Question

In my app, users can tap on image thumbnails to see a full size version. When the thumbnail is tapped a bunch of new views are created in code (i.e. no XML), appended at the end of the view hierarchy and some scaling and rotating transitions happen, then the full size, high res version of the image is displayed. Tapping on the full size image reverses the transitions and removes the new views from the view hierarchy.

I want users to also be able to press the BACK key to reverse the image transitions. However, I can’t seem to catch the KeyEvent. This is what I’m trying at the moment:

        // Set a click listener on the image to reverse everything
        frameView.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View arg0)
            {
                zoomOut(); // This works fine
            }
        });

        // Set the focus onto the frame and then set a key listener to catch the back buttons
        frameView.setFocusable(true);
        frameView.setFocusableInTouchMode(true);
        frameView.requestFocus();
        frameView.setOnKeyListener(new OnKeyListener() {

            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event)
            {
                // The code never even gets here !!!
                if(keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0)
                {
                    zoomOut();
                    return true;
                }
                return false;
            }
        });

EDIT : I’ve had a couple of answers of people providing code snippets to be used within a class that extends Activity. This code I’ve copied above exists in a class that is instantiated in multiple activities; my goal is to have the code that listens for and catches the BACK key event in the one place (like the OnClickListener()) instead of having to have it in every activity (and create long, unwieldy references from each activity to the zoomed object).

Answer 1

@Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
if(keyCode == KeyEvent.KEYCODE_BACK)
{
//Your logic or stuff
return true;
}
else
return super.onKeyUp(keyCode, event);
}

Use the above overide method to handle Back key press event

In these scenario use as below
1) create a activity as below::

/**
 * Top Activity that extends all Activity
 */
package com.com.com;//change your package name

import android.app.Activity;
import android.view.KeyEvent;


public class TopActivity extends Activity {
    protected BaseActivity _activity;


    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        // TODO Auto-generated method stub
        if(keyCode == KeyEvent.KEYCODE_BACK){
            //your stuff if you wanna to have anything
            return true;
        }
        else
            return super.onKeyDown(keyCode, event);
    }
    @Override
    public boolean onKeyUp(int keyCode, KeyEvent event) {
        // TODO Auto-generated method stub
        if(keyCode == KeyEvent.KEYCODE_BACK)
        {
            //your stuff if you wanna to have anything
            return true;
        }
        else
            return super.onKeyUp(keyCode, event);
    }

}

2) Now in your code your every activity extends Acitivity, so change it such that it extend TopActivity like below::

public class YourActivity extends TopActivity {

//Your normal code for each activity…
}

thats it… Try it now