Button 中的 Button (class) 无法应用于 class

Question

我正在编写一个使用 AsyncTask 的 Android 应用程序。我在 "onPostExecute" void 中收到以下错误：

Button (android.content.Context) in Button cannot be applied to >(com.****.OnlineProductList)

我已经尝试将 "this" 语句更改为“getContent()”和“MainAtivity.this ”。当我输入 "get Content()" 时，它说：无法解析当我输入 "MainActivity.this" 时，它说： MainActivity is not an enclosing class


    public class OnlineProductList extends AsyncTask<Void,Void,Void>{


        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);


            System.out.println("Program: " + productData.length / 3 + " Products found");

//create product objects



            Product[] product = new Product[productData.length / 3];
            for (int i = 0; i < product.length; i++) {

                product[i] = new Product(productData[3 * i], productData[1 + 3 * i], Boolean.parseBoolean(productData[2 + 3 * i]));

            }

            //create buttons for available products

            MainActivity.productButton = new Button[product.length];

            for (int i = 0; i < productData.length; i++) {

                MainActivity.productButton[i] = new Button(this);
                MainActivity.productButton[i].setWidth(MainActivity.orderHorizontalLayout.getWidth());
                MainActivity.productButton[i].setHeight(MainActivity.orderHorizontalLayout.getHeight() / 10);
                MainActivity.productButton[i].setText(product[i].name);

                MainActivity.orderHorizontalLayout.addView(MainActivity.productButton[i]);

            }
        }
    }

错误发生在这一行：

MainActivity.productButton[i] = new Button(this);

Answer 1

您需要传递一个 Context 来创建 Button，目前您传递的是 OnlineProductList(AsyncTask) 对象。

您可以将 Context 实例作为构造函数参数（并保留 WeakReference 以避免内存泄漏）传递给 OnlineProductList 并使用 Context 来创建你的 Button.

以下几行内容应该有效，


    public class OnlineProductList extends AsyncTask<Void,Void,Void>{
        private WeakReference<Context> contextRef;

        public OnlineProductList(Context context) {
            contextRef = new WeakReference<>(context);
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);


            System.out.println("Program: " + productData.length / 3 + " Products found");

//create product objects



            Product[] product = new Product[productData.length / 3];
            for (int i = 0; i < product.length; i++) {

                product[i] = new Product(productData[3 * i], productData[1 + 3 * i], Boolean.parseBoolean(productData[2 + 3 * i]));

            }

            //create buttons for available products

            Context context = contextRef.get();
            if (context != null) {
                MainActivity.productButton = new Button[product.length];

                for (int i = 0; i < productData.length; i++) {

                    MainActivity.productButton[i] = new Button(this);
                    MainActivity.productButton[i].setWidth(MainActivity.orderHorizontalLayout.getWidth());
                    MainActivity.productButton[i].setHeight(MainActivity.orderHorizontalLayout.getHeight() / 10);
                    MainActivity.productButton[i].setText(product[i].name);

                    MainActivity.orderHorizontalLayout.addView(MainActivity.productButton[i]);
                }
            }
        }
    }

Button 中的 Button (class) 无法应用于 class

Button (class) in Button cannot be applied to class

java

android

android-context

android-asynctask

android-button