1

问题是我无法刷新我的gridView，当我在 Firestore 中进行更改时，我的 gridView 不会清除，只是从 Firestore 添加新值（图像）。我尝试了很多可以在“stackoverflow”上找到的方法，但没有成功。也许问题ImageAdapter出在我的称呼addSnapshotListener上，我真的不知道。现在我只想在数据更改时刷新我的gridView Firestore，但在最好的情况下，我希望当我从中获取新值时Firestore，它只更新gridView的图像所在的部分，而不是整个gridView.

public class MainActivity extends AppCompatActivity {

private FirebaseFirestore db;
private ArrayList<Items> arrayList;
private ImageAdapter imageAdapter;
private GridView gridView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    gridView = findViewById(R.id.gridViewList);
    db = FirebaseFirestore.getInstance();
    arrayList = new ArrayList<>();
    //arrayList.clear();

    getUrls();

    imageAdapter = new ImageAdapter(MainActivity.this, arrayList);
    gridView.setAdapter(imageAdapter);

}

private void getUrls(){
    gridView.setAdapter(null);
    db.collection("images").addSnapshotListener(new EventListener<QuerySnapshot>() {
        @Override
        public void onEvent(QuerySnapshot value, FirebaseFirestoreException e) {
            if (e != null){
                Toast.makeText(getApplicationContext(), "No images returned", Toast.LENGTH_SHORT).show();
                return;
            }
            for (DocumentSnapshot document : value){
                refresh();
                if (document.get("imageUrl") != null){
                    arrayList.add(new Items(document.get("imageUrl").toString()));
                    refresh();
                }
            }
        }
    });
}


public void refresh() {
    new Handler(Looper.getMainLooper()).post(new Runnable() {
        @Override
        public void run() {
            imageAdapter.notifyDataSetChanged();
            gridView.invalidate();
        }
    });
}

public class ImageAdapter extends BaseAdapter {

private ImageView imageView;
private Context context;
private LayoutInflater inflater;
private ArrayList<Items> list;

public ImageAdapter(Context context, ArrayList<Items> list){
    this.context = context;
    this.list = list;
}

@Override
public int getCount() {
    return list.size();
}

@Override
public Object getItem(int position) {
    return position;
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    if (convertView == null){
        inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = inflater.inflate(R.layout.image_layout, parent, false);
        imageView = convertView.findViewById(R.id.singleImageView);
    }

    /** https://futurestud.io/tutorials/glide-caching-basics */
    Glide.with(context).load(list.get(position).getImageUrl()).apply(RequestOptions.skipMemoryCacheOf(true).centerCrop()).into(imageView);
    return convertView;
}
4

1 回答 1

0

FirebaseUI-Android/Firestore项目有一个适配器可以满足您的需求。这为您管理一个繁重的RecyclerView工作。为了拥有类似 in 的布局GridView，您可以创建GridLayoutManagerin的实例onCreate并将其传递给RecyclerView.setLayoutManager

如果您想自己破解它，那么您可以检查QuerySnapshot一个属性- cf。查看快照之间的更改。要了解如何使用 a 实现它，您可以查看源代码- 特别是方法。documentChangesREMOVEDGridViewRecyclerView.AdatpernotifyItemXXX

于 2018-02-08T21:47:25.747 回答