CODE GLYMPSE

Invoking a Built in Activity

2012-10-27T23:10:00.000-07:00

In addition to the user defined activities, an android application contains a number of built-in activities such as browser, contacts, call_ dallier etc. In this part we are going to see how to call a built-in activity from your own activity. Like the calling of user defined activities a built in activity is also called using the intent object.

We will start with an example, for that create a new android project and named it as BuiltinApp. In this project the main.xml file contain two buttons, first one is for invoking the built-in activity browser and the other one is for dialing a particular number.

The main.xml file for the project is given below.

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

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

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="@string/hello" />

<Button

android:id="@+id/browser"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="Open Browser" />

<Button

android:id="@+id/start_call"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="Make a Call" />

</LinearLayout>

The BuiltinAppActivity.java file is shown bellow.

package com.codeglympse;

import android.app.Activity;

import android.content.Intent;

import android.net.Uri;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

public class BultinAppActivity extends Activity {

Button b1;

Button b2;

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

b1 = (Button) findViewById(R.id.browser);

b2 = (Button) findViewById(R.id.start_call);

b1.setOnClickListener(new OnClickListener()

{

@Override

public void onClick(View arg0)

{

// TODO Auto-generated method stub

Intent i = new Intent(android.content.Intent.ACTION_VIEW,Uri.parse("http://www.google.com"));

startActivity(i);

}

});

b2.setOnClickListener(new OnClickListener()

{

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

Intent i = new Intent(android.content.Intent.ACTION_DIAL,Uri.parse("tel:+571894567"));

startActivity(i);

}

});

}

In the above example we call two built in activities, the browser and dial. Here we also passing a data to the called activity by using the Uri.parse() method. That means here the intent object is an used as an action and data pair object.

Intent i = new Intent(android.content.Intent.ACTION_DIAL,Uri.parse("tel:+571894567"));

Intent i =new Intent(android.content.Intent.ACTION_VIEW,Uri.parse("http://www.google.com"));

For invoking the built in activities like browser, you have set the android permission in the androidmanifest.xml file.The permission is set within the <manifest> </manifest> tag in AndroidManifest.xml file.

AndroidManifest,xml file is given bellow.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.codeglympse"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk android:minSdkVersion="8" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:label="@string/app_name"
android:name=".BultinAppActivity" >
<intent-filter >
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
<uses-permission android:name="android.permission.INTERNET" > </uses-permission>
<uses-permission android:name="android.permission.CALL_PHONE"> </uses-permission>
</manifest>

Output of the project is given bellow.

Passing data to an Activity

2012-10-25T23:39:00.001-07:00

Here we are going to see how to invoke an activity by passing a data to it. Passing of data to an activity is by means of attaching the data to the intent object. The steps you have to follow for invoking an activity by sending a data to it are given bellow.

Step 1:
Create the intent object.

It is the same step that we already see in the start activity and start activity for result.

Example:

Intent i = new Intent("com.codeglympse.SecondActivity");

Step 2:

Create an object of the Bundle class

The Bundle class is the supporting class for passing data to an activity.

Example:

Bundle bundle = new Bundle();

Step 3:

Adding data to bundle object using putString() method

Adding the data to the bumdle object by using the method putString().

Syntax:

bundle_object.putString(key,value);

Here key is used for identifying a specific data from a pair of data. you can get a brief idea about it

from the example provide bellow in this topic.

Example:

bundle.putString("name", "Enter your name");

Step 4:
Attach the Bundle object to the intent by using the method putExtras().
Example:
i.putExtras(bundle);

Step 5:
Now start the activity using either startActivity() or startActivityForResult() method.

Step 6:
In order to receive the data from the intent object the target activity (called activity) must contains the following code segments.

(a) Get back the bundle object using the getIntent() . getExtras();
Example:
Bundle bundle = getIntent().getExtras();
(b) Get the data from the bundle object using getString() method
Example:
String name = bundle.getString("Name"); where "Name" is the key value.

Consider the following example for more details about the concept. Followings are the codes for the android project PassingData.

