在SearchView交互之前，不会填充RecyclerView [英] RecyclerView not populated until SearchView interaction

问题描述

我的recyclerview遇到问题，它具有一个自定义适配器.问题是，当活动打开时，recyclerview为空.当用户在SearchView的文本字段上键入任何内容时，将填充recyclerview并保持填充状态，而不会出现任何问题.我试图更改一些代码的位置来解决此问题，但没有成功.我已在代码下方添加了当前状态和所需状态的屏幕截图.预先感谢.

I'm facing an issue with my recyclerview, which has a custom adapter. Issue is that when the activity opens, recyclerview is empty. When user types anything on SearchView's text field, recyclerview gets populated and stays populated without any problems. I tried to change place of some code to fix this issue, yet no success. I've added the current and desired state screenshots below the codes. Thanks in advance.

AddCourseActivity:

public class AddCourseActivity extends AppCompatActivity{

private RecyclerView mRecyclerView;
private AddCourseAdapter mAdapter;
private List<AddCourseAdapter.AddCourseModel> mModels;
SearchView mSearchView;

@Override
protected void onCreate(Bundle savedInstance) {
    super.onCreate(savedInstance);
    setContentView(R.layout.activity_add_course);
    Kii.initialize(AppConstants.APP_ID, AppConstants.APP_KEY,
            AppConstants.APP_SITE);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setDisplayShowHomeEnabled(true);
    mRecyclerView = (RecyclerView) findViewById(R.id.addcourseRecyclerView);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    String[] courses = new String[]{
            "Math119",
            "Enve101",
            "Chem107",
            "Chem229",
            "Phys105",
            "Math120"};
    mModels = new ArrayList<>();
    mAdapter = new AddCourseAdapter(this, mModels);
    mSearchView = (SearchView) findViewById(R.id.searchView);
    mSearchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
        @Override
        public boolean onQueryTextSubmit(String query) {
            return false;
        }
        @Override
        public boolean onQueryTextChange(String newText) {
            final List<AddCourseAdapter.AddCourseModel> filteredModelList = filter(mModels, newText);
            mAdapter.animateTo(filteredModelList);
            mRecyclerView.scrollToPosition(0);
            return true;
        }
    });
    for (String course: courses) {
        mModels.add(new AddCourseAdapter.AddCourseModel(course));
        mRecyclerView.setAdapter(mAdapter);
        mAdapter.notifyDataSetChanged();
    }
}

private List<AddCourseAdapter.AddCourseModel> filter(List<AddCourseAdapter.AddCourseModel> models, String query) {
    query = query.toLowerCase();
    final List<AddCourseAdapter.AddCourseModel> filteredModelList = new ArrayList<>();
    for (AddCourseAdapter.AddCourseModel model: models) {
        final String text = model.getText().toLowerCase();
        if (text.contains(query)) {
            filteredModelList.add(model);
        }
    }
    return filteredModelList;
}
}

AddCourseAdapter:

public class AddCourseAdapter extends RecyclerView.Adapter<AddCourseAdapter.AddCourseViewHolder> {
private final LayoutInflater mInflater;
private final List<AddCourseModel> mModels;
KiiUser user;
KiiObject object;
KiiBucket userBucket;
Context context;

public AddCourseAdapter(Context context, List<AddCourseModel> models) {
    mInflater = LayoutInflater.from(context);
    mModels = new ArrayList<>(models);
}

@Override
public AddCourseViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    context = parent.getContext();
    final View itemView = mInflater.inflate(R.layout.list_item_add_course, parent, false);
    user = KiiUser.getCurrentUser();
    final String username = user.getUsername();
    userBucket = Kii.user().bucket(username);
    String id = "mycourses";
    object = userBucket.object(id);
    return new AddCourseViewHolder(itemView);
}

@Override
public void onBindViewHolder(final AddCourseViewHolder holder, int position) {
    final AddCourseModel model = mModels.get(position);
    holder.bind(model);
    holder.addButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            final String value = holder.mTextView.getText().toString();
            object.refresh(new KiiObjectCallBack() {
                @Override
                public void onRefreshCompleted(int token, @NonNull KiiObject object, Exception exception) {
                    object.set(value, true);
                    object.saveAllFields(new KiiObjectCallBack() {
                        @Override
                        public void onSaveCompleted(int token, KiiObject object, Exception exception) {
                            Toast.makeText(context,
                                    "Added: " + value,
                                    Toast.LENGTH_SHORT)
                                    .show();
                        }
                    }, false);
                }
            });
            holder.addButton.setVisibility(View.GONE);
            holder.removeButton.setVisibility(View.VISIBLE);
        }
    });
    holder.removeButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(final View v) {
            final String value = holder.mTextView.getText().toString();
            object.refresh(new KiiObjectCallBack() {
                @Override
                public void onRefreshCompleted(int token, @NonNull KiiObject object, Exception exception) {
                    object.set(value, false);
                    object.saveAllFields(new KiiObjectCallBack() {
                        @Override
                        public void onSaveCompleted(int token, @NonNull KiiObject object, Exception exception) {
                            Toast.makeText(context,
                                    "Removed: " + value,
                                    Toast.LENGTH_SHORT)
                                    .show();
                        }
                    }, false);
                }
            });

