Software Development Exam > Software Development Videos > Android Application Development (Mobile App) > Android Application Development Tutorial - 120 - Reading SQLite Database with Cursor
Android Application Development Tutorial - 120 - Reading SQLite Database with Cursor Video Lecture | Android Application Development (Mobile App) - Software Development
FAQs on Android Application Development Tutorial - 120 - Reading SQLite Database with Cursor Video Lecture - Android Application Development (Mobile App) - Software Development
| 1. What is SQLite database in Android application development? |  |
Ans. SQLite is a lightweight, self-contained, and open-source relational database management system that is embedded within an Android application. It allows developers to store and manage structured data locally on the device.
| 2. How can I read data from an SQLite database in Android using a Cursor? | |
Ans. To read data from an SQLite database in Android, you can use the Cursor class. First, you need to create an instance of the SQLiteDatabase class and query the database using the query() method. This will return a Cursor object that you can use to navigate through the result set and retrieve the data.
| 3. What is a Cursor in Android SQLite database? | |
Ans. In Android SQLite database, a Cursor is an interface that provides access to the result set returned by a database query. It allows you to navigate through the rows of the result set and retrieve the values of each column. Cursors are commonly used to read data from SQLite databases in Android applications.
| 4. Can I perform CRUD operations (Create, Read, Update, Delete) using a Cursor in Android SQLite database? | |
Ans. While a Cursor provides read-only access to the result set of a database query, you can still perform CRUD operations using other methods and classes provided by the SQLiteDatabase class. The Cursor is mainly used for retrieving data from the database, but you can use other methods like insert(), update(), and delete() to modify the data.
| 5. Are there any performance considerations when reading data from an SQLite database in Android? | |
Ans. Yes, there are performance considerations when reading data from an SQLite database in Android. It is recommended to avoid unnecessary queries and use proper indexing on frequently accessed columns to improve query performance. Additionally, you should close the Cursor after you have finished using it to release system resources and avoid memory leaks.
Text Transcript from Video
what's up guys welcome to your hundred
and twentieth androids toil for the new
boss in we're going to do in this
tutorial we're basically going to finish
up this get data method here because we
did set up our columns array which has
all of our columns in our database and
now we want to read some information
from those columns and we basically read
information through something called a
cursor so we're going to set a cursor up
and we're just going to set this cursor
to BC and hit equal and how we do or how
we read from our database is again our
open method here we have our database
helper and then we create our database
here from our helper that's that's
writable for the most part so we're
going to refer to our database so we're
going to say our database and the cursor
will allow us to again read from this so
we just hit dot and quarry excuse me
hit that and then the first parameter
yeah we have a lot of parameters that we
have to work with the first one here is
the table name so we have our database
table name called database underscore
table we're going to click that four
columns again it's just our string array
that we set up here so it's going to
give some information about all of our
columns selection everything else we're
going to set to null so you don't have
to worry about that for the most part
again if you guys want a little bit more
information you can you just hover over
the query and you know read about the
parameters the selection and all that
stuff but for example we don't really
care about that we're just going to read
through our columns so now that we have
our cursor set up what we want to do is
again since this is going to return a
string we want to set up a string
variable that's going to return so we're
going to set up string and we're just
going to set this to result and we're
just going to initially set it TV
nothing for the most part and that's
what we're going to return again when
this method is called it's going to run
through here and return a string so
that's the string that we're going to
return
now what we want to do is we have our
cursor and we want to kind of read
through all the entries in our database
but before we do that we need to set up
three ends one for each column index for
the most part so we're going to call I
row four index row and we're going to
set this equal to a cursor dot and we
can say get column index and what this
is going to do is we're going to return
our key value again our key our row ID
and that's basically going to be looking
for that that column for the most part
our cursor is going to be looking for
that column and setting it equal to this
end now we're going to do is we're just
going to copy this and paste this for
all three of our columns change it to I
name and I hotness nice sexy all right
so now we also have to change this to
name and to hotness as well all right so
now we want to actually get through and
