Tech Talk: App Functionality (Android)

Tech TalkApp Functionality

Grooming session of EATL-Prothom Alo Apps Contest 2015

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0

International License.

“ First, solve the problem. Then, write the code. ” - John Johnson

Hello!I am S MAHBUB UZ ZAMANYou can me at mahbub.ninja

Application Fundamentals

Android apps are written in the Java programming language

“

ActivityAn activity represents a single screen with a user interface.

ServiceA service is a component that runs in the background to perform long-running operations or to perform work for remote processes. A service does not provide a user interface.

Content providerEnable applications to share data

Broadcast receiverA Broadcast receiver is a component that responds to system-wide Broadcast announcements.

◦ play music◦ fetch data over network

Database CP

APP 1

APP 2

APP 3

◦ screen has turned off◦ the battery is low◦ a picture was captured◦ Apps can also initiate broadcasts

Activity

Activity Life Cycle

◦ sleep◦ home button◦ back button◦ multitask button

◦ onResume()◦ onPause()

@Override

public void onBackPressed() { … }

@Override

public void onSaveInstanceState(Bundle savedInstanceState) { … }

@Override

public void onRestoreInstanceState(Bundle savedInstanceState) { … }

savedInstanceState.putString("NAME_KEY", "Name");

savedInstanceState.getString("NAME_KEY")

Other Important Methods

Service

Started or Unbounded Service

This service is called by an app component and run in the background even if the caller component is destroyed.

Bounded Service

This service is called by an app component, runs in the background and it offers communication or interaction between the service and the component that launched it. But this type of service is destroyed when all the components that are bound to it are closed

Types Of Service

Broadcast Receiver Broadcast Intents are used to notify applications of system or application events,

public class SMSReceiver extends BroadcastReceiver{ @Override public void onReceive(Context context, Intent intent)

{ Bundle bundle = intent.getExtras(); SmsMessage[] msgs = null; String str = ""; if (bundle != null) { Object[] pdus = (Object[]) bundle.get("pdus"); msgs = new SmsMessage[pdus.length]; for (int i=0; i<msgs.length; i++){ msgs[i] = SmsMessage.createFromPdu((byte[])pdus[i]); str += "SMS from " + msgs[i].getOriginatingAddress(); str += " :"; str += msgs[i].getMessageBody().toString(); str += "\n"; } Toast.makeText(context, str, Toast.LENGTH_SHORT).show();

Intent mainActivityIntent = new Intent(context, MainActivity.class); mainActivityIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); context.startActivity(mainActivityIntent); Intent broadcastIntent = new Intent(); broadcastIntent.setAction("SMS_RECEIVED_ACTION"); broadcastIntent.putExtra("sms", str); context.sendBroadcast(broadcastIntent); } }}

<receiver android:name=".SMSReceiver">

<intent-filter>

<action android:name="android.provider.Telephony.SMS_RECEIVED" />

</intent-filter>

</receiver>

IntentFilter intentFilter;

private BroadcastReceiver intentReceiver = new BroadcastReceiver() {

@Override

public void onReceive(Context context, Intent intent) {

TextView SMSes = (TextView) findViewById(R.id.tv);

SMSes.setText(intent.getExtras().getString("sms"));

}

};

intentFilter = new IntentFilter();

intentFilter.addAction("SMS_RECEIVED_ACTION");

registerReceiver(intentReceiver, intentFilter);

Async Task

.

Async Task

◦ AsyncTask enables proper and easy use of the UI thread. This class allows

to perform background operations and publish results on the UI thread

◦ An asynchronous task is defined by 3 generic types, called Params,

Progress and Result

◦ and 4 steps, called onPreExecute, doInBackground, onProgressUpdate and

onPostExecute.

new DownloadFilesTask().execute(url1, url2, url3);

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {

protected Long doInBackground(URL... urls) {

int count = urls.length;

long totalSize = 0;

for (int i = 0; i < count; i++) {

totalSize += Downloader.downloadFile(urls[i]);

publishProgress((int) ((i / (float) count) * 100));

// Escape early if cancel() is called

if (isCancelled()) break;

}

return totalSize;

}

protected void onProgressUpdate(Integer... progress) {

setProgressPercent(progress[0]);

}

protected void onPostExecute(Long result) {

showDialog("Downloaded " + result + " bytes");

}

}

Sample Code

The three types used by an asynchronous task are the following:

1. Params, the type of the parameters sent to the task upon execution.

2. Progress, the type of the progress units published during the background computation.

3. Result, the type of the result of the background computation.

Not all types are always used by an asynchronous task. To mark a type as unused, simply use the type Void:

AsyncTask's generic types

private class MyTask extends AsyncTask<Void, Void, Void> {}

When an asynchronous task is executed, the task goes through 4 steps:

1. onPreExecute(), invoked on the UI thread before the task is executed. This step is normally used to setup the task, for instance by showing a progress bar in the user interface.

2. doInBackground(Params...), invoked on the background thread immediately after onPreExecute() finishes executing. This step is used to perform background computation that can take a long time. The parameters of the asynchronous task are passed to this step. The result of the computation must be returned by this step and will be passed back to the last step. This step can also use publishProgress(Progress...) to publish one or more units of progress. These values are published on the UI thread, in the onProgressUpdate(Progress...) step.

3. onProgressUpdate(Progress...), invoked on the UI thread after a call to publishProgress(Progress...). The timing of the execution is undefined. This method is used to display any form of progress in the user interface while the background computation is still executing. For instance, it can be used to animate a progress bar or show logs in a text field.

4. onPostExecute(Result), invoked on the UI thread after the background computation finishes. The result of the background computation is passed to this step as a parameter.

The 4 steps

service or a thread?

Service

A service is simply a component that can run in the background even when the user is not interacting with your application. Thus, you should create a service only if that is what you need

Thread

If you need to perform work outside your main thread, but only while the user is interacting with your application, then you should probably instead create a new thread and not a service

SQLite Database

static String DATABSE_NAME = "AVASDB";String TABLE_NAME = "AVAS_BRAIN";static int DATABASE_VERSION_NO = 1;public static SQLiteDatabase db;

public MyAI(Context context) { super(context, DATABSE_NAME, null, DATABASE_VERSION_NO);

}

@Overridepublic void onCreate(SQLiteDatabase db) { String q = "CREATE TABLE " + TABLE_NAME

+ " (id INTEGER PRIMARY KEY AUTOINCREMENT, Name VARCHAR(255));";

db.execSQL(q);}

@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); onCreate(db);

}

SQLiteOpenHelper

public void addRecord(String name) { db = this.getWritableDatabase(); ContentValues values = new ContentValues(); values.put("Name", name); db.insert(TABLE_NAME, null, values); db.close();

}

public List<String> getRecord() { List<String> recordList = new ArrayList<String>(); try { String selectRecord = "SELECT * from " + TABLE_NAME;

SQLiteDatabase db = this.getWritableDatabase(); Cursor cursor = db.rawQuery(selectRecord, null);

if (cursor.moveToFirst()) { do { recordList.add(cursor.getString(1)); } while (cursor.moveToNext()); } cursor.close(); db.close(); } catch (Exception e) { e.printStackTrace(); } return recordList;

}

MyAI db = new MyAI(getApplicationContext());

db.addRecord("A");db.addRecord("B");db.addRecord("C");

Log.v("TAG", db.getRecord().toString());

Activity

http://sqlitebrowser.org

Google Map

◦ Add Marker◦ Mark Path◦ Shortest Path

Better User Experience

https://code.google.com/apis/console

Steps

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

<uses-permission android:name="android.permission.INTERNET" />

<uses-permission android:name="com.google.android.providers.gsf.permission.READ_GSERVICES" />

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

<!-- Required to show current location -->

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

<!-- Required OpenGL ES 2.0. for Maps V2 -->

<uses-feature

android:glEsVersion="0x00020000"

android:required="true" />

<meta-data

android:name="com.google.android.maps.v2.API_KEY"

android:value="******************" />

Manifest FIle

layout file

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

android:layout_width="fill_parent"

android:layout_height="fill_parent" >

<fragment

android:id="@+id/map"

android:name="com.google.android.gms.maps.MapFragment"

android:layout_width="match_parent"

android:layout_height="match_parent"/>

</RelativeLayout>

public class MainActivity extends Activity { private GoogleMap googleMap; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); try { initilizeMap(); } catch (Exception e) { e.printStackTrace(); } } private void initilizeMap() { if (googleMap == null) { googleMap = ((MapFragment) getFragmentManager().findFragmentById( R.id.map)).getMap(); // check if map is created successfully or not if (googleMap == null) { Toast.makeText(getApplicationContext(), "Sorry! unable to create maps", Toast.LENGTH_SHORT) .show(); } } } @Override protected void onResume() { super.onResume(); initilizeMap(); }}

// latitude and longitude

double latitude = 23.7000;

double longitude = 90.3667;

// create marker

MarkerOptions marker = new MarkerOptions().position(new LatLng(latitude, longitude)).title("Dhaka");

// adding marker

googleMap.addMarker(marker);

Add Marker

Recycler View

LinearLayoutManager llm = new LinearLayoutManager(this);rv.setLayoutManager(llm);rv.setHasFixedSize(true);

GridLayoutManager gridLayoutManager = new GridLayoutManager( this,2);rv.setLayoutManager(gridLayoutManager);rv.setHasFixedSize( true);

android.support.v7.widget.RecyclerView

android.support.v7.widget.CardView

Recylcer View Features

Android and Arduino

http://developer.android.com/tools/adk/adk.htmlhttps://play.google.com/store/apps/details?id=com.google.android.apps.adk2

ANDROID M Developer Preview

1. Permissions

2. Power Improvements (two times longer in standby)

3. USB Type-C will also be supported on Android

Thanks!

ANY QUESTIONS?

◦ http://developer.android.com/guide/components/fundamentals.html◦ http://developer.android.com/reference/android/os/AsyncTask.html◦ http://developer.android.com/guide/components/services.html◦ https://events.google.com/io2015/◦ http://www.androidhive.info/2013/08/android-working-with-google-maps-v2/◦ http://code.tutsplus.com/tutorials/getting-started-with-recyclerview-and-

cardview-on-android--cms-23465

Resources