Flutter Tips 70-77

#Day71 MediaQuery

MediaQuery gives the information about screen like height, width, pixels, notch size, Device scale factor & text scale factor set on setting, device theme light/dark , system animation enabled/disabled etc. try on codepen

#Day72 Decimal points

Want to get desired number of digits after decimal?

1. Use number.toStringAsFixed()
2. Parse the String to number.

For convenience we can use extension functions. try on dartpad

#Day73 String multiplication

You can multiply String like numbers.

"Foo"*2 //Foo
"Bar "*5 //Bar Bar Bar Bar Bar

#Day74 enum values

Getting value of enum is not trivial in dart. This simple extension function can get rid of Pain in the enum.

1. Define this extension
2. Start calling .asEnum() in any enum to print the Value.
3. You can use underscore _ if you want space between words.

try in dartpad

#Day75 Don’t be afraid with mixin, it’s here to help

💣 Spoiler : mixin is not related to Animation by any means 😂, its just another keyword like class

But mixin is similar to

fastfood 🍔/ plugin 🧩/ an interface with already implemented methods & state, that is ready to be used without reimplementing those features everywhere we need them

When paired up with a StatefulWidget’s State,TickerProviderStateMixin creates ticker that ticks with every frame which is need by every AnimationController . It also disposes ticker when stateful widget disposes. That’s why we provide this as TickerProvider(vsync) in every AnimationController.

Similarly we use ListMixin to use obvious implementation of List so that we do not have to implement obvious stuffs in every List implementation like ElementList,NodeList,FileList,TouchList etc.

extends (inheritance) => only one class can be inherited along with their public/protected members and behaviours.

implements (contract) => many classes can be implemented but we have to redefine every behaviour.

with(mixin) => Many classes can be mixed in and we can reuse the behaviour of them.

Any class or abstract class can be used as mixin. But we declare mixin, it cannot be extended like normal class or abstract class.

class A{} //Declaring class
mixin B{} //Declaring mixin
class C extends A{} // Valid ✅
class C extends B{} // Invalid ❌

A mixin cannot use another mixin.

mixin C with B{} // Invalid ❌

Conclusion : Use mixin if you want to reuse the behaviour and state of multiple classes

#Day76 CustomPainter

CustomPainter provides canvs to draw different shapes.

1. Define a class and extend CustomPainter.
2. Override paint(canvas,size) method and draw various shapes(circle,arc,rectangle,line etc) inside it.
3. Add a CustomPaint widget on screen and pass the CustomPainter as paint and it’s size.

Output

try on codepen

#Day77 Pause / wait program flow

Do you want pause program flow for a certain duration? You can use Future.delayed() :

await Future.delayed( duration )