material_state.dart 30.5 KB
Newer Older
Ian Hickson's avatar
Ian Hickson committed
1
// Copyright 2014 The Flutter Authors. All rights reserved.
2 3 4
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

5 6
import 'package:flutter/foundation.dart';
import 'package:flutter/rendering.dart';
7
import 'package:flutter/services.dart';
8

9 10
import 'input_border.dart';

11 12 13 14 15 16 17 18
/// Interactive states that some of the Material widgets can take on when
/// receiving input from the user.
///
/// States are defined by https://material.io/design/interaction/states.html#usage.
///
/// Some Material widgets track their current state in a `Set<MaterialState>`.
///
/// See also:
19
///
20
///  * [MaterialStateProperty], an interface for objects that "resolve" to
21
///    different values depending on a widget's material state.
22
/// {@template flutter.material.MaterialStateProperty.implementations}
23 24 25
///  * [MaterialStateColor], a [Color] that implements `MaterialStateProperty`
///    which is used in APIs that need to accept either a [Color] or a
///    `MaterialStateProperty<Color>`.
26 27 28 29 30 31
///  * [MaterialStateMouseCursor], a [MouseCursor] that implements
///    `MaterialStateProperty` which is used in APIs that need to accept either
///    a [MouseCursor] or a [MaterialStateProperty<MouseCursor>].
///  * [MaterialStateOutlinedBorder], an [OutlinedBorder] that implements
///    `MaterialStateProperty` which is used in APIs that need to accept either
///    an [OutlinedBorder] or a [MaterialStateProperty<OutlinedBorder>].
32 33 34 35 36 37
///  * [MaterialStateOutlineInputBorder], an [OutlineInputBorder] that implements
///    `MaterialStateProperty` which is used in APIs that need to accept either
///    an [OutlineInputBorder] or a [MaterialStateProperty<OutlineInputBorder>].
///  * [MaterialStateUnderlineInputBorder], an [UnderlineInputBorder] that implements
///    `MaterialStateProperty` which is used in APIs that need to accept either
///    an [UnderlineInputBorder] or a [MaterialStateProperty<UnderlineInputBorder>].
38 39 40
///  * [MaterialStateBorderSide], a [BorderSide] that implements
///    `MaterialStateProperty` which is used in APIs that need to accept either
///    a [BorderSide] or a [MaterialStateProperty<BorderSide>].
41 42 43 44
///  * [MaterialStateTextStyle], a [TextStyle] that implements
///    `MaterialStateProperty` which is used in APIs that need to accept either
///    a [TextStyle] or a [MaterialStateProperty<TextStyle>].
/// {@endtemplate}
45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77
enum MaterialState {
  /// The state when the user drags their mouse cursor over the given widget.
  ///
  /// See: https://material.io/design/interaction/states.html#hover.
  hovered,

  /// The state when the user navigates with the keyboard to a given widget.
  ///
  /// This can also sometimes be triggered when a widget is tapped. For example,
  /// when a [TextField] is tapped, it becomes [focused].
  ///
  /// See: https://material.io/design/interaction/states.html#focus.
  focused,

  /// The state when the user is actively pressing down on the given widget.
  ///
  /// See: https://material.io/design/interaction/states.html#pressed.
  pressed,

  /// The state when this widget is being dragged from one place to another by
  /// the user.
  ///
  /// https://material.io/design/interaction/states.html#dragged.
  dragged,

  /// The state when this item has been selected.
  ///
  /// This applies to things that can be toggled (such as chips and checkboxes)
  /// and things that are selected from a set of options (such as tabs and radio buttons).
  ///
  /// See: https://material.io/design/interaction/states.html#selected.
  selected,

78 79 80 81 82 83 84
  /// The state when this widget overlaps the content of a scrollable below.
  ///
  /// Used by [AppBar] to indicate that the primary scrollable's
  /// content has scrolled up and behind the app bar.
  scrolledUnder,

