Android session 2

Android Application
Development Session-2
From Beginner to Advanced
By : Ahesanali Suthar
email:ahesanali.suthar@gmail.com

Topics Covered
1.

Android Framework (Activity,Service,Broadcastreceiver,Content Providers)

2.

Android Layout

3.

Basic UI Widgets (Button,TextBox,Choice Box)

1. Android Framework
●

Android App framework have four basic components which are listed
below
1.
2.

Service.

3.

Broadcast Receiver.

4.
●

Activity.

Content Providers

We will see each component in small detail

1. Android Framework
1.

Activity:
● An Activity is an application component that provides a screen with
which users can interact in order to do something, such as dial the
phone, take a photo, send an email, or view a map
●

Each activity is given a window in which to draw its user interface.
The window typically fills the screen.

●

Activity handle events in short for a windows .NET programer Activity
is a code that is generated when we place button in form and double
click on it and Visual Studio IDE generate button1_click() method or
function.

●

Activity decides which Screen(in android terminology it's call View) to
be diaplayed. We are designing the screen in xml fomrat as we seen
in Hello word case we have main.xml which is view for hello word
activity.

1. Android Framework:
Activity
●

In Activity code we setting up the view we have to write following code.
setContentView(R.layout.main);

●

Please note that we have to just mention R.layout.main not R.layout.
main.xml.
As discussed earlier(First PPT) please note that what ever views we are
creating for screen, we are putting it in res/layout folder.

●

●

There can be more than one activity in the app, and all activity must be
declared in the manifest file as follow.
<activity
android:name =".HelloWorldActivity"
android:label ="@string/app_name" >
<intent-filter >
<action android:name ="android.intent.action.MAIN" />
<category android:name ="android.intent.category.LAUNCHER"
/>
</intent-filter >
</activity>

Activity
●

To declare activity in manifest file only <acivity> and </activity> tag is
enough but please note that in above there is also a <intent-filter> tag and
inside intent-filter there is action and category tag. This is for declaring the
activity which runs first when app is started. So from the category we can
figure out that this is the LAUNCHER activity.

●

We can set only one activity as a launcher activity.

●

To read More About Activity Please read:http://developer.android.
com/guide/components/activities.html

Activity

Service
2. Service:
●

Service is an application components that will run in background and do
not have user-interface.

●

Service is executing in background and provide result to activity so activity
updates the user-interface.

●

To user service in application we must have to register service in the
manifest file like activity.

●

To start service from activity Context.startService() is used.

Broadcast Receiver
3. Broadcast Receiver:
●

Android broadcast event when ever some specified actions like call state is
changed (Incoming,outgoing),New Message,Battery is low etc.

●

So broadcast receiver is the application component which receives these
broadcast.

●

To use broadcast receiver we have to declare it in android.manifest or we
can register/unregister it from activity code.

<uses-permission
<receiver

android:name ="android.permission.READ_PHONE_STATE" />

android:name =".BootReceiver">
<intent-filter >
<action android:name ="android.intent.action.
BOOT_COMPLETED" />
</intent-filter >
</receiver>

Service
●

So when ever phone state is changed from IDLE to RINGING our
broadcast receiver is called and we can handle the event.

●

Normally broadcast receiver have less time for execution so we should not
have to do processing much in broadcast receiver instead we should have
to start serivce and have more processing in service code.

Content Providers
4. Content Providers:
●

Content Providers are used for data operations like storing and retrieving
the data.

●

Content providers manage access to a structured set of data. They
encapsulate the data, and provide mechanisms for defining data security .

●

Content providers are the standard interface that connects data in one
process with code running in another process. In short content provider
are more or less same like class any driver which we are normally using
database connection.

●

To read more about content provider please check link:http://developer.
android.com/guide/topics/providers/content-provider-basics.html

2. Android Layouts
●
●

●
●

A layout defines the visual structure for a user interface, such as the UI for
an activity or app widget. You can declare a layout in two ways:
Declare UI elements in XML. Android provides a straightforward XML
vocabulary that corresponds to the View classes and subclasses, such as
those for widgets and layouts.
Instantiate layout elements at runtime. Your application can create View
and ViewGroup objects (and manipulate their properties) programmatically
Common Layout used in app design
1. Linear Layout
2. Relative Layout
3. List View
4. Grid View

2. Android Layouts
1.

Linear Layout : To create linear layout we need to add below code in
layout xml file.Using linear layout we can put other controls either vertically
or horizontally which we can define by android:orientation attribute.
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:paddingLeft="16dp"
android:paddingRight="16dp"
android:orientation="vertical" ></LinearLayout >

2. Android Layouts
2.Relative Layout : is a view group that
displays child views in relative positions. The
position of each view can be specified as
relative to sibling elements.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.
com/apk/res/android"
android:paddingLeft="16dp"
android:paddingRight="16dp" >
<EditText
android:id="@+id/name"
android:layout_height="wrap_content"
android:hint="@string/reminder" />

<Spinner
android:id="@+id/dates"
android:layout_width="0dp"
android:layout_below="@id/name"
android:layout_alignParentLeft="true"
android:layout_toLeftOf="@+id/times" />
<Spinner
android:id="@id/times"
android:layout_below="@id/name"
android:layout_alignParentRight="true" />
<Button
android:layout_below="@id/times"
android:layout_alignParentRight="true"
android:text="@string/done" />

2. Android Layout
3.Listview : ListView is a view group that displays a list of scrollable items. The
list items are automatically inserted to the list using an Adapter that pulls
content from a source such as an array or database query.
●

Lets take an example of network list displayed where we have to display
custom type of item.

2. Android Layout
Mian Activty Layout screen
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".Network" >
<ListView
android:id="@+id/lvNetworkList"
android:layout_height="match_parent"
android:scrollbars="vertical" >
</ListView>
</RelativeLayout>

2. Android Layout
List View Item Detail Desig
<RelativeLayout xmlns:android="http://schemas.android.
android:layout_height="fill_parent" >
<TextView
android:id="@+id/txtNetworkName"
android:layout_width="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="20dp"
android:layout_marginTop="22dp"
android:text="@string/network_name"
android:textAppearance="?android:attr/textAppearanceLarge"

<TextView
android:id="@+id/txtPortType"
android:layout_alignBaseline="@+id/txtNetworkType"
android:layout_alignBottom="@+id/txtNetworkType"
android:layout_alignParentRight="true"
android:layout_marginRight="22dp"
android:text="@string/port_type"
android:textColor="#AAA"
android:textAppearance="?android:
attr/textAppearanceMedium" />
<TextView
android:id="@+id/txtNetworkDscr"
android:layout_alignLeft="@+id/txtNetworkName"
android:layout_alignRight="@+id/txtPortType"
android:layout_below="@+id/txtNetworkName"
android:text="@string/port_type"
android:textAppearance="?android:attr/textAppearanceSmall"

/>
<TextView
android:id="@+id/txtNetworkType"
android:layout_alignLeft="@+id/txtNetworkName"
android:layout_below="@+id/txtNetworkName"
android:layout_marginTop="21dp"
android:text="@string/network_type"
android:textAppearance="?android:
attr/textAppearanceMedium" />

/>
</RelativeLayout>

2. Android Layout
Atcivity Code for Initialize listview
LayoutInflater inflater = (LayoutInflater)
context
private ListView lvNetworkListCode = (ListView) findViewById(R.id.
lvNetworkList);
public ArrayList<NetworkModel> Networks = new
ArrayList<NetworkModel>();
lvNetworkListCode.setAdapter(adapter);
ItemAdapter adapter = new ItemAdapter(this,R.layout.network_item,
Networks);
●

