Cocoa, Objective C - Alert Panels!

Transcription

1 Cocoa, Objective C - Alert Panels By Debasis Das March of 13

2 Alerts are key to any application. Some of the usages of an application alerts are as - To display an informative message - To take confirmation from user before continuing with a transaction - As a success or failure response to the end user. - Giving the user more than one option to take a action (save, dont-save, cancel etc). An NSAlert object displays an application model or as a sheet attached to a document window. Sample 1: Showing a simple alert message with a warning alert style -(void)showsimplealert NSAlert *alert = [[NSAlert alloc] init]; [alert addbuttonwithtitle:@"continue"]; [alert addbuttonwithtitle:@"cancel"]; [alert setmessagetext:@"alert"]; [alert setinformativetext:@ NSWarningAlertStyle \r Do you want to continue with delete of selected records"]; [alert setalertstyle:nswarningalertstyle]; 2 of 13

3 [alert beginsheetmodalforwindow:[self window] modaldelegate:self contextinfo:nil]; - (void)alertdidend:(nsalert *)alert returncode:(nsinteger)returncode contextinfo:(void *)contextinfo /* The following options are deprecated in Use NSAlertFirstButtonReturn instead NSAlertDefaultReturn = 1, NSAlertAlternateReturn = 0, NSAlertOtherReturn = -1, NSAlertErrorReturn = -2 NSOKButton = 1, // NSModalResponseOK should be used NSCancelButton = 0 // NSModalResponseCancel should be used */ if (returncode == NSOKButton) NSLog(@"(returnCode == NSOKButton)"); else if (returncode == NSCancelButton) NSLog(@"(returnCode == NSCancelButton)"); else if(returncode == NSAlertFirstButtonReturn) NSLog(@"if (returncode == NSAlertFirstButtonReturn)"); else if (returncode == NSAlertSecondButtonReturn) NSLog(@"else if (returncode == NSAlertSecondButtonReturn)"); else if (returncode == NSAlertThirdButtonReturn) NSLog(@"else if (returncode == NSAlertThirdButtonReturn)"); else NSLog(@"All Other return code %d",returncode); 3 of 13

4 Sample 2: Showing a simple alert message with a critical alert style -(void)showsimplecriticalalert NSAlert *alert = [[NSAlert alloc] init]; [alert addbuttonwithtitle:@"ok"]; [alert setmessagetext:@"alert"]; [alert setinformativetext:@"nscriticalalertstyle\rplease enter a valid id."]; [alert setalertstyle:nscriticalalertstyle]; [alert beginsheetmodalforwindow:[self window] modaldelegate:self didendselector:@selector(alertdidend:returncode:contextinfo:) contextinfo:nil]; 4 of 13

5 Sample 3: Showing a simple alert message with a informational alert style -(void)showsimpleinformationalalert NSAlert *alert = [[NSAlert alloc] init]; [alert addbuttonwithtitle:@"ok"]; [alert setmessagetext:@"alert"]; [alert setinformativetext:@"nsinformationalalertstyle \r Please enter a valid id."]; [alert setalertstyle:nsinformationalalertstyle]; [alert beginsheetmodalforwindow:[self window] modaldelegate:self didendselector:@selector(alertdidend:returncode:contextinfo:) contextinfo:nil]; 5 of 13

6 Sample 4: Creating an Alert with more than 3 buttons -(void)showsimplealertsheetwithmultiplebuttons NSAlert *alert = [[NSAlert alloc] init]; [alert addbuttonwithtitle:@"button One"]; //will generate a return code of 1000 [alert addbuttonwithtitle:@"button Two"]; //will generate a return code of 1001 [alert addbuttonwithtitle:@"button Three"]; //will generate a return code of 1002 [alert addbuttonwithtitle:@"button Four ]; //will generate a return code of 1003 [alert addbuttonwithtitle:@"button Five"]; //will generate a return code of 1004 [alert setmessagetext:@"alert"]; [alert setinformativetext:@"this is a five buttons alert message"]; [alert setalertstyle:nsinformationalalertstyle]; [alert beginsheetmodalforwindow:[self window] modaldelegate:self didendselector:@selector(alertdidend:returncode:contextinfo:) contextinfo:nil]; Sample 5: Creating an Alert using Factory Methods 6 of 13

