How to learn xml coding

how to learn xml coding

How to Parse and Modify XML in Python?

Learn XML Learn XML AJAX Learn XML DOM Learn XML DTD Learn XML Schema Learn XSLT Learn XPath Learn XQuery. JavaScript Learn JavaScript Learn jQuery Learn React Learn AngularJS Learn JSON Learn AJAX Learn AppML Learn Programming Learn Python Learn Java Learn C++ Learn C# Learn R. Server Side. This tutorial will teach you basic XML concepts and the usage of various types of Java based XML parsers in a simple and intuitive way. Audience This tutorial has been prepared for beginners to help them understand the basic-to-advanced concepts related to XML parsing using Java .

However, no one ever talks about XML, and this can lead to confusion when you open up a new project for the first time and notice that there are actually two different main files and two different types of script. Hence this article, which will serve as your introduction to XML for Android development.

A markup language is slightly different from a programming language. Programming languages create dynamic interactions, whereas markup languages generally handle things like static user interfaces. See this thread. Another example of a markup language is HTML, which defines the what do dough hooks look like of a website.

HTML places the images and text on a website and sets the font and color. Though just to complicate matters, JavaScript is technically a scripting language! Consider the following example given by IBM Developer how to learn xml coding. Here, you and I know the information is an address, but all the browser or computer knows is where to start new lines.

XML is used anywhere that can benefit from adding context to data. It is used across the web to make search smarter and simplify data exchange. XML performs the same function in Android app development: describing data and introducing elements. Specifically, XML sets the layout of things like buttons and images, and defines the font, color, and any text that shows by default. To make those buttons actually do anything, you will need to use a programming language like Java or Kotlin, though.

When you create a new project in Android Studio, you will be greeted by a hierarchy of different files and folders, which can be a little daunting for complete beginners. You just need to concentrate on two files for now: MainActivity. To make life just a little simpler, Android Studio normally opens both these files as soon as it boots up. Read more: Understanding Java syntax.

You can assign any XML file to any Java file with this, and you can create as many of both as you like. However, how to set google as url search engine default MainActivity. To recap, XML describes the views in your activities, and Java tells them how to behave. To make changes to the layout of your app then, you have two what are the chances that a pregnancy test is wrong options.

The first is to use the Design view. The Text view will show you the actual XML code, but the Design view will let you manually edit the layout by dragging and dropping elements into the render of your activity.

XML files can also help store strings. Using the Design view is easier for beginners, though it can lead to complications.

For one, you will run into the limitations of XML early on when the designer refuses to let you drop items into specific places. Without the knowledge of why, this can make designing your app an exercise in frustration! At the same time, having a better understanding of XML will also help when it comes to handling the code. Sometimes XML will be used to describe types of data other than views in your apps; acting as a kind of index that your code can refer to.

You can find this information in the colors. You can then refer to this tag subsequently in your Java code or your XML code to refer to that particular hue.

A how to have dense hair is basically any of the widgets that make up a typical utility app.

Some of these parameters will be compulsory, while others will be optional. As you may already have guessed, a ViewGroup is a group of these views. These are also referred to as layouts, and serve as hierarchical arrangements of views.

A linear layout for example places all its children in a linear vertical or horizontal arrangement. Meanwhile, a ConstraintLayout will allow you to define the positions of views by their relationship with other views in the layout and the boundaries of the activity. This way, the views can maintain their relative positions, even as the dimensions of the device vary.

Some Views can also be ViewGroups, such as the RecyclerViewwhich arranges other views in a scrolling list. If we look at this, it can give us some insight into how XML is used:. In this case, there how to learn xml coding no parent and so the activity itself becomes the default. All parameters are set how to do a belly flop the closing angle bracket. Next, it introduces the EditText and sets parameters such as the width, height, text to show, ID, and position.

The ID is what we will use to refer how to learn xml coding this EditText subsequently in our Java code, should we wish to change what it shows. Because we are using a ConstraintLayout, we need to control the layout how to learn xml coding anchoring it to something else.