Here NetworkModel is the model class have attributes of
single item.
●
ItemAdapter class is the important it has getView method
which will iterate on models arraylist and print one byone item.
private final Context context;
private ArrayList<NetworkModel> Ids;
private final int rowResourceId;
public ItemAdapter(Context context, int resource,
ArrayList<NetworkModel> objects) {
super(context, resource, objects);
this.context = context;
this.Ids = objects;
this.rowResourceId = resource;
}

.getSystemService(Context.
LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate
(rowResourceId, parent, false);
txtNwNameCode = (TextView) rowView.
findViewById(R.id.txtNetworkName);
txtNwDscrCode = (TextView) rowView.
findViewById(R.id.txtNetworkDscr);
txtNwTypeCode = (TextView) rowView.findViewById(R.id.
txtNetworkType);
txtPortTypeCode = (TextView) rowView.
findViewById(R.id.txtPortType);
if (Ids.size() > 0) {
// setting values from model
txtNwNameCode.setText(Ids.get
(position).getNetworkName());
txtNwDscrCode.setText(Ids.get
(position).getNetworkDescr());
txtNwTypeCode.setText("N/W Type:
"+Ids.get(position).getNetworkType());
txtPortTypeCode.setText("Port Type:
"+Ids.get(position).getPortType());

@Override
public View getView(int position, View convertView,
ViewGroup parent) {

}
return rowView;

3. Basic UI Widgets
●
●

In section we will see how to add basic UI controls like text-box,label,
button and checkbox.
Lets consider below UI if we wanted to design.

3. Basic UI Widgets
Layout Design
<LinearLayout xmlns:android="http://schemas.android.
android:orientation="vertical" >
<TextView
android:text="@string/enterNameLable" />
<EditText
android:id="@+id/nameTxt"
android:hint="@string/enterNameHint" />
<CheckBox
android:id="@+id/appendHelloCheck"
android:text="@string/appendHello" />
<RadioGroup
android:id="@+id/radioGroup"
android:layout_height="wrap_content">
<RadioButton
android:id="@+id/maleradio"
android:text="@string/maleLbl"/>

<RadioButton
android:id="@+id/femaleradio"
android:text="@string/femaleLbl" />
</RadioGroup>
<Button
android:id="@+id/showDataBtn"
android:text="@string/okBtnTxt" />
<TextView
android:id="@+id/resultText"
android:layout_height="wrap_content" />
<ImageView
android:src="@drawable/maktabah"
android:contentDescription="@+string/Image" />
</LinearLayout>

3. Basic UI Widgets
Activity Code:

OnClickListener showDataClickListener =new OnClickListener() {

public class Tutorial1Activity extends Activity {

@Override
public void onClick(View v) {

private Button showDataBtn;
String userName = userNametxt.getText().
private EditText userNametxt;
private CheckBox appendCheck;
private RadioGroup maleFemaleRadioGroup;
private TextView resultantText;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.screen1);
initViewCOntrols();
}
public void initViewCOntrols()
{
userNametxt = (EditText) findViewById(R.id.nameTxt);
appendCheck = (CheckBox) findViewById(R.id.
appendHelloCheck);
maleFemaleRadioGroup = (RadioGroup) findViewById(R.id.
radioGroup);

toString();
if(userName.length()>0){
RadioButton maleFRadio =
(RadioButton) findViewById(maleFemaleRadioGroup.
getCheckedRadioButtonId());
if(appendCheck.isChecked()){
resultantText.setText("Hello
"+userName+" n You are"+maleFRadio.getText().toString());
}else
{
resultantText.setText
(userName+" n You are"+maleFRadio.getText().toString());
}
}else
{
userNametxt.setError("Please Enter
Name.");
}

showDataBtn = (Button) findViewById(R.id.showDataBtn);
resultantText = (TextView) findViewById(R.id.resultText);

}
};

showDataBtn.setOnClickListener(showDataClickListener);
}

}

Android session 2

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