Set movement method to the focusable text

The keyboard navigation should work for focusable text, thus
set ArrowKeyMovementMethod to the focusable TextView.

Bug: 244260144
Test: Manually done with demo app
Change-Id: I0b1e046b84641a40cb801e107980504dccd31f8a

core/java/android/widget/TextView.java

@@ -2438,7 +2438,11 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
      * Subclasses override this to specify a default movement method.
      */
     protected MovementMethod getDefaultMovementMethod() {
-        return null;
+        if (isFocusable() || isFocusableInTouchMode()) {
+            return ArrowKeyMovementMethod.getInstance();
+        } else {
+            return null;
+        }
     }
 
     /**
@@ -2653,9 +2657,12 @@ public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
     /**
      * Gets the {@link android.text.method.MovementMethod} being used for this TextView,
      * which provides positioning, scrolling, and text selection functionality.
-     * This will frequently be null for non-EditText TextViews.
+     * By default, this returns an instance of {@link android.text.method.ArrowKeyMovementMethod}
+     * if this View is focusable or focusable in touch mode.
+     *
      * @return the movement method being used for this TextView.
      * @see android.text.method.MovementMethod
+     * @see android.text.method.ArrowKeyMovementMethod
      */
     public final MovementMethod getMovementMethod() {
         return mMovement;