  /// The state when this widget is disabled and cannot be interacted with.
85 86 87 88 89 90 91 92 93 94 95 96 97
  ///
  /// Disabled widgets should not respond to hover, focus, press, or drag
  /// interactions.
  ///
  /// See: https://material.io/design/interaction/states.html#disabled.
  disabled,

  /// The state when the widget has entered some form of invalid state.
  ///
  /// See https://material.io/design/interaction/states.html#usage.
  error,
}

98 99
/// Signature for the function that returns a value of type `T` based on a given
/// set of states.
100
typedef MaterialPropertyResolver<T> = T Function(Set<MaterialState> states);
101

102
/// Defines a [Color] that is also a [MaterialStateProperty].
103
///
104 105 106 107 108 109
/// This class exists to enable widgets with [Color] valued properties
/// to also accept [MaterialStateProperty<Color>] values. A material
/// state color property represents a color which depends on
/// a widget's "interactive state". This state is represented as a
/// [Set] of [MaterialState]s, like [MaterialState.pressed],
/// [MaterialState.focused] and [MaterialState.hovered].
110
///
111 112 113
/// [MaterialStateColor] should only be used with widgets that document
/// their support, like [TimePickerThemeData.dayPeriodColor].
///
114 115 116 117 118
/// To use a [MaterialStateColor], you can either:
///   1. Create a subclass of [MaterialStateColor] and implement the abstract `resolve` method.
///   2. Use [MaterialStateColor.resolveWith] and pass in a callback that
///      will be used to resolve the color in the given states.
///
119 120 121 122 123 124 125 126
/// If a [MaterialStateColor] is used for a property or a parameter that doesn't
/// support resolving [MaterialStateProperty<Color>]s, then its default color
/// value will be used for all states.
///
/// To define a `const` [MaterialStateColor], you'll need to extend
/// [MaterialStateColor] and override its [resolve] method. You'll also need
/// to provide a `defaultValue` to the super constructor, so that we can know
/// at compile-time what its default color is.
127
///
128
/// {@tool snippet}
129
///
130
/// This example defines a `MaterialStateColor` with a const constructor.
131 132
///
/// ```dart
133
/// class MyColor extends MaterialStateColor {
134 135
///   const MyColor() : super(_defaultColor);
///
136 137 138 139 140 141 142 143 144
///   static const int _defaultColor = 0xcafefeed;
///   static const int _pressedColor = 0xdeadbeef;
///
///   @override
///   Color resolve(Set<MaterialState> states) {
///     if (states.contains(MaterialState.pressed)) {
///       return const Color(_pressedColor);
///     }
///     return const Color(_defaultColor);
145 146 147 148
///   }
/// }
/// ```
/// {@end-tool}
149
abstract class MaterialStateColor extends Color implements MaterialStateProperty<Color> {
150 151
  /// Abstract const constructor. This constructor enables subclasses to provide
  /// const constructors so that they can be used in const expressions.
152
  const MaterialStateColor(super.defaultValue);
153

154 155
  /// Creates a [MaterialStateColor] from a [MaterialPropertyResolver<Color>]
  /// callback function.
156 157 158 159 160 161
  ///
  /// If used as a regular color, the color resolved in the default state (the
  /// empty set of states) will be used.
  ///
  /// The given callback parameter must return a non-null color in the default
  /// state.
162
  static MaterialStateColor resolveWith(MaterialPropertyResolver<Color> callback) => _MaterialStateColor(callback);
163 164 165

  /// Returns a [Color] that's to be used when a Material component is in the
  /// specified state.
166
  @override
167
  Color resolve(Set<MaterialState> states);
168 169
}

170 171
/// A [MaterialStateColor] created from a [MaterialPropertyResolver<Color>]
/// callback alone.
172 173 174 175 176 177
///
/// If used as a regular color, the color resolved in the default state will
/// be used.
///
/// Used by [MaterialStateColor.resolveWith].
class _MaterialStateColor extends MaterialStateColor {
178
  _MaterialStateColor(this._resolve) : super(_resolve(_defaultStates).value);
179

180
  final MaterialPropertyResolver<Color> _resolve;
181 182 183 184 185

  /// The default state for a Material component, the empty set of interaction states.
  static const Set<MaterialState> _defaultStates = <MaterialState>{};

  @override
186
  Color resolve(Set<MaterialState> states) => _resolve(states);
187
}
188

189 190 191
/// Defines a [MouseCursor] whose value depends on a set of [MaterialState]s which
/// represent the interactive state of a component.
///
192 193 194 195 196 197 198
/// This kind of [MouseCursor] is useful when the set of interactive
/// actions a widget supports varies with its state. For example, a
/// mouse pointer hovering over a disabled [ListTile] should not
/// display [SystemMouseCursors.click], since a disabled list tile
/// doesn't respond to mouse clicks. [ListTile]'s default mouse cursor
/// is a [MaterialStateMouseCursor.clickable], which resolves to
/// [SystemMouseCursors.basic] when the button is disabled.
199 200 201 202
///
/// To use a [MaterialStateMouseCursor], you should create a subclass of
/// [MaterialStateMouseCursor] and implement the abstract `resolve` method.
///
203
/// {@tool dartpad}
204 205
/// This example defines a mouse cursor that resolves to
/// [SystemMouseCursors.forbidden] when its widget is disabled.
206
///
207
/// ** See code in examples/api/lib/material/material_state/material_state_mouse_cursor.0.dart **
208 209
/// {@end-tool}
///
210
/// This class should only be used for parameters which are documented to take
211
/// [MaterialStateMouseCursor], otherwise only the default state will be used.
212 213 214 215 216 217
///
/// See also:
///
///  * [MouseCursor] for introduction on the mouse cursor system.
///  * [SystemMouseCursors], which defines cursors that are supported by
///    native platforms.
218
abstract class MaterialStateMouseCursor extends MouseCursor implements MaterialStateProperty<MouseCursor> {
219 220
  /// Abstract const constructor. This constructor enables subclasses to provide
  /// const constructors so that they can be used in const expressions.
221 222 223 224 225
  const MaterialStateMouseCursor();

  @protected
  @override
  MouseCursorSession createSession(int device) {
226
    return resolve(<MaterialState>{}).createSession(device);
227 228 229 230 231 232 233
  }

  /// Returns a [MouseCursor] that's to be used when a Material component is in
  /// the specified state.
  ///
  /// This method should never return null.
  @override
234
  MouseCursor resolve(Set<MaterialState> states);
235 236 237 238 239 240 241 242

  /// A mouse cursor for clickable material widgets, which resolves differently
  /// when the widget is disabled.
  ///
  /// By default this cursor resolves to [SystemMouseCursors.click]. If the widget is
  /// disabled, the cursor resolves to [SystemMouseCursors.basic].
  ///
  /// This cursor is the default for many Material widgets.
243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260
  static const MaterialStateMouseCursor clickable = _EnabledAndDisabledMouseCursor(
    enabledCursor: SystemMouseCursors.click,
    disabledCursor: SystemMouseCursors.basic,
    name: 'clickable',
  );

  /// A mouse cursor for material widgets related to text, which resolves differently
  /// when the widget is disabled.
  ///
  /// By default this cursor resolves to [SystemMouseCursors.text]. If the widget is
  /// disabled, the cursor resolves to [SystemMouseCursors.basic].
  ///
  /// This cursor is the default for many Material widgets.
  static const MaterialStateMouseCursor textable = _EnabledAndDisabledMouseCursor(
    enabledCursor: SystemMouseCursors.text,
    disabledCursor: SystemMouseCursors.basic,
    name: 'textable',
  );
261 262
}

263 264
class _EnabledAndDisabledMouseCursor extends MaterialStateMouseCursor {
  const _EnabledAndDisabledMouseCursor({
265 266 267
    required this.enabledCursor,
    required this.disabledCursor,
    required this.name,
268 269 270 271 272
  });

  final MouseCursor enabledCursor;
  final MouseCursor disabledCursor;
  final String name;
273 274 275 276

  @override
  MouseCursor resolve(Set<MaterialState> states) {
    if (states.contains(MaterialState.disabled)) {
277
      return disabledCursor;
278
    }
279
    return enabledCursor;
280 281 282
  }

