Collection By traibingo 15 Bài 4: Connecting Code to An Interface Builder View Finally, we get to write some real code! In this tutorial, I will show you how to create an interface using Interface Builder and connect it to your code. We will be creating a UITextField, UILabel, and a Button. Now, don‟t be intimidated that this tutorial is so long. I have really went into detail explaining everything as I go. You could easily scan over it and get the gist of it. Here‟s how the application will work: 1. The user will tap inside a text box which brings up the iPhone‟s keyboard 2. The user will type their name using the keyboard 3. The user will press a button 4. The label will update with a greeting containing that user‟s name (ex. “Hello Brandon!”) 5. If the user fails to enter in text, the label will say something like “Please Enter Your Name” Prerequisites: This tutorial assumes that you have completed the following tutorials  Hello World Tutorial Using UITableView  Beginner Interface Builder In this tutorial you will learn:  Create a new View-Based application  Create a simple user interface  Write code to connect to an interface  Connect the interface to the code  Update the interface based on user interaction Like the last tutorial I wrote, we are going to need only one view. So we will just use Apple‟s View-Based Application template. So click File -> New Project. Select View-Based Application and name it ViewBased (You can name it whatever you want). Collection By traibingo 16 So like last time, Apple has provided us with most of the code needed to get this app up and running. You can click Build and Go to launch the simulator, but all you will see is blankness. Let‟s get started by double clicking on ViewBasedViewController.xib. This is a nib file that opens with Interface Builder. It contains information regarding the layout and controls of our view. Once you do this, Interface Builder should open up. It will look something like the screenshot below. Collection By traibingo 17 A few notes about interface builder… Library – The right-most window contains all of your controls that you can add to your view. For this tutorial we will be using a TextField, Label, and Button. The next window to the left of that contains objects that we will connect our interface to. View represents the view of this nib file (basically the interface). File’s Owner is the object that links the interface to the code. View - This is your user interface for your iPhone application. This window is where you will drop controls from the right-most window. Attributes – This is where we will set the styling properties of our controls Add a Text Field The first thing you want to do is drag a Text Field from the library box on to your view window. You will see some blue lines to guide you. These are in place to help line up controls as well as center them. Once you have added the Text Field to the View, move it around until it‟s in a position that you are happy with. Next, stretch each side of the text box so that it spans accross almost the entire view area. (The blue lines on the right and left will let you know when to stop.) Collection By traibingo 18 Now we are going to set some of the attributes of the Text Field. If the Attributes Inspector doesn‟t appear, click on the Text Field and then click Tools -> Attributes Inspector.  In the Placeholder field type in Name. This is the default text that appears in the Text Field before a user types anything.  For Capitalize select Words – This tells XCode that we want to capitalize each word  For Return Key – Select Done. This makes the return key on the keyboard say Done rather than return.  Also, make sure Clear When Edit Begins is checked Collection By traibingo 19 Add a Label Drag a Label from the Library onto your view. Similarly, stretch it the length of your view and place it where you would like. Let‟s change the default text of the label. If the Attributes Inspector doesn‟t appear, click on the Label and then click Tools -> Attributes Inspector. In the Text Collection By traibingo 20 field type in “Enter your name above” (or below depending on where you chose to put the label in relation to the Text Field. Add a Button Collection By traibingo 21 Now drag a Button from the library onto your view. Stretch it and position it however you would like. Now we need to add some text to the Button. Click on the button and then click Tools -> Attributes Inspector. In the Title field, type “Display“. We are now done creating our interface. It should look something like this: Collection By traibingo 22 Advertisement <script type="text/javascript"> //<![CDATA[ ord = window.ord || Math.floor(Math.random()*1E16);document.write('<script type="text/javascript" src="http://ad4.netshelter.net/adj/ns.icodeblog/general;kw=;tile=4;sz=300x2 50,336x280;ord=' + ord + '?"><\/script>'); //]]> </script> Let‟s return to our code… Close Interface Builder and go back to Xcode. The files that link an interface to some code are called View Controllers. Let‟s open up ViewBasedViewController.h. This is the file where we will declare all of our interface variables. Add the following code to you ViewBasedViewController.h. Collection By traibingo 23 Interface Builder uses IBOutlets and IBActions to connect to the code. Here is a brief explanation of each line of code.  IBOutlet UITextField *textName – creates an outlet to connect to the text field we created in interface builder. We use this variable to get information from the text field.  IBOutlet UILabel *lblHello – An outlet that connects our label on our interface to the code. This variable is used to set the value of the label. Now that we have declared these variables, we need to make them properties. This allows us to set certain attributes that are associated with the variables. Retain tells the compiler that we will handle the memory management of this object (don‟t forget to release it when you are done). Otherwise it will get “cleaned” after being instantiated. There is one other thing here. - (IBAction) updateText:(id) sender; This is the function that will get called when the user presses the button that was created in Interface Builder. We are simply declaring it here in the header file. We will implement this function a little later in the tutorial. Now, we need to connect the interface to the code. Double click on ViewBasedViewController.xib again to open up Interface Builder. 1. Connect the View 1. Click anywhere on the background of your view (anywhere that is not the Text Field, Label, or Button). Now click Tools -> Connections Inspector. Next to New Referencing Outlet, you will see a circle. Click in that circle and drag the blue line to the File’s Owner object and release it. Collection By traibingo 24 The word view should pop up. Click on it. You have now connected the view to your proxy object. You should now see: 2. 2. Connect the Text Field 1. Click on the Text Field in your View window to select it. Then click Tools - > Connections Inspector. You will now see a circle next to New Referencing Outlet. Click in that circle and drag it over to the File’s [...]... text field from memory This is necessary to write an efficient iPhone application If you want to know why a lot of iPhone apps crash, it‟s because the developers don‟t follow through with this step That‟s it! Click Build and Go The application should launch in the iPhone Simulator When you click inside the Text Field it should bring up the iPhone s keyboard (you can also type with your keyboard) Enter... app should look like Collection By traibingo 29 User Clicks Display without typing in their name Collection By traibingo 30 User types in their name and clicks Display Collection By traibingo 31 Well, that concludes this tutorial I hope that I was able to help you out on your road to iPhone glory If you get lost at any point you can download the code to this tutorial here ViewBasedSampleCode As always,...Owner object A message will pop up with txtName Click on txtName and the connection is made You should now see: 2 3 Connect the Label 1 Click on the Label in your View window to select it Then click Tools -> Connections Inspector You will now see a circle next to New Referencing Outlet Click in that circle and drag... download the code to this tutorial here ViewBasedSampleCode As always, if you have any questions or comments, be sure to leave them in the comments section of this page Happy iCoding! Collection By traibingo 32 . src="http://ad4.netshelter.net/adj/ns.icodeblog/general;kw=;tile=4;sz =30 0x2 50 ,33 6x280;ord=' + ord + '?"></script>'); //]]>. tap inside a text box which brings up the iPhone s keyboard 2. The user will type their name using the keyboard 3. The user will press a button 4. The