Saving Data on Android

update an existing record
, and finally, to 
delete records
.
Upda/ng a TODO
To add the capability to update a record, replace the line of code 
return 0
 in the 
updateToDo
 function with the code below:
// 1
 
val
 todoId = toDo.toDoId.toString() 
// 2
 
val
 db: SQLiteDatabase = writableDatabase 
// 3
 
val
 values = ContentValues() 
values.put(KEY_TODO_NAME, toDo.toDoName) 
values.put(KEY_TODO_IS_COMPLETED, toDo.isCompleted) 
// 4
 
return
 db.update(TABLE_NAME, values, 
"
$KEY_TODO_ID
=?"
, 
arrayOf(todoId))
With this code, you:
1. Prepare the 
todoId
 argument, for the 
Update
 clause.
2. Get a writable instance of the database.
3. Create a 
ContentValues
 object to contain the key/value pairs, and put the TODO 
item's property values in it.
4. Run the update query on the database and return the result of the operation.
Saving Data on Android
Chapter 3: SQLite Database
raywenderlich.com
62

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Run the app. Tap the 
edit icon
 that looks like a pencil next to the record. Update the 
record to a new value and tap 
Update
.
Update a record
Now, the record should reflect any changes you made as it is displayed in the 
RecyclerView
.
Updated record
Saving Data on Android
Chapter 3: SQLite Database
raywenderlich.com
63

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Note
: The update function you just completed is used in multiple places in the 
app. First, it was used in the previous example when changes were made to the 
name of the TODO item. The app also updates TODO items when the 
completed checkbox is checked.
There is one more bit of functionality to add to this app. The app must also be able to 
delete TODO items.
Dele/ng a TODO
In order to delete an item from the database, add the following code to the 
deleteToDo
 function:
val
 db: SQLiteDatabase = writableDatabase 
db.delete(TABLE_NAME, 
"
$KEY_TODO_ID
=?"
, arrayOf(id.toString())) 
db.close()
The above section of code simply gets an instance of the writeable database, runs a 
Delete
 command against it utilizing the correct TODO item 
id
, and closes the 
database. Run the app and tap the 
Delete
 icon that looks like a wastebasket and the 
TODO item magically disappears.
You have successfully written all the CRUD operations for this TODO list app! Now, 
before you are finished, you will add a unit test to the program with