WavyAnimatedTextKit crash on page load.

[hashem78]

Description
Crash on page load with NestedScrollView and SliverAppBar
To Reproduce
Steps to reproduce the behavior:
--> See error

Expected behavior
Animation should start without a crash but instead crashes and then starts.

flutter doctor -v

**[✓] Flutter (Channel beta, 1.22.0-13.0.pre.1, on Linux, locale en_US.UTF-8)
• Flutter version 1.22.0-13.0.pre.1 at /home/mythi/snap/flutter/common/flutter
• Framework revision 89244148cd (18 hours ago), 2020-10-13 22:25:05 +0300
• Engine revision 75bef9f6c8
• Dart version 2.10.1

[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
• Android SDK at /home/mythi/Android
• Platform android-29, build-tools 28.0.3
• ANDROID_HOME = /home/mythi/Android
• Java binary at: /usr/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_265-8u265-b01-0ubuntu2~20.04-b01)
• All Android licenses accepted.

Additional context

NestedScrollView(
        headerSliverBuilder: (_, __) {
          return <Widget>[
            SliverAppBar(
              expandedHeight: 20,
              primary: true,
              elevation: 0,
              backgroundColor: kausBlue,
              title: Container(
                width: 40,
                height: 30,
                child: WavyAnimatedTextKit(
                  speed: Duration(milliseconds: 200),
                  isRepeatingAnimation: true,
                  text: ["Explore..."],
                  textStyle:
                      TextStyle(fontSize: 32.0, fontWeight: FontWeight.bold),
                ),
              ),
              centerTitle: true,
              actions: [
                Hero(
                  tag: "auFlag",
                  child: Image.asset('assests/images/au.png'),
                ),
              ],
            ),
          ];
        },

Error/Crash log:

════════ Exception caught by widgets library ═══════════════════════════════════
The following NoSuchMethodError was thrown building AnimatedBuilder(animation: AnimationController#e63f3(▶ 0.034), dependencies: [MediaQuery], state: _AnimatedState#34271):
The method '-' was called on null.
Receiver: null
Tried calling: -(null)

The relevant error-causing widget was
    WavyAnimatedTextKit 
lib/widgets/sized_tile.dart:121
When the exception was thrown, this was the stack
#0      Object.noSuchMethod  (dart:core-patch/object_patch.dart:51:5))
#1      _WTextPainter.calculateMove 
package:animated_text_kit/src/wavy.dart:236
#2      _WTextPainter.shouldRepaint 
package:animated_text_kit/src/wavy.dart:228
#3      RenderCustomPaint._didUpdatePainter 
package:flutter/…/rendering/custom_paint.dart:440
#4      RenderCustomPaint.foregroundPainter= 
package:flutter/…/rendering/custom_paint.dart:430
...
════════════════════════════════════════════════════════════════════════════════

[awhitford]

Looks like percent or txtInMoInd is null? Why are these static?

Animated-Text-Kit/lib/src/wavy.dart

Lines 234 to 238 in 77152a7

	void calculateMove() {
	double height = _textLayoutInfo[0].height;
	double _percent = percent - txtInMoInd;
	int txtInMoOdd = (percent - .5).floor();
	int txtInMoEven = txtInMoInd * 2;

[hashem78]

Looks like percent or txtInMoInd is null? Why are these static?

Animated-Text-Kit/lib/src/wavy.dart

Lines 234 to 238 in 77152a7

	void calculateMove() {
	double height = _textLayoutInfo[0].height;
	double _percent = percent - txtInMoInd;
	int txtInMoOdd = (percent - .5).floor();
	int txtInMoEven = txtInMoInd * 2;

Not sure, I spent an hour looking into it yesterday but it totally went over my head that the mentioned method in the error is operator-.

You got any idea what these values represent? I could be using some kind of widget that's messing with the values or something of sort.

[SirusCodes]

Looks like percent or txtInMoInd is null? Why are these static?

Animated-Text-Kit/lib/src/wavy.dart

Lines 234 to 238 in 77152a7

	void calculateMove() {
	double height = _textLayoutInfo[0].height;
	double _percent = percent - txtInMoInd;
	int txtInMoOdd = (percent - .5).floor();
	int txtInMoEven = txtInMoInd * 2;

It was set static because every time shouldRepaint was called and percent is set in paint I'm working it...

[SirusCodes]

@awhitford I have created a PR #126 by removing the use of static fields this should solve the problem I guess