custom_container.dart 3.93 KB
Newer Older
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
// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This sample demonstrates how to create a [SelectionContainer] that only
// allows selecting everything or nothing with no partial selection.

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

void main() => runApp(const MyApp());

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: _title,
      home: SelectionArea(
        child: Scaffold(
          appBar: AppBar(title: const Text(_title)),
          body: Center(
            child: SelectionAllOrNoneContainer(
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                children: const <Widget>[
                  Text('Row 1'),
                  Text('Row 2'),
                  Text('Row 3'),
                ],
              ),
            ),
          ),
        ),
      ),
    );
  }
}

class SelectionAllOrNoneContainer extends StatefulWidget {
  const SelectionAllOrNoneContainer({
    super.key,
    required this.child
  });

  final Widget child;

  @override
  State<StatefulWidget> createState() => _SelectionAllOrNoneContainerState();
}

class _SelectionAllOrNoneContainerState extends State<SelectionAllOrNoneContainer> {
  final SelectAllOrNoneContainerDelegate delegate = SelectAllOrNoneContainerDelegate();

  @override
  void dispose() {
    delegate.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return SelectionContainer(
      delegate: delegate,
      child: widget.child,
    );
  }
}

class SelectAllOrNoneContainerDelegate extends MultiSelectableSelectionContainerDelegate {
  Offset? _adjustedStartEdge;
  Offset? _adjustedEndEdge;
  bool _isSelected = false;

  // This method is called when newly added selectable is in the current
  // selected range.
  @override
  void ensureChildUpdated(Selectable selectable) {
    if (_isSelected) {
      dispatchSelectionEventToChild(selectable, const SelectAllSelectionEvent());
    }
  }

  @override
  SelectionResult handleSelectWord(SelectWordSelectionEvent event) {
    // Treat select word as select all.
    return handleSelectAll(const SelectAllSelectionEvent());
  }

  @override
  SelectionResult handleSelectionEdgeUpdate(SelectionEdgeUpdateEvent event) {
    final Rect containerRect = Rect.fromLTWH(0, 0, containerSize.width, containerSize.height);
    final Matrix4 globalToLocal = getTransformTo(null)..invert();
    final Offset localOffset = MatrixUtils.transformPoint(globalToLocal, event.globalPosition);
    final Offset adjustOffset = SelectionUtils.adjustDragOffset(containerRect, localOffset);
    if (event.type == SelectionEventType.startEdgeUpdate) {
      _adjustedStartEdge = adjustOffset;
    } else {
      _adjustedEndEdge = adjustOffset;
    }
    // Select all content if the selection rect intercepts with the rect.
    if (_adjustedStartEdge != null && _adjustedEndEdge != null) {
      final Rect selectionRect = Rect.fromPoints(_adjustedStartEdge!, _adjustedEndEdge!);
      if (!selectionRect.intersect(containerRect).isEmpty) {
        handleSelectAll(const SelectAllSelectionEvent());
      } else {
        super.handleClearSelection(const ClearSelectionEvent());
      }
    } else {
      super.handleClearSelection(const ClearSelectionEvent());
    }
    return SelectionUtils.getResultBasedOnRect(containerRect, localOffset);
  }

  @override
  SelectionResult handleClearSelection(ClearSelectionEvent event) {
    _adjustedStartEdge = null;
    _adjustedEndEdge = null;
    _isSelected = false;
    return super.handleClearSelection(event);
  }

  @override
  SelectionResult handleSelectAll(SelectAllSelectionEvent event) {
    _isSelected = true;
    return super.handleSelectAll(event);
  }
}