Lua帧动画机：序列帧的播放与循环

flowchart TD
A[计帧累加] --> B{攒满一帧时长}
B -- 否 --> A
B -- 是 --> C[帧号加一取模总帧数]
C --> D{单次模式且到末帧}
D -- 是 --> E[停 在末帧定住]
D -- 否 --> F[按帧号取图上屏]
F --> A
E --> A

 fx-frameanim

-- @file FrameAnim.lua
-- 帧动画机 —— 序列帧的播放与循环

local FrameAnim = {}

local CONST = {
    FRAME_COUNT   = 6,
    FPS           = 8,
    LOOP          = true,

    AUTOINC_BASE  = 1153000,
}

local _frame      = 0
local _frameT     = 0
local _playing    = true
local _fps        = CONST.FPS
local _loop       = CONST.LOOP
local _onFrame    = nil
local _scheduler  = nil
local _autoInc    = 0

local function GenID(prefix)
    _autoInc = _autoInc + 1
    return string.format("%s_%d", prefix or "FAM",
        CONST.AUTOINC_BASE + _autoInc)
end

local function ShowTip(msg)
    if msg and msg ~= "" then SL:ShowSystemTips(msg) end
end

function FrameAnim.OnFrame(func)
    _onFrame = func
end

function FrameAnim.Frame()
    return _frame
end

function FrameAnim.TogglePlay()
    _playing = not _playing
end

function FrameAnim.SetSpeed(fps)
    _fps = fps
end

function FrameAnim.SetLoop(loop)
    _loop = loop
end

-- 计帧推进与模式判定：攒满时长翻一页
if not _scheduler then
    _scheduler = SL:Schedule(function(dt)
        if not _playing then return end
        _frameT = _frameT + dt
        if _frameT < 1 / _fps then return end
        _frameT = _frameT - 1 / _fps
        _frame = _frame + 1
        if _frame >= CONST.FRAME_COUNT then
            if _loop then
                _frame = 0
            else
                _frame = CONST.FRAME_COUNT - 1
                _playing = false
                ShowTip("单次播完——停在末帧")
            end
        end
        if _onFrame then
            _onFrame(_frame)
        end
    end, 0.02)
end

function FrameAnim.Play(frames, fps, loop)
    if frames then CONST.FRAME_COUNT = #frames end
    if fps then _fps = fps end
    if loop ~= nil then _loop = loop end
    _frame = 0
    _frameT = 0
    _playing = true
end

function FrameAnim.Unload()
    if _scheduler then SL:Unschedule(_scheduler) end
    _playing = false
    _frame = 0
end

return FrameAnim