If you want to open DropDown dialog below DropdownButton like Spinner in Flutter? Create Custom Class For DropdownButton and write below code.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 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 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 | import 'dart:math' as math; import 'package:flutter/material.dart'; const Duration _kDropdownMenuDuration = Duration(milliseconds: 300); const double _kMenuItemHeight = 48.0; const double _kDenseButtonHeight = 24.0; const EdgeInsets _kMenuItemPadding = EdgeInsets.symmetric(horizontal: 16.0); const EdgeInsetsGeometry _kAlignedButtonPadding = EdgeInsetsDirectional.only(start: 16.0, end: 4.0); const EdgeInsets _kUnalignedButtonPadding = EdgeInsets.zero; const EdgeInsets _kAlignedMenuMargin = EdgeInsets.zero; const EdgeInsetsGeometry _kUnalignedMenuMargin = EdgeInsetsDirectional.only(start: 16.0, end: 24.0); class _DropdownMenuPainter extends CustomPainter { _DropdownMenuPainter({ this.color, this.elevation, this.selectedIndex, this.resize, }) : _painter = new BoxDecoration( // If you add an image here, you must provide a real // configuration in the paint() function and you must provide some sort // of onChanged callback here. color: color, borderRadius: new BorderRadius.circular(2.0), boxShadow: kElevationToShadow[elevation]) .createBoxPainter(), super(repaint: resize); final Color color; final int elevation; final int selectedIndex; final Animation<double> resize; final BoxPainter _painter; @override void paint(Canvas canvas, Size size) { final double selectedItemOffset = selectedIndex * _kMenuItemHeight + kMaterialListPadding.top; final Tween<double> top = new Tween<double>( begin: selectedItemOffset.clamp(0.0, size.height - _kMenuItemHeight), end: 0.0, ); final Tween<double> bottom = new Tween<double>( begin: (top.begin + _kMenuItemHeight).clamp(_kMenuItemHeight, size.height), end: size.height, ); final Rect rect = new Rect.fromLTRB( 0.0, top.evaluate(resize), size.width, bottom.evaluate(resize)); _painter.paint( canvas, rect.topLeft, new ImageConfiguration(size: rect.size)); } @override bool shouldRepaint(_DropdownMenuPainter oldPainter) { return oldPainter.color != color || oldPainter.elevation != elevation || oldPainter.selectedIndex != selectedIndex || oldPainter.resize != resize; } } // Do not use the platform-specific default scroll configuration. // Dropdown menus should never overscroll or display an overscroll indicator. class _DropdownScrollBehavior extends ScrollBehavior { const _DropdownScrollBehavior(); @override TargetPlatform getPlatform(BuildContext context) => Theme.of(context).platform; @override Widget buildViewportChrome( BuildContext context, Widget child, AxisDirection axisDirection) => child; @override ScrollPhysics getScrollPhysics(BuildContext context) => const ClampingScrollPhysics(); } class _DropdownMenu<T> extends StatefulWidget { const _DropdownMenu({ Key key, this.padding, this.route, }) : super(key: key); final _DropdownRoute<T> route; final EdgeInsets padding; @override _DropdownMenuState<T> createState() => new _DropdownMenuState<T>(); } class _DropdownMenuState<T> extends State<_DropdownMenu<T>> { CurvedAnimation _fadeOpacity; CurvedAnimation _resize; @override void initState() { super.initState(); // We need to hold these animations as state because of their curve // direction. When the route's animation reverses, if we were to recreate // the CurvedAnimation objects in build, we'd lose // CurvedAnimation._curveDirection. _fadeOpacity = new CurvedAnimation( parent: widget.route.animation, curve: const Interval(0.0, 0.25), reverseCurve: const Interval(0.75, 1.0), ); _resize = new CurvedAnimation( parent: widget.route.animation, curve: const Interval(0.25, 0.5), reverseCurve: const Threshold(0.0), ); } @override Widget build(BuildContext context) { // The menu is shown in three stages (unit timing in brackets): // [0s - 0.25s] - Fade in a rect-sized menu container with the selected item. // [0.25s - 0.5s] - Grow the otherwise empty menu container from the center // until it's big enough for as many items as we're going to show. // [0.5s - 1.0s] Fade in the remaining visible items from top to bottom. // // When the menu is dismissed we just fade the entire thing out // in the first 0.25s. final MaterialLocalizations localizations = MaterialLocalizations.of(context); final _DropdownRoute<T> route = widget.route; final double unit = 0.5 / (route.items.length + 1.5); final List<Widget> children = <Widget>[]; for (int itemIndex = 0; itemIndex < route.items.length; ++itemIndex) { CurvedAnimation opacity; if (itemIndex == route.selectedIndex) { opacity = new CurvedAnimation( parent: route.animation, curve: const Threshold(0.0)); } else { final double start = (0.5 + (itemIndex + 1) * unit).clamp(0.0, 1.0); final double end = (start + 1.5 * unit).clamp(0.0, 1.0); opacity = new CurvedAnimation( parent: route.animation, curve: new Interval(start, end)); } children.add(new FadeTransition( opacity: opacity, child: new InkWell( child: new Container( padding: widget.padding, child: route.items[itemIndex], ), onTap: () => Navigator.pop( context, new _DropdownRouteResult<T>(route.items[itemIndex].value), ), ), )); } return new FadeTransition( opacity: _fadeOpacity, child: new CustomPaint( painter: new _DropdownMenuPainter( color: Theme.of(context).canvasColor, elevation: route.elevation, selectedIndex: route.selectedIndex, resize: _resize, ), child: new Semantics( scopesRoute: true, namesRoute: true, explicitChildNodes: true, label: localizations.popupMenuLabel, child: new Material( type: MaterialType.transparency, textStyle: route.style, child: new ScrollConfiguration( behavior: const _DropdownScrollBehavior(), child: new Scrollbar( child: new ListView( controller: widget.route.scrollController, padding: kMaterialListPadding, itemExtent: _kMenuItemHeight, shrinkWrap: true, children: children, ), ), ), ), ), ), ); } } class _DropdownMenuRouteLayout<T> extends SingleChildLayoutDelegate { _DropdownMenuRouteLayout({ @required this.buttonRect, @required this.menuTop, @required this.menuHeight, @required this.textDirection, }); final Rect buttonRect; final double menuTop; final double menuHeight; final TextDirection textDirection; @override BoxConstraints getConstraintsForChild(BoxConstraints constraints) { // The maximum height of a simple menu should be one or more rows less than // the view height. This ensures a tappable area outside of the simple menu // with which to dismiss the menu. // -- https://material.google.com/components/menus.html#menus-simple-menus final double maxHeight = math.max(0.0, constraints.maxHeight - 2 * _kMenuItemHeight); // The width of a menu should be at most the view width. This ensures that // the menu does not extend past the left and right edges of the screen. final double width = math.min(constraints.maxWidth, buttonRect.width); return new BoxConstraints( minWidth: width, maxWidth: width, minHeight: 0.0, maxHeight: maxHeight, ); } @override Offset getPositionForChild(Size size, Size childSize) { assert(() { final Rect container = Offset.zero & size; if (container.intersect(buttonRect) == buttonRect) { // If the button was entirely on-screen, then verify // that the menu is also on-screen. // If the button was a bit off-screen, then, oh well. assert(menuTop >= 0.0); assert(menuTop + menuHeight <= size.height); } return true; }()); assert(textDirection != null); double left; switch (textDirection) { case TextDirection.rtl: left = buttonRect.right.clamp(0.0, size.width) - childSize.width; break; case TextDirection.ltr: left = buttonRect.left.clamp(0.0, size.width - childSize.width); break; } return new Offset(left, menuTop); } @override bool shouldRelayout(_DropdownMenuRouteLayout<T> oldDelegate) { return buttonRect != oldDelegate.buttonRect || menuTop != oldDelegate.menuTop || menuHeight != oldDelegate.menuHeight || textDirection != oldDelegate.textDirection; } } class _DropdownRouteResult<T> { const _DropdownRouteResult(this.result); final T result; @override bool operator ==(dynamic other) { if (other is! _DropdownRouteResult<T>) return false; final _DropdownRouteResult<T> typedOther = other; return result == typedOther.result; } @override int get hashCode => result.hashCode; } class _DropdownRoute<T> extends PopupRoute<_DropdownRouteResult<T>> { _DropdownRoute({ this.items, this.padding, this.buttonRect, this.selectedIndex, this.elevation = 8, this.theme, @required this.style, this.barrierLabel, }) : assert(style != null); final List<DropdownMenuItem<T>> items; final EdgeInsetsGeometry padding; final Rect buttonRect; final int selectedIndex; final int elevation; final ThemeData theme; final TextStyle style; ScrollController scrollController; @override Duration get transitionDuration => _kDropdownMenuDuration; @override bool get barrierDismissible => true; @override Color get barrierColor => null; @override final String barrierLabel; @override Widget buildPage(BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) { assert(debugCheckHasDirectionality(context)); final double screenHeight = MediaQuery.of(context).size.height; final double maxMenuHeight = screenHeight - 2.0 * _kMenuItemHeight; final double preferredMenuHeight = (items.length * _kMenuItemHeight) + kMaterialListPadding.vertical; final double menuHeight = math.min(maxMenuHeight, preferredMenuHeight); final double buttonTop = buttonRect.top; final double selectedItemOffset = selectedIndex * _kMenuItemHeight + kMaterialListPadding.top; double menuTop = (buttonTop - selectedItemOffset) - (_kMenuItemHeight - buttonRect.height) / 2.0; const double topPreferredLimit = _kMenuItemHeight; if (menuTop < topPreferredLimit) menuTop = math.min(buttonTop, topPreferredLimit); double bottom = menuTop + menuHeight; final double bottomPreferredLimit = screenHeight - _kMenuItemHeight; if (bottom > bottomPreferredLimit) { bottom = math.max(buttonTop + _kMenuItemHeight, bottomPreferredLimit); menuTop = bottom - menuHeight; } if (scrollController == null) { double scrollOffset = 0.0; if (preferredMenuHeight > maxMenuHeight) scrollOffset = selectedItemOffset - (buttonTop - menuTop); scrollController = new ScrollController(initialScrollOffset: scrollOffset); } final TextDirection textDirection = Directionality.of(context); Widget menu = new _DropdownMenu<T>( route: this, padding: padding.resolve(textDirection), ); if (theme != null) menu = new Theme(data: theme, child: menu); return new MediaQuery.removePadding( context: context, removeTop: true, removeBottom: true, removeLeft: true, removeRight: true, child: new Builder( builder: (BuildContext context) { return new CustomSingleChildLayout( delegate: new _DropdownMenuRouteLayout<T>( buttonRect: buttonRect, menuTop: menuTop, menuHeight: menuHeight, textDirection: textDirection, ), child: menu, ); }, ), ); } void _dismiss() { navigator?.removeRoute(this); } } class CustomDropdownButton<T> extends StatefulWidget { /// Creates a dropdown button. /// /// The [items] must have distinct values and if [value] isn't null it must be among them. /// /// The [elevation] and [iconSize] arguments must not be null (they both have /// defaults, so do not need to be specified). CustomDropdownButton({ Key key, @required this.items, this.value, this.hint, @required this.onChanged, this.elevation = 8, this.style, this.iconSize = 24.0, this.isDense = false, }) : assert(items != null), assert(value == null || items .where((DropdownMenuItem<T> item) => item.value == value) .length == 1), super(key: key); /// The list of possible items to select among. final List<DropdownMenuItem<T>> items; /// The currently selected item, or null if no item has been selected. If /// value is null then the menu is popped up as if the first item was /// selected. final T value; /// Displayed if [value] is null. final Widget hint; /// Called when the user selects an item. final ValueChanged<T> onChanged; /// The z-coordinate at which to place the menu when open. /// /// The following elevations have defined shadows: 1, 2, 3, 4, 6, 8, 9, 12, 16, 24 /// /// Defaults to 8, the appropriate elevation for dropdown buttons. final int elevation; /// The text style to use for text in the dropdown button and the dropdown /// menu that appears when you tap the button. /// /// Defaults to the [TextTheme.subhead] value of the current /// [ThemeData.textTheme] of the current [Theme]. final TextStyle style; /// The size to use for the drop-down button's down arrow icon button. /// /// Defaults to 24.0. final double iconSize; /// Reduce the button's height. /// /// By default this button's height is the same as its menu items' heights. /// If isDense is true, the button's height is reduced by about half. This /// can be useful when the button is embedded in a container that adds /// its own decorations, like [InputDecorator]. final bool isDense; @override _DropdownButtonState<T> createState() => new _DropdownButtonState<T>(); } class _DropdownButtonState<T> extends State<CustomDropdownButton<T>> with WidgetsBindingObserver { int _selectedIndex; _DropdownRoute<T> _dropdownRoute; @override void initState() { super.initState(); // _updateSelectedIndex(); WidgetsBinding.instance.addObserver(this); } @override