feat(android): layoutCompleted event

Author: farfromrefug

packages/collectionview/platforms/android/java/com/nativescript/collectionview/GridLayoutManager.java

@@ -6,8 +6,14 @@
 import java.util.HashMap;
 
 public class GridLayoutManager extends androidx.recyclerview.widget.GridLayoutManager {
+    
     private HashMap<Integer, Integer> childSizesMap = new HashMap();
     public boolean isScrollEnabled = true;
+    public LayoutCompletedListener layoutCompletedListener;
+
+    public interface LayoutCompletedListener {
+        public void onLayoutCompleted();
+    }
 
     public GridLayoutManager(Context context, int spanCount) {
         super(context, spanCount);
@@ -20,6 +26,9 @@ public void  onLayoutCompleted(RecyclerView.State state) {
             View child = getChildAt(i);
             childSizesMap.put(getPosition(child), child.getHeight());
         }
+        if (layoutCompletedListener != null) {
+            layoutCompletedListener.onLayoutCompleted();
+        }
     }
 
    public  int computeVerticalScrollOffset(RecyclerView.State state) {

src/collectionview/index.android.ts

@@ -128,6 +128,7 @@ export enum SnapPosition {
 }
 
 export class CollectionView extends CollectionViewBase {
+    public static layoutCompletedEvent = 'layoutCompleted';
     public static DEFAULT_TEMPLATE_VIEW_TYPE = 0;
     public static CUSTOM_TEMPLATE_ITEM_TYPE = 1;
     public nativeViewProtected: CollectionViewRecyclerView & {
@@ -260,6 +261,13 @@ export class CollectionView extends CollectionViewBase {
             layoutManager = CollectionViewBase.layoutStyles[this.layoutStyle].createLayout(this);
         } else {
             layoutManager = new com.nativescript.collectionview.PreCachingGridLayoutManager(this._context, 1);
+            if (this.hasListeners(CollectionView.layoutCompletedEvent)) {
+                (layoutManager as com.nativescript.collectionview.GridLayoutManager).layoutCompletedListener = new com.nativescript.collectionview.GridLayoutManager.LayoutCompletedListener({
+                    onLayoutCompleted:()=>{
+                        this.notify({eventName:CollectionView.layoutCompletedEvent})
+                    }
+                })
+            }
             // layoutManager = new PreCachingGridLayoutManager(this._context, 1);
             // (layoutManager as any).owner = new WeakRef(this);
         }

src/collectionview/typings/android.d.ts

@@ -10,6 +10,14 @@ declare namespace com {
             }
             export class GridLayoutManager extends androidx.recyclerview.widget.GridLayoutManager {
                 isScrollEnabled: boolean;
+                layoutCompletedListener: LayoutCompletedListener;
+            }
+            export namespace GridLayoutManager {
+
+                export class LayoutCompletedListener {
+                    onLayoutCompleted();
+                    constructor(implementation?: { onLayoutCompleted() });
+                } 
             }
             export class PreCachingGridLayoutManager extends GridLayoutManager {
                 setExtraLayoutSpace(space: number);