Resolves #412 Add 'Support app development' option

lib/pages/widgets/page_loading_error.dart

@@ -0,0 +1,32 @@
+part of '../../main.dart';
+
+class PageLoadingError extends StatelessWidget {
+
+  final String errorText;
+
+  const PageLoadingError({Key key, this.errorText: "Error"}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return Row(
+      mainAxisSize: MainAxisSize.max,
+      crossAxisAlignment: CrossAxisAlignment.center,
+      mainAxisAlignment: MainAxisAlignment.center,
+      children: <Widget>[
+        Column(
+          children: <Widget>[
+            Padding(
+                padding: EdgeInsets.only(top: 40.0, bottom: 20.0),
+                child: Icon(
+                    Icons.error,
+                    color: Colors.redAccent,
+                    size: 48.0
+                )
+            ),
+            Text(this.errorText, style: TextStyle(color: Colors.black45))
+          ],
+        )
+      ],
+    );
+  }
+}

lib/pages/widgets/page_loading_indicator.dart

@@ -0,0 +1,23 @@
+part of '../../main.dart';
+
+class PageLoadingIndicator extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    return Row(
+      mainAxisSize: MainAxisSize.max,
+      crossAxisAlignment: CrossAxisAlignment.center,
+      mainAxisAlignment: MainAxisAlignment.center,
+      children: <Widget>[
+        Column(
+          children: <Widget>[
+            Padding(
+                padding: EdgeInsets.only(top: 40.0, bottom: 20.0),
+                child: CircularProgressIndicator()
+            ),
+            Text("Loading...", style: TextStyle(color: Colors.black45))
+          ],
+        )
+      ],
+    );
+  }
+}

lib/pages/widgets/product_purchase.widget.dart

@@ -0,0 +1,68 @@
+part of '../../main.dart';
+
+class ProductPurchase extends StatelessWidget {
+
+  final ProductDetails product;
+  final onBuy;
+  final purchased;
+
+  const ProductPurchase({Key key, @required this.product, @required this.onBuy, this.purchased}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    String period = "/ ";
+    Color priceColor;
+    if (product.id.contains("month")) {
+      period += "month";
+      priceColor = Colors.deepOrangeAccent;
+    } else {
+      period += "year";
+      priceColor = Colors.amber;
+    }
+    return Card(
+        child: Padding(
+          padding: EdgeInsets.all(Sizes.leftWidgetPadding),
+          child: Flex(
+            direction: Axis.horizontal,
+            children: <Widget>[
+              Expanded(
+                flex: 5,
+                child: Padding(
+                    padding: EdgeInsets.only(right: Sizes.rightWidgetPadding),
+                    child: Column(
+                      crossAxisAlignment: CrossAxisAlignment.start,
+                      children: <Widget>[
+                        Text(
+                          "${product.title}",
+                          style: TextStyle(
+                              fontWeight: FontWeight.bold,
+                              fontSize: 16.0
+                          ),
+                        ),
+                        Container(height: Sizes.rowPadding,),
+                        Text(
+                          "${product.description}",
+                          overflow: TextOverflow.ellipsis,
+                          maxLines: 4,
+                          softWrap: true,
+                        ),
+                        Container(height: Sizes.rowPadding,),
+                        Text("${product.price} $period", style: TextStyle(color: priceColor)),
+                      ],
+                    )
+                ),
+              ),
+              Expanded(
+                flex: 2,
+                child: RaisedButton(
+                  child: Text(this.purchased ? "Bought" : "Buy", style: TextStyle(color: Colors.white)),
+                  color: Colors.blue,
+                  onPressed: this.purchased ? null : () => this.onBuy(this.product),
+                ),
+              )
+            ],
+          ),
+        )
+    );
+  }
+}