(1) PassingDataActivity.java

package com.codeglympse;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
public class PassingDataActivity extends Activity {
int request_code =1;
Button bn;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
bn = (Button) findViewById(R.id.button1);
bn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View arg0)
{
Intent i = new Intent("com.codeglympse.DataActivity");
Bundle extras = new Bundle();
extras.putString("name", "Enter your name here");
i.putExtras(extras);
startActivityForResult(i, request_code);
}
});
}
public void onActivityResult(int requestcode, int resultcode, Intent data)
{
if(requestcode==request_code)
{
if(resultcode==RESULT_OK)
{
Toast.makeText(this,data.getData().toString(), Toast.LENGTH_SHORT).show();
}
}
}
}

(2) Code for the called activity (here it is DataActivity.java )

package com.codeglympse;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class DataActivity extends Activity{
Button bn;
EditText txt;
String defaultname;
@Override
protected void onCreate(Bundle savedInstanceState) {

// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.data_activity);
bn = (Button) findViewById(R.id.b2);
txt = (EditText) findViewById(R.id.editText1);
Bundle extras = getIntent().getExtras();
if(extras!=null)
{
defaultname=extras.getString("name");
}
txt.setHint(defaultname);
bn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent data = new Intent();
data.setData(Uri.parse(txt.getText().toString()));
setResult(RESULT_OK, data);
finish();
}
});
}
}

In the above example we use a method setHint ( ), which is same as setText () except that it is used for providing guidelines for the user. (It is appear in diminished text and when the user begin to fill the text area it will disappear)

Here is the output of the project

Invoking An Activity For Result

2012-10-22T02:18:00.001-07:00

An android application contains number of activities. It is essential to establish the communication between these activities. In android an activity call another one by means of an intent filter. The intent filter is a sub tag of the Activity tag in androidmanifest.xml file.

In an android application an activity can be invoked in any of the following ways.

(1) Invoking an activity using the startActivity method and

(2) Invoking an activity for result using the startActivityForResult method

In the first method an activity calls another activity without expecting any result from it. This is achieved by using just the startActivity() method.

In the second method the calling activity expects a result from the called activity by invoking it using the

startActivityForResult() method.

The startActivityForResult method contains two arguments, first one is the intent object and second one is the request_code. The argument request_code is used for identifying the calling activity. The calling activity sends a request_code to the called activity and the called activity returns the result with the same request code. This will help to identify the exact result from the number of activities responding to the calling activity at same time. The request_code is an integer value. If we use -1 for request_code then the startingActivityForResult() will be same as the startActivity()

Syntax for starting an activity for result as follows.

startActivityForResult(new Intent(""), request_code);

E.g

startActivityForResult("com.codeglympse.SecondActivity", request_code );

In order to get the result for the called activity, the calling activity must contain the onActivityResult method.

public void onActivityResult(int request_code, int result_code, Intent data)

{

}

Here three arguments are present. The first one is the request_code used for identifying the exact activity responding to the request, second one is the result_code used for the identifying weather it is RESULT_OK or RESULT_CANCELLED and the final one is the Intent object which contains the attached data from the called activity.
The sending activity sends the result by means of the intent object with the help of setData method.
intent_obj.setData(Uri.parse(passing_data));
The data is returned to the calling activity by using the method setResult. The setResult method contains two arguments RESULT_OK or RESULT_CANCELLED and the data 0bject.
setResult(RESULT_OK, data_obj);

For more details about the startingActivityForResult, consider the following example.

Create a new android project with name ActivityForResult. In this example we call the second activity SecondActivity from the main activity. For that, we place a button in the first activity xml file as shown bellow.

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

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

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="@string/hello" />

<Button

android:id="@+id/button1"

android:layout_width="wrap_content"

ndroid:layout_height="wrap_content"

android:text="GET RESULT" />

</LinearLayout>

Now create a second activity layout second_layout.xml and a SecondActivity.java class. Place a EditText and a submit button in the second_layout.xml as follows.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<EditText
android:id="@+id/editText1"
android:layout_width="match_parent"
android:layout_height="wrap_content" >
<requestFocus />
</EditText>

<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="submit" />
</LinearLayout>

In order to receive the result, the calling activity must contain the method onActivityResult()
public void onActivityResult(int request_code, int resultcode, Intent data)
{

}

The ActivityForResultActivity.java file is shown bellow.

package com.codeglumpse;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class ActivityForResultActivity extends Activity {
Button bn;
int requestcode=1;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
bn = (Button) findViewById(R.id.button1);
bn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
Intent i = new Intent("com.codeglympse.SecondActivity") ;
startActivityForResult(i,requestcode);
}
});
}

public void onActivityResult(int request_code, int resultcode, Intent data)
{
if(request_code==requestcode)
{
if(resultcode==RESULT_OK)
{
Toast.makeText(this, "Welcome "+data.getData().toString(), Toast.LENGTH_SHORT).show();
}
}
}
}

The SecondActivity.java is as follows.
package com.codeglumpse;
import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;

public class SecondActivity extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.second_layout);
Button bn = (Button) findViewById(R.id.submit);
bn.setOnClickListener(new OnClickListener() {

