android: 2010

Monday 24 May 2010

Custom Adapter

create a class with sub type of BaseAdapter class
it is an abstract class provide the implementation for all the abstract methods.
setAdapter(new classname()) method is used to set the custom adapter to the UI component
layout InFlatter is a class which is used to create the UI programatically.

steps to write the application:

once you create the project in eclipse, go to graphical layout of layout folder:

Now click on Composite, next drag the ListView to the screen, then it looks like this

Now double click on Listview, and control goes to activity_main.xml, we can see the following code:

<ListView

android:id="@+id/listView1"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:layout_alignParentLeft="true"

android:layout_alignParentTop="true"

//you can delete the following below tag

// android:layout_marginLeft="28dp"

// android:layout_marginTop="44dp" >

</ListView>

Advanced UI Components

1. AutoCompleteTextView

Thursday 20 May 2010

Wednesday 19 May 2010

Toast method

Toast is one of the notification method in android which is used to display text on surface for the specified time, once the time limit exceeds automatically it will disappear.

Example program for Toast message:

Go to res folder, click on layout folder, and double click on activity_main.xml file

click on Text Fields icon, select plain text field and drop and drag

double click to go to activity_main.xml file

we will get the following screen shot:

Now write the name of the text file: i.e: "Message":
to write this code, write after <EditText tag, and see the screen shot also

android:hint="Message"

Now click on GraphicalLayout and do the following
click on Text filed icon (ie PersonName ), and drop and drag:

once you draged, create a button icon (display)
To create the Button icon on the surface, click on FormWidgets, choose Button, drag on the surface

double click on button icon to go to activity_main.xml file

Now change the name of Button, and replace with "Display"

Example code:

<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=".MainActivity" >

<TextView

android:id="@+id/textView1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

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

<EditText

android:hint="Message"

android:id="@+id/editText1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignLeft="@+id/textView1"

android:layout_below="@+id/textView1"

android:ems="10" >

</EditText>

<EditText

android:id="@+id/editText2"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignRight="@+id/editText1"

android:layout_below="@+id/editText1"

android:layout_marginRight="26dp"

android:layout_marginTop="34dp"

android:ems="10"

android:inputType="textPersonName" />

<Button

android:id="@+id/button1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_centerVertical="true"

android:layout_toRightOf="@+id/textView1"

android:text="Display" />

</RelativeLayout>

see the following screen shot:

Now we need to access the msg, and if we click display button, it has to display whatever we type in the text field.
go to MainActivity.java of src folder

see the code below:

package com.example.toastdemo1;

import android.os.Bundle;

import android.app.Activity;

import android.view.Menu;

import android.view.View;

import android.view.View.OnClickListener;

import android.widget.Button;

import android.widget.EditText;

import android.widget.Toast;

public class MainActivity extends Activity {

//step 1: create the reference variables for Button, EditText

Button b;

EditText et;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

//step 2: create the objects for Button,

b=(Button)findViewById(R.id.button1);

//step 3: configur the button with xml, add the Listeners events to that button object, and //add packages

b.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

// TODO Auto-generated method stub

//step 5: write the logic for access the text from the text filed

et=(EditText)findViewById(R.id.editText1);

//step 6: read the data from the text field and store into local object String

String msg=et.getText().toString();

//step 7: display in a toast message

Toast.makeText(getApplicationContext(), msg, Toast.LENGTH_LONG).show();

}

});//step 4: write the comment here

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.main, menu);

return true;

}

see the screen shot:

now run the application

Saturday 15 May 2010

simple android application: search contact number and dial

now go to MainActivity.java

package com.example.intenttest;

import android.os.Bundle;

import android.app.Activity;

import android.content.Intent;

import android.view.Menu;

import android.view.View;

public class MainActivity extends Activity {

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

}

public void dial(View v)

{

Intent i=new Intent();

i.setAction(Intent.ACTION_DIAL);

startActivity(i);

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

// Inflate the menu; this adds items to the action bar if it is present.

getMenuInflater().inflate(R.menu.main, menu);

return true;

}

Intents

intents

Intents:

Intents is used to provide communication between activity to activity, activity to service, activity to broad cast receiver.

There are two types of Intents:

1. Explicit intents
2. Implicit intents

Explicit intents:

Defn:
Explicit intents is used to call the user defined activities.

Syntax:
Intent i=new Intent();
i.setComponent(new ComponentName(context, class_name));
startActivity(i);

2 .Implicit Intents:

Implicit Intents is used to call the built in activities.

following methods are used to give additional properties to the Intenet.

setAction()
setData()
putExtras()
getExtras()

Syntax:

Intent i=new Intent();

i.setAction(Intent.ACTION_NAME());

startActivity(i);

simple android application: search contact number and dial

onCreate() method

Operating system calls onCreate() method (in c language, main() is called).

syntax:

public class MainActivity extends android.app.Activity
{
@override
public void onCreate(Bundle savedInstanceState)
{
//call the super class method
super.onCreate(savedInstanceState);
//specify the xml file
setContentView(R.layout.activity_main);
}//end of onCreate()
}

Q: What is Bundle?

Ans: Bundle is a predefined class, it specifies the state of the activity.

Q: What is savedInstanceState?

Ans: It is just varialbe (reference), we can give any name instead of savedInstanceState

Friday 14 May 2010

Creating Activity

Q. What is Activity in android?
Ans:
Activity is a super class, which contains the java code that supports a screen or UI. In other words, building block of the user interface is the activity.
Every application which has UI must inherit it to create window.

Q. Creating the Activity?

Ans: The following steps are involved while we are creating the Activity
step1: while we are creating the Activity class(our own user defined class) must be a sub class of Activity class.
Ex:

public class MainActivity extends android.app.Activity
{
}

Step 2: provide the implementation for the onCreate() method
syntax:
public class MainActivity extends android.app.Activity
{
@override
public void onCreate(Bundle savedInstanceState)
{
//call the super class method
super.onCreate(savedInstanceState);
//specify the xml file
setContentView(R.layout.activity_main);
}//end of onCreate()
}

Q. why should we extend the super class Activity?
Ans: to manage the Life cycle of activity.

Q. What are the Activity Life Cycle?
Ans:

It has 4 states:
1. Does not exist state
2. ForeGround state
3. Background state
4.Activity pause

Q; What are the methods are available in Activity class?

Ans:

onCreate() method
onStart()
onPause()
onResume()
onRestart()
onStop()
onDestroy()

Q: What are the 4 states of activity class

Introduction

What is android and its advantages

What is Android Platform ?

History of Android ?

What is Open Handset Alliance(OHA)

What is Open Source Project?

onCreate() method

Difference between assets folder and drawable folder to access images

Resource files under "res" folder automatically creates an unique hexadecimal index value into R.java file to access java programs.
Whereas access folder images or any file we can not access through R.java.

Note:

Assets folder in real time, we are using in Integration like android with JQuery, android with DOJO integration.

Sunday 9 May 2010

Galleries

Steps to write the Galleries

go to File->New->Android Application Project

Give the Application Name: (you can give any name) Ex:

click on Next button, then the we will get following:

copy the jpg or gif files (photos) and paste into "drawable-hdpi of res folder

Once you pasted into the drawable-hdpi folder, automatically, jpg (or picture) integer varaibles will be created into the R.java file, its reference also will be created in the form of hexa decimal format.
Go to "res" folder of left side, and choose "layout " , double click on "activity_mail.xml" file

Go to Layouts, select LinearLayout(Horizontal) (since i want to scroll my images Horizontally), and drag into the box:

Automatically generates the xml tags, Now you can see the xml tags by double clicking "activity_main.xml" file

Now we need to create the Gallery tags, to do that one, click on GraphicalLayout, click on Images & Media option from the list

now we can see the code, by double clicking activity_main.xml

Now we need to access the images so to do this one we need to create the derived class of BaseAdapter class,
Now im creating a child class of BaseAdapter class

extend the BaseAdapter class, and import that package
Now create the Integer class array in MyAdapter.java, and store the images in that array;

package com.example.gallerydemos;

import android.widget.BaseAdapter;

public class MyAdapter public class MyAdapter extends BaseAdapter

{

Integer myimages[]={R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d,R.drawable.e,R.drawable.f};

}

Now create Context class reference

package com.example.gallerydemos;

import android.widget.BaseAdapter;

import android.content.Context;

public class MyAdapter extends BaseAdapter

{

Integer myimages[]={R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d,R.drawable.e,R.drawable.f};

Context con;

}

Now we will get error derived class, so we need to right click the mouse at that class, choose "add unimplemented methods"

Now we will get the followng window

create parameterized constructor:

package com.example.gallerydemos;

import android.content.Context;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

public class MyAdapter extends BaseAdapter{

Integer myimages[]={R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d,R.drawable.e,R.drawable.f};

Context con;

//Now create a parameterized constructor

public MyAdapter(Context con)

{

super();//call the super class constructor (BaseAdapter)

this.con=con;

}

@Override

public int getCount() {

// TODO Auto-generated method stub

return 0;

}

@Override

public Object getItem(int arg0) {

// TODO Auto-generated method stub

return null;

}

@Override

public long getItemId(int arg0) {

// TODO Auto-generated method stub

return 0;

}

@Override

public View getView(int arg0, View arg1, ViewGroup arg2) {

// TODO Auto-generated method stub

return null;

}

Rewrite the methods like below:

package com.example.gallerydemos;

import android.content.Context;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.ImageView;

public class MyAdapter extends BaseAdapter{

Integer myimages[]={R.drawable.a,R.drawable.b,R.drawable.c,R.drawable.d,R.drawable.e,R.drawable.f};

Context con;

//Now create a parameterized constructor

public MyAdapter(Context con)

{

super();//super class constructor

this.con=con;

}

@Override

public int getCount() {

// TODO Auto-generated method stub

return myimages.length;//total images

}

@Override

public Object getItem(int arg0) {

// TODO Auto-generated method stub

return myimages;

}

@Override

public long getItemId(int arg0) {

// TODO Auto-generated method stub

return arg0;

}

@Override

public View getView(int arg0, View arg1, ViewGroup arg2) {

// TODO Auto-generated method stub

//create ImageView object

ImageView iv=new ImageView(con);

//to display images

iv.setImageResource(myimages[arg0]);

//to give the space between the images

iv.setPadding(52, 0, 52, 0);

//return the imageview object iv

return iv;

}

screen shot is like below:

Now we need to create the Gallery class object in MainActivity.java

Now create the MyAdapter class object (derived class of BaseAdapter) and pass the current class (MainActivity) to MyAdapter class: code looks like the below:

package com.example.gallerydemos;

import android.os.Bundle;

import android.app.Activity;

import android.view.Menu;

import android.widget.Gallery;

public class MainActivity extends Activity {

//creating the reference variable for Gallery

Gallery gal;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);