start reading all of our entries of our
database for the most part so what we're
going to do is we're going to kind of
create a for loop which is going to
start our cursor at the very beginning
and then cycle through read all the data
and kind of loop through and go to the
next entry until there's no entries left
so we're going to do that with a for
loop and we want to start at the
beginning so we are going to say our
cursor dot move to first so that's going
to be the first row and that's where our
cursor is going to start then we're
going to hit it a semicolon and then
we're going to say as long as it's not
equal for the most part again that's our
expression mark there as long as our
cursor does not equal see again dot is
after last so we're going to use this
method so if our cursor is at the
position after the last entry in our
database that's when it's going to stop
and then we're going to just hit
semicolon
and we're just going to move the cursor
forward each time so we're going to say
move to next and then open brackets and
this is where we're going to read the
data
but again just I'm not sure how if we
have done for loops yet or not again
we're just starting our cursor at the
beginning and after it reads through one
time it's going to move to the next
position as long as it's not the
position after the last row in our
database if that makes sense so now we
want to do is we want to set our result
equal to the information that we're
reading so we're going to say result is
equal to basically result as well which
I'll explain in a second we're going to
say cursor our cursor that we set up
whoops
cursor dot get string and then we're
going to basically put the index so
index row for the most part and that's
going to return the value of a row that
it's currently on and then we're just
going to hit plus and then maybe a
spacing quotations to give us a little
space and then again just cursor dot get
string and we're going to say this time
I named plus again another space and
then plus again C dot get string and
this last one will be eye hotness all
right and then we also want to say plus
and then in quotations we're going to do
a backslash n so now let me just talk
about what this is doing again with
finish of our statement so again we're
looping through each time right it
starts at the beginning it's going to
get basically the string of our index
which again is our first column or row
column the ID I'm sorry the row ID
column then it's going to print off a
space and then it's going to you know
get the name
of the first row in our database and
also get the hotness of our first row in
the database and then it's going to
create a new string the next time it
loops through it still has information
from the previous time so that's why we
have this results here and then it's
just going to loop through to the second
for the second row and now let's just
check out our application make sure it
works again we're returning this result
that we set up here but hopefully
everything works here again probably the
most important thing for this tutorial
is use the cursor to read from our
database or a data base which gets the
table and the columns and all that stuff
so let's just make sure application
works scroll down you put an entry like
jinny and we're going to set Gini equal
to be nine that's pretty good and then
we're going to update database heck yeah
and then we're going to hit view
database as you can see Samantha she's
about a six
Jenny's about a nine no one can compete
with me you know I'm just kidding
but yeah it looks like our database is
working that's the entry from a tutorial
ago or couple tutorials ago and it still
saved it to our database so that's
pretty much it for this tutorial guys
hopefully it made some sense hopefully
you guys kind of understand SQL a little
bit better than you did about ten
tutorials ago so I'll catch you guys
later and have a good honor
and twentieth androids toil for the new
boss in we're going to do in this
tutorial we're basically going to finish
up this get data method here because we
did set up our columns array which has
all of our columns in our database and
now we want to read some information
from those columns and we basically read
information through something called a
cursor so we're going to set a cursor up
and we're just going to set this cursor
to BC and hit equal and how we do or how
we read from our database is again our
open method here we have our database
helper and then we create our database
here from our helper that's that's
writable for the most part so we're
going to refer to our database so we're
going to say our database and the cursor
will allow us to again read from this so
we just hit dot and quarry excuse me
hit that and then the first parameter
yeah we have a lot of parameters that we
have to work with the first one here is
the table name so we have our database
table name called database underscore
table we're going to click that four
columns again it's just our string array
that we set up here so it's going to
give some information about all of our
columns selection everything else we're
going to set to null so you don't have
to worry about that for the most part
again if you guys want a little bit more
information you can you just hover over
the query and you know read about the
parameters the selection and all that
stuff but for example we don't really
care about that we're just going to read
