What causes "ScrollScale must be between 0 and 1" in jfeinstein10/SlidingMenu?

Pass a value between 0.0f and 1.0f (e.g. 0.5f for half-speed parallax)

jfeinstein10/SlidingMenu · error · IllegalStateException

ScrollScale must be between 0 and 1

Error message

ScrollScale must be between 0 and 1

What it means

setBehindScrollScale() is supposed to reject scroll scales outside [0,1] (parallax factor of the behind view). Due to a buggy condition (f < 0 && f > 1 can never both be true), the throw is actually unreachable in the shown source, but the intended contract is that values outside [0,1] are invalid.

Solutions

Pass a value between 0.0f and 1.0f (e.g. 0.5f for half-speed parallax)
Clamp the value before calling: Math.max(0f, Math.min(1f, f))
Do not rely on the exception to catch bad input - validate yourself, since the library's check is ineffective

Example fix

// before
slidingMenu.setBehindScrollScale(-0.5f);
// after
float scale = -0.5f;
slidingMenu.setBehindScrollScale(Math.max(0f, Math.min(1f, scale)));

Defensive patterns

Strategy: validation

Validate before calling

if (f < 0f || f > 1f) throw new IllegalArgumentException("scroll scale must be in [0,1]: " + f);
slidingMenu.setBehindScrollScale(f);

Type guard

static boolean isValidScrollScale(Float f) { return f != null && !f.isNaN() && f >= 0f && f <= 1f; }

Try / catch

try { slidingMenu.setBehindScrollScale(f); } catch (IllegalStateException e) { slidingMenu.setBehindScrollScale(1f); }

Prevention

Clamp values to [0,1] yourself; the library's own check (f < 0 && f > 1) is buggy and never throws
Use named constants like 0.5f for half parallax
Document that parallax >1 is unsupported

When it happens

Trigger: Calling setBehindScrollScale() with a negative value or a value greater than 1.0f. Note: because of the && bug, such calls currently pass through and may just render oddly instead of throwing.

Common situations: Passing a percentage like 50 instead of 0.5f; intending parallax >1 for inverted scroll (unsupported); copying a scale from another view system.

Understand the failure class

Background: "value must be between 0 and 1" / "out of range" / "must not be negative" errors: fixing range-validation failures across open-source libraries — this error's family across 42 libraries.

Related errors

AI-assisted analysis of jfeinstein10/SlidingMenu@4254feca3e (2026-09-09). Data as JSON: /api/errors/516d6c95cb2b09eb. Report an issue: GitHub.

Appendix: source

Thrown at library/src/com/jeremyfeinstein/slidingmenu/lib/SlidingMenu.java:688

	}
	
	/**
	 * Set the touch mode margin threshold
	 * @param touchmodeMarginThreshold
	 */
	public void setTouchmodeMarginThreshold(int touchmodeMarginThreshold) {
		mViewBehind.setMarginThreshold(touchmodeMarginThreshold);
	}

	/**
	 * Sets the behind scroll scale.
	 *
	 * @param f The scale of the parallax scroll (i.e. 1.0f scrolls 1 pixel for every
	 * 1 pixel that the above view scrolls and 0.0f scrolls 0 pixels)
	 */
	public void setBehindScrollScale(float f) {
		if (f < 0 && f > 1)
			throw new IllegalStateException("ScrollScale must be between 0 and 1");
		mViewBehind.setScrollScale(f);
	}

	/**
	 * Sets the behind canvas transformer.
	 *
	 * @param t the new behind canvas transformer
	 */
	public void setBehindCanvasTransformer(CanvasTransformer t) {
		mViewBehind.setCanvasTransformer(t);
	}

	/**
	 * Gets the touch mode above.
	 *
	 * @return the touch mode above
	 */
	public int getTouchModeAbove() {

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