Groovy on Android

Who are you?

def speaker = new SZJUG.Speaker(name: 'Alexey Zhokhov', employer: 'Scentbird', occupation: 'Grails Developer', github: 'donbeave', email: '[email protected]', site: 'http://www.zhokhov.com',description: """whole-stack

engineer(back-end, front-end, mobile, UI/UX)""")

Android on Gradle

Groovy is inside the Gradle

You probably know Groovy through Gradle already.

Groovy is a superset of Java.It contains lots of cool stuff that makes Java fun!

So, Why can Groovy be Android' Swift?

Android N supports Java 8

"Android is in the Java stone age state"

But not released

Multi-faceted language:Object-orientedDynamicFunctionalStatic

Groovy is

Straightforward integration with Java.

Java on Android is very verbose

public class FeedActivity { TextView mTextView; void updateFeed() { new FeedTask().execute("http://path/to/feed"); } class FeedTask extends AsyncTask<String, Void, String> { protected String doInBackground(String... params) { DefaultHttpClient httpclient = new DefaultHttpClient(new BasicHttpParams()); HttpPost httppost = new HttpPost(params[0]); InputStream inputStream = null; String result = null;

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try { HttpResponse response = httpclient.execute(httppost); HttpEntity entity = response.getEntity(); inputStream = entity.getContent(); // json is UTF-8 by default BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8); StringBuilder sb = new StringBuilder(); String line = null; while ((line = reader.readLine()) != null) { sb.append(line).append("\n"); } result = sb.toString(); } catch (Exception e) { // Oops

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} finally { try { if (inputStream != null) { inputStream.close(); } } catch (Exception squish) { } } StringBuilder speakers = null; try { JSONObject jObject = new JSONObject(result); JSONArray jArray = jObject.getJSONArray("speakers"); speakers = new StringBuilder(); for (int i = 0; i < jArray.length(); i++) { speakers.append(jArray.getString(i)); speakers.append(" "); } 3/

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} catch (JSONException e) { // do something? } return speakers.toString(); } @Override protected void onPostExecute(String s) { mTextView.setText(s); } }}

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So now, let’s see the equivalent in Groovy

(no kidding either)

class FeedActivity { TextView mTextView void updateFeed() { Fluent.async { def json = new JsonSlurper().parse([:], new URL('http://path/to/feed'), 'utf-8') json.speakers.join(' ') } then { mTextView.text = it } }}

Because I'm lazy, I don't like to write a lot of code.

And Groovy helps me with that.

It's not only for writing less code,

it's also for cool features and good readability.

very consice language, actually

SemicolonsParenthesisreturn keywordpublic keyword

Optional

Sugar syntax

1) Groovy truth

// if (s != null && s.length() > 0) { ...}

if (s) { ... }// easy check for empty maps, list, empty strings

2) Elvis

def name = person.name ?: "unknown"

3) Save navigation

order?.lineItem?.item?.name

Where I have seen it?

Right, Apple's Swift language was inspired by Groovy

4) List, maps (Groovy)

def shoppingList = ["catfish", "water", "tulips", "blue paint"]shoppingList[1] = "bottle of water" def occupations = [ "Malcolm": "Captain", "Kaylee": "Mechanic",]occupations["Jayne"] = "Public Relations"def emptyMap = [:]def emptyList = []

4) List, maps (Swift)

var shoppingList = ["catfish", "water", "tulips", "blue paint"]shoppingList[1] = "bottle of water" var occupations = [ "Malcolm": "Captain", "Kaylee": "Mechanic",]occupations["Jayne"] = "Public Relations"var emptyMap = [:]var emptyList = []

5) Named parameters (Groovy)

def triangleAndSquare = new TriangleAndSquare(size: 10, name: "another test shape")

5) Named parameters (Swift)

var triangleAndSquare = TriangleAndSquare(size: 10, name: "another test shape")

6) @Lazy annotation (Groovy)

class DataManager { @Lazy importer = new DataImporter()}

6) @Lazy annotation (Swift)

class DataManager { @lazy var importer = DataImporter()}

7) Closure (Groovy)

numbers.collect { int number -> def result = 3 * numbers return result}

7) Closure (Swift)

numbers.map({ (number: Int) -> Int in let result = 3 * number return result})

What else is cool in Groovy?

8) Builders import groovy.json.* def json = new JsonBuilder()json.conference { name 'SZJUG' subject 'Groovy on Android' date 2016 time ['13:00', '16:00'] address { place 'GRAPE 联合创业空间 ' street ' 布吉街道吉华路 247 号下水径商业大厦三层 3/f' district ' 龙岗区 ' city ' 深圳市 ' country ' 中国 ' }}

->{ "conference": { "name": "SZJUG", "subject": "Groovy on Android", "date": 2016, "time": [ "13:00", "16:00" ], "address": { "place": "GRAPE 联合创业空间 ", "street": " 布吉街道吉华路 247 号下水径商业大厦三层 3/f'", "district": " 龙岗区 ", "city": " 深圳市 ", "country": " 中国 " } }} JSON

7) Immutability

@Immutable(copyWith = true)class User { String username, email}

7) Immutability

// Create immutable instance of User.def paul = new User('PaulVI', '[email protected]') // will throw an exception on// paul.email = '[email protected]' def tomasz = mrhaki.copyWith(username: 'Tomasz')

8) String interpolation

def level = "badly" println "I love SZJUG $level"

// JavaTextView view = new TextView(context);view.setText(name);view.setTextSize(16f);view.setTextColor(Color.WHITE);

TextView view = new TextView(context)view.with { text = name textSize = 16f textColor = Color.WHITE}

->

How to read text file from SD card?

def f = new FIle("/sdcard/dir/f.txt")if (f.exists() && f.canRead()) { view.text = f.text}

You have to write a lot of anonymous classes EVERYWHERE// Javabutton.setOnClickListener(new View.OnClickListener() { @Override void onClick(View v) { startActivity(intent); }})

button.onClickListener = { startActivity(intent) }->

No native support for generating classes at runtime

Focus on @CompileStatic

Problems

Generate bytecode, that runs at the same speed as java files

How to start?

Gradle pluginbuildscript { dependencies { classpath 'com.android.tools.build:gradle:1.5.0' classpath 'org.codehaus.groovy:gradle-groovy-android-plugin:0.3.10' }} apply plugin: 'groovyx.grooid.groovy-android' dependencies { compile 'org.codehaus.groovy:groovy:2.4.6:grooid'}

Performance

Groovy jar 4.5 MBApplication size 2 MBProGuard only 1 MB! ~8.2 MB of RAM for @CompileStatic if not - slower and more RAM

Frameworks

SwissKnife http://arasthel.github.io/SwissKnife/

def "should display hello text"() { given: def textView = new TextView(RuntimeEnvironment.application) expect: textView.text == "Hello"}

Familiar with that?

Spockhttp://robospock.org/

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