如何从通过 Intent 启动的 activity 中获取新数据？

Question

这个问题有点复杂。在我的 RecyclerView 的自定义适配器的 ViewHolder 中，我实现了一个 onClickListener 并通过 onClick，我传递了一个意图，该意图用文本和 recyclerview 触发 EditItemActivity将项目位置列为附加项。在 EditItemActivity 中，我有一个 TextView，其中包含从意图和 "Save Changes" 按钮传递的文本。该文本属于我的 Recyclerview 列表中的特定列表项。更改文本后，我希望应用程序返回到带有列表的主屏幕，并使用新文本更新该特定项目。

到目前为止，这里是我能够成功实施的：

EditItemActivity 在单击列表项时启动。
当 activity 启动时，它的文本视图与通过 onClick 启动 activity 的列表项具有相同的文本。

我要补充的：

当我更改 EditItemActivity 中的文本并单击 "Save Changes" 按钮时，它会更新同一列表项的文本。

这是我的实现。这是我的适配器中的 ViewHolder，其中包含 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);
        }
    }

这是我更新该列表项文本的尝试：

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();
                }
            }
        });
    }
}

根据请求添加代码

具有列表视图的 class 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 class 实现可序列化。

public class ToDoData implements Serializable{}

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

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，在您的 EditItemActivity 中，

从意图中接收列表为：

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

并将按钮点击的监听器设置为，

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 内部，

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

}

如何从通过 Intent 启动的 activity 中获取新数据？

How to fetch new data from an activity that was launched through an Intent?

android

android-intent

onclicklistener

android-viewholder

android-recyclerview