MELJUN CORTES Android sq lite example2

Android SQLite Example by Nikos Maravitsas on May 25th, 2013 | Filed in: SQLiteDatabase

In this example we are going to see how yo interact with an SQLite database with your Android

Application. SQLite is an Open Source Database for structued data in relational databases. It is

embeded in Android, to you don’t have to do anything special to set up or administer an SQLite

server (e.g like in a Linux box). Android offers a really fast and conviniet API to work with SQLite

databases from applications. It uses a wrapper class, SQLiteOpenHelper which offers three basic

API methods to interact with the database:

onCreate(SQLiteDatabase db), called when the database is created for the first time.

onOpen(SQLiteDatabase db), called when the database has been opened.

onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion), called when the

database needs to be upgraded.

to name a few.

For this tutorial, we will use the following tools in a Windows 64-bit platform:

JDK 1.7

Eclipse 4.2 Juno

Android SKD 4.2

1. Create a new Android Project

Open Eclipse IDE and go to File -> New -> Project -> Android -> Android Application Project. You

have to specify the Application Name, the Project Name and the Package name in the appropriate

text fields and then click Next.

In the next window make sure the “Create activity” option is selected in order to create a new activity

for your project, and click Next. This is optional as you can create a new activity after creating the

project, but you can do it all in one step.

Select “BlankActivity” and click Next.

You will be asked to specify some information about the new activity. In the Layout Name text field

you have to specify the name of the file that will contain the layout description of your app. In our

case the file res/layout/main.xml will be created. Then, click Finish.

2. Create the main layout of the Application

Open res/layout/main.xml file :

And paste the following code :

main.xml:

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

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

03 android:layout_width="match_parent"

04 android:layout_height="match_parent"

05 android:orientation="vertical" >

06 <EditText

07 android:id="@+id/editText1"

08 android:layout_width="wrap_content"

09 android:layout_height="wrap_content"

10 android:layout_alignParentLeft="true"

11 android:layout_alignParentTop="true"

12 android:ems="10" >

13

14 <requestFocus />

15 </EditText>

16

17 <Button

18 android:id="@+id/addBtn"

19 android:layout_width="wrap_content"

20 android:layout_height="wrap_content"

21 android:layout_below="@+id/editText1"

22 android:onClick="addUser"

23 android:text="Add New" />

24

25 <Button

26 android:id="@+id/deleteBtn"

27 android:layout_width="wrap_content"

28 android:layout_height="wrap_content"

29 android:layout_toRightOf="@+id/addBtn"

30 android:layout_below="@+id/editText1"

31 android:onClick="deleteFirstUser"

32 android:text="Delete First" />

33

34 <ListView

35 android:id="@android:id/list"

36 android:layout_width="match_parent"

37 android:layout_height="wrap_content"

38 android:layout_alignParentLeft="true"

39 android:layout_below="@+id/deleteBtn" >

40 </ListView>

41

42 </RelativeLayout>

3. Create a custom SQLiteOpenHelper

Now we have to write the code of the application. First we have to create a

custom SQLiteOpenHelper. We have to create a new class for that. Use the Package Explorer to

navigate to the Package of the source files:

Right click on the package com.javacodegeeks.android.androidsqliteexample and go to

New -> Class, fill out the form as in the picture below and press Finish:

Open the source file and paste the following code:

DataBaseWrapper.java:

01 package com.javacodegeeks.android.example.androidsqliteexample;

02

03 import android.content.Context;

04 import android.database.sqlite.SQLiteDatabase;

05 import android.database.sqlite.SQLiteOpenHelper;

06

07 public class DataBaseWrapper extends SQLiteOpenHelper {

08

09 public static final String STUDENTS = "Students";

10 public static final String STUDENT_ID = "_id";

11 public static final String STUDENT_NAME = "_name";

12

13 private static final String DATABASE_NAME = "Students.db";

14 private static final int DATABASE_VERSION = 1;

15

16 // creation SQLite statement

17 private static final String DATABASE_CREATE = "create table " + STUDENTS

18 + "(" + STUDENT_ID + " integer primary key autoincrement, "

19 + STUDENT_NAME + " text not null);";

20

21 public DataBaseWrapper(Context context) {

22 super(context, DATABASE_NAME, null, DATABASE_VERSION);

23 }

24

25 @Override

26 public void onCreate(SQLiteDatabase db) {

27 db.execSQL(DATABASE_CREATE);

28

29 }

30

31 @Override

32 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

33 // you should do some logging in here

34 // ..

35

36 db.execSQL("DROP TABLE IF EXISTS " + STUDENTS);

37 onCreate(db);

38 }

39

40 }

4. Create a Student class.

So this class will represent a Student stored in a database:

Student.java

01 package com.javacodegeeks.android.example.androidsqliteexample;

02

03 public class Student {

04

05 private int id;

06 private String name;

07

08 public long getId() {

09 return id;

10 }

11

12 public void setId(int id) {

13 this.id = id;

14 }

15

16 public String getName() {

17 return this.name;

18 }

19

20 public void setName(String name) {

21 this.name = name;

22 }

23

24 @Override

25 public String toString() {

26 return name;

27 }

28 }

5. Create a StudentOperations class.

Basically this wrapper will describe and implement the specific database operations (e.g. add,

delete) on a Student object.

StudentOperations.java:

01 package com.javacodegeeks.android.example.androidsqliteexample;

02

03 import java.util.ArrayList;

04 import java.util.List;

05

06 import android.content.ContentValues;

07 import android.content.Context;

08 import android.database.Cursor;

09 import android.database.SQLException;

10 import android.database.sqlite.SQLiteDatabase;

11

12 public class StudentOperations {

13

14 // Database fields

15 private DataBaseWrapper dbHelper;

16 private String[] STUDENT_TABLE_COLUMNS = { DataBaseWrapper.STUDENT_ID, DataBaseWrapper.STUDENT_NAME };

17 private SQLiteDatabase database;

18

19 public StudentOperations(Context context) {

20 dbHelper = new DataBaseWrapper(context);

21 }

22

23 public void open() throws SQLException {

24 database = dbHelper.getWritableDatabase();

25 }

26

27 public void close() {

28 dbHelper.close();

29 }

30

31 public Student addStudent(String name) {

32

33 ContentValues values = new ContentValues();

34

35 values.put(DataBaseWrapper.STUDENT_NAME, name);

36

37 long studId = database.insert(DataBaseWrapper.STUDENTS, null, values);

38

39 // now that the student is created return it ...

40 Cursor cursor = database.query(DataBaseWrapper.STUDENTS,

41 STUDENT_TABLE_COLUMNS, DataBaseWrapper.STUDENT_ID + " = "

42 + studId, null, null, null, null);

43

44 cursor.moveToFirst();

45

46 Student newComment = parseStudent(cursor);

47 cursor.close();

48 return newComment;

49 }

50

51 public void deleteStudent(Student comment) {

52 long id = comment.getId();

53 System.out.println("Comment deleted with id: " + id);

54 database.delete(DataBaseWrapper.STUDENTS,

DataBaseWrapper.STUDENT_ID

55 + " = " + id, null);

56 }

57

58 public List getAllStudents() {

59 List students = new ArrayList();

60

61 Cursor cursor = database.query(DataBaseWrapper.STUDENTS,

62 STUDENT_TABLE_COLUMNS, null, null, null, null, null);

63

64 cursor.moveToFirst();

65 while (!cursor.isAfterLast()) {

66 Student student = parseStudent(cursor);

67 students.add(student);

68 cursor.moveToNext();

69 }

70

71 cursor.close();

72 return students;

73 }

74

75 private Student parseStudent(Cursor cursor) {

76 Student student = new Student();

77 student.setId((cursor.getInt(0)));

78 student.setName(cursor.getString(1));

79 return student;

80 }

81 }

6. Code the MainActivity

Open the source file of the main Activity and paste the following code:

MainActivity.java:

01 package com.javacodegeeks.android.example.androidsqliteexample;

02

03 import java.util.List;

04

05 import android.app.ListActivity;

06 import android.os.Bundle;

07 import android.view.View;

08 import android.widget.ArrayAdapter;

09 import android.widget.EditText;

10

11 public class MainActivity extends ListActivity {

12

13 private StudentOperations studentDBoperation;

14

15 @Override

16 public void onCreate(Bundle savedInstanceState) {

17 super.onCreate(savedInstanceState);

18 setContentView(R.layout.main);

19

20 studentDBoperation = new StudentOperations(this);

21 studentDBoperation.open();

22

23 List values = studentDBoperation.getAllStudents();

24

25 // Use the SimpleCursorAdapter to show the

26 // elements in a ListView

27 ArrayAdapter adapter = new ArrayAdapter(this,

28 android.R.layout.simple_list_item_1, values);

29 setListAdapter(adapter);

30 }

31

32 public void addUser(View view) {

33

34 ArrayAdapter adapter = (ArrayAdapter) getListAdapter();

35

36 EditText text = (EditText) findViewById(R.id.editText1);

37 Student stud =

studentDBoperation.addStudent(text.getText().toString());

38

39 adapter.add(stud);

40

41 }

42

43 public void deleteFirstUser(View view) {

44

45 ArrayAdapter adapter = (ArrayAdapter) getListAdapter();

46 Student stud = null;

47

48 if (getListAdapter().getCount() > 0) {

49 stud = (Student) getListAdapter().getItem(0);

50 studentDBoperation.deleteStudent(stud);

51 adapter.remove(stud);

52 }

53

54 }

55

56 @Override

57 protected void onResume() {

58 studentDBoperation.open();

59 super.onResume();

60 }

61

62 @Override

63 protected void onPause() {

64 studentDBoperation.close();

65 super.onPause();

66 }

67

68 }

7. Run the Application

This is the main screen of our Application:

Now, when you want to add some Students:

And if you click Delete First: