Android : Checkbox doesnt change visual

i have an Activity with a LinearLayout, containing a TextView, a CheckBox and a Button. When i check the CheckBox nothing visible happens, however it behaves correctly. However, when i click on the Button, then the CheckBox is displayed correctly for a moments before the Activity closes(as it should). Also the option is set correctly, so the state of the CheckBox does really change, but it doesn't display the change. Here is my code:

activity_setup_hint.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    tools:context="${packageName}.${activityClass}" >

    <LinearLayout 
        android:background="@drawable/info_box_inset"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal"
        android:layout_marginLeft="@dimen/activity_horizontal_margin"
        android:layout_marginRight="@dimen/activity_horizontal_margin"
        android:padding="20dp">

        <de.myProject.util.FontTextView
            android:id="@+id/calint_txt_msg"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center_horizontal"
            android:textSize="30sp"
            android:text="@string/setup_hint"
            android:textAppearance="?android:attr/textAppearanceLarge" />
    </LinearLayout>

    <de.myProject.FontCheckBox 
        android:id="@+id/dont_show_hint"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="left"
        android:layout_marginTop="5dp"
        android:layout_marginBottom="5dp"
        android:layout_marginLeft="-25dp"
        android:button="@null"
        android:checked="false"
        android:drawableLeft="@drawable/my_checkbox_button"
        android:drawablePadding="50dp"
        android:text="@string/show_hint"
        android:textSize="22sp"
        />


    <de.myProject.util.FontButton
        android:id="@+id/start_but_calibrate"
        style="@style/myButton"
        android:layout_gravity="center"
        android:onClick="onFinishClick"
        android:text="@string/ready" />
</LinearLayout>

SetupHintActivity.java

public class SetupHintActivity extends Activity{

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_setup_hint);
    }

    public void onFinishClick(View view) {
        CheckBox cb = (CheckBox) findViewById(R.id.dont_show_hint);
        SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(this);
        Editor editor = sharedPref.edit();
        editor.putBoolean("dont_show_hint", cb.isChecked());
        editor.apply();

        finish();
    }
}

my_checkbox_button.xml

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">

    <item android:drawable="@drawable/my_button_checked" android:state_checked="true"/>
    <item android:drawable="@drawable/my_button_unchecked" android:state_checked="false"/>
    <item android:drawable="@drawable/my_button_unchecked"/>

</selector>