这个鳕鱼显示所有数组列表我想在数组列表中显示第一行，然后单击按钮显示第二行

Question

这个鳕鱼显示所有数组列表我想在数组列表中显示第一行然后单击按钮显示第二行并再次单击显示第三行然后可以这样做

public void onClick(View v) { babyViewModel.getLetterRecourceID();

这个鳕鱼显示所有数组列表我想在数组列表中显示第一行然后单击按钮显示第二行并再次单击显示第三行然后可以这样做

activity_english 中的 cod 写出第一个代码

activity_englishletters
package com.example.learnn;

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProviders;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.learnn.databinding.ActivityEnglishcolorsBinding;
import com.example.learnn.databinding.ActivityEnglishlettersBinding;
import com.example.learnn.ui.BabyListAdapter;
import com.example.learnn.ui.BabyModel;
import com.example.learnn.ui.BabyViewModel;

import java.util.ArrayList;

public class EnglishlettersActivity extends AppCompatActivity {

    BabyViewModel babyViewModel;
    ImageView imagee,next;
    RecyclerView recycler;
    private int index = 0;
    ArrayList arrayList,letterList;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        ActivityEnglishlettersBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_englishletters);

        imagee = (ImageView)findViewById(R.id.imagee);
        recycler = (RecyclerView)findViewById(R.id.recycler);

        final BabyListAdapter adapter = new BabyListAdapter();
        recycler.setAdapter(adapter);
        recycler.setLayoutManager(new LinearLayoutManager(this));

        babyViewModel = ViewModelProviders.of(this).get(BabyViewModel.class);
        babyViewModel.letterRecourceIDMutableLiveData.observe(this, new Observer<ArrayList<BabyModel>>() {
            @Override
            public void onChanged(ArrayList<BabyModel> babyModels) {
                adapter.setList(babyModels);
            }
        });

        binding.next.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                babyViewModel.getLetterRecourceID();
                index = index+1;
                if (index < letterList.size()) {
                    imagee.setBackgroundResource( (int) letterList.get( index  ) );
                    return;
                }

                if (index == letterList.size()) {
                    imagee.setBackgroundResource( (int) letterList.get( 0 ) );
                    index = 0;
                }
            }
        });
    }


}


viewModel

package com.example.learnn.ui;

import com.example.learnn.R;

import java.util.ArrayList;

import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;

public class BabyViewModel extends ViewModel {

    ArrayList arrayList;

    public MutableLiveData<ArrayList<BabyModel>> letterRecourceIDMutableLiveData = new MutableLiveData<>();


    public void getLetterRecourceID(){
        letterRecourceIDMutableLiveData.setValue(getDataFromDatabase());
     }

     private ArrayList<BabyModel> getDataFromDatabase(){
        ArrayList<BabyModel> arrayList = new ArrayList<>();
         arrayList.add(new BabyModel(R.drawable.a));
         arrayList.add(new BabyModel(R.drawable.b));
         arrayList.add(new BabyModel(R.drawable.c));
         arrayList.add(new BabyModel(R.drawable.d));
         arrayList.add(new BabyModel(R.drawable.e));
         return arrayList;
    }
}

adapter

package com.example.learnn.ui;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.example.learnn.R;

import java.util.ArrayList;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

public class BabyListAdapter extends RecyclerView.Adapter<BabyListAdapter.BabyViewHolder> {

    private ArrayList<BabyModel> letterList = new ArrayList<>();

    @NonNull
    @Override
    public BabyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new BabyViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.litter_list_item, parent, false));
    }

    @Override
    public void onBindViewHolder(@NonNull BabyViewHolder holder, int position) {
        holder.image.setImageResource(letterList.get(position).getLetterRecourceID());

    }

    @Override
    public int getItemCount() {
        return letterList.size();
    }


    public void setList(ArrayList<BabyModel> letterList) {
        this.letterList = letterList;
        notifyDataSetChanged();
    }

    public class BabyViewHolder extends RecyclerView.ViewHolder {
        ImageView image;
        public BabyViewHolder(@NonNull View itemView) {
            super(itemView);
            image = itemView.findViewById(R.id.imagee);



        }
    }
}

Answer 1

所以，作为初学者，您将拥有一个全局索引

int index=0;

然后点击按钮：

babyViewModel.letterRecourceIDMutableLiveData.observe(this, new Observer<ArrayList<BabyModel>>() {
        @Override
        public void onChanged(ArrayList<BabyModel> babyModels) {
            List<BabyModel> list = babyModels.subList(0, index);
            adapter.setList(list);
            index++;
        }
    });