Make popup of the key pressed in a customized keyboard

For just showing the enlarged previews, KeyboardView should be doing it by default. You don't want to set a popupKeyboard value as this is for a special mini keyboard that shows on long presses.

I assume you were following this tutorial. Take note of these lines in section 3.3:

// Do not show the preview balloonsmKeyboardView.setPreviewEnabled(false);

Instead set this to true.

Complete Solution

In your activity's layout:

<android.inputmethodservice.KeyboardView    android:id="@+id/keyboardview"    android:layout_width="fill_parent"    android:layout_height="wrap_content"    android:layout_alignParentBottom="true"    android:layout_centerHorizontal="true"    android:focusable="true"    android:focusableInTouchMode="true"    android:keyPreviewOffset="12dp"    android:keyPreviewLayout="@layout/kbpreview"    android:visibility="visible" />

The important properties here are keyPreviewLayout, keyPreviewOffset and keyPreviewHeight.

layout/kbpreview.xml

<?xml version="1.0" encoding="utf-8"?><TextView xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:gb="http://schemas.android.com/apk/res-auto"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:padding="10dp"    android:background="@color/red"    android:textSize="30dp" />

xml/kb.xml

<?xml version="1.0" encoding="utf-8"?><Keyboard xmlns:android="http://schemas.android.com/apk/res/android"    android:keyWidth="12.50%p"    android:keyHeight="10%p" >    <Row>        <Key android:codes="55"    android:keyLabel="7" android:keyEdgeFlags="left" />        <Key android:codes="56"    android:keyLabel="8" />        <Key android:codes="57"    android:keyLabel="9" />        <Key android:codes="65"    android:keyLabel="A" android:horizontalGap="6.25%p" />        <Key android:codes="66"    android:keyLabel="B" />        <Key android:codes="55006" android:keyLabel="CLR" android:keyEdgeFlags="right"/>    </Row>    <!-- and whatever else... --></Keyboard>

In your activity code

    Keyboard mKeyboard = new Keyboard(this, R.xml.kb);    // Lookup the KeyboardView    KeyboardView mKeyboardView = (KeyboardView) findViewById(R.id.keyboardview);    // Attach the keyboard to the view    mKeyboardView.setKeyboard(mKeyboard);    // Key listener required    mKeyboardView.setOnKeyboardActionListener(myListener);

Result

with the '5' key pressed:

You may also find it useful to check out the KeyboardView source code.