void dispose() { WidgetsBinding.instance.removeObserver(this); _removeDropdownRoute(); super.dispose(); } // Typically called because the device's orientation has changed. // Defined by WidgetsBindingObserver @override void didChangeMetrics() { _removeDropdownRoute(); } void _removeDropdownRoute() { _dropdownRoute?._dismiss(); _dropdownRoute = null; } @override void didUpdateWidget(CustomDropdownButton<T> oldWidget) { super.didUpdateWidget(oldWidget); _updateSelectedIndex(); } void _updateSelectedIndex() { assert(widget.value == null || widget.items .where((DropdownMenuItem<T> item) => item.value == widget.value) .length == 1); _selectedIndex = null; for (int itemIndex = 0; itemIndex < widget.items.length; itemIndex++) { if (widget.items[itemIndex].value == widget.value) { _selectedIndex = itemIndex; return; } } } TextStyle get _textStyle => widget.style ?? Theme.of(context).textTheme.subhead; void _handleTap() { final RenderBox itemBox = context.findRenderObject(); final Rect itemRect = itemBox.localToGlobal(Offset.zero) & itemBox.size; final TextDirection textDirection = Directionality.of(context); final EdgeInsetsGeometry menuMargin = ButtonTheme.of(context).alignedDropdown ? _kAlignedMenuMargin : _kUnalignedMenuMargin; assert(_dropdownRoute == null); _dropdownRoute = new _DropdownRoute<T>( items: widget.items, buttonRect: menuMargin.resolve(textDirection).inflateRect(itemRect), padding: _kMenuItemPadding.resolve(textDirection), selectedIndex: -1, elevation: widget.elevation, theme: Theme.of(context, shadowThemeOnly: true), style: _textStyle, barrierLabel: MaterialLocalizations.of(context).modalBarrierDismissLabel, ); Navigator.push(context, _dropdownRoute) .then<void>((_DropdownRouteResult<T> newValue) { _dropdownRoute = null; if (!mounted || newValue == null) return; if (widget.onChanged != null) widget.onChanged(newValue.result); }); } // When isDense is true, reduce the height of this button from _kMenuItemHeight to // _kDenseButtonHeight, but don't make it smaller than the text that it contains. // Similarly, we don't reduce the height of the button so much that its icon // would be clipped. double get _denseButtonHeight { return math.max( _textStyle.fontSize, math.max(widget.iconSize, _kDenseButtonHeight)); } @override Widget build(BuildContext context) { assert(debugCheckHasMaterial(context)); // The width of the button and the menu are defined by the widest // item and the width of the hint. final List<Widget> items = new List<Widget>.from(widget.items); int hintIndex; if (widget.hint != null) { hintIndex = items.length; items.add(new DefaultTextStyle( style: _textStyle.copyWith(color: Theme.of(context).hintColor), child: new IgnorePointer( child: widget.hint, ignoringSemantics: false, ), )); } final EdgeInsetsGeometry padding = ButtonTheme.of(context).alignedDropdown ? _kAlignedButtonPadding : _kUnalignedButtonPadding; Widget result = new DefaultTextStyle( style: _textStyle, child: new Container( padding: padding.resolve(Directionality.of(context)), height: widget.isDense ? _denseButtonHeight : null, child: new Row( mainAxisAlignment: MainAxisAlignment.spaceBetween, mainAxisSize: MainAxisSize.min, children: <Widget>[ // If value is null (then _selectedIndex is null) then we display // the hint or nothing at all. Expanded( child: new IndexedStack( index: _selectedIndex ?? hintIndex, alignment: AlignmentDirectional.centerStart, children: items, ), ), new Icon(Icons.arrow_drop_down, size: widget.iconSize, // These colors are not defined in the Material Design spec. color: Theme.of(context).brightness == Brightness.light ? Colors.grey.shade700 : Colors.white70), ], ), ), ); if (!DropdownButtonHideUnderline.at(context)) { final double bottom = widget.isDense ? 0.0 : 8.0; result = new Stack( children: <Widget>[ result, new Positioned( left: 0.0, right: 0.0, bottom: bottom, child: new Container( height: 1.0, decoration: const BoxDecoration( border: Border( bottom: BorderSide(color: Color(0xFFBDBDBD), width: 0.0))), ), ), ], ); } return new Semantics( button: true, child: new GestureDetector( onTap: _handleTap, behavior: HitTestBehavior.opaque, child: result), ); } } |
You can use above class like this.
1 2 3 4 5 | CustomDropdownButton( value: _selectedCompany, items: _dropdownMenuItems, onChanged: onChangeDropdownItem, ), |
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