Question

这是一个复杂的问题。在我的RecyclerView的自定义适配器的ViewHolder中，我已经实现了onClickListener并通过onClick，我正在通过文本和recyclerview传递EditItemActivity的意图将项目位置列为附加项目。在EditItemActivity中，我有一个TextView，其中包含从intent传递的文本和“Save Changes”按钮。该文本属于我的Recyclerview列表中的特定列表项。在我更改文本后，我希望应用程序返回到包含列表的主屏幕，并使用新文本更新该特定项目。

到目前为止，我能够成功实施：

EditItemActivity就会启动。
当活动启动时，它的textview与onClick启动活动的列表项具有相同的文本。

我要添加的内容：

当我更改EditItemActivity中的文字并单击“保存更改”按钮时，它会更新同一列表项的文本。

这是我的实施。我的适配器中的ViewHolder包含onClick：

public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
        TextView todoView;

        public ViewHolder(View itemView) {
            super(itemView);
            itemView.setOnClickListener(this);
            todoView = itemView.findViewById(R.id.to_do_display);
        }

        @Override
        public void onClick(View view) {
            Toast.makeText(context, "position = " + getAdapterPosition(), Toast.LENGTH_SHORT).show();
            Intent intent = new Intent(context, EditItemActivity.class);
            intent.putExtra("data", todoView.getText());
            intent.putExtra("position", getAdapterPosition());
            context.startActivity(intent);
        }
    }

这是我尝试更新该列表项的文本：

public class EditItemActivity extends AppCompatActivity {

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

        final ToDoData toDoData = new ToDoData(this);
        final ToDoAdapter toDoAdapter = new ToDoAdapter(this);

        final EditText editToDo = (EditText)findViewById(R.id.edit_todo_item);
        Button button = (Button)findViewById(R.id.save_changes);
        final String text = getIntent().getExtras().getString("data");
        final String position = getIntent().getExtras().getString("position");
        editToDo.setText(text);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if(editToDo.getText().toString() != text){
                    toDoData.setToDo(editToDo.getText().toString());
                    toDoAdapter.notifyDataSetChanged();
                    finish();
                }
            }
        });
    }
}

根据要求添加代码

具有listview的类的代码：

public class MainActivity extends AppCompatActivity {

    private List<ToDoData> toDoList = new ArrayList<>();

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

        final ToDoAdapter toDoAdapter = new ToDoAdapter(toDoList, this);

        final EditText toDoInput = (EditText)findViewById(R.id.add_todo);
        Button toDoAdd = (Button)findViewById(R.id.add_item);

        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this);
        RecyclerView toDoDisplay = (RecyclerView) findViewById(R.id.toDoDisplayRecyclerView);
        toDoDisplay.setAdapter(toDoAdapter);
        toDoDisplay.setHasFixedSize(true);
        toDoDisplay.setLayoutManager(layoutManager);


        toDoAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                ToDoData newToDoData = new ToDoData(MainActivity.this);
                newToDoData.setToDo(toDoInput.getText().toString());
                toDoList.add(newToDoData);
                toDoAdapter.notifyDataSetChanged();
                toDoInput.setText("");
            }
        });
    }
}

适配器代码：

public class ToDoAdapter extends RecyclerView.Adapter<ToDoAdapter.ViewHolder> {

    private List<ToDoData> toDoList;
    private Context context;

    public ToDoAdapter(List<ToDoData> todoList, Context context) {
        this.toDoList = todoList;
        this.context = context;
    }

    public ToDoAdapter(Context context){}

    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
        TextView todoView;

        public ViewHolder(View itemView) {
            super(itemView);
            itemView.setOnClickListener(this);
            todoView = itemView.findViewById(R.id.to_do_display);
        }

        @Override
        public void onClick(View view) {
            Toast.makeText(context, "position = " + getAdapterPosition(), Toast.LENGTH_SHORT).show();
            Intent intent = new Intent(context, EditItemActivity.class);
            intent.putExtra("data", todoView.getText());
            intent.putExtra("position", getAdapterPosition());
            context.startActivity(intent);
        }
    }

    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.to_do_list_item, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position){
        ToDoData todoPosition = toDoList.get(position);

        holder.todoView.setText(todoPosition.getToDo());
    }

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

ToDoData.class

public class ToDoData implements Serializable{
    private String toDoString;

    public ToDoData(String todoString){
        this.toDoString = todoString;
    }

    public ToDoData(Context context){}

    public String getToDo() {
        return toDoString;
    }

    public void setToDo(String toDoString) {
        this.toDoString = toDoString;
    }
}

Answer 1

使您的ToDoData类实现Serializable。

public class ToDoData implements Serializable{}

现在，将List<ToDoData>与positon和data一起传递给EditItemActivity，并通过Intent传递：

Intent intent = new Intent(MainActivity.this, EditItemActivity.class);
intent.putExtra("data", todoView.getText());
intent.putExtra("position", getAdapterPosition());
//along with data and position, we are passing the list as well.
intent.putExtra("LIST", (Serializable) toDoList); //this 'list' is your toDoList that you pass to the adapter (and gets populated into the view)
startActivity(intent);

现在，在EditItemActivity中，

从意图中接收列表：

Intent i = getIntent();
list = (List<ToDoData>) i.getSerializableExtra("LIST");

并将按钮单击的侦听器设置为

toDoAdd.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        // set the new input of user from toDoInput into the list 
        list.set(position, *object_of_ToDoData_with_updated_user_input*);
        startActivity(new Intent(EditItemActiviy.this, MainActivity.class));

    }
});

在MainActivity中，

@Override
protected void onResume() {
    super.onResume();
    toDoAdapter.notifyDataSetChanged();

}

如何从通过Intent启动的活动中获取新数据？

1 个答案: