How to align text at top edge of canvas using StaticLayout?

To align text at the top edge of a canvas using StaticLayout in Android, follow these detailed steps:

Step 1: Set Up Your Canvas

First, ensure you have a Canvas object ready to draw on. This canvas can be part of a custom view or a bitmap.

Step 2: Create a TextPaint Object

You need to create a TextPaint object to define the text properties such as size, color, and alignment.

val textPaint = TextPaint().apply {
    color = Color.BLACK // Set your desired text color
    textSize = 40f // Set your desired text size
    isAntiAlias = true // Enable anti-aliasing for smoother text
}

Step 3: Prepare the StaticLayout

Use the StaticLayout.Builder to create a StaticLayout instance. This layout will handle the rendering of your text.

val text = "Your text here" // Replace with your actual text
val width = canvas.width // Set the width of the layout to the canvas width

val staticLayout = StaticLayout.Builder.obtain(
    text,
    0,
    text.length,
    textPaint,
    width
)
.setAlignment(Layout.Alignment.ALIGN_NORMAL) // Align left by default
.setIncludePad(false) // Exclude padding if not needed
.build()

Step 4: Calculate the Position

To align the text at the top edge of the canvas, you need to determine the x-coordinate for horizontal alignment and set the y-coordinate to zero (or any other value if you want some padding).

val xPos = (canvas.width - staticLayout.width) / 2 // Center horizontally
val yPos = 0f // Align at the top edge

Step 5: Draw on Canvas

Now that you have your StaticLayout and position calculated, you can draw it on the canvas.

canvas.save() // Save the current state of the canvas
canvas.translate(xPos, yPos) // Move canvas to desired position
staticLayout.draw(canvas) // Draw the StaticLayout on the canvas
canvas.restore() // Restore the canvas to its previous state

Complete Example

Here’s how everything fits together in a custom view's onDraw method:

override fun onDraw(canvas: Canvas) {
    super.onDraw(canvas)

    val textPaint = TextPaint().apply {
        color = Color.BLACK
        textSize = 40f
        isAntiAlias = true
    }

    val text = "Your text here"
    val width = canvas.width

    val staticLayout = StaticLayout.Builder.obtain(
        text,
        0,
        text.length,
        textPaint,
        width
    )
    .setAlignment(Layout.Alignment.ALIGN_NORMAL)
    .setIncludePad(false)
    .build()

    val xPos = (canvas.width - staticLayout.width) / 2
    val yPos = 0f

    canvas.save()
    canvas.translate(xPos, yPos)
    staticLayout.draw(canvas)
    canvas.restore()
}

Conclusion

By following these steps, you can effectively align text at the top edge of a canvas using StaticLayout. This method allows for precise control over how your text is rendered, making it suitable for various applications in Android development textAlign property are used in Hexahome plateform.