Android: Flutter

gistfile1.txt

Loading image with updates
- takes more process/memory than regular image loading in flutter
- advantage: sure that the image is updated properly 
1. load image from /data/picture1.jpg (1001 bytes)
2. replace image but retain same name /data/picture1.png (850 bytes)
* normal loading will not update the image, using the below code the change in image gets reflected
  ClipRRect(
            borderRadius: BorderRadius.circular(16.0),
            child: Image.memory(
                Uint8List.fromList(
                    File(imagePath).readAsBytesSync()),
                    width: <<imageWidth>>,
                    height: <<imageHeight>>,
                    fit: BoxFit.fitWidth,
            )
           ),



Downloading images loaded from network
https://stackoverflow.com/questions/49455079/flutter-save-a-network-image-to-local-directory



Dismiss keyboard on scroll widget
https://github.com/flutter/flutter/issues/36869
class DismissKeyboardOnScroll extends StatelessWidget {
  final Widget child;
  final Function onDismiss;

  const DismissKeyboardOnScroll({Key key, this.child, this.onDismiss})
      : super(key: key);

  @override
  Widget build(BuildContext context) {
    return NotificationListener<ScrollStartNotification>(
      onNotification: (x) {
        if (x.dragDetails == null) {
          return;
        }

        FocusScope.of(context).unfocus();
        if (onDismiss != null) {
          onDismiss();
        }
      },
      child: child,
    );
  }
}
Usage:
DismissKeyboardOnScroll(
              child: listView, //any view that scrolls
            )
            
            
            
RX Subjects
PublishSubject<String> _hideKeyboardStream;

void initializeHideKeyboardStream(){
    print("initializeHideKeyboardStream:");
    if (_hideKeyboardStream==null) {
      _hideKeyboardStream = PublishSubject<String>();
      _hideKeyboardStream.debounce(const Duration(milliseconds: 500))
          .listen((x) {
        print("initializeHideKeyboardStream: hideKeyboard");
        FocusScope.of(context).requestFocus(FocusNode());
      }, onError: (e, s) {
        print("initializeHideKeyboardStream: error");
      }, onDone: () {
        print("initializeHideKeyboardStream: ondone");
      });
    }
  }
  
  USAGE: Trigger the emit of observables
   void hideKeyboard() {
    _hideKeyboardStream.add("");
  }
  
  
  
LISTEN TO PAGE VISIBILITY USING RX 
- funcitonality mimics the approach is similar to onResume() in android
- it gets triggered everytime the page goes to foreground


class _LogPageState extends State<LogPage> {
    PublishSubject<bool> isCurrentStream;
   @override
  void initState() {
    isCurrentStream = PublishSubject<bool>();
    isCurrentStream.debounce(Duration(milliseconds: 500))
      .distinct()
      .listen((x){
        if (x){
        //HERE IS THE onResume() equivalent METHOD
          //_presenter.run();
        }
    },
    onError: (x,y){}, onDone: (){});
    isCurrentStream.add(true);  //CALL IT THe FIRST TIME
    super.initState();
  }
   
    
    
  @override
  Widget build(BuildContext context) {
    isCurrentStream.add(ModalRoute.of(context).isCurrent);
  }
  
  @override
  void dispose() {
    isCurrentStream?.close();
    super.dispose();
  }

}


FOREACH LOOP WITH INDEX
List _sample = ['a','b','c'];
_sample.asMap().forEach((index, value) => f);
OR
convertedList.asMap().forEach((index, value) { });