@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
Intent data = new Intent();
EditText tx = (EditText) findViewById(R.id.editText1);
data.setData(Uri.parse(tx.getText().toString()));
setResult(RESULT_OK,data);
finish();
}
});
}
}

Here is the editing done in the AndroidManifest.xml file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.codeglumpse"
android:versionCode="1"
android:versionName="1.0" >

<uses-sdk android:minSdkVersion="8" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:label="@string/app_name"
android:name=".ActivityForResultActivity" >
<intent-filter >
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:label="@string/second"
android:name=".SecondActivity" >
<intent-filter >
<action android:name="com.codeglympse.SecondActivity" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>

Here is the output of the project

Installing Eclipse And Android SDK

2012-10-01T02:49:00.002-07:00

For preparing your computer for android development you need the following software packages.
(1) Java development kit (jdk).
(2) Eclipse IDE
(3) Android Development tool (ADT) for Eclipse
(4) Android software Development Kit (SDK).

Install Java Development Kit:
First you have to download the java development kit. Select the correct version such as OS (Windows, Linux, Solaris, Mac) and type of OS (32 bit or 64 bit). Install the package. You can download the jdk from the following link.
Jdk download

Installing Eclipse IDE:
Eclipse is the recommended IDE for android development. Like jdk you can download it free from the eclipse official website. Select the appropriate version. I recommend Eclipse classic version. You can download Eclipse from the following link.
Eclipse download

After the successful download extract the files into any location. You get a folder named eclipse, open it and double click the icon named "eclipse". Now you get the eclipse IDE main window.
Installing ADT for Eclipse:
Now click the help tab and select "Install New Software" option.

Now go to android developer site and copy the URL for eclipse plugin. You can use the flowing link for getting the eclipse plugin.
Eclipse Plugin
or You can copy it from here "https://dl-ssl.google.com/android/eclipse/". Paste this to the work with option and expand the Developer tools option and tick it.

Now press the next button and continue the installation according to the instructions from the installer window.
Installing Android SDK:

Now we are going to install the the android sdk. For that open the window tab in eclipse ide and choose the Android SDK Manager.

Install all the required packages form the Android SDK Manager window.

Creating the AVD:

Now its time for creating the AVD for testing your android projects. An AVD is nothing but a virtual android phone or tab environment for testing the android apps you created.

For creating an AVD select the window tab and choose the AVD Manager option in eclipse IDE.

Select the new button and you got a new window named Create new Android Virtual Device (AVD).

Provide any appropriate name for your AVD, choose the Target and specifie the SD card memory size and click the Create AVD button. Here i give the name as MyVirtualPhone, choose API level 8 and SD card size 1024 MiB.

Now start the AVD using the start and launch buttons and you will get the following AVD

Inheritance in java

2012-09-26T02:52:00.003-07:00

Inheritance is one of the major object oriented concepts in java, in which the object of one class shows the properties of another class. In other words we can say that inheritance is the relationships between classes. Consider the following example.

Here DRAW_SHAPE is a class, DRAW_CIRCLE and DRAW_ RECTANGLE are another two classes. All we know that Rectangle and Circles are basically coming under the category Shape. That means if we create an object of the class DRAW_ CIRCLE or DRAW_ RECTANGLE it is possible to access all the members of the class SHAPE using that object. Or we can say that SHAPE is the super class or parent class of the two classes DRAW_ RECTANGLE and DRAW SHAPE.

In java the "extends" keyword is used for inheritance. All the child classes extends the parent class. The parent class is also called the super class. The programmatic view of the above example is given bellow.

class DRAW_SHAPE

{

}

class DRAW_CIRCLE extends DRAW_SHAPE

{

}

class DRAW_REACTNGLE extends DRAW_SHAPE

{

}

Consider the following example to know more about inheritance in java

class DrawShape
{
String shape;
DrawShape(String shape)
{
this.shape = shape;
}
public String finishDrawing()
{
return "Drawing of "+shape+" success";
}
}

class DrawCircle extends DrawShape
{
DrawCircle(String shape)
{
super(shape);
}
public String draw()
{
return "Drawing of circle started";
}
}

class DrawRectangle extends DrawShape
{
DrawRectangle(String shape)
{
super(shape);
}
public String draw()
{
return "Drawing of rectangle started";
}
}

public class DrawingDemo
{
public static void main(String args[])
{
DrawCircle circle = new DrawCircle("Circle");
DrawRectangle rectangle = new DrawRectangle("Rectangle");
System.out.println(circle.draw());
System.out.println(rectangle.draw());
System.out.println(circle.finishDrawing());
System.out.println(rectangle.finishDrawing());
}
}

Here is the output of the program:

MULTIPLE ACTIVITY

2012-09-22T02:21:00.000-07:00

Now we are going to discuss about how to handle multiple activities in an android app. I explain it with an example.Open the eclipse IDE and start a new project with name MultipleActivityApp.
Create the layout for second Activity:
Expand the layout folder in res folder and right click the layout folder select other option and select the new Android XML file.