  @override
283
  String get debugDescription => 'MaterialStateMouseCursor($name)';
284 285
}

286 287 288 289 290 291
/// Defines a [BorderSide] whose value depends on a set of [MaterialState]s
/// which represent the interactive state of a component.
///
/// To use a [MaterialStateBorderSide], you should create a subclass of a
/// [MaterialStateBorderSide] and override the abstract `resolve` method.
///
292 293 294 295 296
/// This class enables existing widget implementations with [BorderSide]
/// properties to be extended to also effectively support `MaterialStateProperty<BorderSide>`
/// property values. [MaterialStateBorderSide] should only be used with widgets that document
/// their support, like [ActionChip.side].
///
297
/// {@tool dartpad}
298 299 300
/// This example defines a subclass of [MaterialStateBorderSide], that resolves
/// to a red border side when its widget is selected.
///
301
/// ** See code in examples/api/lib/material/material_state/material_state_border_side.0.dart **
302 303 304 305 306
/// {@end-tool}
///
/// This class should only be used for parameters which are documented to take
/// [MaterialStateBorderSide], otherwise only the default state will be used.
abstract class MaterialStateBorderSide extends BorderSide implements MaterialStateProperty<BorderSide?> {
307 308
  /// Abstract const constructor. This constructor enables subclasses to provide
  /// const constructors so that they can be used in const expressions.
309 310 311 312 313 314 315
  const MaterialStateBorderSide();

  /// Returns a [BorderSide] that's to be used when a Material component is
  /// in the specified state. Return null to defer to the default value of the
  /// widget or theme.
  @override
  BorderSide? resolve(Set<MaterialState> states);
316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368

  /// Creates a [MaterialStateBorderSide] from a
  /// [MaterialPropertyResolver<BorderSide?>] callback function.
  ///
  /// If used as a regular [BorderSide], the border resolved in the default state
  /// (the empty set of states) will be used.
  ///
  /// Usage:
  /// ```dart
  /// ChipTheme(
  ///   data: Theme.of(context).chipTheme.copyWith(
  ///     side: MaterialStateBorderSide.resolveWith((Set<MaterialState> states) {
  ///       if (states.contains(MaterialState.selected)) {
  ///         return const BorderSide(width: 1, color: Colors.red);
  ///       }
  ///       return null;  // Defer to default value on the theme or widget.
  ///     }),
  ///   ),
  ///   child: Chip(),
  /// )
  ///
  /// // OR
  ///
  /// Chip(
  ///   ...
  ///   side: MaterialStateBorderSide.resolveWith((Set<MaterialState> states) {
  ///     if (states.contains(MaterialState.selected)) {
  ///       return const BorderSide(width: 1, color: Colors.red);
  ///     }
  ///     return null;  // Defer to default value on the theme or widget.
  ///   }),
  /// )
  /// ```
  static MaterialStateBorderSide resolveWith(MaterialPropertyResolver<BorderSide?> callback) =>
      _MaterialStateBorderSide(callback);
}

/// A [MaterialStateBorderSide] created from a
/// [MaterialPropertyResolver<BorderSide>] callback alone.
///
/// If used as a regular side, the side resolved in the default state will
/// be used.
///
/// Used by [MaterialStateBorderSide.resolveWith].
class _MaterialStateBorderSide extends MaterialStateBorderSide {
  const _MaterialStateBorderSide(this._resolve);

  final MaterialPropertyResolver<BorderSide?> _resolve;

  @override
  BorderSide? resolve(Set<MaterialState> states) {
    return _resolve(states);
  }
369 370 371 372 373 374 375 376 377
}

