Android Compose 平铺图像以用小图案填充背景的方法是什么?
不旋转位图的简单方法可能是这样的:
@Composable
fun TileImage() {
val pattern = ImageBitmap.imageResource(R.drawable.pattern_bitmap)
Canvas(modifier = Modifier.fillMaxSize()) {
// rotate(degrees = -15f) { // The rotation does not produce the desired effect
val totalWidth = size.width / pattern.width
val totalHeight = size.height / pattern.height
var x = 0f
var y = 0f
for (i in 0..totalHeight.toInt()) {
y = (i * pattern.height).toFloat()
for (j in 0..totalWidth.toInt()) {
x = (j * pattern.width).toFloat()
drawImage(
pattern,
colorFilter = giftColorFilter,
topLeft = Offset(x, y)
)
}
}
// }
}
}
在 Android XML 中,您可以轻松创建 XML 来重复位图
<bitmap xmlns:android="http://schemas.android.com/apk/res/android"
android:src="@drawable/pattern_bitmap"
android:tileMode="repeat" />
或者,如果您需要平铺矢量,您可以使用自定义 Drawable 类来实现您的目标
TileDrawable(AppCompatResources.getDrawable(context, R.drawable.pattern_vector), Shader.TileMode.REPEAT)
class TileDrawable(drawable: Drawable, tileMode: Shader.TileMode, private val angle: Float? = null) : Drawable() {
private val paint: Paint = Paint().apply {
shader = BitmapShader(getBitmap(drawable), tileMode, tileMode)
}
override fun draw(canvas: Canvas) {
angle?.let {
canvas.rotate(it)
}
canvas.drawPaint(paint)
}
override fun setAlpha(alpha: Int) {
paint.alpha = alpha
}
override fun getOpacity() = PixelFormat.TRANSLUCENT
override fun setColorFilter(colorFilter: ColorFilter?) {
paint.colorFilter = colorFilter
}
private fun getBitmap(drawable: Drawable): Bitmap {
if (drawable is BitmapDrawable) {
return drawable.bitmap
}
val bmp = Bitmap.createBitmap(
drawable.intrinsicWidth, drawable.intrinsicHeight,
Bitmap.Config.ARGB_8888
)
val c = Canvas(bmp)
drawable.setBounds(0, 0, drawable.intrinsicWidth, drawable.intrinsicHeight)
drawable.draw(c)
return bmp
}
}
根据拉菲尔的回答,我能够想出一些更简洁的东西。希望 Compose 能够提供一些内置功能,让这一切在未来变得更简单。
val image = ImageBitmap.imageResource(R.drawable.my_image)
val brush = remember(image) { ShaderBrush(ImageShader(image, TileMode.Repeated, TileMode.Repeated)) }
Box(Modifier
.fillMaxSize()
.background(brush)) {
}
如果你想使用原生画布,你可以在 jetpack compose 中执行类似的操作。
Canvas(
modifier = Modifier
.fillMaxSize()
) {
val paint = Paint().asFrameworkPaint().apply {
isAntiAlias = true
shader = ImageShader(pattern, TileMode.Repeated, TileMode.Repeated)
}
drawIntoCanvas {
it.nativeCanvas.drawPaint(paint)
}
paint.reset()
}
如果您想将重复限制在一定的高度和宽度,您可以在画布中使用剪辑修改器,如下所示,否则它将填满整个屏幕。
Canvas(
modifier = Modifier
.width(300.dp)
.height(200.dp)
.clip(RectangleShape)
) {
----
}
我找不到任何现有的扩展来加载矢量资源并将其转换为组成 ImageBitmap,因此这里是如何基于加载 BitmapDrawable:
的标准扩展来执行此操作的示例fun ImageBitmap.Companion.vectorImageResource(res: Resources, @DrawableRes id: Int): ImageBitmap {
return requireNotNull(ResourcesCompat.getDrawable(res, id, null))
.toBitmap()
.asImageBitmap()
}
@Composable
fun ImageBitmap.Companion.vectorImageResource(@DrawableRes id: Int): ImageBitmap {
val context = LocalContext.current
val value = remember { TypedValue() }
context.resources.getValue(id, value, true)
val key = value.string!!.toString() // image resource must have resource path.
return remember(key) { vectorImageResource(context.resources, id) }
}
然后可以将生成的 ImageBitmap 传递给上面 Erik Uggeldahl 的示例。
val brush = remember(image) { ShaderBrush(ImageShader(image, TileMode.Repeated, TileMode.Repeated)) }