Flutter - How to center widget inside list view

Solving this question with shrinkWrap = true is a hack. The whole point of centering widgets inside a ListView is to have bounciness and scrolling enabled. Using shrinkWrap doesn't achieve this, it looks visually correct but it behaves completely wrong.

The solution is to place a Container as the only children in the ListView, and give it a minimum height equal to the available space for the height (Use LayoutBuilder to measure the maximum height for the widget). Then as the Container's child, you can either place a Center or Column (with MainAxisAlignment.center) widget and from there you can add whatever widgets you intended to center.

Below is the code to solve the example in the question:

Scaffold(
  appBar: AppBar(),
  body: LayoutBuilder(
    builder: (context, constraints) => ListView(
      children: [
        Container(
          padding: const EdgeInsets.all(20.0),
          constraints: BoxConstraints(
            minHeight: constraints.maxHeight,
          ),
          child: Center(
            child: Text('ABC'),
          ),
        )
      ],
    ),
  ),
);

Vertically Center & Horizontal Center:

Scaffold(
  appBar: new AppBar(),
  body: Center(
    child: new ListView(
      shrinkWrap: true,
        padding: const EdgeInsets.all(20.0),
        children: [
          Center(child: new Text('ABC'))
        ]
    ),
  ),
);

Only Vertical Center

Scaffold(
  appBar: new AppBar(),
  body: Center(
    child: new ListView(
      shrinkWrap: true,
        padding: const EdgeInsets.all(20.0),
        children: [
          new Text('ABC')
        ]
    ),
  ),
);

Wrap your widget into container

Container(alignment: Alignment.center, ...)

or

Container(alignment: Alignment.centerLeft, ...)