Slide Transition | Flutter - Not able to implement the desired

Question

I am trying to implement animation in Flutter.

I got the following result. But what I am trying to achieve is that the illustration starts sliding from the faded part, like it should display 10% of the image then linearly increase as it slides. But here it slides from the bottom of the screen and behind the other widgets. I just want the image to be visible in its restricted part of the column only.

Here is the code for the same:

This is the initialisation part

  late AnimationController controller;
  late Animation<Offset> offset;
    
      @override
  void initState() {
    super.initState();

    controller =
        AnimationController(vsync: this, duration: const Duration(seconds: 3));

    offset = Tween<Offset>(begin: const Offset(0.0, 1.0), end: Offset.zero)
        .animate(controller);

    controller.forward();
  }

Here is the code in return widget

ShaderMask(
          shaderCallback: (rect) {
            return const LinearGradient(
              begin: Alignment.topCenter,
              end: Alignment.bottomCenter,
              colors: [
                Colors.white,
                Colors.white,
                Colors.white,
                Colors.transparent
              ],
            ).createShader(
                Rect.fromLTRB(0, 0, rect.width, rect.height));
          },
          blendMode: BlendMode.dstIn,
          //page illustration
          //slides from bottom to up
          child: SlideTransition(
            position: offset,
            child: Image.asset(
              onboardingEntries[index]["imageUrl"],
              height: 350,
            ),
          ),
        ),

Answer 1

Just use ClipRect to clip the image. It clips the child on its original layout.

Check it out (also the live demo on DartPad):

Here's the code:

import 'dart:async';

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: 'Flutter Demo',
      debugShowCheckedModeBanner: false,
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key}) : super(key: key);

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> with TickerProviderStateMixin {
  late AnimationController controller;
  late Animation<Offset> offset;
  late NetworkImage _image;

  @override
  void initState() {
    super.initState();

    controller =
        AnimationController(vsync: this, duration: const Duration(seconds: 3));

    offset = Tween<Offset>(begin: const Offset(0.0, 1.0), end: Offset.zero)
        .animate(controller);

    _image =
        const NetworkImage('https://source.unsplash.com/random/225x400?cars');
    Timer.run(
        () => precacheImage(_image, context).then((_) => controller.forward()));
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: ClipRect(
          child: ShaderMask(
            shaderCallback: (rect) {
              return const LinearGradient(
                begin: Alignment.topCenter,
                end: Alignment.bottomCenter,
                colors: [
                  Colors.white,
                  Colors.white,
                  Colors.white,
                  Colors.transparent
                ],
              ).createShader(Rect.fromLTRB(0, 0, rect.width, rect.height));
            },
            blendMode: BlendMode.dstIn,
            child: SlideTransition(
              position: offset,
              child: Image(
                image: _image,
                height: 350,
              ),
            ),
          ),
        ),
      ),
    );
  }
}