948ae15ca5
Our examples have been growing organically over time. This patch cleans them up to illustrate specific aspects of Flutter.
93 lines
2.7 KiB
Dart
93 lines
2.7 KiB
Dart
// Copyright 2015 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:flutter/material.dart';
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import 'package:flutter/rendering.dart';
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// Material design colors. :p
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List<Color> _kColors = <Color>[
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Colors.teal[500],
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Colors.amber[500],
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Colors.purple[500],
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Colors.lightBlue[500],
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Colors.deepPurple[500],
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Colors.lime[500],
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];
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/// A simple model object for a dot that reacts to pointer pressure.
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class Dot {
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Dot({ Color color }) : _paint = new Paint()..color = color;
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final Paint _paint;
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Point position = Point.origin;
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double radius = 0.0;
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void update(PointerEvent event) {
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position = event.position;
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radius = 5 + (95 * event.pressure);
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}
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void paint(Canvas canvas, Offset offset) {
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canvas.drawCircle(position + offset, radius, _paint);
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}
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}
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/// A render object that draws dots under each pointer.
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class RenderDots extends RenderConstrainedBox {
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RenderDots() : super(additionalConstraints: const BoxConstraints.expand());
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/// State to remember which dots to paint.
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final Map<int, Dot> _dots = <int, Dot>{};
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/// Makes this render object hittable so that it receives pointer events.
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bool hitTestSelf(Point position) => true;
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/// Processes pointer events by mutating state and invalidating its previous
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/// painting commands.
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void handleEvent(PointerEvent event, BoxHitTestEntry entry) {
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if (event is PointerDownEvent) {
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Color color = _kColors[event.pointer.remainder(_kColors.length)];
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_dots[event.pointer] = new Dot(color: color)..update(event);
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markNeedsPaint();
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} else if (event is PointerUpEvent || event is PointerCancelEvent) {
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_dots.remove(event.pointer);
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markNeedsPaint();
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} else if (event is PointerMoveEvent) {
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_dots[event.pointer].update(event);
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markNeedsPaint();
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}
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}
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/// Issues new painting commands.
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void paint(PaintingContext context, Offset offset) {
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final Canvas canvas = context.canvas;
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canvas.drawRect(offset & size, new Paint()..color = const Color(0xFFFFFFFF));
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for (Dot dot in _dots.values)
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dot.paint(canvas, offset);
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super.paint(context, offset);
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}
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}
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void main() {
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RenderParagraph paragraph = new RenderParagraph(
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new StyledTextSpan(
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new TextStyle(color: Colors.black87),
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[ new PlainTextSpan("Touch me!") ]
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)
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);
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RenderStack stack = new RenderStack(
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children: <RenderBox>[
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new RenderDots(),
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paragraph,
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]
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);
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// Prevent the RenderParagraph from filling the whole screen so
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// that it doesn't eat events.
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final StackParentData paragraphParentData = paragraph.parentData;
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paragraphParentData
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..top = 40.0
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..left = 20.0;
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new RenderingFlutterBinding(root: stack);
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}
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