Name the file as second_layout.(It is necessory to name all the XML files in small letters) and click finish. Edit the second_layout.xml as shown bellow.

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

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

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical" >

<TextView

android:id="@+id/textView1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="HELLO FROM SECOND ACTIVITY" />

</LinearLayout>

Create the Activity:

Expand the project folder and expand the folder with name src. Right click the package (here it is com.codeglympse) select new class( if the class option is not found then select the other option and select the class)

Name the class as SecondActivity and click finish.

Now make the SecondActivity.java file extends the Activity class and link the layout and activity class of the second activity using the statement setContentView(R.layout.second_layout). Here the second_layout is the name of the XML file which we have already created. SecondActivity.java file is shown below

package com.codeglympse;

import android.app.Activity;

import android.os.Bundle;

public class SecondActivity extends Activity

{

@Override

protected void onCreate(Bundle savedInstanceState)

{

// TODO Auto-generated method stub

super.onCreate(savedInstanceState);

setContentView(R.layout.second_layout);

}

Add a button with id 'bn' and text 'NEXT ACTIVITY' in the main.xml as shown bellow.

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

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

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

<TextView

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="HELLO FROM MAIN ACTIVITY" />

<Button

android:id="@+id/bn"

android:layout_width="148dp"

android:layout_height="wrap_content"

android:text="NEXT ACTIVITY" />

</LinearLayout>

Now go to the MultipleActivity.java file and create an intent for the new activity in the onClickListener of the button.
Intent in = new Intent(getApplicationContext(),SecondActivity.class);

startActivity(in);

MultipleActivity.java is shown bellow

package com.codeglympse;

import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

public class MultipleActivity extends Activity {

/** Called when the activity is first created. */

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Button bn = (Button) findViewById(R.id.bn);

bn.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View arg0) {

// TODO Auto-generated method stub

Intent in = new Intent(getApplicationContext(),SecondActivity.class);

startActivity(in);

}

});

}

Now open the AndroidManifest.xml and specify the Second Activity name there.

<activity

android:label="@string/app_name"

android:name=".SecondActivity" >

</activity>

The AndroidManifest.xml file is shown below.

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

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

package="com.codeglympse"

android:versionCode="1"

android:versionName="1.0" >

<uses-sdk android:minSdkVersion="8" />

<application

android:icon="@drawable/ic_launcher"

android:label="@string/app_name" >

<activity

android:label="@string/app_name"

android:name=".MultipleActivity" >

<intent-filter >

</intent-filter>

</activity>

<activity

android:label="@string/app_name"

android:name=".SecondActivity" >

</activity>

</application>

</manifest>

Run the application and you got the following output.

Android Versions

2012-09-17T04:16:00.002-07:00

Android available Versions

Introduction To Android

2012-09-17T04:04:00.001-07:00

Every day the mobile phone technologies changes very rapidly. Now the mobiles phones are not only used for the calling purpose, but used for listening music’s, watching movies, surfing the internet etc. Android is the latest mobile operating platform developed from the java. Now android is the most essential component in the smart phone industry. It is the most popular OS for smartphones. The android mobile operating system was developed by the android Inc. founded by Andy Rubin, Rich Miner, Chris White and Nick Sears in 2003. Later in 2005 Android Inc. was acquired by Google. One of the key feature of the Android is it is an open source platform.

Creating the First android app

2012-09-11T03:37:00.003-07:00

The first android app is the "Hello World" app. Following are the steps for creating the first android app. Open eclipse IDE and Click file ---new -----project---Android Project---next .
Here i give the name of the project as FirstApp. Note that every project name must start with capital letters only.

Press next and here i take the target name 2.2

Press next and set Application Name as FirstApp, package name as com.codeglympse(reverse of my blog URL ), tick the Create Activity and name it as StartActivity, select the Minimum sdk Version to 8 and press finish.
Now expand the project folder, then expand the res folder then again expand the layout foler.

Double click the main.xml file and you will get the following form in eclipse.

Now click the main.xml tag at the bottom of the form.

In the bellow code, you have to edit only the code segment shown in bold.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
    <TextView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="HELLO FROM MY FIRST PROJECT" />
</LinearLayout>

Now run the application.
Right click the project folder on project explorer and select run as --- Android application
Output :