Using Android Palette with Glide in Open Event Organizer Android App

Open Event Organizer is an Android Application for the Event Organizers and Entry Managers. The core feature of the App is to scan a QR code from the ticket to validate an attendee’s check in. Other features of the App are to display an overview of sales, ticket management and basic editing in the Event Details. Open Event API Server acts as a backend for this App. The App uses Navigation Drawer for navigation in the App. The side drawer contains menus, event name, event start date and event image in the header. Event name and date is shown just below the event image in a palette. For a better visibility Android Palette is used which extracts prominent colors from images. The App uses Glide to handle image loading hence GlidePalette library is used for palette generation which integrates Android Palette with Glide. I will be talking about the implementation of GlidePalette in the App in this blog.

The App uses Data Binding so the image URLs are directly passed to the XML views in the layouts and the image loading logic is implemented in the BindingAdapter class. The image loading code looks like:

GlideApp
   .with(imageView.getContext())
   .load(Uri.parse(url))
   ...
   .into(imageView);

 

So as to implement palette generation for event detail label, it has to be implemented with the event image loading. GlideApp takes request listener which implements methods on success and failure where palette can be generated using the bitmap loaded. With GlidePalette most of this part is covered in the library itself. It provides GlidePalette class which is a sub class of GlideApp request listener which is passed to the GlideApp using the method listener. In the App, BindingAdapter has a method named bindImageWithPalette which takes a view container, image url, a placeholder drawable and the ids of imageview and palette. The relevant code is:

@BindingAdapter(value = {"paletteImageUrl", "placeholder", "imageId", "paletteId"}, requireAll = false)
public static void bindImageWithPalette(View container, String url, Drawable drawable, int imageId, int paletteId) {
   ImageView imageView = (ImageView) container.findViewById(imageId);
   ViewGroup palette = (ViewGroup) container.findViewById(paletteId);

   if (TextUtils.isEmpty(url)) {
       if (drawable != null)
           imageView.setImageDrawable(drawable);
       palette.setBackgroundColor(container.getResources().getColor(R.color.grey_600));
       for (int i = 0; i < palette.getChildCount(); i++) {
           View child = palette.getChildAt(i);
           if (child instanceof TextView)
               ((TextView) child).setTextColor(Color.WHITE);
       }
       return;
   }
   GlidePalette<Drawable> glidePalette = GlidePalette.with(url)
       .use(GlidePalette.Profile.MUTED)
       .intoBackground(palette)
       .crossfade(true);

   for (int i = 0; i < palette.getChildCount(); i++) {
       View child = palette.getChildAt(i);
       if (child instanceof TextView)
           glidePalette
               .intoTextColor((TextView) child, GlidePalette.Swatch.TITLE_TEXT_COLOR);
   }
   setGlideImage(imageView, url, drawable, null, glidePalette);
}

 

The code is pretty obvious. The method checks passed URL for nullability. If null, it sets the placeholder drawable to the image view and default colors to the text views and the palette. The GlidePalette object is generated using the initializer method with which takes the image URL. The request is passed to the method setGlideImage which loads the image and passes the GlidePalette to the GlideApp as a listener. Accordingly, the palette is generated and the colors are set to the label and text views accordingly. The container view in the XML layout looks like:

<LinearLayout
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:orientation="vertical"
   app:paletteImageUrl="@{ event.largeImageUrl }"
   app:placeholder="@{ @drawable/header }"
   app:imageId="@{ R.id.image }"
   app:paletteId="@{ R.id.eventDetailPalette }">

 

Links:
1. Documentation for Glide Image Loading Library
2. GlidePalette Github Repository
3. Android Palette Official Documentation

Continue Reading

Adding Static Code Analyzers in Open Event Orga Android App

This week, in Open Event Orga App project (Github Repo), we wanted to add some static code analysers that run on each build to ensure that the app code is free of potential bugs and follows a certain style. Codacy handles a few of these things, but it is quirky and sometimes produces false positives. Furthermore, it is not a required check for builds so errors can creep in gradually. We chose checkstyle, PMD and Findbugs for static analysis as they are most popular for Java. The area they work on kind of overlaps but gives security regarding code quality. Findbugs actually analyses the bytecode instead of source code to find possible JVM bugs.

Adding dependencies

The first step was to add the required dependencies. We chose the library android-check as it contained all 3 libraries and was focused on Android and easily configurable. First, we add classpath in project level build.gradle

dependencies {
   classpath 'com.noveogroup.android:check:1.2.4'
}

 

Then, we apply the plugin in app level build.gradle

apply plugin: 'com.noveogroup.android.check'

 

This much is enough to get you started, but by default, the build will not fail if any violations are found. To change this behaviour, we add this block in app level build.gradle

check {
   abortOnError true
}

 

There are many configuration options available for the library. Do check out the project github repo using the link provided above

Configuration

The default configuration is of easy level, and will be enough for most projects, but it is of course configurable. So we took the default hard configs for 3 analysers and disabled properties which we did not need. The place you need to store the config files is the config folder in either root project directory or the app directory. The name of the config file should be checkstyle.xml, pmd.xml and findbugs.xml

These are the default settings and you can obviously configure them by following the instructions on the project repo

Checkstyle

For checkstyle, you can find the easy and hard configuration here

The basic principle is that if you need to add a check, you include a module like this:

<module name="NewlineAtEndOfFile" />

 

If you want to modify the default value of some property, you do it like this:

<module name="RegexpSingleline">
   <property name="format" value="\s+$" />
   <property name="minimum" value="0" />
   <property name="maximum" value="0" />
   <property name="message" value="Line has trailing spaces." />
   <property name="severity" value="info" />
</module>

 

And if you want to remove a check, you can ignore it like this:

<module name="EqualsHashCode">
   <property name="severity" value="ignore" />
</module>

 

It’s pretty straightforward and easy to configure.

