Question

所以我有一个包含ViewPager的Activity，它包含一些片段，包括一个带有RecyclerView的片段。您可以单击RecyclerView上的其中一个项目来编辑其所有详细信息，这可以通过启动第二个活动来完成，该活动包含特定于该项目的可编辑字段。

但是，假设我改变了项目的名称。现在我按Save或后退按钮或其他任何关闭此活动并返回第一个活动。由于名称现在可能不同，因此RecyclerView也应该更新项目名称。

但是如何检测此事件？我如何基本上“在关闭第二个Activity时，在第一个Activity的ViewPager中的片段中的RecyclerView中通知该项目已更改”？

我可以使用class Animal def animal_sound @sound = "roar" @sound + " "+"animal" end # This reader-method lets us see the value of the @eye_colour instance-variable def eye_colour "My eyes are: #{@eye_colour}" end # This writer-method lets us set the value of the @eye_colour instance variable def eye_colour=(new_colour) @eye_colour = new_colour end end class Human < Animal def human_sound @sound + " "+"human" end # inherits the colour-methods from Animal end # when you create a new instance of human, you can give them an eye-colour human = Human.new human.eye_colour = "Green" human.eye_colour # => "My eyes are: Green" # if you create a new instance of human, you can give them a different eye colour human2 = Human.new human2.eye_colour = "Brown" human2.eye_colour # => "My eyes are: Brown" # but the first human is still the original colour - # because the variable contains a value just for *that* instance. # This is what it means to be an instance-variable human.eye_colour # => "My eyes are: Green"吗？如果我使用onActivityResult从片段中调用第二个Activity，我可以在同一片段中定义startActivityForResult，然后以某种方式使用Intent数据来查看，“好吧，我需要刷新此位置RecyclerView“？

Answer 1

我可以使用onActivityResult吗？

是。以下是您可以使用它的方法：

在RecyclerView中点击某个项目时，您会跟踪所点击项目的适配器位置。

您从片段中开始第二个结果活动。

// adapterPosition is the position of the clicked item
Intent intent = new Intent(getActivity(), SecondActivity.class);
intent.putExtras("adapter_position", adapterPosition);
startActivityForResult(intent, 1);

在SecondActivity中，将adapterPosition设置为结果Intent的一部分。处理SecondActivity会导致您的片段。

在SecondActivity

    // adapterPosition is what you received from your fragment
    Intent result = new Intent();
    result.putExtra("adapter_position", adapterPosition);
    // put other stuff you might need
    setResult(Activity.RESULT_OK, result);
    finish();

片段

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == 1) {
        if(resultCode == Activity.RESULT_OK){
            int adapterPosition = data.getIntExtra("adapter_position");
            // Update your RecyclerAdapter data. 
            // You will need to define this method in your RecyclerAdapter

            yourAdapter.notifyItemChanged(adapterPosition);
        }
        else {
            // Some error/cancel handling
        }
    }
}

Answer 2

从片段中调用startActivityForResult来更新您的项目并发送它的当前位置。

intent.putExtra(POSITION_OF_RECYCLERVIEW,position);

并在DetailActivity的“保存”按钮上调用setResult（）

之类的方法

 private void setResult(){

        Intent intent = new Intent();
        intent.putExtra("UPDATE_POS", position);
        intent.putExtra("yourModelClassOrDataType",dataToUpdate);
        setResult(RESULT_OK, intent);
        finish();
 }

Answer 3

在RecyclerView中点击某个项目时，通过将该位置放入意图并使用startActivityForResult(intent,1)开始第二个活动来跟踪所点击项目的适配器位置。

在fragment：

中

    // adapterPosition is the position of the clicked item
    Intent intent = new Intent(getActivity(), SecondActivity.class);
    intent.putExtras("adapter_position", adapterPosition);
    startActivityForResult(intent, 1);

您将发送adapterPosition以及用户在SecondActivity返回片段时检索到的任何新数据。您可以通过将其添加到结果Intent中来发送，如下面的代码所示。

在SecondActivity：

中

    // adapterPosition is what you received from your fragment
    Intent result = new Intent();
    result.putExtra("adapter_position", adapterPosition);
    result.putExtra("new_item_name", itemName);
    // put other stuff you might need
    setResult(Activity.RESULT_OK, result);
    finish();

现在，在fragment中，您可以从SecondActivity检索adapterPosition和新数据。然后使用我在doSomethingWithNewData下面命名的方法使用新数据操作原始列表。您需要创建此方法。使用新数据更新列表后，在调用我调用updateAdapter的适配器中的方法时，将此列表传递给适配器。这是您添加到适配器的方法。

回到fragment：

@Override
public void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == 1) {
        if(resultCode == Activity.RESULT_OK){
            if(data != null){
                int adapterPosition = data.getIntExtra("adapter_position", -1); 
                String itemName = data.getStringExtra("new_item_name", -1);

                // Do something with the data passed back to fragment
                // ie. update the list attached to RecyclerView's adapter
                yourList = doSomethingWithNewData(adapterPosition, itemName);

                // add this method to your adapter passing new list
                yourAdapter.updateAdapter(yourList); 
            }    
        }
        else {
            // Some error/cancel handling
        }
    }
}

最后，这是你的适配器。您可以在此处将updateAdapter方法添加到适配器的末尾。在updateAdapter中，您将传递新的更新列表，并通过notifyDataSetChanged()通知数据已更改。

在YourAdapter：

private class YourAdapter extends RecyclerView.Adapter<YourAdapter.YourViewHolder>{
    List<Object> yourList;

    public YourAdapter(List yourList){
        this.yourList = yourList;
    }

    public class YourViewHolder extends RecyclerView.ViewHolder {

        TextView text_1;
        TextView text_2;

        public NoteViewHolder(View itemView) {
            super(itemView);

            text_1 = (TextView)itemView.findViewById(R.id.text_1);
            text_2 = (TextView)itemView.findViewById(R.id.text_2);
        }

    }

    public YourAdapter.YourViewHolder onCreateViewHolder(ViewGroup parent, int viewType){
        // inflate a layout to contain a single row from your list
        View view = LayoutInflater.from(parent.getContext())
                 .inflate(R.layout.single_row_from_list, parent, false);
        NoteViewHolder yVH = new YourViewHolder(view);
        return yVH;
    }

    @Override
    public void onBindViewHolder(NotesAdapter.NoteViewHolder holder, int position) {

        // set the texts using your modeled list
        holder.text_1.setText(yourList.get(position).getTitle());
        holder.text_2.setText(yourList.get(position).getMessage());

    }

    @Override
    public int getItemCount() {
        // set item count to the size of your list
        return yourList.size();
    }

    // this is the method to add to the adapter
    public void updateAdapter(List<Object> yourList){
        this.yourList = yourList; // assign data passed in to the adapter list

        // notify that the data has changed
        notifyDataSetChanged();
    }
}

如何在活动结束时触发重新加载？

3 个答案: