Question

我有一个gridView，它显示默认的addImage按钮作为最后一项。当gridView中显示某些内容时它很有效，但是如果我将空列表传递给适配器，则默认图像不会显示。为什么是这样？

适配器代码：

public class GridImageAdapter extends ArrayAdapter<String> {

private Context mContext;
private LayoutInflater mInflater;
private int layoutResource;
private ArrayList<String> imageURLs;
private static final int NUM_GRID_COLUMNS = 3;

public GridImageAdapterSettingFragment(Context context, int layoutResource, ArrayList<String> imageURLs) {
    super(context, layoutResource, imageURLs);
    this.mContext = context;
    this.mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.layoutResource = layoutResource;
    this.imageURLs = imageURLs;

}

private static class ViewHolder{
    SquareImageView image;
}

@Override
public int getCount() {
    return imageURLs.size()+1;
}

public void removeItem(int position){
    imageURLs.remove(position);
    notifyDataSetChanged();
}

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

    final GridImageAdapterSettingFragment.ViewHolder holder;

    if(convertView == null) {
        convertView = mInflater.inflate(layoutResource, parent, false);
        holder = new GridImageAdapterSettingFragment.ViewHolder();
        holder.image = convertView.findViewById(R.id.gridImageView);

        convertView.setTag(holder);

    } else {

        holder = (GridImageAdapterSettingFragment.ViewHolder) convertView.getTag();
    }

    if(position==imageURLs.size()){

        holder.image.setImageResource(R.drawable.ic_add_image);


    } else {
        String imageURL = getItem(position);
        final ImageLoader imageLoader = ImageLoader.getInstance();
        imageLoader.displayImage(imageURL, holder.image, new ImageLoadingListener() {
            @Override
            public void onLoadingStarted(String imageUri, View view) {

            }

            @Override
            public void onLoadingFailed(String imageUri, View view, FailReason failReason) {

            }

            @Override
            public void onLoadingComplete(String imageUri, View view, Bitmap loadedImage) {

            }

            @Override
            public void onLoadingCancelled(String imageUri, View view) {

            }
        });

    }

    return convertView;
}

在片段中，我正在查询Firebase数据库，以便将图像添加到数据列表中。

private void setupGridView(){

    final List<Photo> photos = new ArrayList<Photo>();
    final ArrayList<String> imgUrls = new ArrayList<String>();

    myRef = FirebaseDatabase.getInstance().getReference();
    Query query = myRef.child(getString(R.string.dbname_user_photos))
            .child(FirebaseAuth.getInstance().getCurrentUser().getUid());
    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            if(dataSnapshot.exists()){

                //Add images into the list and call adapter to set up GridView.

            } else {
                //problem here!
                GridImageAdapter adapter = new GridImageAdapter(getActivity(), R.layout.layout_grid_imageview, imgUrls);
                Log.d(TAG, "onDataChange: emptylist is " + imgUrls);
                mGridView.setAdapter(adapter);
            }
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
            Log.d(TAG, "onCancelled: query cancelled.");
        }
    });
}

我的gridView项目视图布局文件和片段布局文件中的GridView如下：

<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal">

<com.aaron.xxxxxxxx.Utils.SquareImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/gridImageView"
    android:scaleType="centerCrop"/>

 <GridView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@id/photo_tv"
            android:numColumns="3"
            android:layout_marginLeft="10dp"
            android:verticalSpacing="2dp"
            android:horizontalSpacing="2dp"
            android:stretchMode="none"
            android:gravity="center"
            android:layout_marginTop="3dp"
            android:id="@+id/gridView"/>

Answer 1

而不是使用此代码，

if(position==imageURLs.size()){
         holder.image.setImageResource(R.drawable.ic_add_image);
} else {
....
}

只需将默认图片添加到该列表（您将传递给gridview）作为最后一项。

Answer 2

试试这个

<com.aaron.xxxxxxxx.Utils.SquareImageView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/gridImageView"
    android:src="@drawable/ic_add_image"
    android:scaleType="centerCrop"/>

为什么我的gridView没有显示默认图像

2 个答案: