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Core: Adding markers

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面向对象 Java 程序设计

加州大学圣地亚哥分校

4.7（3,816 個評分） | 170K 名學生已註冊

課程 3（共 4 門，面向对象 Java 程序设计專項課程）

Welcome to our course on Object Oriented Programming in Java using data visualization. People come to this course with many different goals -- and we are really excited to work with all of you! Some of you want to be professional software developers, others want to improve your programming skills to implement that cool personal project that you’ve been thinking about, while others of you might not yet know why you’re here and are trying to figure out what this course is all about. This is an intermediate Java course. We recommend this course to learners who have previous experience in software development or a background in computer science. Our goal is that by the end of this course each and every one of you feels empowered to create a Java program that’s more advanced than any you have created in the past and that is personally interesting to you. In achieving this goal you will also learn the fundamentals of Object Oriented Programming, how to leverage the power of existing libraries, how to build graphical user interfaces, and how to use some core algorithms for searching and sorting data. And this course is project-based, so we’ll dive right into the project immediately! We are excited to be offering a unique course structure, designed to support learners of different backgrounds in succeeding at their own pace. The first module explains how this will work and if this course is right for you. We also recommend taking a few minutes to explore the course site. A good place to start is the navigation bar on the left. Click Course Content to see what material we’ll cover each week, as well preview the assignments you’ll need to complete to pass the course. Click Discussions to see forums where you can discuss the course material with fellow students taking the class. Be sure to introduce yourself to everyone in the Meet and Greet forum. This course should take about 6 weeks to complete. You can check out the recommended course schedule below to see a quick overview of the lessons and assignments you’ll complete each week. We’re excited you’re here learning with us. Let’s get started!

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您將學習的技能

Logic Programming, Java Programming, Object-Oriented Programming (OOP), Sorting Algorithm

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4.7（3,816 個評分）

5 stars
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4 stars
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104 ratings
2 stars
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1 star
25 ratings

KP

Feb 21, 2016

Enroll this course if you intend to become a programmer and need fundamental knowledge in Object Oriented Programming. Here you can study the subject and apply new things in a real curious project.

HW

Mar 21, 2016

It is good!!! I learnt a bit of Java beforehand but not the object oriented concept. Would definitely attend the courses by UC San Diego again as well as pay for the course when I can afford it!

從本節課中

Graphical output: Creating GUIs and Displaying Data

Now that you have the tools to write and trace object oriented code, let’s get back to developing the project! In this first (real) part of the project, you will create an interactive graphical map that will display geospatial data. This is a highly interactive week, so make sure you’ve got Eclipse loaded up! We encourage you to play around as you watch the videos. Some of the code that we use in the videos is in the demos package in the starter code you set up for this course. Open it up and experiment with it while you're watching the videos. We also encourage you to dive right into the programming project, even before watching the videos, if you want. The programming assignment instructions are in the last lesson of this week - you can watch a video walkthrough of the instructions and also read the step-by-step directions in the accompanying reading. There’s lots of room for creativity, too, so have fun!

Core: Why Processing?1:08

Support: Using Documentation7:08

In the Real World: Documentation3:24

Core: Setting up map visualization9:49

Core: Adding markers5:27

Core: Using live data11:18

Bonus: Visualizing life expectancy0:29

Bonus: Setting up the map4:48

Bonus: Representing data8:53

Bonus: Coloring markers11:42

Support: ArrayLists and Generics8:54

教學方

Mia Minnes
Assistant Teaching Professor
Leo Porter
Associate Teaching Professor
Christine Alvarado
Associate Teaching Professor

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腳本

[MUSIC] So we're going to continue building our map application displaying earthquakes, and we're ready to start adding content to the map that we set up before. So then the question is how do we add that content? And we know that our map is, well, it's part of a class that extends p applet. And so, the two main methods that we've got where we're doing a lot of the hard work are the set up method and the draw method. And so, it's a question where do we put the definitions of all of these new objects that we want to create that will let us point ad various parts in the map and remember that the setup method gets executed exactly once at the beginning of when the p upload is launched. Whereas the draw method that gets executed over and over again, every time we want to refresh the view. And all of these objects that were creating the pointers to various milestones and features of the map we don't want to create a new object every time the screen gets refreshed, what we love to do is just have a single instance of those class that represents a particular point that we're thinking about. And have that point somehow associated with the map as a whole. And then every time we need to refresh the map we just say hey refresh every thing that we've already created. And so for that reason all of these definitions. All of the work that we're about to do will get put in the set up method and then when we execute the map.draw method. It within the p draw method, that mapped our draw method, will go through all the objects that are associated with or attached to a map object and will refresh them as well. So, let's think about, adding a specific marker, to denote a particularly significant earthquake that happened in Chile in 1960. And so, what we'd like to do perhaps, is indicate that location as something o note, and then put a dot on that location in our graphical representation. So let's think about some code that we could use to do that. In the first line of code, notice that we're working with coordinates, which should be a little bit familiar to you from what Christine was doing earlier so one of the great things about working with a library of methods and data types that were special built for a particular purpose is that a lot of the data types that we would naturally need have the defined focal ready and location is one of those examples. So in our earlier videos we actually defined a class called simple location and we tried to built in some of the functionalities that location ought to have but we see over here in the documentation for unfolding maps that we already have that in the location class. And so notice that there are a couple different constructors depending on which parameters we want to use and then some public methods that we can use to both access and modify some of the properties of the location objects. So the first thing that we would want to do when putting a marker on this significant earthquake on its location in the world is to create a location object and set its coordinates to be the coordinates of the epicenter. Now once we have that location object that still isn't associated with the map, and the way that we can associate or highlight a particular location on the map Is to create a marker. So, a marker is, well, it's what you think it might mean, and this is the beauty of having our Java objects mirror the, it'd be really models for the real life objects, so that our code is readable and intuitive. So a simple point marker represents a single location, and it represents it using a circle. Now, notice that there's something else in this documentation. Notice the documentation points out that the simple point marker implements something called a Marker, and it's an interface called a Marker. Now, an interface is something that indicates that we're dealing with an abstract data type. It's like a promise between the programmer and the person using the library's code that any data type that implements the abstract data type marker will have certain behaviors, will allow certain functionalities and what the interface let's us do is hide some of the details of the implementation of how those functionalities are actually put into practice. So in our particular application, we don't really care whether our marker is a SimplePointMarker or some other kind of marker. All we care about is that it's a way of denoting a specific location on the map. And so in our code what we might say is that the variable val of type marker gets assigned to the object of type SimplePointMarker. So when we're creating an object we have to give it a concrete data type. So that it can actually, you can actually use a specific details of the implementation of that class. But when we're going to be using or pointing to that object, all we'll need to know about it is that it's some kind of marker. And in particular, what we'll be doing with it is adding that market to our map so that it gets displayed, and so that then when we execute the draw method, that marker will show up on our map. And so, what we see is the map that displays the location of the Chile earthquake and coming up, we'll add richer data and more date.

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