将数据从片段传递到自定义适配器(用于ListView)

时间:2018-02-19 00:44:53

标签: java android listview android-fragments adapter

我试图将从片段中的捆绑包中检索到的数据发送到ListView的适配器,以便根据以前的用户选择显示数据。

我可以记录正确的数据被发送到我的片段,但是当我尝试将该数据传递到我的适配器的构造函数时,ListView没有被填充。我不确定这是否是将数据传输到适配器的正确方法,特别是因为数据不是来自游标。

在我的片段中,这是相关的代码:

public class AddEditRecipeActivityFragment extends Fragment {
ListView mListView;
private IngredientListAdapter mIngredientListAdapter;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    Log.d(TAG, "onCreateView: starts");
    View view = inflater.inflate(R.layout.fragment_add_edit_recipe, container, false);


    mNameTextView = (EditText) view.findViewById(R.id.addedit_name);
    mAddItem = (ImageButton) view.findViewById(R.id.addGrocery);
    mDescriptionTextView = (EditText) view.findViewById(R.id.addedit_description);
    mMealType = (EditText) view.findViewById(R.id.addedit_meal);
    mSaveButton = (Button) view.findViewById(R.id.addedit_save);

    mListView = (ListView) view.findViewById(R.id.lstIngredient);


    Bundle arguments = getArguments();

    String addedGrocery = arguments.getString("GroceryName");

    String addedGroceryGrams = arguments.getString("grams");

    Log.d(TAG, "onCreateView: retrieved ingredient = " + addedGrocery
            + " retrieved amount = " + addedGroceryGrams );

   mIngredientListAdapter = new IngredientListAdapter(getActivity(), null,
            0, addedGrocery, addedGroceryGrams ) ;
    mListView.setAdapter(mIngredientListAdapter);


.... }

这是我的适配器代码,从CursorAdapter类修改:

public class IngredientListAdapter  extends CursorAdapter {
private static final String TAG = "IngredientListAdapter";

private LayoutInflater mInflater;
private Context mContext;
private String mIngredient;
private String mGrams;

public IngredientListAdapter(Context context, Cursor c, int flags, String ingredient, String grams) {
    super(context, c, flags);
    mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.mIngredient = ingredient;
    this.mGrams = grams;
}

public View newView(Context context, Cursor cursor, ViewGroup parent) {
    View view = mInflater.inflate(R.layout.ingrediend_listview, parent, false);
    ViewHolder holder = new ViewHolder();
    holder.ingredient = (TextView) view.findViewById(R.id.ingredient);
    holder.amount = (TextView) view.findViewById(R.id.amount);
    view.setTag(holder);

    return view;
}


public void bindView(View view, Context context, Cursor cursor) {
    ViewHolder holder = (ViewHolder) view.getTag();

    Log.d(TAG, "bindView: Starts");

    Log.d(TAG, "bindView: ingredient = " + mIngredient);

    holder.ingredient.setText(mIngredient);
    holder.amount.setText(mGrams);


}

static class ViewHolder {
    TextView ingredient;
    TextView amount;
 }
}

当我尝试查看我的IngredientListAdapter类的日志时,根本没有显示任何内容。这很奇怪,因为我有另一个扩展CursorAdapter的适配器,那些日志正在运行 - 可能是因为它们涉及游标参数?

我明显遗漏了一些重要的事情,我们非常感谢任何帮助!

2 个答案:

答案 0 :(得分:0)

我不想在这里提出新的答案,但评论行太短,无法扩展我的观点。

第一个让你的适配器应该有两件事要管理的图像。第一件事是每个列表视图的项目的视图。你已经通过添加视图持有者来完成它。第二件事是视图的数据。因为您使用Cursor适配器,所以您不需要准备此适配器内的List<E>。光标为你做了。但是,您忘记通过将null传递给constructer来准备它。

请慢慢阅读this article。这对你有好处。

你的问题在这里:

public class AddEditRecipeActivityFragment extends Fragment {
...

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
...
    // The cursor's null
    mIngredientListAdapter = new IngredientListAdapter(getActivity(), null, 0, addedGrocery, addedGroceryGrams ) ;
    mListView.setAdapter(mIngredientListAdapter);
...
}

在这里:

public class IngredientListAdapter  extends CursorAdapter {
...
public IngredientListAdapter(Context context, Cursor c, int flags, String ingredient, String grams) {
    super(context, c, flags);  // c null now
    mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    this.mIngredient = ingredient;
    this.mGrams = grams;
}
...

希望得到这个帮助。

答案 1 :(得分:0)

另一个答案中提到的主要问题是,您的Cursor参数为null,这告诉CursorAdapter您不想拥有任何内容所有这些都在您的ListView中,因此无法显示任何内容。

由于您实际上并未使用Cursor,因此扩展CursorAdapter不是一个好选择。扩展ArrayAdapter会更合适。

您的适配器可能如下所示:

public class IngredientAdapter extends ArrayAdapter<Ingredient> {
    public IngredientAdapter(Context context, ArrayList<Ingredient> ingredients) {
       super(context, 0, ingredients);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
       // Get the data item for this position
       Ingredient ingredient = getItem(position);    
       // Check if an existing view is being reused, otherwise inflate the view
       if (convertView == null) {
          convertView = LayoutInflater.from(getContext()).inflate(R.layout.item_ingredient, parent, false);
       }
       // Lookup view for data population
       TextView ingredientName = (TextView) convertView.findViewById(R.id.ingredientName);
       TextView ingredientAmt = (TextView) convertView.findViewById(R.id.ingredientAmt);
       // Populate the data into the template view using the data object
       ingredientName.setText(ingredient.name);
       ingredientAmt.setText(ingredient.amt);
       // Return the completed view to render on screen
       return convertView;
   }
}

Ingredient将是您创建的类,用于保存每种成分的信息。您也可以向适配器添加ViewHolder,但不是必需的。

而不是将addedGroceryaddedGroceryGrams值直接传递给构造函数,而只允许您在ListView中使用一个项目,或者使用多个项目相同的值,您应传入包含信息的ArrayListIngredient个对象:

mIngredientListAdapter = new IngredientAdapter(getActivity(), ingredients);
mListView.setAdapter(mIngredientListAdapter);