Hola, I’m Hieu, a Software Engineer

Every Flutter team hits this. The list works fine with twenty items in development, ships, and then a user with eight hundred saved items reports that scrolling stutters and the app feels heavy. The instinct is to blame ListView , or Flutter, or the device. ListView is fine. In every slow list I have profiled, the cause was one of four things, and they are distinguishable in about ten minutes. First: find out which thread is late Before changing anything, run in profile mode on a real device and open the DevTools performance view. Each frame is drawn as two bars: UI thread long → build and layout are expensive. Your itemBuilder is doing too much. Raster thread long → painting is expensive. Shadows, blurs, opacity layers, saveLayer, large images. That distinction eliminates half the possible fixes immediately. Adding RepaintBoundary to a list whose UI thread is the bottleneck does nothing; simplifying widget structure in a list whose raster thread is saturated by a Backdro...

Scrolling is the interaction users feel most and describe least. “It feels sluggish”, “it doesn’t stop where I expect”, “it bounces wrong on Android”. Those complaints all point at one small class: ScrollPhysics . Most Flutter developers only ever meet it through the three named subclasses — BouncingScrollPhysics , ClampingScrollPhysics , NeverScrollableScrollPhysics . Underneath, it is a compact interface with four decision points, and understanding those turns “the list stops in a weird place” from a mystery into a two-line fix. What the class actually decides Method Decides applyPhysicsToUserOffset How a finger’s movement maps to scroll offset — resistance when overscrolling applyBoundaryConditions How much of a requested offset to refuse at the edges createBallisticSimulation What happens after the finger lifts: fling, settle, snap, or nothing tolerance When a simulation is considered finished Plus two properties worth knowing: shouldAcceptUserOffset (...