字符键的文本大小. android:keyTextSize可以帮助您.

Size of the text for character keys. android:keyTextSize can help.

在您的布局xml文件中进行设置，如下所示:

Set this in your layout xml file, like this:

<android.inputmethodservice.KeyboardView
    android:id="@+id/keyboard_view"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:keyBackground="@drawable/key_background"
    android:keyTextColor="@android:color/white"
    android:keyTextSize="20sp"/>