flowlayout add header and footer:iOS implement

doric-js/index.d.ts

@@ -143,6 +143,11 @@ declare module 'doric/lib/src/ui/panel' {
         onShow(): void;
         onHidden(): void;
         onEnvChanged(): void;
+        /**
+          * Build view of the current Panel
+          * This could be called any times at any time when necessary.
+          * @param rootView root view of this panel
+          */
         abstract build(rootView: Group): void;
         addHeadView(type: string, v: View): void;
         allHeadViews(): IterableIterator<Map<string, View>>;

doric-js/lib/src/ui/panel.d.ts

@@ -10,6 +10,11 @@ export declare abstract class Panel {
     onShow(): void;
     onHidden(): void;
     onEnvChanged(): void;
+    /**
+     * Build view of the current Panel
+     * This could be called any times at any time when necessary.
+     * @param rootView root view of this panel
+     */
     abstract build(rootView: Group): void;
     private __data__?;
     private __root__;

doric-js/src/ui/panel.ts

@@ -43,6 +43,11 @@ export abstract class Panel {
         this.__root__.children.length = 0
         this.build(this.__root__)
     }
+    /**
+     * Build view of the current Panel
+     * This could be called any times at any time when necessary.
+     * @param rootView root view of this panel
+     */
     abstract build(rootView: Group): void
 
     private __data__?: object