/// Defines an [OutlinedBorder] whose value depends on a set of [MaterialState]s
/// which represent the interactive state of a component.
///
/// To use a [MaterialStateOutlinedBorder], you should create a subclass of an
/// [OutlinedBorder] and implement [MaterialStateOutlinedBorder]'s abstract
/// `resolve` method.
///
378
/// {@tool dartpad}
379 380 381 382
/// This example defines a subclass of [RoundedRectangleBorder] and an
/// implementation of [MaterialStateOutlinedBorder], that resolves to
/// [RoundedRectangleBorder] when its widget is selected.
///
383
/// ** See code in examples/api/lib/material/material_state/material_state_outlined_border.0.dart **
384 385 386 387 388 389 390 391 392
/// {@end-tool}
///
/// This class should only be used for parameters which are documented to take
/// [MaterialStateOutlinedBorder], otherwise only the default state will be used.
///
/// See also:
///
///  * [ShapeBorder] the base class for shape outlines.
abstract class MaterialStateOutlinedBorder extends OutlinedBorder implements MaterialStateProperty<OutlinedBorder?> {
393 394
  /// Abstract const constructor. This constructor enables subclasses to provide
  /// const constructors so that they can be used in const expressions.
395 396 397 398 399 400 401 402 403
  const MaterialStateOutlinedBorder();

  /// Returns an [OutlinedBorder] that's to be used when a Material component is
  /// in the specified state. Return null to defer to the default value of the
  /// widget or theme.
  @override
  OutlinedBorder? resolve(Set<MaterialState> states);
}

404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563

/// Defines a [TextStyle] that is also a [MaterialStateProperty].
///
/// This class exists to enable widgets with [TextStyle] valued properties
/// to also accept [MaterialStateProperty<TextStyle>] values. A material
/// state text style property represents a text style which depends on
/// a widget's "interactive state". This state is represented as a
/// [Set] of [MaterialState]s, like [MaterialState.pressed],
/// [MaterialState.focused] and [MaterialState.hovered].
///
/// [MaterialStateTextStyle] should only be used with widgets that document
/// their support, like [InputDecoration.labelStyle].
///
/// To use a [MaterialStateTextStyle], you can either:
///   1. Create a subclass of [MaterialStateTextStyle] and implement the abstract `resolve` method.
///   2. Use [MaterialStateTextStyle.resolveWith] and pass in a callback that
///      will be used to resolve the color in the given states.
///
/// If a [MaterialStateTextStyle] is used for a property or a parameter that doesn't
/// support resolving [MaterialStateProperty<TextStyle>]s, then its default color
/// value will be used for all states.
///
/// To define a `const` [MaterialStateTextStyle], you'll need to extend
/// [MaterialStateTextStyle] and override its [resolve] method. You'll also need
/// to provide a `defaultValue` to the super constructor, so that we can know
/// at compile-time what its default color is.
abstract class MaterialStateTextStyle extends TextStyle implements MaterialStateProperty<TextStyle> {
  /// Abstract const constructor. This constructor enables subclasses to provide
  /// const constructors so that they can be used in const expressions.
  const MaterialStateTextStyle();

  /// Creates a [MaterialStateTextStyle] from a [MaterialPropertyResolver<TextStyle>]
  /// callback function.
  ///
  /// If used as a regular text style, the style resolved in the default state (the
  /// empty set of states) will be used.
  ///
  /// The given callback parameter must return a non-null text style in the default
  /// state.
  static MaterialStateTextStyle resolveWith(MaterialPropertyResolver<TextStyle> callback) =>
      _MaterialStateTextStyle(callback);

  /// Returns a [TextStyle] that's to be used when a Material component is in the
  /// specified state.
  @override
  TextStyle resolve(Set<MaterialState> states);
}

/// A [MaterialStateTextStyle] created from a [MaterialPropertyResolver<TextStyle>]
/// callback alone.
///
/// If used as a regular text style, the style resolved in the default state will
/// be used.
///
/// Used by [MaterialStateTextStyle.resolveWith].
class _MaterialStateTextStyle extends MaterialStateTextStyle {
  const _MaterialStateTextStyle(this._resolve);

  final MaterialPropertyResolver<TextStyle> _resolve;

