This Generic Activity provides events to detect the presence of android's SoftKeyboard

ActivitySoftKeyboard.java

import android.app.Activity;
import android.graphics.Rect;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewTreeObserver;

/**
 * This Activity provides the possibility to register a Listener
 * to monitor the SoftKeyboard presence.
 * Its not an exact science, but gets the job done.
 * Detecting changes that occurred on the registered layout root
 * the observer can suppose if the keyboard is present or not.
 * 
 * - To use start the monitoring with {@link #startDetectRootViewChanges(View)}
 *   and override {@link #onKeyBoardOn()} {@link #onKeyBoardOff()}
 * 
 */
public class ActivitySoftKeyboard extends Activity {
    
    protected final String TAG = getClass().getSimpleName();

    @Override
    protected void onDestroy() {
        super.onDestroy();

        // Remove LayoutChange listener
        stopDetectRootViewChanges();
    }

    /**
     * Detecting Layout Root changes
     * - {@link #startDetectRootViewChanges(View)} must be called on {@link #onCreate(Bundle)}
     * - Detect if SoftKeyboard is On/Off
     *      {@link #onKeyBoardOn()} {@link #onKeyBoardOff()}
     * - Register event for layout changes
     *      {@link #onRootLayoutChanged(int)}
     */
    protected View mActivityRootView;
    protected ViewTreeObserver.OnGlobalLayoutListener mLayoutListener;

    /**
     * Create a new Global Layout Listener
     */
    private ViewTreeObserver.OnGlobalLayoutListener createLayoutListener() {
        Log.d(TAG, "createLayoutListener");
        final int KEYBOARD_GREATER_THAN = 125;
        return new ViewTreeObserver.OnGlobalLayoutListener() {
            @Override
            public void onGlobalLayout() {
                Rect rect = new Rect();

                mActivityRootView.getWindowVisibleDisplayFrame(rect);

                int heightDiff = mActivityRootView.getHeight() - (rect.bottom - rect.top);
                if (heightDiff>0) onRootLayoutChanged(heightDiff);
                if (heightDiff > KEYBOARD_GREATER_THAN) { // if more than 100 pixels, its probably a keyboard...
                    Log.d(TAG, "onGlobalLayout(). Probabaly a keyBoard. > heightDiff[" + heightDiff + "]");
                    onKeyBoardOn();
                    mIsKeyboardOn = true;
                } else {
                    if (mIsKeyboardOn) {
                        onKeyBoardOff();
                        mIsKeyboardOn = false;
                    }
                }
            }
        };
    }

    /**
     * Start to detect changed on Root layout height
     * - Register a Root view
     * - Create and starts a Global Layout Listener
     * - Register root view layout events
     *      {@link #onKeyBoardOn()}
     *      {@link #onKeyBoardOff()}
     *      {@link #onRootLayoutChanged(int)}
     * @param activityRootView  Root layout to be monitored
     */
    protected void startDetectRootViewChanges(final View activityRootView) {
        Log.d(TAG, "startDetectRootViewChanges()");
        mActivityRootView = activityRootView;
        mIsKeyboardOn = false;

        mLayoutListener = createLayoutListener();
        mActivityRootView.getViewTreeObserver().addOnGlobalLayoutListener(mLayoutListener);

    }

    /**
     * Remove Global Layout change listener
     */
    protected void stopDetectRootViewChanges() {
        Log.d(TAG, "stopDetectRootViewChanges()");
        if ( mActivityRootView != null )
            mActivityRootView.getViewTreeObserver().removeOnGlobalLayoutListener(mLayoutListener);
    }


    private Boolean mIsKeyboardOn;
    /**
     * Controls if SoftKeyBoard is on/off
     * - May return null if {@link #startDetectRootViewChanges(View)} wasn't called
     */
    protected Boolean isKeyboardOn() {
        Log.d(TAG, "isKeyboardOn()");
        return mIsKeyboardOn;
    }

    /**
     * Called on SoftKeyBoard is ON
     * - Depends on {@link #startDetectRootViewChanges(View)}
     * - It must be called more than one time
     */
    protected void onKeyBoardOn() {
        Log.d(TAG, "onKeyBoardOn()");
    }
    /**
     * Called on SoftKeyBoard is OFF
     * - Depends on {@link #startDetectRootViewChanges(View)}
     * - It must be called more than one time
     */
    protected synchronized void onKeyBoardOff() {
        Log.d(TAG, "onKeyBoardOff()");
    }
    /**
     * Called when Root Layout view changes
     * - Depends on {@link #startDetectRootViewChanges(View)}
     * @param heightDiff    Height Difference between current
     *                      Root View an available Windo size
     */
    protected void onRootLayoutChanged(int heightDiff) {
        Log.d(TAG, "onRootLayoutChanged(heightDiff[" + heightDiff + "])");
    }
}