import master.flame.danmaku.danmaku.model.Duration; //导入依赖的package包/类
public BaseDanmaku createDanmaku(int type, float viewportWidth, float viewportHeight, float viewportSizeFactor, float scrollSpeedFactor) {
    boolean sizeChanged = updateViewportState(viewportWidth, viewportHeight, viewportSizeFactor);
    if (this.MAX_Duration_Scroll_Danmaku == null) {
        this.MAX_Duration_Scroll_Danmaku = new Duration(this.REAL_DANMAKU_DURATION);
        this.MAX_Duration_Scroll_Danmaku.setFactor(scrollSpeedFactor);
    } else if (sizeChanged) {
        this.MAX_Duration_Scroll_Danmaku.setValue(this.REAL_DANMAKU_DURATION);
    }
    if (this.MAX_Duration_Fix_Danmaku == null) {
        this.MAX_Duration_Fix_Danmaku = new Duration(COMMON_DANMAKU_DURATION);
    }
    if (sizeChanged && viewportWidth > 0.0f) {
        updateMaxDanmakuDuration();
        float scaleX = 1.0f;
        float scaleY = 1.0f;
        if (this.CURRENT_DISP_WIDTH > 0 && this.CURRENT_DISP_HEIGHT > 0) {
            scaleX = viewportWidth / ((float) this.CURRENT_DISP_WIDTH);
            scaleY = viewportHeight / ((float) this.CURRENT_DISP_HEIGHT);
        }
        if (viewportHeight > 0.0f) {
            updateSpecialDanmakusDate(scaleX, scaleY);
        }
    }
    switch (type) {
        case 1:
            return new R2LDanmaku(this.MAX_Duration_Scroll_Danmaku);
        case 4:
            return new FBDanmaku(this.MAX_Duration_Fix_Danmaku);
        case 5:
            return new FTDanmaku(this.MAX_Duration_Fix_Danmaku);
        case 6:
            return new L2RDanmaku(this.MAX_Duration_Scroll_Danmaku);
        case 7:
            BaseDanmaku instance = new SpecialDanmaku();
            this.sSpecialDanmakus.addItem(instance);
            return instance;
        default:
            return null;
    }
}