Implement focus handing in RadioButtonGroup and CheckboxGroup (#10440)

Fixes #10429

* implement focus handing in RadioButtonGroup, fixes #10429

* Merge branch 'master' of https://github.com/vaadin/framework into radiobuttongroup-focus

* merge

* Merge branch 'master' of https://github.com/vaadin/framework into radiobuttongroup-focus

* fix initial focus handling also on CheckBoxGroup and add tests

* add license headers

* Merge branch 'master' of https://github.com/vaadin/framework into radiobuttongroup-focus

* changed client to use lambdas and refactored focus testing to parent class

* made FocusTest abstract

* Merge branch 'master' of https://github.com/vaadin/framework into radiobuttongroup-focus

* don't allow focusing on disabled items & refactor focusing first item

3 files changed, 56 insertions, 1 deletions

diff --git a/client/src/main/java/com/vaadin/client/ui/VCheckBoxGroup.java b/client/src/main/java/com/vaadin/client/ui/VCheckBoxGroup.java
index 93975d2926..f78c98ee27 100644
--- a/client/src/main/java/com/vaadin/client/ui/VCheckBoxGroup.java
+++ b/client/src/main/java/com/vaadin/client/ui/VCheckBoxGroup.java
@@ -23,6 +23,7 @@ import java.util.Map;
 import java.util.function.BiConsumer;
 
 import com.google.gwt.aria.client.Roles;
+import com.google.gwt.core.client.Scheduler;
 import com.google.gwt.dom.client.Element;
 import com.google.gwt.event.dom.client.ClickEvent;
 import com.google.gwt.event.dom.client.ClickHandler;
@@ -235,4 +236,14 @@ public class VCheckBoxGroup extends FocusableFlowPanelComposite
                 .remove(selectionChanged);
     }
 
+    /**
+     * Set focus to the first check box.
+     */
+    @Override
+    public void focus() {
+        // If focus is set on creation, need to wait until options are populated
+        Scheduler.get().scheduleDeferred(() -> {
+            getWidget().focusFirstEnabledChild();
+        });
+    }
 }
diff --git a/client/src/main/java/com/vaadin/client/ui/VRadioButtonGroup.java b/client/src/main/java/com/vaadin/client/ui/VRadioButtonGroup.java
index 91ea471543..479e41a9b5 100644
--- a/client/src/main/java/com/vaadin/client/ui/VRadioButtonGroup.java
+++ b/client/src/main/java/com/vaadin/client/ui/VRadioButtonGroup.java
@@ -24,6 +24,7 @@ import java.util.Optional;
 import java.util.function.Consumer;
 
 import com.google.gwt.aria.client.Roles;
+import com.google.gwt.core.client.Scheduler;
 import com.google.gwt.dom.client.Element;
 import com.google.gwt.event.dom.client.ClickEvent;
 import com.google.gwt.event.dom.client.ClickHandler;
@@ -40,6 +41,7 @@ import com.vaadin.client.widgets.FocusableFlowPanelComposite;
 import com.vaadin.shared.Registration;
 import com.vaadin.shared.data.DataCommunicatorConstants;
 import com.vaadin.shared.ui.ListingJsonConstants;
+
 import elemental.json.JsonObject;
 
 /**
@@ -272,8 +274,29 @@ public class VRadioButtonGroup extends FocusableFlowPanelComposite
     }
 
     /**
+     * Set focus to the selected radio button (or first radio button if there is
+     * no selection).
+     */
+    @Override
+    public void focus() {
+        // If focus is set on creation, need to wait until options are populated
+        Scheduler.get().scheduleDeferred(() -> {
+            // if there's a selected radio button, focus it
+            for (String key : keyToOptions.keySet()) {
+                RadioButton radioButton = keyToOptions.get(key);
+                if (radioButton != null && radioButton.getValue()) {
+                    radioButton.setFocus(true);
+                    return;
+                }
+            }
+            // otherwise focus the first enabled child
+            getWidget().focusFirstEnabledChild();
+        });
+    }
+
+    /**
      * Updates the selected state of a radio button.
-     * 
+     *
      * @param radioButton
      *            the radio button to update
      * @param value
@@ -282,5 +305,6 @@ public class VRadioButtonGroup extends FocusableFlowPanelComposite
     protected void updateItemSelection(RadioButton radioButton, boolean value) {
         radioButton.setValue(value);
         radioButton.setStyleName(CLASSNAME_OPTION_SELECTED, value);
+
     }
 }
diff --git a/client/src/main/java/com/vaadin/client/widgets/ChildFocusAwareFlowPanel.java b/client/src/main/java/com/vaadin/client/widgets/ChildFocusAwareFlowPanel.java
index d1f7882dff..a0fc6a1499 100644
--- a/client/src/main/java/com/vaadin/client/widgets/ChildFocusAwareFlowPanel.java
+++ b/client/src/main/java/com/vaadin/client/widgets/ChildFocusAwareFlowPanel.java
@@ -153,6 +153,26 @@ public class ChildFocusAwareFlowPanel extends FocusableFlowPanel
         }
     }
 
+    /**
+     * Put focus in the first child Widget that can be focused and is not
+     * disabled.
+     */
+    public void focusFirstEnabledChild() {
+        for (int i = 0; i < getWidgetCount(); i++) {
+            Widget widget = getWidget(i);
+            if (!(widget instanceof FocusWidget)) {
+                continue;
+            }
+            FocusWidget focusableChild = (FocusWidget) widget;
+            if (focusableChild.isEnabled()) {
+                focusableChild.setFocus(true);
+                break;
+            }
+
+        }
+
+    }
+
     private void addHandlers(Widget widget) {
         if (focusRegistrations.containsKey(widget)) {
             assert blurRegistrations.containsKey(widget);