从 FirebaseRecyclerAdapter 获取文档 ID 并将值传递到新页面

Question

我有一个显示文档列表的 FirestoreRecyclerAdapter。我在列表中的每个项目旁边都有一个按钮。单击此按钮时，我想获取所选项目的唯一 ID，然后将用户带到显示该项目的个人详细信息的页面。本质上，我想将单击的文档的 ID 传递到下一页。但是，我的按钮在单击时会引发空指针异常。这段代码来自我的 ClubAdapter 类。public class ClubAdapter1 extends FirestoreRecyclerAdapter<Club, ClubAdapter1.ClubHolder> {    private String clubId;    private Context context;    public ClubAdapter1(@NonNull FirestoreRecyclerOptions<Club> options) {        super(options);    }    @Override    protected void onBindViewHolder(@NonNull ClubHolder holder, int position, @NonNull Club model) {        holder.lblName.setText(model.getClubName());        //getting the ID of the particular event clicked        clubId = getSnapshots().getSnapshot(position).getId();        holder.btnDetails.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                Intent i = new Intent(context, ViewSingleClub.class);                i.putExtra("id", clubId);                context.startActivity(i);            }        });    }    @NonNull    @Override    public ClubHolder onCreateViewHolder(@NonNull ViewGroup parent, int i) {        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.clublist_layout, parent, false);        return new ClubHolder(v);    }    class ClubHolder extends RecyclerView.ViewHolder {        TextView lblName;        Button btnDetails;        public ClubHolder(@NonNull View itemView) {            super(itemView);            lblName = itemView.findViewById(R.id.lblName);            btnDetails = itemView.findViewById(R.id.btnDetails);        }    }}我不断收到错误， Intent i = new Intent(context, ViewSingleClub.class); 我认为这可能与我的上下文变量引用自身有关，但也不确定我是否正确获取了 ID。有人能帮忙吗？

Answer 1

这是因为您正在分配“自身的上下文”。从初始化适配器的类中传递上下文。

假设我有名为“ClubAdapter”的适配器和名为“ClubClass”的调用类

在俱乐部类：

ClubAdapter clubAdapter = new ClubAdapter(list, context);

// if you'r calling it from activity then pass "Activity.this" and if fragment then "getContext()" as context.

并在 ClubAdapter

public class ClubAdapter extends RecyclerView.Adapter<ClubAdapter.ClubHolder> {

    private Context context;

    private List<String> list;

   

    public ClubAdapter(List<String> list, Context context) {

        this.list = list;

        this.context = context;

    }

    

    @NonNull

    @Override

    public ClubHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {

        View itemView = LayoutInflater.from(viewGroup.getContext())

                .inflate(R.layout.item_sample, viewGroup, false);

        return new ClubHolder(itemView, context);

    }

    

    

    public class ClubHolder extends RecyclerView.ViewHolder {

        private Context context;

        private ClunHolder(@NonNull View itemView,Context context) {

            super(itemView);

            this.context = context;

           

        }

        }

}

或者你可以制作这样的界面。

public interface RecycleViewOnItemClickListener {

    void onItemClick(int position);

}

并将其从调用类传递给您的适配器。

假设我有名为“SampleAdapter”的适配器并调用名为“SampleClass”的类在“SampleClass”中，您可以将适配器中的接口作为参数传递。

SampleAdapter sampleAdapter = new SampleAdapter(list, new RecycleViewOnItemClickListener() {

            @Override

            public void onItemClick(int position) {

                // do what you want to perform

            }

        });

在“俱乐部适配器”中

public class ClubAdapter extends RecyclerView.Adapter<ClubAdapter.ClubHolder> {

        private RecycleViewOnItemClickListener recycleViewOnItemClickListener;

        private List<String> list;

       

        public ClubAdapter(List<String> list, RecycleViewOnItemClickListener recycleViewOnItemClickListener) {

            this.list = list;

            this.recycleViewOnItemClickListener = recycleViewOnItemClickListener;

        }

        

        @NonNull

        @Override

        public ClubHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {

            View itemView = LayoutInflater.from(viewGroup.getContext())

                    .inflate(R.layout.item_sample, viewGroup, false);

            return new ClubHolder(itemView, recycleViewOnItemClickListener);

        }

        

        

        public class ClubHolder extends RecyclerView.ViewHolder {

            private RecycleViewOnItemClickListener recycleViewOnItemClickListener;

            private ClunHolder(@NonNull View itemView,RecycleViewOnItemClickListener recycleViewOnItemClickListener) {

                super(itemView);

                this.recycleViewOnItemClickListener = recycleViewOnItemClickListener;

               //you can callback onItemClick method from here on button click event so it give callback in "ClubActivity".

               btn.setOnClickListener(new View.OnClickListener() {

                @Override

                public void onClick(View v) {

                    recycleViewOnItemClickListener.onItemClick(getAdapterPosition());

                }

            });

            }

            }

            }

Answer 2

要解决此问题，请在方法中移动以下代码行，onBindViewHolder()如下所示：

holder.btnDetails.setOnClickListener(new View.OnClickListener() {

    @Override

    public void onClick(View v) {

        Intent i = new Intent(context, ViewSingleClub.class);

        i.putExtra("id", clubId);

        context.startActivity(i);

    }

});

看，我在holder.btnDetails.

编辑：

根据您的意见，还请进行以下操作。将构造函数更改为：

public ClubAdapter1(@NonNull FirestoreRecyclerOptions<Club> options, Context context) {

    super(options);

    this.context = context;

}

当您在活动中创建适配器类的对象时，还将 传递context给构造函数。