Android Basics

Sample Log-in Screen:

User Interface:

                Username and password edit field with login Button.(main.xml)

main.xml

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

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

android:orientation="vertical" android:layout_width="fill_parent"

android:layout_height="fill_parent">

<LinearLayout android:id="@+id/LinearLayout01"

android:layout_height="wrap_content" android:layout_width="fill_parent">

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content" android:id="@+id/UserNameText"

android:text="UserName" android:typeface="sans" android:textStyle="bold"></TextView>

<EditText android:layout_height="wrap_content" android:hint="User Name"

android:layout_width="fill_parent" android:id="@+id/username"></EditText>

</LinearLayout>

<LinearLayout android:id="@+id/LinearLayout02"

android:layout_height="wrap_content" android:layout_width="fill_parent">

<TextView android:layout_width="wrap_content"

android:layout_height="wrap_content" android:id="@+id/PasswordText"

android:text="Password" android:textStyle="bold"></TextView>

<EditText android:layout_height="wrap_content" android:hint="Password"

android:singleLine="true" android:layout_width="fill_parent"

android:id="@+id/password"></EditText>

</LinearLayout>

<Button android:layout_height="wrap_content" android:id="@+id/login"

android:text="Login" android:layout_gravity="center"

android:layout_width="100px"></Button>

</LinearLayout>

Activity:

               On Clicking on login button , displays an dialog with username

LoginActivity.java

package com.login;

import android.app.Activity;

import android.app.AlertDialog;

import android.app.AlertDialog.Builder;

import android.content.Context;

import android.content.DialogInterface;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

public class LoginActivity extends Activity {

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

// Retrieve username and password using id.

EditText userName = null;

EditText password = null;

// Button

Button loginButton = null;

Context context = null;

@Override

public void onCreate(Bundle savedInstanceState) 

{

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

userName = (EditText)findViewById(R.id.username);

password = (EditText)findViewById(R.id.password);

loginButton = (Button)findViewById(R.id.login);

loginButton.setOnClickListener(new Button.OnClickListener() 

{

@Override

public void onClick(View arg0)

{

showDialog();

}

});

}

/**

 * On clicking login button, dialog is displayed with userName

 */

private void showDialog() 

{

Builder alert = new AlertDialog.Builder(this);

alert.setMessage("Welcome "+userName.getText()+"!!!!");

alert.setPositiveButton("OK", new DialogInterface.OnClickListener() {

@Override

public void onClick(DialogInterface arg0, int arg1) {

}

});

alert.show();

}

}

Output:

Simple List View Component:

User Interface:

Composed of single list view component(main.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent">
    <ListView android:id="@+id/ListView01" android:layout_width="fill_parent"
        android:layout_height="fill_parent" android:dividerHeight="1px">
    </ListView>
</LinearLayout>

Activity:

In this activity , we retrieve list view component  and bind the data to the list view using array adapter.

package com.example;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class ListViewActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        String[] tech= {"java", "blackberry","android"};
        setContentView(R.layout.main);
        ListView mylist = (ListView)findViewById(R.id.ListView01);       
        ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1,tech);
        mylist.setAdapter(adapter);
       
    }
}

Output :