Enhancing Rotation in Phimp.me using Horizontal Wheel View


To implement rotation of an image in Phimp.me,  we have implemented Horizontal Wheel View feature. It is a custom view for user input that models horizontal wheel controller. How did we include this feature using jitpack.io?

Step 1: 

The jitpack.io repository has to be added to the root build.gradle:

allprojects {
repositories {
maven { url "https://jitpack.io" }

Then, add the dependency to your module build.gradle:

compile 'com.github.shchurov:horizontalwheelview:0.9.5'

Sync the Gradle files to complete the installation.

Step 2: Setting Up the Layout

Horizontal Wheel View has to be added to the XML layout file as shown below:


app:normalColor="@color/black" />


It has to be wrapped inside a Frame Layout to give weight to the view.
To display the angle by which the image has been rotated, a simple text view has to be added just above it.

android:textSize="14sp" />

Step 3: Updating the UI

First, declare and initialise objects of HorizontalWheelView and TextView.

HorizontalWheelView horizontalWheelView = (HorizontalWheelView) findViewById(R.id.horizontalWheelView);
TextView tvAngle= (TextView) findViewById(R.id.tvAngle);


Second, set up listener on the HorizontalWheelView and update the UI accordingly.

horizontalWheelView.setListener(new HorizontalWheelView.Listener() {
public void onRotationChanged(double radians) {

updates the angle and updateImage() updates the image to be rotated. The following functions have been defined below:

private void updateText() {
String text = String.format(Locale.US, "%.0f°", horizontalWheelView.getDegreesAngle());

private void updateImage() {
int angle = (int) horizontalWheelView.getDegreesAngle();
//Code to rotate the image using the variable 'angle'

is a method of ‘rotatePanel’ which is an object of RotateImageView, a custom view to rotate the image.

Let us have a look at some part of the code inside RotateImageView.

private int rotateAngle;

‘rotateAngle’ is a global variable to hold the angle by which image has to be rotated.

public void rotateImage(int angle) {
rotateAngle = angle;

The method invalidate() is used to trigger UI refresh and every time UI is refreshed, the draw() method is called.
We have to override the draw() method and write the main code to rotate the image in it.

The draw() method is defined below:

public void draw(Canvas canvas) {
if (bitmap == null)
maxRect.set(0, 0, getWidth(), getHeight());// The maximum bounding rectangle

scale = 1;
if (wrapRect.width() > getWidth()) {
scale = getWidth() / wrapRect.width();

canvas.scale(scale, scale, canvas.getWidth() >> 1,
canvas.getHeight() >> 1);
canvas.drawRect(wrapRect, bottomPaint);
canvas.rotate(rotateAngle, canvas.getWidth() >> 1,
canvas.getHeight() >> 1);
canvas.drawBitmap(bitmap, srcRect, dstRect, null);

private void calculateWrapBox() {
matrix.reset(); // Reset matrix is ​​a unit matrix
int centerX = getWidth() >> 1;
int centerY = getHeight() >> 1;
matrix.postRotate(rotateAngle, centerX, centerY); // After the rotation angle


And here you go:


Refer to Github- Horizontal Wheel View for more functions and for a sample application.

Automatic Signing and Publishing of Android Apps from Travis

As I discussed about preparing the apps in Play Store for automatic deployment and Google App Signing in previous blogs, in this blog, I’ll talk about how to use Travis Ci to automatically sign and publish the apps using fastlane, as well as how to upload sensitive information like signing keys and publishing JSON to the Open Source repository. This method will be used to publish the following Android Apps:

Current Project Structure

The example project I have used to set up the process has the following structure:

It’s a normal Android Project with some .travis.yml and some additional bash scripts in scripts folder. The update-apk.sh file is standard app build and repo push file found in FOSSASIA projects. The process used to develop it is documented in previous blogs. First, we’ll see how to upload our keys to the repo after encrypting them.

Encrypting keys using Travis

Travis provides a very nice documentation on encrypting files containing sensitive information, but a crucial information is buried below the page. As you’d normally want to upload two things to the repo – the app signing key, and API JSON file for release manager API of Google Play for Fastlane, you can’t do it separately by using standard file encryption command for travis as it will override the previous encrypted file’s secret. In order to do so, you need to create a tarball of all the files that need to be encrypted and encrypt that tar instead. Along with this, before you need to use the file, you’ll have to decrypt in in the travis build and also uncompress it for use.

So, first install Travis CLI tool and login using travis login (You should have right access to the repo and Travis CI in order to encrypt the files for it)

Then add the signing key and fastlane json in the scripts folder. Let’s assume the names of the files are key.jks and fastlane.json

Then, go to scripts folder and run this command to create a tar of these files:

tar cvf secrets.tar fastlane.json key.jks


secrets.tar will be created in the folder. Now, run this command to encrypt the file

travis encrypt-file secrets.tar


A new file secrets.tar.enc will be created in the folder. Now delete the original files and secrets tar so they do not get added to the repo by mistake. The output log will show the the command for decryption of the file to be added to the .travis.yml file.

Decrypting keys using Travis

But if we add it there, the keys will be decrypted for each commit on each branch. We want it to happen only for master branch as we only require publishing from that branch. So, we’ll create a bash script prep-key.sh for the task with following content

set -e


if [ "$TRAVIS_PULL_REQUEST" != "false" -o "$TRAVIS_REPO_SLUG" != "iamareebjamal/android-test-fastlane" -o "$TRAVIS_BRANCH" != "$DEPLOY_BRANCH" ]; then
    echo "We decrypt key only for pushes to the master branch and not PRs. So, skip."
    exit 0

openssl aes-256-cbc -K $encrypted_4dd7_key -iv $encrypted_4dd7_iv -in ./scripts/secrets.tar.enc -out ./scripts/secrets.tar -d
tar xvf ./scripts/secrets.tar -C scripts/


Of course, you’ll have to change the commands and arguments according to your need and repo. Specially, the decryption command keys ID

The script checks if the repo and branch are correct, and the commit is not of a PR, then decrypts the file and extracts them in appropriate directory

Before signing the app, you’ll need to store the keystore password, alias and key password in Travis Environment Variables. Once you have done that, you can proceed to signing the app. I’ll assume the variable names to be $STORE_PASS, $ALIAS and $KEY_PASS respectively

Signing App

Now, come to the part in upload-apk.sh script where you have the unsigned release app built. Let’s assume its name is app-release-unsigned.apk.Then run this command to sign it

cp app-release-unsigned.apk app-release-unaligned.apk
jarsigner -verbose -tsa http://timestamp.comodoca.com/rfc3161 -sigalg SHA1withRSA -digestalg SHA1 -keystore ../scripts/key.jks -storepass $STORE_PASS -keypass $KEY_PASS app-release-unaligned.apk $ALIAS


Then run this command to zipalign the app

${ANDROID_HOME}/build-tools/25.0.2/zipalign -v -p 4 app-release-unaligned.apk app-release.apk


Remember that the build tools version should be the same as the one specified in .travis.yml

This will create an apk named app-release.apk

Publishing App

This is the easiest step. First install fastlane using this command

gem install fastlane


Then run this command to publish the app to alpha channel on Play Store

fastlane supply --apk app-release.apk --track alpha --json_key ../scripts/fastlane.json --package_name com.iamareebjamal.fastlane


You can always configure the arguments according to your need. Also notice that you have to provide the package name for Fastlane to know which app to update. This can also be stored as an environment variable.

