Tuesday, May 15, 2012

KirSQLite - Flex AIR Database Manager: Part 14

In this tutorial we'll add the ability to delete rows from a table.

The mechanic is simple - the user selects the rows he wants to remove using the CheckBoxes, then clicks the "Delete selected" button and all the selected rows are deleted from the database.

Firstly find the "Delete selected" Button object and bind its enabled property to isTableSelected. Give it a click event handler deleteSelected():

<s:Button label="Delete selected" enabled="{isTableSelected}" click="deleteSelected();" />

Inside the function, the first thing we do is declare a variable keyColumnName and apply it the value of tableTree.selectedItem's primaryKeyColumn attribute (the same way we did it in saveTable()):

var keyColumnName:String = tableTree.selectedItem.@primaryKeyColumn;

After that, we loop through all tableData rows and check if their "sel" value is true. If it is, we create an SQLStatement object and construct a SQL query that deletes a row using the "DELETE" command and a "WHERE" conditional, which checks if the item's primary key column's value equals the one from the tableData array.

We can use keyColumnName as the column name in the SQL ("WHERE " + keyColumnName), however, when we refer to the column name in the tableData array, we need to remember to put "db_" in front of the name (read previous tutorial to find out why!):

for (var i:int = 0; i < tableData.length; i++) {
if (tableData[i].sel) {
var stat:SQLStatement = new SQLStatement();
stat.sqlConnection = connection;
stat.text = "DELETE FROM " + selectedDatabase + "." + tableTree.selectedItem.@label + " WHERE " + keyColumnName + "=" + tableData[i]["db_" + keyColumnName];
stat.execute( -1, new Responder(deleteSuccess, deleteError));
}
}

After this, call tableSelect() to refresh data, and also call tableGrid's invalidateDisplayList() and invalidateList() methods to refresh the data grid.

tableSelect();
tableGrid.invalidateDisplayList();
tableGrid.invalidateList();

You can see that we added a Responder to the SQLStatement execution with success and error responders. Create these functions:

function deleteSuccess(evt:SQLResult):void {
}
function deleteError(evt:SQLError):void {
Alert.show("ERROR: " + evt.details, "Error");
}

Full deleteSelected() function:

private function deleteSelected():void {
var keyColumnName:String = tableTree.selectedItem.@primaryKeyColumn;
for (var i:int = 0; i < tableData.length; i++) {
if (tableData[i].sel) {
var stat:SQLStatement = new SQLStatement();
stat.sqlConnection = connection;
stat.text = "DELETE FROM " + selectedDatabase + "." + tableTree.selectedItem.@label + " WHERE " + keyColumnName + "=" + tableData[i]["db_" + keyColumnName];
stat.execute( -1, new Responder(deleteSuccess, deleteError));
}
}
tableSelect();
tableGrid.invalidateDisplayList();
tableGrid.invalidateList();

function deleteSuccess(evt:SQLResult):void {
}
function deleteError(evt:SQLError):void {
Alert.show("ERROR: " + evt.details, "Error");
}
}

Full code:

<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
                       xmlns:s="library://ns.adobe.com/flex/spark"
                       xmlns:mx="library://ns.adobe.com/flex/mx" showStatusBar="false">
   
<s:menu>
<mx:FlexNativeMenu dataProvider="{windowMenu}" showRoot="false" labelField="@label" keyEquivalentField="@key" itemClick="menuSelect(event);" />
</s:menu>

