext());
   final View customView = inflater.inflate(R.layout.example,parent,false);

    final GEvent gEvent = getItem(position);


    rowView = customView;


    holder.title = (TextView) customView.findViewById(R.id.geventTitle);
    holder.profileName = (TextView) customView.findViewById(R.id.geventProfileName);
    holder.readMore = (TextView) customView.findViewById(R.id.geventReadMoreButton);
    holder.eventPic = (ImageView) customView.findViewById(R.id.geventEventPhoto);

   View.OnClickListener view =new View.OnClickListener() {

       View updatedView;

        @Override
        public void onClick(View v) {
            if(gEvent.isWantsToReadMore()){                        //wants to read less
                Log.i("Entered the condition","Read less");
                customView.findViewById(R.id.geventEventPhoto).setAlpha(0.5f);
            }
            else{                                       //wants to read more
                Log.i("Entered the condition","Read more");
                customView.findViewById(R.id.geventEventPhoto).setAlpha(1f);
            }
            gEvent.setWantsToReadMore(!gEvent.isWantsToReadMore());

            updatedView = customView;

        }



    };

    holder.readMore.setOnClickListener(view);

    holder.title.setText(gEvent.getTitle());
    holder.profileName.setText(gEvent.getProfileUsername());

    if(!gEvent.isHasSetPhoto())
    {
        Log.i("Entered the condition","Check");

        fetchPhotoURI(gEvent);

        if(eventImage!=null){


            Picasso.with(mContext)
                    .load(eventImage)
                    .into(holder.eventPic);

            gEvent.setHasSetPhoto(true);

            Log.i("Set COndition","True");
        }

    }

    return customView;

}

public void fetchPhotoURI(GEvent gEvent){



    FirebaseStorage fbStorage = FirebaseStorage.getInstance();

    StorageReference storageReference = fbStorage.getReferenceFromUrl("gs://XXXXX");

    final StorageReference pathRef= storageReference.child("gEvent/"+gEvent.getUuid()+"/photo.jpg");



    try{

       pathRef.getDownloadUrl().addOnSuccessListener(new OnSuccessListener<Uri>() {
            @Override
            public void onSuccess(Uri uri) {
                setEventImage(uri);
            }
        });

    }catch (Exception e){
        e.printStackTrace();
    }


}

public class Holder{

    TextView profileName;
    TextView title;
    TextView description;
    TextView details;
    TextView readMore;

    CircleImageView profilePic;
    ImageView eventPic;


}

public void readMoreFunction(View view,boolean wantsToReadMore){


    notifyDataSetChanged();

}

}

现在我遇到的问题是，每当用户点击read more按钮时，视图确实会发生变化，但我无法更新listview中的特定行，即Alpha值的变化不会发生变化。在listview中反映出来，我首先想到的是因为我没有更新由适配器在getView（）中返回的View，但现在似乎并非如此。

我尝试过使用notifyDataSetChanged（），但这对我来说似乎不起作用。我应该改变什么？提前谢谢。

Answer 1

所以，虽然我们已经在this chat中找到了解决方案，但我在这里回答其他人提供参考。

这里的问题是在更改alpha值后视图不会自动更新。

因此，要更新视图，我们可以使用invalidate()方法，最终代码如下所示：

    ....
    @Override
    public void onClick(View v) {
        if(gEvent.isWantsToReadMore()){                        //wants to read less
            Log.i("Entered the condition","Read less");
            customView.findViewById(R.id.geventEventPhoto).setAlpha(0.5f);
            // To make the view redraw itself, use invalidate()
            customView.findViewById(R.id.geventEventPhoto).invalidate();

        }
        else{                                       //wants to read more
            Log.i("Entered the condition","Read more");
            customView.findViewById(R.id.geventEventPhoto).setAlpha(1f);
            // To make the view redraw itself, use invalidate()
            customView.findViewById(R.id.geventEventPhoto).invalidate();
        }
    ...

列表视图行更新

1 个答案: