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Adding Labels6:24 with Ben Deitch
In this video we'll add labels to our chart to give us a better idea of what's going on!
We just finished turning our boring stock chart into an exciting candlestick chart. 0:00 But without knowing what prices these are, it's not a very useful chart. 0:04 So let's add a few labels to give us some price info. 0:08 Let's start at the top of the class by creating a new paint object for our text. 0:12 And let's name it textPaint. 0:16 So Ctrl or Cmd + D to duplicate this. 0:18 And then name it textPaint. 0:21 Then, inside the constructor we need to set a few properties of our new 0:24 paint object. 0:27 The first property we need to set is the color. 0:29 So let's type textPaint.setColor then pass in Color.WHITE. 0:31 The next property we need to set is the text size. 0:39 We can do that with the setTextSize function. 0:42 So textPaint.setTextSize and 0:44 let's pass in 40f to make our text about 40 pixels tall. 0:47 Finally, since we want our labels to go on the right side of the screen, 0:53 we need to have our text be right aligned. 0:57 To do this, we can call textPaint.setTextAlign and 0:59 pass in Paint.Align.RIGHT. 1:07 And now that we've got our textPaint, 1:11 all that's left is to use it to draw our labels. 1:13 Inside the onDraw function, below our for loop where we draw our candlesticks. 1:16 Let's add another loop to loop from the minPrice to the maxPrice. 1:23 for (int i =, and we'll have to 1:28 cast this as an int, minPrice. 1:32 While i is less than maxPrice, i++. 1:36 Then, inside this loop, let's add a line and label for every $20 increment. 1:46 Let's start by checking if i divides evenly into 20. 1:52 We can do this by saying if (i %20 == 0). 1:55 And if it is then we'll draw our label and add a horizontal line. 2:02 Starting with the horizontal line let's type canvas.drawLine and 2:07 pass in 0 for the starting x. 2:13 getYPosition of i for the starting y. 2:17 Then width for the stopX and 2:22 getYPosition of i again for the stopY. 2:25 And finally strokePaint for the paint. 2:29 Also we don't want these lines to be quite as wide as our candle lines. 2:34 So let's add a line above this one and call strokePaint.setStrokeWidth. 2:38 And only make this one pixel wide, nice. 2:45 Last but not least, we just need to draw our text. 2:50 Let's add a line below where we draw our line. 2:53 Ad then call canvas.drawText. 2:55 And then let's pass in our text as i + an empty string to cast it to a string. 3:00 And then let's pass in width for the x value. 3:07 And getYPosition of i for the Y value. 3:11 And then our textPaint for the paint. 3:17 Then let's run the app. 3:21 And there are our labels, but it doesn't look that good. 3:27 Our labels are covering up part of the chart. 3:30 And also it'd be nice if the labels were centered on their lines, 3:32 instead of being above them. 3:36 Back in the code, let's first fix the issue of our labels covering up the chart. 3:38 To do this, we're just going to make our chart a little less wide. 3:43 Inside the onDraw method above where we set rectWidth let's create a new float 3:47 named chartWidth. 3:52 And let's set that equal to width, minus the size of our text. 3:57 Which we can find by using textPaint.measureText and 4:01 passing in the text we'd like to measure. 4:05 Let's go with 1000 as a string to make sure we have enough room for the price. 4:09 Once we've got our chartWidth variable we just need to update rectWidth to 4:15 use it instead of our width. 4:18 Also we should update our horizontal lines to use chartWidth as well. 4:26 So here we should change width to chartWidth, awesome. 4:32 Now that we've made some space for our text. 4:36 Let's also lower it a bit to make each label match up with its own line. 4:38 To do this we just need to add half of the text's height to its Y value. 4:43 Unfortunately to get the text height, we first need to get a textBounds object. 4:47 So up at the top of the class let's add two new fields. 4:52 One float for our textHeight and one Rect which we'll need to import. 4:57 And we'll call it textBounds. 5:02 And we also need to initialize it. 5:07 So let's set it equal to a new Rect. 5:09 Then at the bottom of our constructor after our textPaint has been set up. 5:11 Let's call textPaint.getTexBounds. 5:17 This function takes in a string, and a start and end point of that string. 5:21 It also takes in a rectangle which updates to be a bounding box around our string 5:26 from start to end. 5:31 Since we're only concerned with the height of our text. 5:32 Let's just pass in 0 as a string for the text and then 0 and 5:35 1 for the start and end and also our textBounds. 5:41 Then on the next line let's set 5:47 textHeight = textBounds.height. 5:51 Finally back on the bottom of onDraw, let's add, 5:56 textHeight / 2 to the y value of our text. 6:02 Then let's run the app and see if we got it. 6:07 Nice, great job! 6:13 Those are some awesome looking candlesticks. 6:16 Coming up, we'll see how we can modify our code and 6:18 add our chart view in XML instead of in MainActivity. 6:21
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