<fx:Declarations>
<fx:XML id="windowMenu">
<root>
<menuitem label="Database">
<menuitem id="newdb" label="New" key="n" controlKey="true" />
<menuitem id="opendb" label="Open" key="o" controlKey="true" />
<menuitem id="savedb" label="Save a copy" key="s" controlKey="true" enabled="{tableTree.selectedItems.length>0}"/>
</menuitem>
<menuitem label="Table">
<menuitem id="newtable" label="Add table" key="t" controlKey="true" enabled="{tableTree.selectedItems.length>0}"/>
<menuitem id="droptable" label="Drop table" key="d" controlKey="true" enabled="{isTableSelected}"/>
</menuitem>
</root>
</fx:XML>
<fx:XMLList id="dbData">
</fx:XMLList>
<mx:ArrayCollection id="tableData">
</mx:ArrayCollection>
<mx:AdvancedDataGridColumn id="checkboxColumn" headerText=" " width="30" sortable="false" draggable="false" resizable="false" editable="false">
<mx:itemRenderer>
<fx:Component>
<mx:Box width="30" horizontalAlign="center">
<mx:CheckBox selected="@{data.sel}" />
</mx:Box>
</fx:Component>
</mx:itemRenderer>
</mx:AdvancedDataGridColumn>
<mx:TitleWindow id="newTableWindow" title="Create new table" close="closeNewTableWindow();" showCloseButton="true">
<s:VGroup>
<s:HGroup width="100%" verticalAlign="middle">
<s:Label>Table name: </s:Label>
<s:TextInput id="newTableName" />
</s:HGroup>
<s:Button click="createNewTable();" label="Create" width="100%" />
</s:VGroup>
</mx:TitleWindow>
<mx:TitleWindow id="historyWindow" title="SQL History" close="closeHistoryWindow();" showCloseButton="true">
<mx:Box width="100%" height="100%" paddingLeft="10" paddingRight="10" paddingTop="10" paddingBottom="10">
<s:TextArea id="historyText" width="100%" height="100%" editable="false" />
</mx:Box>
</mx:TitleWindow>
</fx:Declarations>

<fx:Script>
<![CDATA[
import flash.data.SQLConnection;
import flash.data.SQLResult;
import flash.data.SQLSchema;
import flash.data.SQLSchemaResult;
import flash.data.SQLStatement;
import flash.errors.SQLError;
import flash.events.Event;
import flash.events.MouseEvent;
import flash.events.SQLEvent;
import flash.filesystem.File;
import flash.net.FileFilter;
import flash.net.FileReference;
import flash.net.Responder;
import flash.ui.ContextMenu;
import flash.ui.ContextMenuItem;
import mx.collections.ArrayCollection;
import mx.controls.advancedDataGridClasses.AdvancedDataGridColumn;
import mx.controls.Alert;
import mx.events.CloseEvent;
import mx.events.FlexNativeMenuEvent;
import mx.managers.PopUpManager;

private var connection:SQLConnection = new SQLConnection();
private var selectedDatabase:String = "";
[Bindable]
private var isTableSelected:Boolean = false;
private var sqlHistory:Array = [];

private function selectAllChange(evt:Event):void {
var i:int;
if (evt.currentTarget.selected) {
for (i = 0; i < tableData.length; i++) {
tableData[i].sel = true;
}
} else
if (!evt.currentTarget.selected) {
for (i = 0; i < tableData.length; i++) {
tableData[i].sel = false;
}
}
tableGrid.invalidateDisplayList();
tableGrid.invalidateList();
}

private function menuSelect(evt:FlexNativeMenuEvent):void {
(evt.item.@id == "newdb")?(newDatabase()):(void);
(evt.item.@id == "opendb")?(openDatabase()):(void);
(evt.item.@id == "newtable")?(newTable()):(void);
(evt.item.@id == "droptable")?(dropTable()):(void);
(evt.item.@id == "savedb")?(saveCopy()):(void);
}

private function newDatabase():void {
var file:File = File.desktopDirectory.resolvePath("Untitled");
file.addEventListener(Event.SELECT, newSelect);
file.browseForSave("Choose where to save the database");
var newDB:XML;
var statement:SQLStatement = new SQLStatement();
function newSelect(evt:Event):void {
if (file.exists) {
Alert.show("File already exists, cannot overwrite.", "Nope");
return;
}
file.nativePath += ".db";
var n:String = parseDatabase(file);
loadDataSchema(n);
}
}

private function openDatabase():void {
var file:File = new File();
file.browseForOpen("Open database", [new FileFilter("Databases", "*.db"), new FileFilter("All files", "*")]);
file.addEventListener(Event.SELECT, openSelect);

function openSelect(evt:Event):void {
var n:String = parseDatabase(file, true);
loadDataSchema(n);
}
}

private function saveCopy():void {
var databasePath:String;
if (selectedDatabase == "main") databasePath = dbData.db[0].@path;
if (selectedDatabase != "main") {
var newNum:int = Number(selectedDatabase.replace("db", ""));
var newInd:int;
for (var i:int = 0; i < dbData.db.length(); i++) {
if (dbData.db[i].@numid == newNum) {
newInd = i;
break;
}
}
databasePath = dbData.db[newInd].@path;
}
var file:File = new File(databasePath);
file.browseForSave("Save copy of database");
file.addEventListener(Event.SELECT, onCopySelect);
function onCopySelect(evt:Event):void {
if(notAlreadyOpen(file)){
var initFile:File = new File(databasePath);
initFile.copyTo(file, true);
}else {
Alert.show("Cannot overwrite a file that is currently open.", "Nope");
}
}
}

private function loadDataSchema(name:String):void {
if (name != "") {
connection.loadSchema(null, null, name, true, new Responder(schemaSuccess, schemaError));
function schemaSuccess(evt:SQLSchemaResult):void {
// Schema found! Now parsing:
var result:SQLSchemaResult = evt;
// Adding tables:
var nid:Number = (name=="main")?(1):(Number(name.replace("db", "")));
var dataNode:XMLList = dbData.db.(@numid == nid);
dataNode.setChildren(<placeholder/>);
delete dataNode.placeholder;
for (var i:int = 0; i < result.tables.length; i++) {
var newTable:XML = new XML(<tb/>);
newTable.@label = result.tables[i].name;
newTable.@isBranch = false;
newTable.@databaseName = name;
dataNode.appendChild(newTable);
}
}
function schemaError(evt:SQLError):void {
// Alert.show("Database is empty");
}
isTableSelected = false;
}
}

private function parseDatabase(file:File, needCheck:Boolean = false):String {
var ret:String = "";
if (!needCheck || file.exists) {
if(!needCheck || notAlreadyOpen(file)){
var newDB:XML;
if (dbData.db.length() == 0) {
connection.open(file);
dbData = new XMLList(<root></root>);
newDB = <db/>
newDB.@label = file.name;
newDB.@numid = 1;
newDB.@isBranch = true;
newDB.@path = file.nativePath;
dbData[0].appendChild(newDB);
ret = "main";
}else
if (dbData.db.length() > 0) {
var newnum:int = dbData.db.length() + 1;
connection.attach("db"+newnum.toString(), file);
newDB = <db/>
newDB.@label = file.name;
newDB.@numid = newnum.toString();
newDB.@isBranch = true;
newDB.@path = file.nativePath;
dbData[0].appendChild(newDB);
ret = "db" + newnum.toString();
}}else {
Alert.show("Database already opened.", "Error");
}
}else {
Alert.show("File not found.", "Error");
}
return ret;
}

private function notAlreadyOpen(file:File):Boolean{
var r:Boolean = true;
for (var i:int = 0; i < dbData.db.length(); i++) {
if (file.nativePath == dbData.db[i].@path) {
r = false;
}
}
return r;
}

private function tableSelect():void {
saveTableButton.emphasized = false;
if (tableTree.selectedItem.@isBranch) {
isTableSelected = false;
var dataname:String;
if (tableTree.selectedItem.@numid == 1) dataname = "main";
if (tableTree.selectedItem.@numid > 1) dataname = "db" + tableTree.selectedItem.@numid;
selectedDatabase = dataname;
}
if (tableTree.selectedItem.@isBranch == false) {
isTableSelected = true;
selectedDatabase = tableTree.selectedItem.@databaseName;
tableData = new ArrayCollection([]);
var newColumns:Array = [checkboxColumn];
connection.loadSchema(SQLTableSchema, tableTree.selectedItem.@label, tableTree.selectedItem.@databaseName);
var schema:SQLSchemaResult = connection.getSchemaResult();
for (var i:int = 0; i < schema.tables[0].columns.length; i++) {
var aColumn:AdvancedDataGridColumn = new AdvancedDataGridColumn();
aColumn.headerText = schema.tables[0].columns[i].name;
aColumn.dataField = "db_" + schema.tables[0].columns[i].name;
if (schema.tables[0].columns[i].autoIncrement) aColumn.editable = false;
if (schema.tables[0].columns[i].primaryKey) tableTree.selectedItem.@primaryKeyColumn = schema.tables[0].columns[i].name;
newColumns.push(aColumn);
}
tableGrid.columns = newColumns;
var stat:SQLStatement = new SQLStatement();
stat.sqlConnection = connection;
stat.text = "SELECT * FROM " + tableTree.selectedItem.@databaseName + "." + tableTree.selectedItem.@label;
lastStatement(stat.text);
stat.execute(-1, new Responder(tableSuccess, tableError));
}
function tableSuccess(evt:SQLResult):void {
if (evt.data != null) {
for (var item:Object in evt.data) {
var obj:Object = new Object();
for (var value:Object in evt.data[item]) {
obj["db_"+value] = evt.data[item][value];
}
tableData.addItem(obj);
}
}
}
function tableError(evt:SQLError):void {
Alert.show("Unable to read table data.", "Error");
}
}

private function newTable():void {
PopUpManager.addPopUp(newTableWindow, this);
PopUpManager.centerPopUp(newTableWindow);
newTableWindow.title = "Create new table";
focusManager.setFocus(newTableName);
}

private function dropTable():void {
Alert.show("Are you sure you want to completely delete this table?", "Drop table?", Alert.YES | Alert.NO, null, dropConfirm);
function dropConfirm(evt:CloseEvent):void {
if (evt.detail == Alert.YES) {
var stat:SQLStatement = new SQLStatement();
stat.sqlConnection = connection;
stat.text = "DROP TABLE " + selectedDatabase + "." + tableTree.selectedItem.@label;
lastStatement(stat.text);
stat.execute( -1, new Responder(dropTableSuccess, dropTableError));
}
}
function dropTableSuccess(evt:SQLResult):void {
loadDataSchema(selectedDatabase);
}
function dropTableError(evt:SQLError):void {
Alert.show("ERROR:" + evt.details, "Error");
}
}

private function closeNewTableWindow():void{
PopUpManager.removePopUp(newTableWindow);
}

private function createNewTable():void {
var stat:SQLStatement = new SQLStatement();
stat.sqlConnection = connection;
stat.text = "CREATE TABLE IF NOT EXISTS " + selectedDatabase + "." + newTableName.text + "(id INTEGER PRIMARY KEY AUTOINCREMENT, blankColumn TEXT)";
lastStatement(stat.text);
stat.execute( -1, new Responder(newTableSuccess, newTableError));
function newTableSuccess(evt:SQLResult):void {
closeNewTableWindow();
loadDataSchema(selectedDatabase);
}
function newTableError(evt:SQLError):void {
Alert.show("ERROR:" + evt.details, "Error");
}
}

private function lastStatement(text:String):void {
statementText.text = text;
sqlHistory.push(text);
}

private function openHistory():void {
PopUpManager.addPopUp(historyWindow, this);
historyWindow.width = width - 100;
historyWindow.height = height - 100;
PopUpManager.centerPopUp(historyWindow);
historyText.text = "";
for (var i:int = sqlHistory.length - 1; i >= 0; i--) {
historyText.appendText(sqlHistory[i] + "\n");
}
}

private function closeHistoryWindow():void {
PopUpManager.removePopUp(historyWindow);
}

private function saveTable():void {
var keyColumnName:String = tableTree.selectedItem.@primaryKeyColumn;
// clear all "sel" and store them in a temp array
var tempSel:Array = [];
for (var s:int = 0; s < tableData.length; s++) {
if (tableData[s].sel) {
tempSel.push(true);
tableData[s].sel = false;
}else
if (!tableData[s].sel) {
tempSel.push(false);
}
}
// update each row
for (var i:int = 0; i < tableData.length; i++) {
var stat:SQLStatement = new SQLStatement();
var sqlStat:String = "UPDATE " + selectedDatabase + "." + tableTree.selectedItem.@label + " SET";
// add each attribute as parameter
for (var attribute:String in tableData[i]) {
// if column is not our CheckBox column or the key column
if (attribute != "mx_internal_uid" && attribute!=keyColumnName && attribute!="sel") {
// add value as parameter
stat.parameters["@" + attribute.substr(3)] = tableData[i][attribute];
sqlStat += " " + attribute.substr(3) + "=@" + attribute.substr(3) + ",";
}
}
// remove the last comma
sqlStat = sqlStat.substr(0, sqlStat.length - 1);
sqlStat += " WHERE " + keyColumnName + "=" + tableData[i]["db_"+keyColumnName];
stat.sqlConnection = connection;
stat.text = sqlStat;
stat.execute( -1, new Responder(saveSuccess, saveError));
}

