How to draw and animate designs with Flutter CustomPaint Widget

How to draw and animate designs with Flutter CustomPaint Widget

Flutter is one of the quintessential choices for developers, as it enables them to create an attractive User Interface at a favorable FPS. But, how do you make the UI interactive? By adding visual designs and animations, your Flutter application UI can become amazing. Fortunately, it is easy to incorporate these animations into UI. Flutter presents you with several widgets, and one of them is CustomPaint. with Flutter CustomPaint Widget, developers can access low-level graphics.

It may be complicated and time-consuming to create custom designs in native iOS and Android environments. But these are things of the past. Flutter’s Hot Reload feature and the CustomPaint widget can result in efficient and fast creation.

Flutter CustomPaint Widget- Get a basic concept

Beginners in the Flutter app development field may not be familiar with the CustomPaint widget. Several widgets are intended to maintain functionality and features. While they do not serve your purpose, you have to draw designs on your own. Customizations, like color substitution and opacity adjustment, are easy to achieve.

But you may need to draw an arrow, load a fancy animation, and create other fancy animations. In these cases, as widgets are not effective, you must render shapes.

Some major parameters of the widget are foregroundPaint, painter, and Child. Painter and foregroundPaint are simply for painting purposes and define what you need to draw on your canvas. You can render the Child over the background. The foregroundPainter instructions are present in the Child.

What are Flutter widgets – Flutter CustomPaint Widget

Before talking about the steps for creating animations with the CustomPaint widget, it is essential to have a basic concept about widgets.

Flutter developers use widgets for declaring and designing UI. As they have learned about the iOS and Android development process, they know the link between UIViews.

However, widgets are something more than UI. They are better than structural components, including images, text, buttons, and lists. A widget discloses something, which defines your choose design. It also deals with user interactions. For instance, Margin, Padding, and Center are widgets. Similarly, Layout rows and columns refer to widgets.

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Thus, widgets work like blueprints, and Flutter relies on them to generate views. Flutter widgets are of 2 types. The sensitive state-full widgets respond to anything that happens in the boundary. Moreover, you can rebuild them while any transformation to the state is identified. On the contrary, stateless widgets have no state sensitiveness, and they are static during the life cycle.

Flutter developers also deal with Container widgets wrapping around child widgets for defining the alignment. There are also Row and Column widgets. Row widgets help with the horizontal arrangement of children. Moreover, to detect the child widgets’ position, two major properties are crossAxisalignment and mainAxisalignment. There is no scrolling with the Row widgets. But, to get scrollable widget lines, developers can use ListView.

On the contrary, a Column widget ensures the vertical arrangement of its children. Based on the mainAxisAlignment properties, the children need to be placed. A Column widget works in a way similar to the row widget. Nevertheless, the mainAxisAlignment of column widget is always vertical.

What are the challenges in drawing shapes in Flutter?

It may be easy to draw circles and lines. However, there are issues when you need to create a curved shape. The biggest challenge is to identify the control points at the time of developing it. When you create a UI with several curves, it is tricky to create a perfect place for these control points.

Canvas is the ultimate solution for drawing path with the use of drawPath method. The Path class plays a role in controlling the pointer. Developers and designers can draw the path with this drawPath.

Indeed, Flutter has a Hot Reload feature to make the design process fast. But, placing the control points is important.

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Guide to using CustomPaint to draw designs

Using CustomPaint, you can deal with-

  •       Size– You have to mention the canvas size.
  •       ShapePainter– CustomPainter is an abstract class, and it comes from CustomPainter. Implementation of the right methods is important.
  •       Paint– It is another method for repainting the object.
  •       shouldRepaint– While providing the new instance, shouldRepaint is necessary.

When you have mentioned the Child widget in the CustomPaint, the canvas size needs to be identical. The canvas part may also be similar to the child widget’s size.

Canvas is useful for drawing anything, and it is an interface to track graphical activities.

To draw lines, the Flutter app development company needs to write proper codes. Variables must mention the ending and starting position of the coordinates.

Developers using the canvas can apply the drawLine method and draw a line perfectly between offset positions. The shouldRepaint method will return something false, and you do not need to draw the line again. Another alternative is available to let you draw the line with a Path.

To make the best use of the Path, you have to input another relevant property of the variable. But, when you have not done it, the line may not be visible.

The moveTo process is useful for the adjustment of the present state to the desired coordinate.

Another method, lineTo, is effective in creating a line starting from the present position to the desired spot on your canvas.

Similarly, to use paint for your path and display it on your screen, you can choose the drawPath method.

Flutter developers also deal with Container widgets wrapping around child widgets for defining the alignment.

There are also Row and Column widgets. Row widgets help with horizontal arrangement of children. Moreover, to detect the child widgets’ position, two major properties are crossAxisalignment and mainAxisalignment. There is no scrolling with the Row widgets. But, to get scrollable widget lines, developers can use ListView.

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In the case of Expanded Widget, developers wrap it around the Child. But, it has optional usage. A Flex factor is essential with the child widgets, and it closes the space based on the priority. There may be some warning strips when the row’s children are wider while compared to the row.

Guide to creating a circle for your interface

Users may draw a circle at the central part with the use of the drawCircle process. The painted object and the radius are also relevant to it.

Guide to drawing polygons

The most acceptable way to draw polygon shapes is to create a circle. Based on the angles, you can start calculating the coordinates. Apply basic trigonometry to make your decision.

How to add animations to your Flutter interface

There are few steps to animate any shape, like a polygon.

The first step is to get StatefulWidget by converting the MyPainter Widget. You have to define 2 major variables- controller and animation.

Turn on the animation variable and controller in the iniState() process.

When the rotation is infinite, you have to do the animation repeatedly after accomplishing it. Use Controller.forward to deal with animated objects.

It is a comprehensive tutorial on how to create different designs and make animations with the use of the CustomPaint widget. You can look for a professional Flutter app developer to design a complicated UI with an attractive design. Imagine any shape and draw it on Flutter UI.

Author Bio:

Rushabh Patel is Founder and CEO of Siddhi InfoSoft, a web and mobile app development company focused on creating experiences that connect, perform & inspire. We believe in delivering perfect business solutions by adopting the latest.

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