  @override
  TextStyle resolve(Set<MaterialState> states) => _resolve(states);
}

/// Defines a [OutlineInputBorder] that is also a [MaterialStateProperty].
///
/// This class exists to enable widgets with [OutlineInputBorder] valued properties
/// to also accept [MaterialStateProperty<OutlineInputBorder>] values. A material
/// state input border property represents a text style which depends on
/// a widget's "interactive state". This state is represented as a
/// [Set] of [MaterialState]s, like [MaterialState.pressed],
/// [MaterialState.focused] and [MaterialState.hovered].
///
/// [MaterialStateOutlineInputBorder] should only be used with widgets that document
/// their support, like [InputDecoration.border].
///
/// To use a [MaterialStateOutlineInputBorder], you can either:
///   1. Create a subclass of [MaterialStateOutlineInputBorder] and implement the abstract `resolve` method.
///   2. Use [MaterialStateOutlineInputBorder.resolveWith] and pass in a callback that
///      will be used to resolve the color in the given states.
///
/// If a [MaterialStateOutlineInputBorder] is used for a property or a parameter that doesn't
/// support resolving [MaterialStateProperty<OutlineInputBorder>]s, then its default color
/// value will be used for all states.
///
/// To define a `const` [MaterialStateOutlineInputBorder], you'll need to extend
/// [MaterialStateOutlineInputBorder] and override its [resolve] method. You'll also need
/// to provide a `defaultValue` to the super constructor, so that we can know
/// at compile-time what its default color is.
abstract class MaterialStateOutlineInputBorder extends OutlineInputBorder implements MaterialStateProperty<InputBorder> {
  /// Abstract const constructor. This constructor enables subclasses to provide
  /// const constructors so that they can be used in const expressions.
  const MaterialStateOutlineInputBorder();

  /// Creates a [MaterialStateOutlineInputBorder] from a [MaterialPropertyResolver<InputBorder>]
  /// callback function.
  ///
  /// If used as a regular input border, the border resolved in the default state (the
  /// empty set of states) will be used.
  ///
  /// The given callback parameter must return a non-null text style in the default
  /// state.
  static MaterialStateOutlineInputBorder resolveWith(MaterialPropertyResolver<InputBorder> callback) =>
      _MaterialStateOutlineInputBorder(callback);

  /// Returns a [InputBorder] that's to be used when a Material component is in the
  /// specified state.
  @override
  InputBorder resolve(Set<MaterialState> states);
}

/// A [MaterialStateOutlineInputBorder] created from a [MaterialPropertyResolver<OutlineInputBorder>]
/// callback alone.
///
/// If used as a regular input border, the border resolved in the default state will
/// be used.
///
/// Used by [MaterialStateTextStyle.resolveWith].
class _MaterialStateOutlineInputBorder extends MaterialStateOutlineInputBorder {
  const _MaterialStateOutlineInputBorder(this._resolve);

  final MaterialPropertyResolver<InputBorder> _resolve;

  @override
  InputBorder resolve(Set<MaterialState> states) => _resolve(states);
}

/// Defines a [UnderlineInputBorder] that is also a [MaterialStateProperty].
///
/// This class exists to enable widgets with [UnderlineInputBorder] valued properties
/// to also accept [MaterialStateProperty<UnderlineInputBorder>] values. A material
/// state input border property represents a text style which depends on
/// a widget's "interactive state". This state is represented as a
/// [Set] of [MaterialState]s, like [MaterialState.pressed],
/// [MaterialState.focused] and [MaterialState.hovered].
///
/// [MaterialStateUnderlineInputBorder] should only be used with widgets that document
/// their support, like [InputDecoration.border].
///
/// To use a [MaterialStateUnderlineInputBorder], you can either:
///   1. Create a subclass of [MaterialStateUnderlineInputBorder] and implement the abstract `resolve` method.
///   2. Use [MaterialStateUnderlineInputBorder.resolveWith] and pass in a callback that
///      will be used to resolve the color in the given states.
///
/// If a [MaterialStateUnderlineInputBorder] is used for a property or a parameter that doesn't
/// support resolving [MaterialStateProperty<UnderlineInputBorder>]s, then its default color
/// value will be used for all states.
///
/// To define a `const` [MaterialStateUnderlineInputBorder], you'll need to extend
/// [MaterialStateUnderlineInputBorder] and override its [resolve] method. You'll also need
/// to provide a `defaultValue` to the super constructor, so that we can know
/// at compile-time what its default color is.
abstract class MaterialStateUnderlineInputBorder extends UnderlineInputBorder implements MaterialStateProperty<InputBorder> {
  /// Abstract const constructor. This constructor enables subclasses to provide
  /// const constructors so that they can be used in const expressions.
  const MaterialStateUnderlineInputBorder();

