Tips: KTX可以直接将bitmap转为Drawable
val drawable1 = ColorDrawable()
val bitmap1 = drawable1.toBitmap()
Drawable 也可以直接转为BitMap
val bitmap = Bitmap.createBitmap(20,20,Bitmap.Config.ARGB_8888)
val drawable = bitmap.toDrawable(resources)
toDrawable源码:
/** Create a [BitmapDrawable] from this [Bitmap]. */
public inline fun Bitmap.toDrawable(
resources: Resources
): BitmapDrawable = BitmapDrawable(resources, this)
toBitmap源码:
public fun Drawable.toBitmap(
@Px width: Int = intrinsicWidth,
@Px height: Int = intrinsicHeight,
config: Config? = null
): Bitmap {
if (this is BitmapDrawable) {
if (bitmap == null) {
// This is slightly better than returning an empty, zero-size bitmap.
throw IllegalArgumentException("bitmap is null")
}
if (config == null || bitmap.config == config) {
// Fast-path to return original. Bitmap.createScaledBitmap will do this check, but it
// involves allocation and two jumps into native code so we perform the check ourselves.
if (width == bitmap.width && height == bitmap.height) {
return bitmap
}
return Bitmap.createScaledBitmap(bitmap, width, height, true)
}
}
val (oldLeft, oldTop, oldRight, oldBottom) = bounds
val bitmap = Bitmap.createBitmap(width, height, config ?: Config.ARGB_8888)
setBounds(0, 0, width, height)
draw(Canvas(bitmap))
setBounds(oldLeft, oldTop, oldRight, oldBottom)
return bitmap
}
Bitmap: bit 位 ,map 映射,也就是像素映射到内存对象
Drawable: ColorDrawable 默认范围0.0 需要制定Bounds
drawable 内部维持绘制规则 可以使bitmap color 等
bitmap是像素信息
bitmap和drawable 互转本质上是创建彼此的一个对象实例
bitmapDrawable通过canvas.drawBitmap
自定义Drawable:
drawable 是一个接口 需要实现四个方法:
class MatchDrawable : Drawable() {
override fun draw(canvas: Canvas) {
}
override fun setAlpha(alpha: Int) {
}
override fun setColorFilter(colorFilter: ColorFilter?) {
}
override fun getOpacity(): Int {
}
}
setColor KTX 可以写 "#0085d0".toColorInt
大多数情况可以使用系统自带的drawable 比如 colorDrawable BitmapDrawable等