            holder.addButton.setVisibility(View.VISIBLE);
            holder.removeButton.setVisibility(View.GONE);
        }
    });
}

@Override
public int getItemCount() {
    return mModels.size();
}

public void animateTo(List<AddCourseModel> models) {
    applyAndAnimateRemovals(models);
    applyAndAnimateAdditions(models);
    applyAndAnimateMovedItems(models);
}

private void applyAndAnimateRemovals(List<AddCourseModel> newModels) {
    for (int i = mModels.size() - 1; i >= 0; i--) {
        final AddCourseModel model = mModels.get(i);
        if (!newModels.contains(model)) {
            removeItem(i);
        }
    }
}

private void applyAndAnimateAdditions(List<AddCourseModel> newModels) {
    for (int i = 0, count = newModels.size(); i < count; i++) {
        final AddCourseModel model = newModels.get(i);
        if (!mModels.contains(model)) {
            addItem(i, model);
        }
    }
}

private void applyAndAnimateMovedItems(List<AddCourseModel> newModels) {
    for (int toPosition = newModels.size() - 1; toPosition >= 0; toPosition--) {
        final AddCourseModel model = newModels.get(toPosition);
        final int fromPosition = mModels.indexOf(model);
        if (fromPosition >= 0 && fromPosition != toPosition) {
            moveItem(fromPosition, toPosition);
        }
    }
}

public AddCourseModel removeItem(int position) {
    final AddCourseModel model = mModels.remove(position);
    notifyItemRemoved(position);
    return model;
}

public void addItem(int position, AddCourseModel model) {
    mModels.add(position, model);
    notifyItemInserted(position);
}

public void moveItem(int fromPosition, int toPosition) {
    final AddCourseModel model = mModels.remove(fromPosition);
    mModels.add(toPosition, model);
    notifyItemMoved(fromPosition, toPosition);
}

public class AddCourseViewHolder extends RecyclerView.ViewHolder {
    private final TextView mTextView;
    private final ImageButton addButton;
    private final ImageButton removeButton;

    public AddCourseViewHolder(View itemView) {
        super(itemView);
        mTextView = (TextView) itemView.findViewById(R.id.addCourseTV);
        addButton = (ImageButton) itemView.findViewById(R.id.addButton);
        removeButton = (ImageButton) itemView.findViewById(R.id.removeButton);
    }

    public void bind(AddCourseModel model) {
        mTextView.setText(model.getText());
    }
}

public static class AddCourseModel {
   private final String mText;

   public AddCourseModel(String text) {
       this.mText = text;
   }

   public String getText() {
       return mText;
   }
}
}

当前初始状态:

所需的初始状态:

推荐答案

这种情况在您的Adapter构造函数中

The case is in your Adapter constructor

public AddCourseAdapter(Context context, List<AddCourseModel> models) {
    mInflater = LayoutInflater.from(context);
    mModels = new ArrayList<>(models);
}

您创建一个新的ArrayList，它最初是从模型列表中填充的(此刻为空). 稍后，您将填充初始模型arraylist，而不是在适配器中创建的列表.

You create new ArrayList which initially populated from the models list (which is empty at this moment). Later you populate initial models arraylist, not the one created in adapter.

您可以:

a)移动

for (String course: courses) {
        mModels.add(new AddCourseAdapter.AddCourseModel(course));
        mRecyclerView.setAdapter(mAdapter);
        mAdapter.notifyDataSetChanged();
    }

在这些行之间

mModels = new ArrayList<>();
mAdapter = new AddCourseAdapter(this, mModels);

像这样

mModels = new ArrayList<>();

for (String course: courses) {
  mModels.add(new AddCourseAdapter.AddCourseModel(course));
}
mAdapter = new AddCourseAdapter(this, mModels);
mRecyclerView.setAdapter(mAdapter);

OR

b)将Adapter构造函数重写为

b) rewrite the Adapter constructor to

public AddCourseAdapter(Context context, List<AddCourseModel> models) {
        mInflater = LayoutInflater.from(context);
        mModels = models;
    }

这篇关于在SearchView交互之前，不会填充RecyclerView的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！