Application Development Overview on Android OS

Kanak & Pankaj

Overview/Design Guidelines

• A Mobile Operating System

• Uses a modified version of the Linux kernel

• Allows developers to write code in java language

• Third party application can be built using java and android framework

Android 2.1 & Above

With

Eclipse IDE

Overview/Design GuidelinesWhat's in an App

Starting with the Project

Layouts & Screen Sizes

• FrameLayoutLayout that acts as a view frame to display a single object.

• LinearLayout

A layout that organizes its children into a single horizontal or vertical row. It creates

a scrollbar if the length of the window exceeds the length of the screen.

• RelativeLayout

Enables you to specify the location of child objects relative to each other (child A

to the left of child B) or to the parent (aligned to the top of the parent).

• ListView

Displays a scrolling single column list.

Common Layouts

• ScrollViewA vertically scrolling column of elements. Spinner Displays a single item at a time from a bound list, inside a one-row textbox. Rather like a one-row

• TabHost

It provides a tab selection list that monitors clicks and enables the application to

change the screen whenever a tab is clicked.

• TableLayoutA tabular layout with an arbitrary number of rows and columns, each cell holding the widget of your choice. The rows resize to fit the largest column. The cell borders are not visible.

Layouts & Screen SizesCommon Layouts

Layouts & Screen SizesScreen Sizes

Android runs on a variety of devices that offer different

screen sizes and densities

• xlarge screens are at least 960dp x 720dp• large screens are at least 640dp x 480dp• normal screens are at least 470dp x 320dp• small screens are at least 426dp x 320dp

To support multiple screen size

• Explicitly declare in the manifest which screen sizes your applicationsupports

• Provide different layouts for different screen sizes• Provide different bitmap drawables for different screen densities

Layouts & Screen SizesScreen Sizes

Manifest parameters for Screen sizes

<supports-screens android:resizeable=["true"| "false"]

android:smallScreens=["true" | "false"]

android:normalScreens=["true" | "false"]

android:largeScreens=["true" | "false"]

android:xlargeScreens=["true" | "false"]

android:anyDensity=["true" | "false"]

android:requiresSmallestWidthDp="integer"

android:compatibleWidthLimitDp="integer"

android:largestWidthLimitDp="integer"/>

Challenges faced while building Naukri App

• Installing SDK for different Version of Android

• Choosing right IDE for development

• Using Spinner to choose value from the dropdown on runtime and from set of array

• Calling spinner on clicking ImageView

• Choosing right layout to build XML

• Optimizing layout and making it re-usable

• Saving preferences

• Implementing multiple clicks on single activity

• Calling multiple activity for result on single activity

• Creating complete view on runtime

• Finishing activities correctly

Setting Up an Activity to set background image and music

Background can contain image as well as music. Their time out can be handled

using simple threads in java.

Permissions Required –

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

Setting up the Content View –

protected void onCreate(Bundle savedInstanceState) {

// TODO Auto-generated method stub

super.onCreate(savedInstanceState);

setContentView(R.layout.amazing);

}

Introduction to Media Player and Sound Pool –

MediaPlayer theSong = MediaPlayer.create(this, R.raw.uninvited);

theSong.start();

theSong.release();

Setting Up an Activity to set background image and music

On pause Activity –

@Override

protected void onPause() {

// TODO Auto-generated method stub

super.onPause();

//theSong.stop(); // ---- this is same as Mediaplayer.release() the only differnece is release method releases the other objects related to it and stop method abruptly stops the object

theSong.release();

finish();

}

Creating a LIST/MENU and referencing the selected Item

Extending ListActivity instead of Activity

Setting List –

ArrayAdapter<String> adapter = new ArrayAdapter<String>(MenuApp.this, android.R.layout.simple_list_item_1, classes);

setListAdapter(adapter);

OnListItemClick()

Setting MenuKey –

MenuInflater blowUp = getMenuInflater();

blowUp.inflate(R.menu.cool_menu, menu);

OnOptionsItemSelected()

Setting Up buttons and text views

Button add = (Button) findViewById(R.id.bAdd);

Button sub = (Button) findViewById(R.id.bSub);

TextView display = (TextView) findViewById(R.id.tvDisplay);

Setting onClickListeners() for button clicks –

add.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {

// TODO Auto-generated method stub

counter++;

display.setText("Your Total is: " + counter);

//display.setText(Integer.toString(counter));

}

});

Setting Up buttons and text views

sub.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {

// TODO Auto-generated method stub

counter--;

display.setText("Your total is : " + counter);

}

});

SETTING UP A FORM WITH EDITBOXES AND TOGGLE BUTTON AND

SIMPLE BUTTONS

final ToggleButton passTog = (ToggleButton) findViewById(R.id.tbPassword);

final EditText Name = (EditText) findViewById(R.id.etName);

final EditText MobNum = (EditText) findViewById(R.id.etMobileNumber);

final EditText EmailId = (EditText) findViewById(R.id.etEmailID);

final EditText Password = (EditText) findViewById(R.id.etPassword);

SETTING UP A FORM WITH EDITBOXES AND TOGGLE BUTTON AND SIMPLE BUTTONS

Setting the input type for password field on the basis of toggle button-

passTog.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {

// TODO Auto-generated method stub

if(passTog.isChecked()){

Password.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);

}else{

Password.setInputType(InputType.TYPE_CLASS_TEXT);

}

}

});

SETTING UP A FORM WITH EDITBOXES AND TOGGLE BUTTON AND SIMPLE BUTTONS

Setting Alert Boxes –

new AlertDialog.Builder(TextActs.this)

.setMessage("Please fill in the valid email address, mobile number and password should be minimum 6 characters long")

.setTitle("Validation Error")

.setCancelable(true)

.setNeutralButton(android.R.string.ok,

new DialogInterface.OnClickListener() {

public void onClick(DialogInterface dialog, intwhichButton){}

})

.show();

SENDING AN EMAIL FROM APPLICATION

Permission Required –

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

Setting Up Email intent –

String emailaddress[] = { emailAdd };

String message = “Some MEssage";

Intent emailIntent = new Intent(android.content.Intent.ACTION_SEND);

emailIntent.putExtra(android.content.Intent.EXTRA_EMAIL, emailaddress);

emailIntent.putExtra(android.content.Intent.EXTRA_SUBJECT, "I hate you!");

emailIntent.setType("plain/text");

emailIntent.putExtra(android.content.Intent.EXTRA_TEXT, message);

startActivity(emailIntent);

SAVING PREFERENCES

Preferences in Androids are like cookies on browsers which are saved in

the phone memory and can be accessed any time during the application.

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

<EditTextPreference android:title="Edit Text”android:key="name"

android:summary="Enter your name” />

<CheckBoxPreference android:title="Music” android:defaultValue="true"

android:key="checkbox” android:summary="for the start screen">

</CheckBoxPreference>

<ListPreference android:title="list” android:key="list” android:summary="Choose from” android:entries="@array/list” android:entryValues="@array/lValues"

></ListPreference>

</PreferenceScreen>

Questions/Comments

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