  /// Creates a [MaterialStateUnderlineInputBorder] from a [MaterialPropertyResolver<InputBorder>]
  /// callback function.
  ///
apeltop's avatar
apeltop committed
564
  /// If used as a regular input border, the border resolved in the default state (the
565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593
  /// empty set of states) will be used.
  ///
  /// The given callback parameter must return a non-null text style in the default
  /// state.
  static MaterialStateUnderlineInputBorder resolveWith(MaterialPropertyResolver<InputBorder> callback) =>
      _MaterialStateUnderlineInputBorder(callback);

  /// Returns a [InputBorder] that's to be used when a Material component is in the
  /// specified state.
  @override
  InputBorder resolve(Set<MaterialState> states);
}

/// A [MaterialStateUnderlineInputBorder] created from a [MaterialPropertyResolver<UnderlineInputBorder>]
/// callback alone.
///
/// If used as a regular input border, the border resolved in the default state will
/// be used.
///
/// Used by [MaterialStateTextStyle.resolveWith].
class _MaterialStateUnderlineInputBorder extends MaterialStateUnderlineInputBorder {
  const _MaterialStateUnderlineInputBorder(this._resolve);

  final MaterialPropertyResolver<InputBorder> _resolve;

  @override
  InputBorder resolve(Set<MaterialState> states) => _resolve(states);
}

594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611
/// Interface for classes that [resolve] to a value of type `T` based
/// on a widget's interactive "state", which is defined as a set
/// of [MaterialState]s.
///
/// Material state properties represent values that depend on a widget's material
/// "state".  The state is encoded as a set of [MaterialState] values, like
/// [MaterialState.focused], [MaterialState.hovered], [MaterialState.pressed].  For
/// example the [InkWell.overlayColor] defines the color that fills the ink well
/// when it's pressed (the "splash color"), focused, or hovered. The [InkWell]
/// uses the overlay color's [resolve] method to compute the color for the
/// ink well's current state.
///
/// [ButtonStyle], which is used to configure the appearance of
/// buttons like [TextButton], [ElevatedButton], and [OutlinedButton],
/// has many material state properties.  The button widgets keep track
/// of their current material state and [resolve] the button style's
/// material state properties when their value is needed.
///
612
/// {@tool dartpad}
613 614 615 616 617 618
/// This example shows how you can override the default text and icon
/// color (the "foreground color") of a [TextButton] with a
/// [MaterialStateProperty]. In this example, the button's text color
/// will be `Colors.blue` when the button is being pressed, hovered,
/// or focused. Otherwise, the text color will be `Colors.red`.
///
619
/// ** See code in examples/api/lib/material/material_state/material_state_property.0.dart **
620 621 622
/// {@end-tool}
///
/// See also:
623
///
624
/// {@macro flutter.material.MaterialStateProperty.implementations}
625 626
abstract class MaterialStateProperty<T> {

627
  /// Returns a value of type `T` that depends on [states].
628
  ///
629 630 631
  /// Widgets like [TextButton] and [ElevatedButton] apply this method to their
  /// current [MaterialState]s to compute colors and other visual parameters
  /// at build time.
632
  T resolve(Set<MaterialState> states);
633

