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shouldRepaint method

bool shouldRepaint (covariant CustomPainter oldDelegate)

<span class="feature">override</span>

<p>Called whenever a new instance of the custom painter delegate class is provided to the <a href="https:api.flutter.dev/flutter/rendering/RenderCustomPaint-class.html">RenderCustomPaint</a> object, or any time that a new <a href="https:api.flutter.dev/flutter/widgets/CustomPaint-class.html">CustomPaint</a> object is created with a new instance of the custom painter delegate class (which amounts to the same thing, because the latter is implemented in terms of the former).</p> <p>If the new instance represents different information than the old instance, then the method should return true, otherwise it should return false.</p> <p>If the method returns false, then the <a href="../../custom_painters_language_icon/LanguageIcon/paint.md">paint</a> call might be optimized away.</p> <p>It's possible that the <a href="../../custom_painters_language_icon/LanguageIcon/paint.md">paint</a> method will get called even if <a href="../../custom_painters_language_icon/LanguageIcon/shouldRepaint.md">shouldRepaint</a> returns false (e.g. if an ancestor or descendant needed to be repainted). It's also possible that the <a href="../../custom_painters_language_icon/LanguageIcon/paint.md">paint</a> method will get called without <a href="../../custom_painters_language_icon/LanguageIcon/shouldRepaint.md">shouldRepaint</a> being called at all (e.g. if the box changes size).</p> <p>If a custom delegate has a particularly expensive paint function such that repaints should be avoided as much as possible, a <a href="https:api.flutter.dev/flutter/widgets/RepaintBoundary-class.html">RepaintBoundary</a> or <a href="https:api.flutter.dev/flutter/rendering/RenderRepaintBoundary-class.html">RenderRepaintBoundary</a> (or other render object with <a href="https:api.flutter.dev/flutter/rendering/RenderObject/isRepaintBoundary.html">RenderObject.isRepaintBoundary</a> set to true) might be helpful.</p> <p>The <code>oldDelegate</code> argument will never be null.</p>

Implementation​

@override
bool shouldRepaint(covariant CustomPainter oldDelegate) \{
  return true;
\}