Findbugs

For findbugs, you can find the easy and hard configuration here

Findbugs configuration exists in the form of filters where we list resources it should skip analyzing, like:

<Match>
   <Class name="~.*\.BuildConfig" />
</Match>

 

If we want to ignore a particular pattern, we can do so like this:

<!-- No need to force hashCode for simple models -->
<Match>
   <Bug pattern="HE_EQUALS_USE_HASHCODE " />
</Match>

 

Sometimes, you’d want to only ignore a pattern only for certain files or fields. Findbugs supports regex to match such items:

<!-- Don't complain about rules in tests. -->
<Match>
   <Field name="~.*mockitoRule"/>
   <Bug pattern="URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD" />
</Match>

 

You can also annotate your code to suppress warning in the particular class, mehod or field rather than disabling it for the whole project. For that, you need to add findbugs annotations dependency in the project

compile 'com.google.code.findbugs:findbugs-annotations:3.0.1'

 

And then use it like this:

@SuppressFBWarnings(
   value = "ICAST_IDIV_CAST_TO_DOUBLE",
   justification = "We want granularity to be integer")
public void showChart(LineChart lineChart) {
   ...
}

 

It also allows setting the justification of suppressing the rule for clarity

PMD

For findbugs, you can find the easy and hard configuration here

Like checkstyle, you have to first add a rule set to tell PMD which checks to perform:

<rule ref="rulesets/java/android.xml" />

 

If you want to modify the default value of the rule, you can do it like this:

<rule ref="rulesets/java/codesize.xml/TooManyMethods">
   <properties>
       <property name="maxmethods" value="15" />
   </properties>
</rule>

 

Or if you want to entirely exclude a rule, you can do it like this:

<rule ref="rulesets/java/basic.xml">
   <exclude name="OverrideBothEqualsAndHashcode" />
</rule>

 

PMD also supports suppressing warnings in the code itself using annotations. You don’t require any external libraries for it as it supports the in built java.lang.SuppessWarnings annotations. You can use it like this:

@SuppressWarnings("PMD.AvoidInstantiatingObjectsInLoops") // Entries cannot be created outside loop
private LineDataSet setData(Map<String, Long> map, String label) throws ParseException {
   ...
}

 

As you can see, we need to prepend “PMD.” to the rule name so that there are no clashes while annotation processing. Remember to comment the reason for suppressing the warning so that your co-developers know and can remove it in future if criteria does not meet anymore.

There is a lot more to learn about these static analyzers, which you can read upon in their official documentation:

Continue Reading

Migrations make us crazy!

Our Open Event team is not small, so problems with migrations occur very often. I’d like to describe how to solve these common problems and avoid Contributors frustration. Because more of us didn’t know how to solve this problems at the beginning so we wasted a lot of time to find a source of problem.

The most common mistake is that we forget run migration on Heroku. Developer is sometimes surprised because something works for him but he forgets to run migration on server. These small mistakes lead to huge problems and at that time our app throws a lots of bugs related to database. We can often see “Internal server error”.Screen Shot 2016-06-17 at 22.55.25.png So if developer changes table he has to run migration!

[email protected]:/vagrant$ python manage.py db migrate

But above command Quite often doesn’t solve our problem, because We face other problems while updating DB for example

alembic.util.exc.CommandError: Multiple head revisions are present for given argument ‘head’; please specify a specific target revision, ‘<branchname>@head’ to narrow to a specific head, or ‘heads’ for all heads

this problem is caused by two developers which push code to Github with migrations without merging two heads to achieve one head.

So to solve this problem you only have to know ids of two heads

[email protected]:/vagrant$ python manage.py db heads

e38935822969 (head)
f55fde3d62b1 (head)

Then you have to merge it

[email protected]:/vagrant$ python manage.py db merge e38935822969 f55fde3d62b1

Generating /vagrant/migrations/versions/ecb671d1eb4b_.py … done

Upgrade DB

[email protected]:/vagrant$ python manage.py db upgrade

INFO [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO [alembic.runtime.migration] Will assume transactional DDL.
INFO [alembic.runtime.migration] Running upgrade 00ea66754d06 -> d84f976530e1, empty message
INFO [alembic.runtime.migration] Running upgrade d84f976530e1 -> 1b3e4f5f56bd, empty message
INFO [alembic.runtime.migration] Running upgrade 1b3e4f5f56bd -> e38935822969, empty message
INFO [alembic.runtime.migration] Running upgrade e38935822969, f55fde3d62b1 -> ecb671d1eb4b, empty message

And finally run migrations

[email protected]:/vagrant$ python manage.py db migrate
INFO [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO [alembic.runtime.migration] Will assume transactional DDL.
INFO [alembic.ddl.postgresql] Detected sequence named ‘role_id_seq’ as owned by integer column ‘role(id)’, assuming SERIAL and omitting
INFO [alembic.ddl.postgresql] Detected sequence named ‘microlocation_id_seq’ as owned by integer column ‘microlocation(id)’, assuming SERIAL and omitting….

Continue Reading
Close Menu