through our columns so now that we have
our cursor set up what we want to do is
again since this is going to return a
string we want to set up a string
variable that's going to return so we're
going to set up string and we're just
going to set this to result and we're
just going to initially set it TV
nothing for the most part and that's
what we're going to return again when
this method is called it's going to run
through here and return a string so
that's the string that we're going to
return
now what we want to do is we have our
cursor and we want to kind of read
through all the entries in our database
but before we do that we need to set up
three ends one for each column index for
the most part so we're going to call I
row four index row and we're going to
set this equal to a cursor dot and we
can say get column index and what this
is going to do is we're going to return
our key value again our key our row ID
and that's basically going to be looking
for that that column for the most part
our cursor is going to be looking for
that column and setting it equal to this
end now we're going to do is we're just
going to copy this and paste this for
all three of our columns change it to I
name and I hotness nice sexy all right
so now we also have to change this to
name and to hotness as well all right so
now we want to actually get through and
start reading all of our entries of our
database for the most part so what we're
going to do is we're going to kind of
create a for loop which is going to
start our cursor at the very beginning
and then cycle through read all the data
and kind of loop through and go to the
next entry until there's no entries left
so we're going to do that with a for
loop and we want to start at the
beginning so we are going to say our
cursor dot move to first so that's going
to be the first row and that's where our
cursor is going to start then we're
going to hit it a semicolon and then
we're going to say as long as it's not
equal for the most part again that's our
expression mark there as long as our
cursor does not equal see again dot is
after last so we're going to use this
method so if our cursor is at the
position after the last entry in our
database that's when it's going to stop
and then we're going to just hit
semicolon
and we're just going to move the cursor
forward each time so we're going to say
move to next and then open brackets and
this is where we're going to read the
data
but again just I'm not sure how if we
have done for loops yet or not again
we're just starting our cursor at the
beginning and after it reads through one
time it's going to move to the next
position as long as it's not the
position after the last row in our
database if that makes sense so now we
want to do is we want to set our result
equal to the information that we're
reading so we're going to say result is
equal to basically result as well which
I'll explain in a second we're going to
say cursor our cursor that we set up
whoops
cursor dot get string and then we're
going to basically put the index so
index row for the most part and that's
going to return the value of a row that
it's currently on and then we're just
going to hit plus and then maybe a
spacing quotations to give us a little
space and then again just cursor dot get
string and we're going to say this time
I named plus again another space and
then plus again C dot get string and
this last one will be eye hotness all
right and then we also want to say plus
and then in quotations we're going to do
a backslash n so now let me just talk
about what this is doing again with
finish of our statement so again we're
looping through each time right it
starts at the beginning it's going to
get basically the string of our index
which again is our first column or row
column the ID I'm sorry the row ID
column then it's going to print off a
space and then it's going to you know
get the name
of the first row in our database and
also get the hotness of our first row in
the database and then it's going to
create a new string the next time it
loops through it still has information
from the previous time so that's why we
have this results here and then it's
just going to loop through to the second
for the second row and now let's just
check out our application make sure it
works again we're returning this result
that we set up here but hopefully
everything works here again probably the
most important thing for this tutorial
is use the cursor to read from our
database or a data base which gets the
table and the columns and all that stuff
so let's just make sure application
works scroll down you put an entry like
jinny and we're going to set Gini equal
to be nine that's pretty good and then
we're going to update database heck yeah
and then we're going to hit view
database as you can see Samantha she's
about a six
Jenny's about a nine no one can compete
with me you know I'm just kidding
but yeah it looks like our database is
working that's the entry from a tutorial
ago or couple tutorials ago and it still
saved it to our database so that's
pretty much it for this tutorial guys
hopefully it made some sense hopefully
you guys kind of understand SQL a little
bit better than you did about ten
tutorials ago so I'll catch you guys
later and have a good honor
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Dec 23, 2024 Last updated |
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