7 -(void)showalertfromfactorymethod NSAlert *alert = [NSAlert alertwithmessagetext:@"delete the record?" defaultbutton:@"ok" alternatebutton:@"cancel" otherbutton:nil informativetextwithformat:@"deleted records cannot be restored."]; [alert beginsheetmodalforwindow:[self window] modaldelegate:self didendselector:@selector(alertdidend:returncode:contextinfo:) contextinfo:nil]; 7 of 13

8 Sample 6: Creating an Alert using Functional API -(void)showalertusingfunctionalapi you really want to delete the selected rows?", // sheet // default button label nil, // no third // other button label [self window], // window, the sheet is attached to. self, // The delegate for the NULL, // no need for did-dismiss selector nil, // context is no undo for this operation."); //didendselector //A selector for a method implemented by modaldelegate. This method is sent when the modal session is ended, but before the sheet is dismissed. //diddismissselector //A selector for a method implemented by modaldelegate. This method is sent after the sheet is dismissed in the event 8 of 13

9 Sample 7: Creating an Alert with Help button in the alert -(void)showalertwithhelp NSAlert *alert = [[NSAlert alloc] init]; [alert addbuttonwithtitle:@"ok"]; [alert addbuttonwithtitle:@"cancel"]; [alert setmessagetext:@"alert"]; [alert setinformativetext:@"please enter an id."]; [alert setalertstyle:nswarningalertstyle]; [alert setshowshelp:yes]; [alert setdelegate:self]; [alert beginsheetmodalforwindow:[self window] modaldelegate:self didendselector:@selector(alertdidend:returncode:contextinfo:) contextinfo:nil]; - (BOOL)alertShowHelp:(NSAlert *)alert NSLog(@"%s", func ); NSString *path = [[NSBundle mainbundle] pathforresource:@"credits" oftype:@"rtf"]; BOOL flag = [[NSWorkspace sharedworkspace] openfile:path]; return flag; 9 of 13

10 -(void)testdeprecatedalertmethods NSInteger integ = Format", BUTTON"); //The Flow stops here and the next line is not executed till the time user clicks on a button on the alert panel NSInteger criticalinteg = BUTTON"); NSLog(@"integ %ld",integ); NSLog(@"criticalInteg %ld",criticalinteg); 10 of 13

11 Sample 8: Creating a custom alert sheet and positioning it at a particular point -(void)showcustomsheet if (_customsheet) //Check the mycustomsheet instance variable to make sure the custom sheet does not already exist. [NSBundle owner: self]; [NSApp beginsheet: self.customsheet modalforwindow: self.window modaldelegate: self contextinfo: nil]; // Sheet is up here. - (IBAction)closeMyCustomSheet: (id)sender 11 of 13

12 [NSApp endsheet:_customsheet]; - (void)didendsheet:(nswindow *)sheet returncode:(nsinteger)returncode contextinfo: (void *)contextinfo NSLog(@"%s", func ); NSLog(@"return Code %d",returncode); [sheet orderout:self]; The below method is required to have a different point to show the alert from - (NSRect)window:(NSWindow *)window willpositionsheet:(nswindow *)sheet usingrect:(nsrect)rect NSLog(@"%s", func ); if (sheet == self.customsheet) NSLog(@"if block"); NSRect fieldrect = [self.showalertbutton frame]; fieldrect.size.height = 0; return fieldrect; else NSLog(@"else block"); return rect; 12 of 13

13 Sample 9: Creating a alert sheet with additional information displayed in an accessory view -(void)showalertwithdetailedinformation:(nsstring *)detailedinformation NSTextView *accessory = [[NSTextView alloc] initwithframe:nsmakerect(0,0,200,50)]; NSFont *font = [NSFont systemfontofsize:[nsfont systemfontsize]]; NSDictionary *textattributes = [NSDictionary dictionarywithobject:font forkey:nsfontattributename]; [accessory inserttext:[[nsattributedstring alloc] initwithstring:detailedinformation attributes:textattributes]]; [accessory seteditable:no]; [accessory setdrawsbackground:yes]; [accessory setbackgroundcolor:[nscolor cyancolor]]; NSAlert *alert = [[NSAlert alloc] init]; [alert setmessagetext:@"message text."]; [alert setinformativetext:@"informative text."]; [alert setaccessoryview:accessory]; [alert runmodal]; 13 of 13