634
  /// Resolves the value for the given set of states if `value` is a
635 636 637
  /// [MaterialStateProperty], otherwise returns the value itself.
  ///
  /// This is useful for widgets that have parameters which can optionally be a
638 639
  /// [MaterialStateProperty]. For example, [InkWell.mouseCursor] can be a
  /// [MouseCursor] or a [MaterialStateProperty<MouseCursor>].
640
  static T resolveAs<T>(T value, Set<MaterialState> states) {
641
    if (value is MaterialStateProperty<T>) {
642
      final MaterialStateProperty<T> property = value;
643 644 645 646 647 648 649
      return property.resolve(states);
    }
    return value;
  }

  /// Convenience method for creating a [MaterialStateProperty] from a
  /// [MaterialPropertyResolver] function alone.
650 651 652 653
  static MaterialStateProperty<T> resolveWith<T>(MaterialPropertyResolver<T> callback) => _MaterialStatePropertyWith<T>(callback);

  /// Convenience method for creating a [MaterialStateProperty] that resolves
  /// to a single value for all states.
654 655 656 657 658 659 660
  ///
  /// If you need a const value, use [MaterialStatePropertyAll] directly.
  ///
  // TODO(darrenaustin): Deprecate this when we have the ability to create
  // a dart fix that will replace this with MaterialStatePropertyAll:
  // https://github.com/dart-lang/sdk/issues/49056.
  static MaterialStateProperty<T> all<T>(T value) => MaterialStatePropertyAll<T>(value);
661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690

  /// Linearly interpolate between two [MaterialStateProperty]s.
  static MaterialStateProperty<T?>? lerp<T>(
    MaterialStateProperty<T>? a,
    MaterialStateProperty<T>? b,
    double t,
    T? Function(T?, T?, double) lerpFunction,
  ) {
    // Avoid creating a _LerpProperties object for a common case.
    if (a == null && b == null) {
      return null;
    }
    return _LerpProperties<T>(a, b, t, lerpFunction);
  }
}

class _LerpProperties<T> implements MaterialStateProperty<T?> {
  const _LerpProperties(this.a, this.b, this.t, this.lerpFunction);

  final MaterialStateProperty<T>? a;
  final MaterialStateProperty<T>? b;
  final double t;
  final T? Function(T?, T?, double) lerpFunction;

  @override
  T? resolve(Set<MaterialState> states) {
    final T? resolvedA = a?.resolve(states);
    final T? resolvedB = b?.resolve(states);
    return lerpFunction(resolvedA, resolvedB, t);
  }
691 692
}

693 694
class _MaterialStatePropertyWith<T> implements MaterialStateProperty<T> {
  _MaterialStatePropertyWith(this._resolve);
695 696 697 698

  final MaterialPropertyResolver<T> _resolve;

  @override
699
  T resolve(Set<MaterialState> states) => _resolve(states);
700
}
701

702 703 704 705 706 707 708
/// Convenience class for creating a [MaterialStateProperty] that
/// resolves to the given value for all states.
class MaterialStatePropertyAll<T> implements MaterialStateProperty<T> {

  /// Constructs a [MaterialStateProperty] that always resolves to the given
  /// value.
  const MaterialStatePropertyAll(this.value);
709

710
  /// The value of the property that will be used for all states.
711
  final T value;
712 713

  @override
714
  T resolve(Set<MaterialState> states) => value;
715 716

  @override
717
  String toString() => 'MaterialStatePropertyAll($value)';
718
}
719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741

/// Manages a set of [MaterialState]s and notifies listeners of changes.
///
/// Used by widgets that expose their internal state for the sake of
/// extensions that add support for additional states. See
/// [TextButton.statesController] for example.
///
/// The controller's [value] is its current set of states. Listeners
/// are notified whenever the [value] changes. The [value] should only be
/// changed with [update]; it should not be modified directly.
class MaterialStatesController extends ValueNotifier<Set<MaterialState>> {
  /// Creates a MaterialStatesController.
  MaterialStatesController([Set<MaterialState>? value]) : super(<MaterialState>{...?value});

  /// Adds [state] to [value] if [add] is true, and removes it otherwise,
  /// and notifies listeners if [value] has changed.
  void update(MaterialState state, bool add) {
    final bool valueChanged = add ? value.add(state) : value.remove(state);
    if (valueChanged) {
      notifyListeners();
    }
  }
}