Why can't I cast an object of type View to KeyboardView

Question

I have defined a custom KeyboardView like this:

    public class MyKeyboardView extends KeyboardView
    {
        public MyKeyboardView(Context context, AttributeSet attrs)
        {
            super(context, attrs);
            ...

and somewhere in my code I have:

    MyKeyboardView myKbView = (MyKeyboardView) myViewGroup.findViewWithTag("MyKeyboardView");

where myViewGroup comes from inflating the following xml file:

    <?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_alignParentBottom="true"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" >

    <android.gesture.GestureOverlayView
        android:id="@+id/gestureOverlayView"
        android:gestureColor="#00000000"
        android:layout_width="match_parent"
        android:tag="MyGestureOverlayView"
        android:layout_height="wrap_content">

        <android.inputmethodservice.KeyboardView
            android:id="@+id/keyboard"
            android:keyBackground="@drawable/orange_keyboard_keys_background"
            android:keyTextColor="#ff8710"
            android:background="#4c4c4c"
            android:tag="MyKeyboardView"
            android:keyTextSize="21sp"
            android:keyPreviewLayout="@layout/key_preview_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>

    </android.gesture.GestureOverlayView>

</LinearLayout>

and this is what Logcat says:

    03-09 22:52:29.274: E/deliKey(21719): java.lang.ClassCastException:
    android.inputmethodservice.KeyboardView cannot be cast to
    com.parasum.delikey.MyKeyboardView

WHY?

Answer 1

Both android.inputmethodservice.KeyboardView and com.parasum.delikey.MyKeyboardView are indeed descendants of View, but neither is a descendant of the other. It's analogous to Views and Strings. They're both descendants of Object, but you can't cast between them.

Answer 2

It looks like you are not creating a com.parasum.delikey.MyKeyboardView but rather a android.inputmethodservice.KeyboardView.

Try replacing the line in your layout xml:

<android.inputmethodservice.KeyboardView

with

<com.parasum.delikey.MyKeyboardView

Answer 3

You cannot cast this way as you declared the view in XML as android.inputmethodservice.KeyboardView.

You need to change your XML and declare it as MyKeyboardView:

<com.parasum.delikey.MyKeyboardView
        android:id="@+id/keyboard"
        android:keyBackground="@drawable/orange_keyboard_keys_background"
        android:keyTextColor="#ff8710"
        android:background="#4c4c4c"
        android:tag="MyKeyboardView"
        android:keyTextSize="21sp"
        android:keyPreviewLayout="@layout/key_preview_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

---

You currently declare your visual element as KeyboardView class. Then you try to cast it to MyKeyboardView class. This cannot work as a class cannot be cast to a class that inherits from it (a class cannot be cast to its child class). This is the way it works in Java.