Update tab button text when the data changes

Fixes #870

widget/tabcontainer.go

@@ -347,8 +347,10 @@ func (t *tabContainerRenderer) Refresh() {
 	t.line.Refresh()
 
 	for i, child := range t.container.Items {
-		old := t.objects[i]
+		tab := t.tabBar.Objects[i].(*tabButton)
+		tab.setText(child.Text)
 
+		old := t.objects[i]
 		if old == child.Content {
 			continue
 		}
@@ -403,6 +405,15 @@ func (b *tabButton) MinSize() fyne.Size {
 	return b.BaseWidget.MinSize()
 }
 
+func (b *tabButton) setText(text string) {
+	if text == b.Text {
+		return
+	}
+
+	b.Text = text
+	b.Refresh()
+}
+
 func (b *tabButton) CreateRenderer() fyne.WidgetRenderer {
 	b.ExtendBaseWidget(b)
 	var icon *canvas.Image
@@ -529,6 +540,7 @@ func (r *tabButtonRenderer) Objects() []fyne.CanvasObject {
 }
 
 func (r *tabButtonRenderer) Refresh() {
+	r.label.Text = r.button.Text
 	r.label.Color = theme.TextColor()
 	r.label.TextSize = theme.TextSize()
 

widget/tabcontainer_test.go

@@ -467,3 +467,20 @@ func TestTabButtonRenderer_ApplyTheme(t *testing.T) {
 
 	assert.NotEqual(t, textSize, customTextSize)
 }
+
+func Test_tabButtonRenderer_SetText(t *testing.T) {
+	item := &TabItem{Text: "Test", Content: NewLabel("Content")}
+	tabs := NewTabContainer(item)
+	tabRenderer := test.WidgetRenderer(tabs).(*tabContainerRenderer)
+	tabButton := tabRenderer.tabBar.Objects[0].(*tabButton)
+	renderer := test.WidgetRenderer(tabButton).(*tabButtonRenderer)
+
+	assert.Equal(t, "Test", renderer.label.Text)
+
+	tabButton.setText("Temp")
+	assert.Equal(t, "Temp", renderer.label.Text)
+
+	item.Text = "Replace"
+	tabs.Refresh()
+	assert.Equal(t, "Replace", renderer.label.Text)
+}