Question

我正在尝试对两个游标中的值求和，并将结果放入文本视图中。当光标只返回一个值时，它可以完美地运行，但是当返回的值超过一个时，我必须将光标放入while循环中，它将停止工作。

主要的游标是ingredientsCursor返回一个或多个列表（这是有效的），然后在while循环中，两个游标从主游标中获取结果以执行两个单独的查询，然后将结果相乘并添加到要显示的运行总计中。

当我在没有while循环的情况下运行代码时，知道我只会从ingredientsCursor获得一个结果，一切正常，当有多个结果时我必须使用while循环。我已经将总数设置为一个全局变量，如果出现问题但仍然只是获得空白区域。

使用结果显示工作显示（无静止循环）

        final Cursor ingredientsCursor = adapter.getRecipesIngredients(recipeCode);
        ingredientsCursor.moveToFirst();

        String name = ingredientsCursor.getString(ingredientsCursor.getColumnIndex("ingredient_name"));

        final Cursor c = adapter.getRecipeCalories(name);
        c.moveToFirst();
        int cal = c.getInt(c.getColumnIndex("calories"));

        final Cursor m = adapter.getMeasurement(recipeCode, name);
        m.moveToFirst();
        int meas = m.getInt(m.getColumnIndex("measurement"));

        int total = cal * meas;

        recipeCalories.setText("Calories:" + total);

使用While循环，显示空白

    final Cursor ingredientsCursor = adapter.getRecipesIngredients(recipeCode);
    ingredientsCursor.moveToFirst();
    while(ingredientsCursor.moveToNext())
    {
        String name = ingredientsCursor.getString(ingredientsCursor.getColumnIndex("ingredient_name"));

        final Cursor c = adapter.getRecipeCalories(name);
        c.moveToFirst();
        int cal = c.getInt(c.getColumnIndex("calories"));

        final Cursor m = adapter.getMeasurement(recipeCode, name);
        m.moveToFirst();
        int meas = m.getInt(m.getColumnIndex("measurement"));

        int MainActivity.total = cal * meas;

    }

    recipeCalories.setText("Calories:" + MainActivity.total);

Answer 1

每次while循环运行时，都会覆盖MainActivity.total。尝试将所有总值放在值列表中并显示数据。

Answer 2

您将覆盖每个循环步骤的总值。

  final Cursor ingredientsCursor = adapter.getRecipesIngredients(recipeCode);
    ingredientsCursor.moveToFirst();
    while(ingredientsCursor.moveToNext())
    {
        String name = ingredientsCursor.getString(ingredientsCursor.getColumnIndex("ingredient_name"));

        final Cursor c = adapter.getRecipeCalories(name);
        c.moveToFirst();
        int cal = c.getInt(c.getColumnIndex("calories"));

        final Cursor m = adapter.getMeasurement(recipeCode, name);
        m.moveToFirst();
        int meas = m.getInt(m.getColumnIndex("measurement"));
        // here is your error
        int MainActivity.total = cal * meas;

    }

您需要将代码更改为：

   final Cursor ingredientsCursor = adapter.getRecipesIngredients(recipeCode);
    ingredientsCursor.moveToFirst();
    int sum = 0;
    while(ingredientsCursor.moveToNext())
    {
        String name = ingredientsCursor.getString(ingredientsCursor.getColumnIndex("ingredient_name"));

        final Cursor c = adapter.getRecipeCalories(name);
        c.moveToFirst();
        int cal = c.getInt(c.getColumnIndex("calories"));

        final Cursor m = adapter.getMeasurement(recipeCode, name);
        m.moveToFirst();
        int meas = m.getInt(m.getColumnIndex("measurement"));

        sum += (cal * meas);

    }

    recipeCalories.setText("Calories:" + sum);

从TextView的光标求和值

2 个答案: