Use case of SQLite

Example diagram:

Activity_main.xml:

<textview
Android:id= "@+id/t1"
Android:layout_width= "Wrap_content"
android:layout_height= "Wrap_content"
Android:textsize= "20DP"
android:layout_margintop= "10DP"
android:layout_marginleft= "10DP"
android:text= "Name:"/>

<edittext
Android:id= "@+id/text_name"
Android:layout_width= "200DP"
android:layout_height= "Wrap_content"
android:hint= "Input Name"
android:layout_torightof= "@+id/t1"
android:layout_marginleft= "100DP"
android:layout_marginright= "10DP"
/>
<textview
Android:id= "@+id/t2"
Android:layout_width= "Wrap_content"
android:layout_height= "Wrap_content"
android:text= "Password:"
android:layout_margintop= "20DP"
android:layout_marginleft= "10DP"
android:layout_below= "@+id/t1"
Android:textsize= "20DP"/>
<edittext
Android:id= "@+id/text_password"
Android:layout_width= "200DP"
android:layout_height= "Wrap_content"
android:hint= "Input Password"
android:layout_below= "@+id/text_name"
android:layout_torightof= "@id/t2"
android:layout_marginleft= "65DP"
android:layout_marginright= "10DP"
/>
<button
Android:id= "@+id/btn_reg"
Android:layout_width= "128DP"
android:layout_height= "Wrap_content"
android:layout_below= "@+id/t2"
android:layout_margintop= "30DP"
android:text= "Register"

/>

<button
Android:id= "@+id/btn_del"
Android:layout_width= "128DP"
android:layout_height= "Wrap_content"
android:layout_below= "@+id/t2"
android:layout_margintop= "30DP"
android:layout_torightof= "@+id/btn_reg"
android:text= "Delete"

/>
<button
Android:id= "@+id/btn_sel"
Android:layout_width= "128DP"
android:layout_height= "Wrap_content"
android:layout_below= "@+id/t2"
android:layout_margintop= "30DP"
android:layout_torightof= "@id/btn_del"
android:text= "Query"

/>
<linearlayout
Android:id= "@+id/layout"
android:layout_below= "@id/btn_sel"
android:layout_height= "Match_parent"
android:orientation= "Vertical"
Android:layout_width= "Match_parent"
>
</LinearLayout>
</RelativeLayout>

Mainactivity.java:

public class Mainactivity extends appcompatactivity implements view.onclicklistener{
LinearLayout Layout;
EditText Name,password;
Button Bt_reg,bt_del,bt_sel;
List<user> userlist;
Private Mydatabasehelper DBHelper;
@Override
protected void OnCreate (Bundle savedinstancestate) {
Super.oncreate (savedinstancestate);
Setcontentview (R.layout.activity_main);
Initview ();
}
private void Initview () {
layout= (LinearLayout) Findviewbyid (r.id.layout);
Name= (EditText) Findviewbyid (r.id.text_name);
Password= (EditText) Findviewbyid (R.id.text_password);
Bt_reg= (Button) Findviewbyid (R.id.btn_reg);
Bt_del= (Button) Findviewbyid (R.id.btn_del);
Bt_sel= (Button) Findviewbyid (R.id.btn_sel);
Bt_reg.setonclicklistener (this);
Bt_del.setonclicklistener (this);
Bt_sel.setonclicklistener (this);
Userlist=new arraylist<user> ();

}
public void OnClick (view view) {
Switch (View.getid ()) {

Case R.id.btn_reg:
if (Name.gettext (). ToString (). Matches ("[a-za-z]*") && Name.gettext (). ToString (). Length () > 5 && Name.gettext (). ToString (). Length () < && Password.gettext (). ToString (). Matches ("[0-9]*") && Password.gettext (). ToString (). Length () > 2 && password.gettext (). ToString (). Length () < 7) {
DBHelper = new Mydatabasehelper (This, "create_user.db", NULL, 1);
Sqlitedatabase db = Dbhelper.getreadabledatabase ();
Db.execsql ("INSERT into User (Name,password) VALUES (?,?)", New String[]{name.gettext (). toString (), Password.gettext () . toString ()});
Db.close ();
Toast.maketext (Mainactivity.this, "registered successfully", Toast.length_short). Show ();

} else
Toast.maketext (mainactivity.this, "Input not valid", Toast.length_short). Show ();
Break

Case R.id.btn_del:
if (Name.gettext (). ToString (). Length ()! = 0 && Password.gettext (). ToString (). Length ()! = 0) {
User user = null;
DBHelper = new Mydatabasehelper (This, "create_user.db", NULL, 1);
Sqlitedatabase db = Dbhelper.getreadabledatabase ();
cursor cursor = db.rawquery ("SELECT *" + "from user where Name=?", New String[]{name.gettext (). toString ()});
if (Cursor.movetofirst ()) {
int id = cursor.getint (cursor.getcolumnindex ("id"));
String name = cursor.getstring (Cursor.getcolumnindex ("name"));
String password = cursor.getstring (cursor.getcolumnindex ("password"));
user = new User (ID, name, password);
Cursor.close ();

if (User.getpassword (). Equals (Password.gettext (). toString ())) {
Db.execsql ("Delete from user where name=?", New String[]{name.gettext (). toString ()});
Toast.maketext (mainactivity.this, "delete succeeded", Toast.length_short). Show ();

} else
Toast.maketext (mainactivity.this, "Incorrect password", Toast.length_short). Show ();

Db.close ();
}
}
else if (Name.gettext (). ToString (). Length ()! = 0 && Password.gettext (). ToString (). Length () = = 0) {
User user = null;
DBHelper = new Mydatabasehelper (This, "create_user.db", NULL, 1);
Sqlitedatabase db = Dbhelper.getreadabledatabase ();
cursor cursor = db.rawquery ("SELECT *" + "from user where Name=?", New String[]{name.gettext (). toString ()});
if (Cursor.movetofirst ()) {
int id = cursor.getint (cursor.getcolumnindex ("id"));
String name = cursor.getstring (Cursor.getcolumnindex ("name"));
String password = cursor.getstring (cursor.getcolumnindex ("password"));
user = new User (ID, name, password);
Cursor.close ();
if (User.getname (). Equals (Name.gettext (). toString ())) {
Db.execsql ("Delete from user where name=?", New String[]{name.gettext (). toString ()});
Toast.maketext (mainactivity.this, "delete succeeded", Toast.length_short). Show ();

} else
Toast.maketext (mainactivity.this, "user does not exist", toast.length_short). Show ();

Db.close ();
}

}
Break

Case R.id.btn_sel:

Layout.removeallviews ();

if (Name.gettext (). ToString (). Length () = = 0 && password.gettext (). ToString (). Length () = = 0) {
DBHelper = new Mydatabasehelper (This, "create_user.db", NULL, 1);
Sqlitedatabase db = Dbhelper.getreadabledatabase ();
cursor cursor = db.rawquery ("SELECT * from user", null);

if (Cursor.movetofirst ()) {
do {
int id = cursor.getint (cursor.getcolumnindex ("id"));
String name = cursor.getstring (Cursor.getcolumnindex ("name"));
String password = cursor.getstring (cursor.getcolumnindex ("password"));
User user = new user (ID, name, password);
Userlist.add (user);
} while (Cursor.movetonext ());
}
for (User user:userlist) {
TextView TV = new TextView (this);
Tv.settext (User.tostring ());
Tv.settextsize (20);
Layout.addview (TV);
}
Userlist.clear ();
Cursor.close ();
Db.close ();


} else if (Name.gettext (). ToString (). Length ()! = 0 && Password.gettext (). ToString (). Length () = = 0) {

DBHelper = new Mydatabasehelper (This, "create_user.db", NULL, 1);
Sqlitedatabase db = Dbhelper.getreadabledatabase ();
cursor cursor = db.rawquery ("SELECT *" + "from user where Name=?", New String[]{name.gettext (). toString ()});
User user = null;

if (Cursor.movetofirst ()) {
int id = cursor.getint (cursor.getcolumnindex ("id"));
String name = cursor.getstring (Cursor.getcolumnindex ("name"));
String password = cursor.getstring (cursor.getcolumnindex ("password"));
user = new User (ID, name, password);
Cursor.close ();
Db.close ();

TextView TV = new TextView (this);
Tv.settext (User.tostring ());
Tv.settextsize (20);
Layout.addview (TV);
}
}

else if (Name.gettext (). toString (). Length ()!=0) {
Dbhelper=new Mydatabasehelper (This, "create_user.db", null,1);
Sqlitedatabase db=dbhelper.getreadabledatabase ();
Cursor cursor=db.rawquery ("SELECT *" + "from user where Name=?", New String[]{name.gettext (). toString ()});
User User=null;

if (Cursor.movetofirst ()) {
int id = cursor.getint (cursor.getcolumnindex ("id"));
String name = cursor.getstring (Cursor.getcolumnindex ("name"));
String Password =cursor.getstring (cursor.getcolumnindex ("password"));
User=new User (Id,name,password);
Cursor.close ();
Db.close ();

if (User.getpassword (). Equals (Password.gettext (). toString ())) {
TextView TV = new TextView (this);
Tv.settext (User.tostring ());
Tv.settextsize (20);
Layout.addview (TV);
}
else if (Password.gettext (). toString (). Length () ==0) {
Toast.maketext (mainactivity.this, "user does not exist", toast.length_short). Show ();
}

Else
Toast.maketext (mainactivity.this, "Incorrect password", Toast.length_short). Show ();
}}
Break
}}}

   Mydatabasehelper.java 
   
 public class Mydatabasehelper extends Sqliteopenhelper {

  public static final String Create_user = "CREATE TABLE USER ("///creation of tables named Create_user 
 + "ID integer primary key autoincrement," 
 + "Name text NOT NULL," 
 + "password integer not nul L) "; 
 Private Context Mcontext; 
//Four parameters are Context, the database name created, a custom value returned at query time (typically null), the version number of the database 
 Public mydatabasehelper (context context, String nam        E, sqlitedatabase.cursorfactory factory, int version) {
 Super (context, name, factory,version); 
 Mcontext = context; 
} 
 @Override 
 public void onCreate (Sqlitedatabase db) {
 Db.execsql (create_user);//execute this build statement  Toast.maketext (Mcontext, "", Toast.length_short). Show ();//toast is the use of a popup prompt 
} 
 @Override 
 Pu Blic void Onupgrade (sqlitedatabase db,int oldversion,int newversion) {
 Db.execsql ("drop table if exists User"); br> onCreate (DB); 
} 
} 
 
  

User.java

public class User {
    private String name;
    private String password;
    private int id;

    Public User (int id,string name,string password) {
        Super ();
        This.id = ID;
        THIS.name = name;
        This.password = password;
    }
    public void setId (int id) {
        This.id = ID;
    }
    public void SetName (String name) {
        THIS.name = name;
    }
    public void SetPassword (String password) {
        This.password = password;
    }
    public int getId () {
        return ID;
    }
    Public String GetName () {
        return name;
    }
    Public String GetPassword () {
        return password;
    }
    Public String toString () {
        Return "Id:" +this.id+ "    Name:" +this.name+ "    password:" +this.password;
    }
}

Use case of SQLite