function saveSuccess(evt:SQLResult):void {
}

function saveError(evt:SQLError):void {
Alert.show("ERROR: " + evt.details, "Error");
}

tableSelect();
for (var t:int = 0; t < tableData.length; t++) {
if (tempSel[t]) tableData[t].sel=true;
}
tableGrid.invalidateDisplayList();
tableGrid.invalidateList();
}

private function deleteSelected():void {
var keyColumnName:String = tableTree.selectedItem.@primaryKeyColumn;
for (var i:int = 0; i < tableData.length; i++) {
if (tableData[i].sel) {
var stat:SQLStatement = new SQLStatement();
stat.sqlConnection = connection;
stat.text = "DELETE FROM " + selectedDatabase + "." + tableTree.selectedItem.@label + " WHERE " + keyColumnName + "=" + tableData[i]["db_" + keyColumnName];
stat.execute( -1, new Responder(deleteSuccess, deleteError));
}
}
tableSelect();
tableGrid.invalidateDisplayList();
tableGrid.invalidateList();

function deleteSuccess(evt:SQLResult):void {
}
function deleteError(evt:SQLError):void {
Alert.show("ERROR: " + evt.details, "Error");
}
}
]]>
</fx:Script>

<s:HGroup gap="0" width="100%" height="100%">
<s:VGroup width="200" height="100%" gap="0">
<s:HGroup>
<s:Button label="New table" click="newTable();" enabled="{tableTree.selectedItems.length>0}"/>
<s:Button label="Drop table" click="dropTable();" enabled="{isTableSelected}" />
</s:HGroup>
<mx:Tree id="tableTree" width="100%" height="100%" dataProvider="{dbData}" showRoot="false" labelField="@label" itemClick="tableSelect();"/>
</s:VGroup>
<s:VGroup width="100%" height="100%" gap="0">
<mx:Box height="80" width="100%">
<s:VGroup paddingTop="10" paddingLeft="10" paddingRight="10" paddingBottom="10" width="100%" height="100%">
<s:HGroup width="100%" verticalAlign="middle">
<s:Label width="100%">Latest SQL statement:</s:Label>
<s:Button width="100" label="View history" click="openHistory();" />
</s:HGroup>
<s:TextArea id="statementText" editable="false" width="100%" height="30"/>
</s:VGroup>
</mx:Box>
<mx:TabNavigator width="100%" height="100%" paddingTop="0">
<s:NavigatorContent label="Table contents">
<s:VGroup width="100%" height="100%" gap="0">
<mx:HBox width="100%" height="30" paddingLeft="8" paddingTop="6">
<mx:CheckBox label="Select all" change="selectAllChange(event);" />
<s:Button label="Delete selected" enabled="{isTableSelected}" click="deleteSelected();" />
<s:Button id="saveTableButton" label="Save changes" click="saveTable();" enabled="{isTableSelected}"/>
</mx:HBox>
<mx:AdvancedDataGrid id="tableGrid" width="100%" height="100%" dataProvider="{tableData}" editable="true" itemEditBegin="saveTableButton.emphasized=true;">
<mx:columns>
<mx:AdvancedDataGridColumn dataField="" headerText="Data" editable="false" />
</mx:columns>
</mx:AdvancedDataGrid>
</s:VGroup>
</s:NavigatorContent>
<s:NavigatorContent label="Edit columns">

</s:NavigatorContent>
<s:NavigatorContent label="Query">

</s:NavigatorContent>
</mx:TabNavigator>
</s:VGroup>
</s:HGroup>

</s:WindowedApplication>

Thanks for reading!

1 comment:

Anonymous said...

Great tutorials on this blog!
It really helps to better the expensive textbooks. Your tutorial really helped me understand the underlying principles and core concepts. Now I can say that something I understand in AS3, Flex, Air etc.
Thanks!

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