Android双Activity中RecyclerView仅显示一条数据的问题排查求助

我要做一个包含两个Activity的简单应用：Activity A（MainActivity）带RecyclerView，Activity B（UploadActivity）负责上传EditText的输入数据。现在RecyclerView创建和数据传递功能正常，但列表只能显示一条数据，求排查错误原因。

相关代码 #

包含RecyclerView的Activity A（MainActivity） #

public class MainActivity extends AppCompatActivity {

private ArrayList<MainData> list;
private MainAdapter adapter;
private RecyclerView recyclerView;
private LinearLayoutManager linearLayoutManager;

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

    recyclerView = (RecyclerView) findViewById(R.id.rv);

    linearLayoutManager = new LinearLayoutManager(this);

    recyclerView.setLayoutManager(linearLayoutManager);

    list = (ArrayList<MainData>) getIntent().getSerializableExtra("list");

    adapter = new MainAdapter(list);

    recyclerView.setAdapter(adapter);

    adapter.notifyDataSetChanged();
}

负责上传数据的Activity B（UploadActivity） #

public class upload extends AppCompatActivity {

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

    Button button = (Button) findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            Intent intent = new Intent(upload.this, MainActivity.class);

            ArrayList<MainData> list = new ArrayList<>();

            EditText edit = (EditText) findViewById(R.id.edittext_name);

            EditText edit_main = (EditText) findViewById(R.id.edittext_main);

            list.add(new MainData(edit.getText().toString(), edit_main.getText().toString()));

            intent.putExtra("list",list);

            startActivity(intent);

            finish();

        }
    });
}

Adapter代码 #

public class MainAdapter extends RecyclerView.Adapter<MainAdapter.CustomViewHolder> {
    private ArrayList<MainData> list;

    public MainAdapter(ArrayList<MainData> list) {
        this.list = list;
    }

    @NonNull
    @Override
    public MainAdapter.CustomViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_list, parent, false);
        CustomViewHolder holder = new CustomViewHolder(view);
        return holder;
    }
    
    @Override
    public void onBindViewHolder(@NonNull MainAdapter.CustomViewHolder holder, int position) {
        //holder.iv_profile.setImageResource(list.get(position).getIv_profile());
        holder.tv_name.setText(list.get(position).getTv_name());
        holder.tv_content.setText(list.get(position).getTv_content());
        holder.itemView.setTag(position);
    }

    @Override
    public int getItemCount() {
        return (null != list ? list.size() : 0);
    }

    public void remove(int position) {
        try {
            list.remove(position); 
            notifyItemRemoved(position);
        } catch (IndexOutOfBoundsException ex) {
            ex.printStackTrace();
        }
    }

    public class CustomViewHolder extends RecyclerView.ViewHolder {
        protected ImageView iv_profile;
        protected TextView tv_name;
        protected TextView tv_content;

        public CustomViewHolder(@NonNull View itemView) {
            super(itemView);
            this.iv_profile = (ImageView) itemView.findViewById(R.id.iv_profile);
            this.tv_name = (TextView) itemView.findViewById(R.id.tv_name);
            this.tv_content = (TextView) itemView.findViewById(R.id.tv_content);
        }
    }
}

错误原因分析 #

每次从UploadActivity跳转到MainActivity时，你都新建了一个ArrayList，只添加当前输入的一条数据再传递。这意味着每次跳转都会完全重置数据列表，而不是在原有列表基础上追加新数据。同时，MainActivity每次被启动都会创建新实例，之前的列表数据不会被保留。

解决方案 #

方案1：用单例存储全局列表（简单快速） #

创建单例类统一管理数据列表，让所有Activity共享同一个实例：

public class DataManager {
    private static DataManager instance;
    private ArrayList<MainData> dataList;

    private DataManager() {
        dataList = new ArrayList<>();
    }

    public static synchronized DataManager getInstance() {
        if (instance == null) {
            instance = new DataManager();
        }
        return instance;
    }

    public ArrayList<MainData> getDataList() {
        return dataList;
    }

    public void addData(MainData data) {
        dataList.add(data);
    }
}

修改UploadActivity的点击事件：

button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        EditText edit = (EditText) findViewById(R.id.edittext_name);
        EditText edit_main = (EditText) findViewById(R.id.edittext_main);
        // 向全局列表添加新数据
        DataManager.getInstance().addData(new MainData(edit.getText().toString(), edit_main.getText().toString()));
        
        Intent intent = new Intent(upload.this, MainActivity.class);
        startActivity(intent);
        finish();
    }
});

修改MainActivity的初始化逻辑：

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

    recyclerView = (RecyclerView) findViewById(R.id.rv);
    linearLayoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(linearLayoutManager);

    // 获取全局共享的列表实例
    list = DataManager.getInstance().getDataList();
    adapter = new MainAdapter(list);
    recyclerView.setAdapter(adapter);
}

方案2：用ActivityResultContracts传递数据（符合Android规范） #

让MainActivity启动UploadActivity，待UploadActivity返回数据后，MainActivity将新数据追加到原有列表：

1. 修改MainActivity的跳转逻辑

// 在MainActivity中添加跳转至UploadActivity的按钮事件
Button goUploadBtn = findViewById(R.id.btn_go_upload);
goUploadBtn.setOnClickListener(v -> {
    registerForActivityResult(new ActivityResultContracts.StartActivityForResult(), result -> {
        if (result.getResultCode() == RESULT_OK && result.getData() != null) {
            MainData newData = (MainData) result.getData().getSerializableExtra("new_data");
            if (newData != null) {
                list.add(newData);
                adapter.notifyItemInserted(list.size() - 1);
            }
        }
    }).launch(new Intent(this, upload.class));
});

2. 修改UploadActivity的返回逻辑

button.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        EditText edit = (EditText) findViewById(R.id.edittext_name);
        EditText edit_main = (EditText) findViewById(R.id.edittext_main);
        MainData newData = new MainData(edit.getText().toString(), edit_main.getText().toString());
        
        Intent intent = new Intent();
        intent.putExtra("new_data", newData);
        setResult(RESULT_OK, intent);
        finish();
    }
});

3. 确保MainActivity的列表初始化正确

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

    recyclerView = (RecyclerView) findViewById(R.id.rv);
    linearLayoutManager = new LinearLayoutManager(this);
    recyclerView.setLayoutManager(linearLayoutManager);

    // 初始化空列表，避免空指针
    if (list == null) {
        list = new ArrayList<>();
    }
    adapter = new MainAdapter(list);
    recyclerView.setAdapter(adapter);
}

额外注意事项 #

1. 必须确保MainData类实现Serializable接口，否则无法通过Intent传递：

public class MainData implements Serializable {
    private String tv_name;
    private String tv_content;

    public MainData(String tv_name, String tv_content) {
        this.tv_name = tv_name;
        this.tv_content = tv_content;
    }

    // getter方法
    public String getTv_name() {
        return tv_name;
    }

    public String getTv_content() {
        return tv_content;
    }
}

2. 如果需要重启App后保留数据，可使用SharedPreferences或Room数据库实现持久化存储。

内容的提问来源于stack exchange，提问作者Chanyoung