7 copy & paste snippets for Android

I listed seven common tasks that Android developers often face, it’s the kind of stuff that interrupts your train of tought and makes you think “Oh God.. this is boring and I have other things to do, let’s google for some code”.
And here it is. In no particular order.
Just copy and paste, no questions asked.

How to rotate a Bitmap in Android

This will rotate any Bitmap to the desired angle, in degrees.

How to copy a file in Android

The smart way, without that nasty new buffer[1024] thing.

How to delete a directory in Android

Yes, the directory itself and all the files and subdirectories recursively.

How to convert a byte array into an hexadecimal String

I will probably google this in the future and find my own post.

How to convert Android dps to pixels

You are welcome.

How to copy a directory in Android

Again yes, the directory itself and all the files and subdirectories recursively.

How to extract a zip archive in Android

This will extract any zip archive to the desired location on the filesystem.


Using BitmapShader in Android

Recently I had to implement some custom UI controls for one of our customers, and some of these controls involved drawing Bitmaps with rounded corners.
Android provides a handy approach to this problem, all the magic can be done with a little help from a class named BitmapShader.

With BitmapShader you can draw bitmaps in any shape and even more, here’s an example:


What BitmapShaderdoes is basically providing a pixel source to a Paint object, when you draw something on a Canvasyou have to specify the Paintinstance that will be used to paint your stuff, if that Paintis bound to a BitmapShader you’ll get your stuff painted using the Bitmap that the BitmapShaderwas created with.

Here’s how to create a BitmapShaderobject:

With the BitmapShaderin place you can now draw anything you want using a Paint which is bound to the shader, the binding can be achieved with the setShader() method of the Paint class:

Now everything is in place and you can start drawing your bitmaps, following is a list of what I did in the example screenshot above and the code I used to achieve each sample, also note that in order to draw on a Canvas I created a custom View subclass and I added the drawing code inside the onDraw() method, in a real scenario however try to avoid allocating stuff inside the onDraw() method.

Rounded corners


Bottom corners rounded


Top corners rounded




Narrow oval


Wide oval



How to get the SHA1 hash sum of a String in Android

Here’s one piece of code that comes very handy in some situations, just copy and paste this to get the SHA1 hash sum from a text String. The Hash is returned as an hex encoded human readable String, see below for an example of use:

Here’s how to use this:

The code above will print this output:

String: Hello World
SHA1 HASH: 0a4d55a8d778e5022fab701977c5d840bbc486d0

Enjoy 😉