The View is now being pulled between those four points and will therefore sit comfortably at the point in the middle.

If you switch to the Design view, you can see this in action, denoted by small white arrows. Notice that we end this section with an ending tag: a forward slash, followed by the name, and the closing angle bracket.

After that, we also need to create a closing tag to close off the ConstraintLayout ViewGroup. We could now introduce a new type of layout, or we could use nested layouts by adding a new ViewGroup tag inside the ConstraintLayout tags.

In reality, XML is actually supremely simple and follows only a few set rules. The main complication is learning all of the different views and all of the different properties each needs defined. Fortunately, how to learn xml coding can find a lot of this information what serial killer are you quiz, or simply use the design view to experiment and see what is proforma income statement the code should look.

An example of a constraint layout using a button.

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Free Free CSS has free website templates coded using HTML & CSS in its gallery. The HTML website templates that are showcased on Free are the best that can be found in . Dear Twitpic Community - thank you for all the wonderful photos you have taken over the years. We have now placed Twitpic in an archived state. Free XML Programming Tutorial. XML, or eXtensible Markup Language, is a programming language standard for the Internet. XML provides a method to define data formats. XML is a rich system for defining a variety of documents and data structures: invoices, news feeds, glossaries, real estate properties, or custom data feeds.

And all the code used in the book is available to customers in a downloadalbe archive. As always, you can download this excerpt as a PDF if you prefer. Who here has heard of XML? Okay, just about everybody. So, what is XML? A significant portion of the group leans forward eagerly, wanting to learn more. The others either roll their eyes in anticipation of hype and half-formed theories, or cringe in fear of a long, dry history of markup languages.

XML is extensible. It lets you define your own tags, the order in which they occur, and how they should be processed or displayed.

Another way to think about extensibility is to consider that XML allows all of us to extend our notion of what a document is: it can be a file that lives on a file server, or it can be a transient piece of data that flows between two computer systems as in the case of Web Services. The most recognizable feature of XML is its tags, or elements to be more accurate. However, XML allows you to define your own set of tags.

XML is a meta-language: a language that allows us to create or define other languages. More on this later. Okay, we know what it is, but why do we need XML? We need it because HTML is specifically designed to describe documents for display in a Web browser, and not much else. HTML rarely if ever provides information about how the document is structured or what it means. Semantics is the study of meaning in language. Humans are much better at semantics than computers, because humans are really good at deriving meaning.

From there, you could make the leap to other wild cats, then to house cats and maybe even dogs cats and dogs are both pets, after all. Needless to say, computers are really bad at this game, which is a shame, as many computing tasks require semantic skill.

However, even a cursory glance at the rest of the document reveals some very human errors. This last product listing also displays a price before the description, and the price is italicized instead of appearing in bold. The computer would be able only to render the document to a browser with the styles associated with each tag.

Notice that this new document contains absolutely no information about display. Essentially, XML allows you to separate information from presentation — just one of its many powerful abilities. In the example above, we know that a product listing contains products, and that each product has a name, a description, a price, and a shipping cost.

You could say, rightly, that each XML document is self-describing , and is readable by both humans and software. Now, everyone makes mistakes, and XML programmers are no exception. To ensure that everyone plays by the rules, you need a DTD a document type definition , or schema. Once you have a DTD in place, anyone who creates product listings for your application will have to follow the rules.

I want to examine the contents of a typical XML file, character by character. The simplest XML elements contain an opening tag, a closing tag, and some content. In XML, content is usually parsed character data. If you use attributes on any elements, then attribute values must be single- or double-quoted. No longer can you get by with bare attribute values like you did in HTML! The following is okay in HTML:. Also, if you nest your elements improperly i.

In XML, this improper nesting of elements would cause the program reading the document to raise an error. As XML allows you to create any language you want, the inventors of XML had to institute a special rule, which happens to be closely related to the proper nesting rule.

This is called an attribute. You can think of attributes as adjectives — they provide additional information about the element that may not make any sense as content.

What information should be contained in an attribute? What should appear between the tags of an element? Some developers including me!

Another common rule of thumb is to consider the length of the data. Potentially large data should be placed inside a tag; shorter data can be placed in an attribute. In other parts of our DVD listing, the information seems a little bare. One way to do so is with the addition of attributes:. It would be smarter, from an architectural point of view, to have a separate listing of actors with unique IDs to which you could link. Some XML elements are said to be empty — they contain no content whatsoever.

Familiar examples are the img and br elements in HTML. Remember that in XML all opening tags must be matched by a closing tag. For empty elements, you can use a single empty-element tag to replace this:.

I mentioned entities earlier. An entity is a handy construct that, at its simplest, allows you to define special characters for insertion into your documents. XML, true to its extensible nature, allows you to create your own entities. What a time-saver! XML documents are more then just a sequence of elements. This feature, combined with all that content encapsulated in opening and closing tags, takes all XML documents far past the realm of mere data and into the revered halls of information.

Data can comprise a string of characters or numbers, such as But the only way to turn this data into information and therefore make it useful is to add context to it — once you have context, you can be sure about what the data represents. When you take into account the second point — that an XML document is really a hierarchy of objects — all sorts of possibilities open up.

Remember what we discussed before — that, in an XML document, one element contains all the others? Well, that root element becomes the root of our hierarchical tree. You can think of that tree as a family tree, with the root element having various children in this case, product elements , and each of those having various children name, description, and so on.

In turn, each product element has various siblings other product elements and a parent the root , as shown in Figure 1. Figure 1. The logical structure of an XML document. Because what we have is a tree, we should be able to travel up and down it, and from side to side, with relative ease. Before, we talked about transforming data into information by adding context. Earlier in this chapter, I made a point about XML allowing you to separate information from presentation.

For example, if you stored your information in a word processing program, it would contain all kinds of information about the way it should appear on the printed page — lots of bolding, font sizes, and tables. Unfortunately, if that document also had to be posted to the Web as an HTML document, someone would have to convert it either manually or via software , clean it up, and test it. If yet another person wanted to take the same information and use it in a slide presentation, they might run the risk of using outdated information from the HTML version.

As you can see, it can get pretty messy! If you made changes to the XML file, the other files would also change automatically once you passed the XML file through the process. This notion, by the way, is an essential component of single-sourcing — i.

As you can see, separating information from presentation makes your XML documents reusable, and can save hassles and headaches in environments in which a lot of information needs to be stored, processed, handled, and exchanged. That means the publisher can generate sample PDFs for its Website, make print-ready files for the printer, and potentially create ebooks in the future. All formats will be generated from the same source, and all will be created using different style sheets to process the base XML files.

One of the most powerful advantages of XML, of course, is that it allows you to define your own language. However, this most powerful feature also exposes a great weakness of XML. If all of us start defining our own languages, we run the risk of being unable to understand anything anyone else says.

A valid document, then, is nothing more then a well-formed document that adheres to its DTD. For the most part, you will only care that your documents are well formed.

Well-formedness alone allows you to create ad hoc XML documents that can be generated, added to an application, and tested quickly. The first thing we want to do is to create an XML document.

If you have Internet Explorer 5 or higher installed on your machine, you can view your newly-created XML file. As Figure 1. Notice the little minus signs next to some of the XML nodes? A minus sign in front of a node indicates that the node contains other nodes. If you click the minus sign, Internet Explorer will collapse all the child nodes belonging to that node, as shown in Figure 1. Collapsing nodes displaying in Internet Explorer.

The little plus sign next to the first product node indicates that the node has children. Clicking on the plus sign will expand any nodes under that particular node. In this way, you can easily display the parts of the document on which you want to focus. Now, open your XML document in any text editing tool and scroll down to the cost node of the second product. Save your work and reload Internet Explorer.

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