Question

我的数据库保存如下：

在另一个活动中，我将使用“ temas”值将其显示为带有水平RecyclerView的标签。我现在的问题是我只能检索所有其他元素的元素0。（在这种情况下，为“ Feminismo”）。我正在尝试在onBindViewHolder内使用一个增量器，以便可以将其从0更改为1到2，然后一直打开，但是似乎不起作用。

这是我的ArticleActivity：

public class ArticlesActivity extends AppCompatActivity {

    private TextView txtTitle, txtAutor, txtDate;
    private RecyclerView articleTags;
    private String articleKey;
    private DatabaseReference articleRef, articleTagRef;

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

        articleKey = getIntent().getStringExtra("articleKey");

        articleRef = FirebaseDatabase.getInstance().getReference().child("Artigos").child(articleKey);
        articleTagRef = articleRef.child("temas");

        initializeFields();

        articleTags = findViewById(R.id.articlesActRecyclerView);
        articleTags.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false));
    }

    @Override
    protected void onStart() {
        super.onStart();

        FirebaseRecyclerOptions options = new FirebaseRecyclerOptions.Builder<String>()
                .setQuery(articleTagRef, String.class)
                .build();

        FirebaseRecyclerAdapter<String, ArticleViewHolder> adapter = new FirebaseRecyclerAdapter<String, ArticleViewHolder>(options) {
            @Override
            protected void onBindViewHolder(@NonNull final ArticleViewHolder holder, final int position, @NonNull String model) {
                Toast.makeText(ArticlesActivity.this, Integer.toString(position), Toast.LENGTH_SHORT).show();
                articleTagRef.addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        if (dataSnapshot.exists()) {
                            if (dataSnapshot.hasChildren()) {
                                holder.tags.setText(dataSnapshot.child(Integer.toString(position)).getValue().toString());
                            }
                        }
                    }

                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });
            }

            @NonNull
            @Override
            public ArticleViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
                View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.recycler_article_tags, viewGroup, false);
                ArticleViewHolder viewHolder = new ArticleViewHolder(view);
                return viewHolder;
            }
        };

        articleTags.setAdapter(adapter);
        adapter.startListening();
    }

    public class ArticleViewHolder extends RecyclerView.ViewHolder {

        private TextView tags;

        public ArticleViewHolder(@NonNull View itemView) {
            super(itemView);

            tags = itemView.findViewById(R.id.recyclerArticleTag);
        }

    }

    private void initializeFields() {
        txtTitle = findViewById(R.id.txtArticleActTitle);
        txtAutor = findViewById(R.id.txtArticleActAutor);
        txtDate = findViewById(R.id.txtArticleActDate);
    }

这是Article xml（相当标准的一个）：

<?xml version="1.0" encoding="utf-8"?>
<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"
    android:padding="6dp"
    tools:context=".ArticlesActivity">

    <TextView
        android:id="@+id/txtArticleActTitle"
        android:textSize="26sp"
        android:textStyle="bold"
        android:text="Article Title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/txtArticleActAutor"
        android:textSize="24sp"
        android:textStyle="bold"
        android:layout_below="@id/txtArticleActTitle"
        android:text="Article Autor"
        android:layout_marginTop="4dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/txtArticleActDate"
        android:text="Article Date"
        android:layout_below="@id/txtArticleActAutor"
        android:textSize="20sp"
        android:layout_marginTop="4dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

    <android.support.v7.widget.RecyclerView
        android:id="@+id/articlesActRecyclerView"
        android:layout_below="@id/txtArticleActDate"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </android.support.v7.widget.RecyclerView>

</RelativeLayout>

有人可以建议如何做到吗？

Answer 1

您可以使用Mapper.Initialize(cfg => { cfg.CreateMissingTypeMaps = false; cfg.CreateMap<SourceBase, TargetBase>().ConvertUsing(s=>Mapper.Map(s, s.A == null ? (TargetBase)new TargetB() : new TargetA())); cfg.CreateMap<SourceBase, TargetA>().ForMember(d=>d.ValueA, o=>o.MapFrom(s=>s.A.ValueA)); cfg.CreateMap<SourceBase, TargetB>().ForMember(d=>d.ValueB, o=>o.MapFrom(s=>s.B.ValueB)); });遍历快照的子节点：

DataSnapshot.getChildren()

Answer 2

我对Recycler方法进行了一些更改，即新方法：

@Override
    protected void onStart() {
        super.onStart();

        FirebaseRecyclerOptions options = new FirebaseRecyclerOptions.Builder<Tags>()
                .setQuery(articleTagRef, Tags.class)
                .build();
        FirebaseRecyclerAdapter<Tags, ArticleViewHolder> adapter = new FirebaseRecyclerAdapter<Tags, ArticleViewHolder>(options) {
            @Override
            protected void onBindViewHolder(@NonNull final ArticleViewHolder holder, final int position, @NonNull Tags model) {
                String tagKey = getRef(position).getKey();
                articleTagRef.child(tagKey).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        if (dataSnapshot.exists()) {
                            if (dataSnapshot.hasChild("tagName")) {
                                String tagName = dataSnapshot.child("tagName").getValue().toString();
                                holder.tags.setTextSize(20);
                                holder.tags.setPadding(8,8,8,8);
                                holder.tags.setText(tagName);
                            }
                        }
                    }
                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });
            }
            @NonNull
            @Override
            public ArticleViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
                View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.recycler_article_tags, viewGroup, false);
                ArticleViewHolder viewHolder = new ArticleViewHolder(view);
                return viewHolder;
            }
        };
        articleTags.setAdapter(adapter);
        adapter.startListening();
    }

我也创建了一个Tags类：

public class Tags {
    private String tagName;

    public Tags() {
    }

    public Tags(String tagName) {
        this.tagName = tagName;
    }

    public String getTagName() {
        return tagName;
    }

    public void setTagName(String tagName) {
        this.tagName = tagName;
    }
}

在recycler_article_tags.xml和wrap_content上也将RelativeLayout更改为TextView：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    <TextView
        android:background="@drawable/buttons"
        android:id="@+id/recyclerArticleTag"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginRight="6dp" />
</RelativeLayout>

最后，数据库现在如下所示：

如何从增量名称“表”中检索数据？

2 个答案: