Android overview

AndroidAndroidFramework and Application Framework and Application

OverviewOverview

By: Ashish AgrawalBy: Ashish Agrawal

12/04/23Android Overview 1

AgendaMobile Application Development (MAD)

Introduction to Android platform

Platform architecture

Application building blocks

Lets Debug

Development tools.


Introduction to AndroidOpen software platform for mobile development

A complete stack – OS, Middleware, Applications

Powered by Linux operating system

Fast application development in Java

Open source under the Apache 2 license



Application Framework


• API interface

• Activity manager – manages application life cycle.

Applications


• Built in and user apps

• Can replace built in apps

Application LifecycleApplication run in their own processes (VM, PID)

Processes are started and stopped as needed to run an application's components

Processes may be killed to reclaim resources


Application Building BlocksActivity

Fragments

Intents

Service (Working in the background)

Content Providers

Broadcast receivers

Action bar


ActivitiesTypically correspond to one UI screen

Run in the process of the .APK which installed them

But, they can:Be facelessBe in a floating windowReturn a value



Fragments


Fragment represents a behavior or a portion of user interface in an Activity. You can combine multiple fragments in a single activity to build a multi-pane UI and reuse a fragment in multiple activities.

Fragments


Intents An intent is an abstract description of an operation to be

performed.

Launch an activity

Explicit

Ex: Intent intent = new Intent(MyActivity.this, MyOtherActivity.class)

Implicit : Android selects the best

Ex: Intent intent = new Intent(Intent.ACTION_DIAL, Uri.parse(“tel:

555-2368”));

startActivity()

Extra parameter Ex: intent.putExtra(name, property);


Intent FilterRegister Activities, Services, and Broadcast

Receivers as being capable of performing an action on a particular kind of data.

Components that respond to broadcast ‘Intents’

Way to respond to external notification or alarms

Apps can invent and broadcast their own Intent


ServicesFaceless components that run in the background

No GUI, higher priority than inactive Activities

Usage: responding to events, polling for data, updating Content Providers. However, all in the main thread

E.g. music player, network download etc…

Intent service = new Intent(context, WordService.class);

context.startService(service);12/04/23Android Overview 15

Using the Service

Start the service

Intent serviceIntent = new Intent();

serviceIntent.setAction

("com.wissen.testApp.service.MY_SERVICE");

startService(serviceIntent);


Bind the serviceServiceConnection conn = new ServiceConnection() {

@Overridepublic void onServiceConnected(ComponentName

name, IBinder service) { }

@Overridepublic void onServiceDisconnected(ComponentName

arg0) {}

}bindService(new Intent("com.testApp.service.MY_SERVICE"), conn, Context.BIND_AUTO_CREATE);}


Async Task

Asycn task enables easy and proper use of UI thread. This class allows to perform background operations and publish results on the main thread.


Async Task (Example) 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)); } return totalSize; }

protected void onProgressUpdate(Integer... progress) { setProgressPercent(progress[0]); }

protected void onPostExecute(Long result) { showDialog("Downloaded " + result + " bytes"); } }


ContentProvidersEnables sharing of data across applications

E.g. address book, photo gallery

Provides uniform APIs for:queryingdelete, update and insert.

Content is represented by URI and MIME type


Example private void displayRecords() { String columns[] = new String[] { People.NAME, People.NUMBER }; Uri mContacts = People.CONTENT_URI; Cursor cur = managedQuery(mContacts, columns, null, null, null ); if (cur.moveToFirst()) { String name = null; String phoneNo = null; do { name = cur.getString(cur.getColumnIndex(People.NAME)); phoneNo = cur.getString(cur.getColumnIndex(People.NUMBER));} while (cur.moveToNext()); } }


Broadcast ReceiversA broadcast receiver is a class which extends

BroadcastReceiver and which is registered as a receiver in an Android Application via the AndroidManifest.xml file(or via code).

<receiver android:name="MyPhoneReceiver"> <intent-filter> <action android:name="android.intent.action.PHONE_STATE"> </action> </intent-filter> </receiver>


Broadcast Receiverspublic class MyBroadcastReceiver extends BroadcastReceiver

{ @Override public void onReceive(Context context, Intent intent) { Toast.makeText(context,

”BR.”,Toast.LENGTH_LONG).show(); } }


ActionBar


ActionBarHome Icon area: The icon on the top left-hand side of the

action bar is sometimes called the “Home” icon. Title area: The Title area displays the title for the action

bar.Tabs area: The Tabs area is where the action bar paints

the list of tabs specified. The content of this area is variable.

Action Icon area: Following the Tabs area, the Action Icon area shows some of the option menu items as icons.

Menu Icon area: The last area is the Menu area. It is a single standard menu icon.


Debugging

•Reading and Writing Logs

Log.d("MyActivity”, position);

•adb logcat

• Toast :

Toast toast = Toast.makeText(context, text, duration);

toast.show();

Eclipse

developer.android.com


Debugging Cont.

•Hierarchy Viewer•Connect your device or launch an emulator.•If you have not done so already, install the application you want to work with.•Run the application, and ensure that its UI is visible.•From a terminal, launch hierarchyviewer


Debugging Cont.


adb shell dumpsys activity

Debugging Cont.


Profiling for memory

Development Tools

Eclipse

developer.android.com


Thank You.


Technology

Android overview