Android App and Game Development: Customizing Dialogs –The Easiest Way

Native dialogs in Android are boring! if you are developing an app having some cool and customized theme then doing something about those dull dialogs is a must. They wouldn’t just compliment the overall look of your application. I faced this kinda scenario recently and while experimenting and trying different suggestions on forums, I finally got around it and made it to work!

First things first, as far as my experience went, AlertDialog is not going to help you here. It just don’t get rid of that black background that is there by default (talking about gingerbread dialogs here). No matter what you do, it’ll always show the black background from behind your image (if you have any). Anyways, to create a custom dialog, we need to create a layout first in a separate xml file. Here’s an example:

This is just a simple layout having a background image that has irregular borders. Now we just need to write a few lines of code in order to make it work:

Here, we are setting the background color to transparent in order to get rid of the default dialog background color. After that, we just need to assign the layout resource to the dialog and that gets the job done.

Notice the resultDlg.getWindow().clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND); This will remove the dim effect that makes your parent layout a bit darker. You can also set some additional flags like adding a blurred effect to the background/host activity from which this dialog is invoked. To do this, simply use the addFlags function with FLAG_BLUR_BEHIND flag. Here’s the exact statement:

resultDlg.getWindow().addFlags(WindowManager.LayoutParams.FLAG_BLUR_BEHIND);

This will create a very nice blur effect which I find more neat than the original dim effect. And that ends this post here. Feel free to comment and ask questions, I’ll try to answer them as swiftly as I can.

Android App Development–Posting Status On Twitter Through Twitter4J

Recently, I had to implement Twitter sharing in my new app that I have been working on recently. Upon searching about how to do this, I found out a library called Twitter4J. This library has some decent functions but it’s not that simple to implement as compared to the Facebook SDK which handles all the stuff within and exposes some handlers for post-authentication tasks.

Anyhow, I continued my research about using this library and found out some implementations that launch the browser for authentication and then invoking your application back when the process is complete. From there onwards, things become simple.

I however didn’t like the idea and rolled over my sleeves to code what I had in my mind. Instead of loading the browser, all I did was put a webview in my activity to load the authentication url in it. Upon completing authentication, it is redirected to the callback url that is specified while initializing the twitter object. Checkout the code below:

 

You can specify any custom URL in place of CALLBACKURL (which is defined as a constant in my class). After this, all you have to do is to place a check in your WebViewClient’s onPageStarted method to find out if the authentication is done and the twitter has redirect you back to your callback URL.

Almost done! Now you can use the updateStatus function to update the status on Twitter.

Android Game Programming: The Game Loop

The starting point of any game project is writing a game loop. This is one of the most integral and crucial part of any game, whether small or large. So it must be given due attention and one should choose the most appropriate and optimized way of doing it.

The Android game programming is no exception and there are several ways of managing and writing this game loop. Here I’ll discuss some approaches that I found in SDK samples and other resources (excluding OpenGL part). There are some basic steps to follow before writing these game loops.

The first step is to create your own View or Layout by extending an existing Layout or View (like LinearLayout or SurfaceView). Then override its onDraw method to control the rendering over this surface. The general concept is, that you call some update function that calculates the dynamics of the new frame and then post an invalidate command that ultimately forces the View to draw itself, hence creating a simple basis for drawing and refreshing the objects on this surface.

1. Using TimerTask and Timer

One way of creating this loop is to extend the LinearLayout class and override its onDraw function. Then add a Timer object in the child class. Look at the code chunk below:

You then need to write some functions to start/stop this timer. They should look something like below:

The schedule function of the timer object takes a TimerTask object and the time after which the Timer task is run. Here the UpdateTask is a custom class that extends the TimerTask and overrides its run function.

 

The postInvalidate function forces the View to redraw itself and the update function is a local function that you have to write yourself (you can name it anything) to calculate game’s next frame.

2. Creating a Custom Handler

This scheme is used in the Snake game that comes with the SDK’s samples. In this approach, you create a custom class by extending the Handler class and overriding its handleMessage function. The custom handle should be written inside you game view so that it can access the update and invalidate functions of your view. The child handler class should look like this:

Now you need to create an instance of this class in your game view class and then call its sleep function from your method that you will use to update your game’s frame. In the code snippet above, the sleep method calls some internal message handlers to make sure that the message is sent and handled appropriately. To find out more details about this approach, refer to the Snake game that comes with SDK samples.

3. Using SurfaceView, SurfaceHolder and a Custom Thread

This approach is considered more appropriate if one wants to write a game that is more real-time. Some SDK samples like LunarLander and JetBoy also implement this technique.

This method use the SurfaceView class to create its main game view class. The game view class in turn needs to handle the SurfaceHolder call back and then use it to get the underlying canvas which can be used to carryout the required drawing routines.

All the core game logic is written in the custom thread that uses it’s overridden ‘run’ method to update the game objects and redraw the view. This method contains a while(true) type of loop that repeatedly calls the drawing and updating routines. To draw the game objects, the method uses the SurfaceHolder’s lockCanvas method to get the underlying canvas object and then uses that object to do the drawings.

This approach doesn’t use the view or layout’s onDraw method and hence doesn’t require calling the invalidate method as the other two approaches do. Instead it clears the screen itself by calling the Canvas object’s drawBackground or drawColor routines.

Since there’s no delay or wait time mechanism in this approach, therefore, it allows the system to do the update and draw processing as fast as it possible increasing the refresh time of the game’s frames.

This wraps up the post here. I hope it is helpful for those seeking out to develop games on the Android platform.

Checkerzzz – Gameplay Video

Here’s the ‘teaser trailer’ 😛 or a gameplay video of my first Android game. This all started off with some experimentation with the platform, eventually been developed into a full game having mutliplayer game option (for now) and a working menu system :D. All graphics programming is done using the core graphics functions of the Android SDK.

The first version of this game will be available to download from Android market soon. After that, i will start working on the newer version which would have some additional (hopefully exciting) features. 🙂