1 00:00:08,830 --> 00:00:14,790 Module 13 is all about doing text IO in XNA games. 2 00:00:14,790 --> 00:00:16,919 So here are the module learning objectives. 3 00:00:21,960 --> 00:00:26,290 And just as a reminder, this is the final module in the course. 4 00:00:26,290 --> 00:00:28,940 So we're going to look at Text IO. 5 00:00:28,940 --> 00:00:31,570 IO stands for input and output. 6 00:00:31,570 --> 00:00:35,400 And the text input that we're going to do, we'll cover today. 7 00:00:35,400 --> 00:00:40,640 So in this lecture we're going to use keyboard input to control our character in 8 00:00:40,640 --> 00:00:43,250 the game, and then next time we'll 9 00:00:43,250 --> 00:00:47,640 do text output to display important game information, 10 00:00:47,640 --> 00:00:51,580 like score, which is a hugely important piece of game information. 11 00:00:51,580 --> 00:00:53,100 That's for next time. 12 00:00:53,100 --> 00:00:56,150 This time, we're going to cover the keyboard 13 00:00:56,150 --> 00:00:59,840 input part of the equation, if you will. 14 00:00:59,840 --> 00:01:03,720 So, you should start off with an in lecture quiz about keyboard input. 15 00:01:08,900 --> 00:01:14,040 And now, we'll go to the code that I all ready have opened up. 16 00:01:14,040 --> 00:01:19,370 And we'll look at how we can use keyboard input to control a fish in the game. 17 00:01:19,370 --> 00:01:22,860 So the end result is this. 18 00:01:22,860 --> 00:01:26,980 I drive a fish around, I'm still eating bears, I guess that's a thing for me. 19 00:01:26,980 --> 00:01:29,990 In this particular game, I can eat bears with the tail of my 20 00:01:29,990 --> 00:01:33,960 fish and all kinds of stuff, so, not nearly as sophisticated as that 21 00:01:33,960 --> 00:01:36,800 previous game that we saw, but. 22 00:01:36,800 --> 00:01:39,700 I can still drive around, I'm using the arrow keys to drive around with the 23 00:01:39,700 --> 00:01:43,440 keyboard so that you know that I'm not, you know, using a controller or something. 24 00:01:44,500 --> 00:01:49,770 So the first thing we do, remember when we got mouse input and processed it. 25 00:01:49,770 --> 00:01:56,123 We called the mouse.getstate method. When we used the game pad for input. 26 00:01:56,123 --> 00:01:59,280 We used the game pad.get state method, 27 00:01:59,280 --> 00:02:04,820 so it shouldn't surprise you at all that here when we're going to use the keyboard, 28 00:02:04,820 --> 00:02:11,050 we call the keyboard.get state method and it returns to us a keyboard 29 00:02:11,050 --> 00:02:17,760 state object. So go do another in lecture quiz. 30 00:02:17,760 --> 00:02:18,900 And I'll open up the Help. 31 00:02:23,880 --> 00:02:30,950 Keyboard state, if we search on that and go look at the Keyboard State members, 32 00:02:33,010 --> 00:02:36,650 we see that there are a number of 33 00:02:36,650 --> 00:02:39,890 methods that we're probably going to find fairly useful. 34 00:02:39,890 --> 00:02:42,430 We can get the pressed keys. 35 00:02:42,430 --> 00:02:47,640 So we can get an array of all the keys that are currently pressed, we can check 36 00:02:47,640 --> 00:02:54,870 if a particular key is down, and we can check if a particular key is up. 37 00:02:54,870 --> 00:02:59,060 Those are the three methods that you're most likely to use a lot. 38 00:02:59,060 --> 00:03:03,890 As you're dealing with this keyboard state object that gets returned from the 39 00:03:03,890 --> 00:03:10,030 keyboard get state method. So back to our code. 40 00:03:10,030 --> 00:03:13,000 We can see that I'm getting the state here. 41 00:03:13,000 --> 00:03:15,650 And in fact, right here, to make it so I 42 00:03:15,650 --> 00:03:19,820 can just exit from this game by pressing the Esc key. 43 00:03:19,820 --> 00:03:23,840 I've used keyboard, which I just got up here, 44 00:03:25,160 --> 00:03:29,780 I'm calling the IsKeyDown method, which returns true or false. 45 00:03:31,100 --> 00:03:37,560 And I'm passing in a value from the enumeration keys. 46 00:03:37,560 --> 00:03:44,310 So keys has, enumerates, basically, every, every conceivable key on the keyboard, 47 00:03:44,310 --> 00:03:50,340 that's probably not precisely accurate given our international student body 48 00:03:50,340 --> 00:03:55,100 here, but, lots of keys in the keys enumeration. 49 00:03:55,100 --> 00:04:01,868 And so, you did something similar already in the project increment, right where you 50 00:04:01,868 --> 00:04:06,380 called keyboard.getstate.IsKeyDownkeys.enter to 51 00:04:06,380 --> 00:04:08,072 move from the opening 52 00:04:08,072 --> 00:04:10,831 screen on to the actual game play. 53 00:04:10,831 --> 00:04:12,963 Now, now you get to see how that actually works, 54 00:04:12,963 --> 00:04:15,407 if you hadn't figured that out already, so that gets us 55 00:04:15,407 --> 00:04:18,497 the keyboard state, how do we actually use it to move our fish around. 56 00:04:18,497 --> 00:04:24,425 If we come down here to the update method and go to Definition by right 57 00:04:24,425 --> 00:04:30,170 clicking, and go to Definition, we see that here's what we do. 58 00:04:31,270 --> 00:04:35,930 We check if the key is down and it's the right key, now I don't 59 00:04:35,930 --> 00:04:40,600 mean the correct key, I mean the right arrow key, then we change the x 60 00:04:40,600 --> 00:04:43,690 property here. We'll look at that in a moment. 61 00:04:43,690 --> 00:04:45,180 By the fish move amount. 62 00:04:45,180 --> 00:04:49,710 So driving with the keyboard is like moving this around with the game pad. 63 00:04:49,710 --> 00:04:51,730 It's not following the mouse. 64 00:04:51,730 --> 00:04:56,150 It's applying fish for us to, if you will, to move the fish around. 65 00:04:56,150 --> 00:05:03,380 And there's a little bit of extra processing here where the fish. 66 00:05:03,380 --> 00:05:05,675 Art asset is actually the fish 67 00:05:05,675 --> 00:05:06,350 [LAUGH] 68 00:05:06,350 --> 00:05:10,460 the fish facing both ways. That's a tongue twister. 69 00:05:10,460 --> 00:05:14,930 The fish facing both ways, and so I pick which way it should be 70 00:05:14,930 --> 00:05:19,750 pointing, to the right or to the left, based on, based on its direction. 71 00:05:19,750 --> 00:05:23,720 So, let's go take a look at the X property And the fish move amount. 72 00:05:23,720 --> 00:05:27,180 We'll do it in exactly the opposite order from what I just said. 73 00:05:27,180 --> 00:05:31,000 So the fish move amount just gives us the speed of the fish. 74 00:05:31,000 --> 00:05:34,190 Basically how many pixels it would move. 75 00:05:34,190 --> 00:05:37,178 So this is not physics-based movement in any way. 76 00:05:37,178 --> 00:05:43,130 This is five pixels per update if in fact the appropriate key is pressed. 77 00:05:44,180 --> 00:05:47,880 The other thing that we should look at is the x property. 78 00:05:48,940 --> 00:05:52,570 Because this is the x location in the center of the fish. 79 00:05:52,570 --> 00:05:55,380 And, here's the interesting part for us, right? 80 00:05:55,380 --> 00:05:56,050 We're changing the 81 00:05:56,050 --> 00:06:00,270 drawrectangle, and that's fine, because we're changing the drawrectangle x 82 00:06:00,270 --> 00:06:03,900 based on the idea that the x property is centered. 83 00:06:03,900 --> 00:06:06,230 But we also are making sure that 84 00:06:06,230 --> 00:06:08,810 we're keeping the fish clamped within the window, 85 00:06:08,810 --> 00:06:10,580 so we can't drive the fish outside 86 00:06:10,580 --> 00:06:12,800 the window, even though we're using the keyboard. 87 00:06:14,130 --> 00:06:16,790 So back to the update method, 88 00:06:18,890 --> 00:06:25,630 we can see that we have four different if statements, one for right, one for left. 89 00:06:25,630 --> 00:06:27,500 One for up, and one for down. 90 00:06:27,500 --> 00:06:31,610 And only left and right change the source rectangles because I only have two images. 91 00:06:31,610 --> 00:06:34,810 We don't make the face, the fish face up or down. 92 00:06:36,050 --> 00:06:40,650 So, you might be wondering, because I know I would be, what 93 00:06:40,650 --> 00:06:44,850 happens if you press, press both left and right at the same time? 94 00:06:44,850 --> 00:06:46,670 Well, it turns around. 95 00:06:46,670 --> 00:06:49,580 You should actually walk through the code and see why 96 00:06:49,580 --> 00:06:54,150 if Im holding both left and right down, it's turning around. 97 00:06:54,150 --> 00:06:58,770 And the other thing that you can do is you can of course move diagonally. 98 00:06:58,770 --> 00:07:02,790 Now, I don't know if you can actually tell from this. 99 00:07:02,790 --> 00:07:05,900 But if I'm moving left and right, I'm moving 100 00:07:05,900 --> 00:07:10,490 it five pixels per update and if I'm moving diagonally, 101 00:07:10,490 --> 00:07:15,980 I'm moving at five times the square root of two pixels per update because 102 00:07:15,980 --> 00:07:20,070 of the way this is set up that I can move by fish amount. 103 00:07:20,070 --> 00:07:25,540 Horizontally and move by fish amount vertically in a single update. 104 00:07:25,540 --> 00:07:28,960 There's actually a very famous bug in Doom. 105 00:07:28,960 --> 00:07:35,830 So, it's called the Doom strafe 40 bug. And it essentially happens for exactly 106 00:07:35,830 --> 00:07:38,010 this reason. Because, the, okay. 107 00:07:38,010 --> 00:07:38,870 Maybe not exactly. 108 00:07:38,870 --> 00:07:40,670 But, the same idea. 109 00:07:40,670 --> 00:07:43,350 That, moving diagonally, you can move faster 110 00:07:43,350 --> 00:07:46,280 than if you're moving horizontally or vertically. 111 00:07:46,280 --> 00:07:51,580 So, it, it's, not rocket science, but it's not worth spending 112 00:07:51,580 --> 00:07:53,840 the time it would take in this lecture to fix this 113 00:07:53,840 --> 00:07:56,820 particular bug, but you should know that there is, in fact, 114 00:07:56,820 --> 00:08:00,940 a bug here, a very famous bug that you could fix if 115 00:08:00,940 --> 00:08:05,840 you worked at it a little bit. just as a hint, if you decide to do 116 00:08:05,840 --> 00:08:11,090 that, figuring out what the move amount should be, based 117 00:08:11,090 --> 00:08:16,640 on the keys that are currently pressed. 118 00:08:16,640 --> 00:08:17,930 So, for example, if they're going to move 119 00:08:17,930 --> 00:08:20,710 diagonally, if you change the move amount to 120 00:08:20,710 --> 00:08:26,470 be 5 divided by square root of 2 And then move it that amount horizontally and 121 00:08:26,470 --> 00:08:29,870 that amount vertically, you'll have solved this bug. 122 00:08:29,870 --> 00:08:32,960 The, the speed of movement will always be the same 123 00:08:32,960 --> 00:08:36,760 no matter in which of the eight possible directions they're moving. 124 00:08:38,770 --> 00:08:42,350 Ok, the only other, so really that's it for 125 00:08:42,350 --> 00:08:46,910 keyboard input, but let's actually add the capability cause you 126 00:08:46,910 --> 00:08:50,020 know some gamers like to use these keys that 127 00:08:50,020 --> 00:08:53,100 have w's, and a's, and s's and d's on them. 128 00:08:53,100 --> 00:08:55,920 So we can add wasd support, a well. 129 00:08:57,030 --> 00:08:57,850 Fairly quickly. 130 00:09:00,100 --> 00:09:06,370 of course, W is not to the right, so that would be a really wacky way to do it. 131 00:09:06,370 --> 00:09:12,489 So let's add WASD support, 132 00:09:12,489 --> 00:09:18,159 right, left. Now I finally get to use W. 133 00:09:22,290 --> 00:09:23,880 And down. 134 00:09:23,880 --> 00:09:31,530 And so if I F5 again, you can tell that I'm actually driving with w, s a, and d. 135 00:09:31,530 --> 00:09:34,720 And of course, both if I want to go super fast on the diagonal. 136 00:09:35,740 --> 00:09:39,440 So, you should now go do an in lecture quiz. 137 00:09:40,710 --> 00:09:44,600 About getting the state and how that works. 138 00:09:49,490 --> 00:09:53,720 Then you should do another in lecture quiz about how we 139 00:09:53,720 --> 00:09:59,330 process the keys that we have extracted from the keyboard state or. 140 00:09:59,330 --> 00:10:04,670 More precisely, how do we process the keyboard state in useful ways? 141 00:10:07,760 --> 00:10:11,140 And, really, that's all there is to doing keyboard input. 142 00:10:11,140 --> 00:10:15,770 You can see significant parallels between using a mouse for input 143 00:10:15,770 --> 00:10:18,870 and a game pad for input and a keyboard for input. 144 00:10:18,870 --> 00:10:22,260 We get the state of the input device And then we examine 145 00:10:22,260 --> 00:10:29,100 the state of the input device and process that state in appropriate ways. 146 00:10:29,100 --> 00:10:33,600 That's it for keyboard input. Next time we will see how to use 147 00:10:33,600 --> 00:10:40,270 text output in our XNA games so we can display important textual information.