Let’s take a look at what we are going to build.
The secret is to clip canvas before drawing the text!
private fun drawText(canvas: Canvas, paint: Paint, start: Int, end: Int) { canvas.save() rect.set(start, 0, end, height) canvas.clipRect(rect) val textString = text.toString() paint.getTextBounds(textString, 0, textString.length, bounds) val x = width / 2 - bounds.width() / 2 val fontMetrics = changePaint.fontMetrics val dy = (fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom val baseline = height / 2 + dy canvas.
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Drawing text can be tricky at times, let’s look at some examples.
First, let’s look at some terminologies used here.
Some most important keywords are:
baseline: the line where the text “sits on” ascent: The recommended distance above the baseline for singled spaced text descent: The recommended distance below the baseline for singled spaced text top: The maximum distance above the baseline for the tallest glyph in the font at a given text size bottom: The maximum distance below the baseline for the lowest glyph in the font at a given text size A picture is worth 1000 words:
You: Master, I heard this PECS in the JAVA world. But I’m deeply puzzled by it.
Master: Do you know what it stands for?
You: Producer Extends Consumer Super?
Master: In order to understand it, you shall stop thinking about what these words mean, it’s not helpful at all. Just follow my questions.
You: Yes, Master. Please start.
Master: There are plants, then there are fruits, then there are apples and pears.