This is all for this blog, you can read more about travis CLI, fastlane features and signing process in these links below:

Enabling Google App Signing for Android Project

Signing key management of Android Apps is a hectic procedure and can grow out of hand rather quickly for large organizations with several independent projects. We, at FOSSASIA also had to face similar difficulties in management of individual keys by project maintainers and wanted to gather all these Android Projects under singular key management platform:

To handle the complexities and security aspect of the process, this year Google announced App Signing optional program where Google takes your existing key’s encrypted file and stores it on their servers and asks you to create a new upload key which will be used to sign further updates of the app. It takes the certificates of your new upload key and maps it to the managed private key. Now, whenever there is a new upload of the app, it’s signing certificate is matched with the upload key certificate and after verification, the app is signed by the original private key on the server itself and delivered to the user. The advantage comes where you lose your key, its password or it is compromised. Before App Signing program, if your key got lost, you had to launch your app under a new package name, losing your existing user base. With Google managing your key, if you lose your upload key, then the account owner can request Google to reassign a new upload key as the private key is secure on their servers.

There is no difference in the delivered app from the previous one as it is still finally signed by the original private key as it was before, except that Google also optimizes the app by splitting it into multiple APKs according to hardware, demographic and other factors, resulting in a much smaller app! This blog will take you through the steps in how to enable the program for existing and new apps. A bit of a warning though, for security reasons, opting in the program is permanent and once you do it, it is not possible to back out, so think it through before committing.

For existing apps:

First you need to go to the particular app’s detail section and then into Release Management > App Releases. There you would see the Get Started button for App Signing.

The account owner must first agree to its terms and conditions and once it’s done, a page like this will be presented with information about app signing infrastructure at top.

So, as per the instructions, download the PEPK jar file to encrypt your private key. For this process, you need to have your existing private key and its alias and password. It is fine if you don’t know the key password but store password is needed to generate the encrypted file. Then execute this command in the terminal as written in Step 2 of your Play console:

java -jar pepk.jar –keystore={{keystore_path}} –alias={{alias}} –output={{encrypted_file_output_path}} –encryptionkey=eb10fe8f7c7c9df715022017b00c6471f8ba8170b13049a11e6c09ffe3056a104a3bbe4ac5a955f4ba4fe93fc8cef27558a3eb9d2a529a2092761fb833b656cd48b9de6a

You will have to change the bold text inside curly braces to the correct keystore path, alias and the output file path you want respectively.

Note: The encryption key has been same for me for 3 different Play Store accounts, but might be different for you. So please confirm in Play console first

When you execute the command, it will ask you for the keystore password, and once you enter it, the encrypted file will be generated on the path you specified. You can upload it using the button on console.

After this, you’ll need to generate a new upload key. You can do this using several methods listed here, but for demonstration we’ll be using command line to do so:

keytool -genkey -v -keystore {{keystore_path}} -alias {{alias_name}} -keyalg RSA -keysize 2048 -validity 10000

The command will ask you a couple of questions related to the passwords and signing information and then the key will be generated. This will be your public key and be used for further signing of your apps. So keep it and the password secure and handy (even if it is expendable now).

After this step, you need to create a PEM upload certificate for this key, and in order to do so, execute this command:

keytool -export -rfc -keystore {{keystore_path}} -alias {{alias_name}} -file {{upload_certificate.pem}}

After this is executed, it’ll ask you the keystore password, and once you enter it, the PEM file will be generated and you will have to upload it to the Play console.

If everything goes right, your Play console will look something like this:


Click enrol and you’re done! Now you can go to App Signing section of the Release Management console and see your app signing and new upload key certificates


You can use the SHA1 hash to confirm the keys as to which one corresponds to private and upload if ever in confusion.

For new apps:

For new apps, the process is like a walk in park. You just need to enable the App Signing, and you’ll get an option to continue, opt-out or re-use existing key.


If you re-use existing key, the process is finished then and there and an existing key is deployed as the upload key for this app. But if you choose to Continue, then App Signing will be enabled and Google will use an arbitrary key as private key for the app and the first app you upload will get its key registered as the upload key


This is the screenshot of the App Signing console when there is no first app uploaded and you can see that it still has an app signing certificate of a key which you did not upload or have access to.

If you want to know more about app signing program, check out these links: