coco
105 lines
3.7 KiB
Markdown
105 lines
3.7 KiB
Markdown
# Pie Charts
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Like all other primary chart and graph classes in Androidplot, `PieChart` is simply a composition
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of widgets along with convenience methods. The real work is actually done by `PieWidget`.
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# Basic Usage
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Pie charts are composed of one or more values called Segments which combines a vaue and a label:
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```java
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Segment segment = new Segment("my segment", 10);
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```
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Displaying a `Segment` to a pie chart also requires a `SegmentFormatter`. `SegmentFormatter` is what defines
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the visual characteristics of the associated `Segment`; color, border thickness,
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segment offset, label text style (if any) etc. The below code instantiates a new `SegmentFormatter`
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with a segment color of red:
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```java
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SegmentFormatter formatter = new SegmentFormatter(Color.RED);
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```
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Finally, the `Segment` must be added to the pie chart along with it's `SegmentFormatter`:
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```java
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pie.addSegment(segment, formatter);
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```
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# Donut Size
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By default, `PieChart` draws it's self as a ring. The amount of empty space in the middle of
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the pie is called the `donutSize`. Setting a `donutSize` of 0 causes the `PieChart` to draw it's
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self as a full circle.
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Setting `donutSize` programmatically:
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```java
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// draw pie with an empty inner space radius equal to 50% of the pie's radius.
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pieRenderer.setDonutSize(0.5, PieRenderer.DonutMode.PERCENT);
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// donut size may also be expressed in pixels:
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pieRenderer.setDonutSize(PixelUtils.dpToPix(30), PieRenderer.DonutMode.PIXELS);
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```
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# Segment Orientation
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Each `Segment` is drawn in the order it was added to the `PieChart` clockwise from `startDegs`
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which by default is 0.
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Using the image above, to move Segment0 to the Northeast quadrant
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of the pie (currently occupied by Segment3) `startDeg` should be set to 90:
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```java
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pie.getRenderer(PieRenderer.class).setStartDegs(90);
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```
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# Extent
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The `extentDegs` value determines the number of degrees running clockwise from `startDegs` that
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represent 100% of the pie chart. The formal description is a little obtuse but is easy to understand
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through example. You could for instance use `extentDegs` in conjunction with `startDegs` to represent
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the full pie as a gauge:
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```java
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// start the first segment at 5 degrees;
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pie.getRenderer(PieRenderer.class).setStartDegs(165);
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pie.getRenderer(PieRenderer.class).setExtentDegs(150);
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```
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Which produces a pie chart profile like this:
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# SegmentFormatter
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As mentioned above, `SegmentFormatter` defines how a `Segment` is visually represented in a `PieChart`.
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In addition to basic color / border line styling params, there are several parameters available
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to visually distinguish a segment:
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## Offset
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Value in pixels used to "shift" the position of the segment outward relative to the center of the `PieChart`.
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The visual effect is equivalent to cutting up a pie and dragging one piece out and away from the rest of the pie:
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## RadialInset
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Value in degrees used to shrink the radial edges of the segment inward. The visual effect is equivalent
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to shaving the edges off of a slice of pie, resulting in a narrower slice of pie:
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## InnerInset
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Value in pixels used to shrink the inner section of the pie. The visual effect is equivalent to
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cutting the tip off of a slice of pie:
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## OuterInset
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Value in pixels used to shrink the outer edge of the pie. The visual effect is equivalent to evenly
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shaving the crust off of a slice of pie:
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See the DemoApp's
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[pie chart example source](../demoapp/src/main/java/com/androidplot/demos/SimplePieChartActivity.java) for a comprehensive usage example.
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