替换而不是将项目添加到 Arraylist

Posted 2023-04-13

【中文标题】替换而不是将项目添加到 Arraylist

【英文标题】：Replace Instead Of Adding Item To Arraylist

【发布时间】：2021-08-23 07:30:09

【问题描述】：

我正在构建一个应用程序来练习 arraylist 和 recyclerView。

在主要活动中，我有“添加”按钮，而不是可以将内容添加到 arraylit 以显示在 recyclerView 中，但是，第一次添加新行时它工作正常，但是当我尝试添加另一个时，它用新行替换我添加的第一行。

如果你能指出我做错了什么，我会很高兴，谢谢。

添加线路活动：

public void AddButton(View view)

    if (imageUri != null && !mEditText.getText().toString().isEmpty())

        Intent intent = new Intent(AddCompany.this,MainActivity.class);
        intent.putExtra("isAddNewCompany", true);
        intent.putExtra("CompanyImage", imageUri.toString());
        intent.putExtra("CompanyName", mEditText.getText().toString());
        startActivity(intent);

    

MainActivity OnCreate 与视图：

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

        Intent intent = getIntent();

        ArrayList<String> listTitle = new ArrayList<>();

        ArrayList<String> listPicture = new ArrayList<>();


        if (intent.getBooleanExtra("isAddNewCompany",false))

            String CompanyImage = intent.getStringExtra("CompanyImage");
            String companyName = intent.getStringExtra("CompanyName");

            listTitle.add(companyName);
            listPicture.add(CompanyImage);

        




        // set up the RecyclerView
        RecyclerView recyclerView = findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        RecyclerAdapter adapter = new RecyclerAdapter(this,listPicture,listTitle);


        adapter.setClickListener(new RecyclerAdapter.ItemClickListener() 
            @Override
            public void onItemClick(View view, int position) 
                Log.e("Position Number - ", String.valueOf(position));
                Toast.makeText(MainActivity.this, adapter.getItem(position), Toast.LENGTH_SHORT).show();

            
        );

        recyclerView.setAdapter(adapter);

    

RecyclerView 适配器：

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.ViewHolder> 

    private final ArrayList<String> mData;
    private final ArrayList<String> mImageView;
    private final LayoutInflater mInflater;
    private ItemClickListener mClickListener;

    // data is passed into the constructor
    RecyclerAdapter(Context context, ArrayList<String> imageView, ArrayList<String> data) 
        this.mInflater = LayoutInflater.from(context);
        this.mData = data;
        this.mImageView = imageView;
    

    // inflates the row layout from xml when needed
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) 
        View view = mInflater.inflate(R.layout.recyclerview_row, parent, false);
        return new ViewHolder(view);
    

    // binds the data to the TextView in each row
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) 
        String animal = mData.get(position);
        String picture = mImageView.get(position);

        Picasso.get().load(picture).into(holder.myImageView);
        holder.myTextView.setText(animal);

    

    // total number of rows
    @Override
    public int getItemCount() 
        return mData.size();
    


    // stores and recycles views as they are scrolled off screen
    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener 
        TextView myTextView;
        ImageView myImageView;

        ViewHolder(View itemView) 
            super(itemView);
            myTextView = itemView.findViewById(R.id.tvAnimalName);
            myImageView = itemView.findViewById(R.id.imageView);

            itemView.setOnClickListener(this);

        

        @Override
        public void onClick(View view) 
            if (mClickListener != null) mClickListener.onItemClick(view, getAdapterPosition());
        
    

    // convenience method for getting data at click position
    String getItem(int id) 
        return mData.get(id);
    

    // allows clicks events to be caught
    void setClickListener(ItemClickListener itemClickListener) 
        this.mClickListener = itemClickListener;
    

    // parent activity will implement this method to respond to click events
    public interface ItemClickListener 
        void onItemClick(View view, int position);
    

【问题讨论】：

你在 recyclerview 中只看到一个值吗？@Mr.Goomer

是的，当我尝试添加另一个时，它只是替换我已经添加的内容

【参考方案1】：

当您开始活动时，每次都会创建新的列表实例，这就是您只有一个值的原因。如果您想要已经添加的值，请使用相同的列表实例。

     List<String> listTitle;

      List<String> listPicture;

public List<String> getLisPictureInstance()
    if(listPicture ==null)
    listPicture = new ArrayList<>();
    return listPicture ;



public List<String> getListTitleInstance()
    if(listTitle ==null)
    listTitle = new ArrayList<>()
    return listTitle ;


        if (intent.getBooleanExtra("isAddNewCompany",false))

            String CompanyImage = intent.getStringExtra("CompanyImage");
            String companyName = intent.getStringExtra("CompanyName");

            getListTitleInstance().add(companyName);
            getLisPictureInstance().add(CompanyImage);

        

【讨论】：

Hey androidLearner 感谢您的回复。它仍在替换行而不是添加另一行..