Center row child and right-align

You can create this with Stack

       Card(child: Padding(
              padding: const EdgeInsets.all(16.0),
              child: Stack(
                children: <Widget>[
                  Center(child: Text('PLAY QUEUE'),),
                  Container(
                    alignment: Alignment.centerRight,
                    child: Text('CLEAR'),
                  )
                ],
              ),
            ),
          ),

This is a job for a Stack!

You can put the Text widgets into the Stack as individual children and use a Positioned widget to right-align the "clear" one.

This is what the Material AppBar widget does for this exact scenario.

To place the Container at right side inside the Row, I have used Expanded!

Once I have to place a child Container inside Row, and here Row have already some other children widgets before that Container starting from default direction left to right side and the Container were exactly trailing after earlier childrens.

and here my Container width was 40.0 and remaining width inside the Row were around 100.0 after leading childrens.

thus, I used below said to push the Container right side to the Row.

child: Row(
    children: <Widget>[
      Container(
        padding: EdgeInsets.only(left: 8.0, right: 8.0),
        child: CircleAvatar(
          child: ClipOval(
            child: _musicIcon,
            clipBehavior: Clip.antiAlias,
          ),
        ),
      ),
      Column(
        crossAxisAlignment: CrossAxisAlignment.start,
        mainAxisAlignment: MainAxisAlignment.start,
        children: <Widget>[
          Container(
            padding: EdgeInsets.only(top: 8.0, bottom: 3.0),
            constraints: BoxConstraints(maxWidth: 280.0),
            child: Text("some0"),
          ),
          Row(
            children: <Widget>[
              Container(
                constraints: BoxConstraints(maxWidth: 200.0),
                child: Text("some1"),
              ),
              Container(
                padding: EdgeInsets.only(left: 10.0, right: 10.0),
                child: Text("some2"),
              ),
              Container(
                constraints: BoxConstraints(minWidth: 20.0),
                child: Text("some3"),
              ),
            ],
          ),
        ],
      ),
      Expanded(
        child: Container(
            width: 40.0,
            margin: EdgeInsets.only(right: 8.0),
            alignment: Alignment.centerRight,
            child: GestureDetector(
              onTap: () {
                // doing something
              },
              child: Padding(
                padding: EdgeInsets.only(left: 18.0, right: 0.0),
                child: CircleAvatar(
                  child: _getActionFlareActor(
                      _musicURL, _musicTitle, true),
                ),
              ),
            )),
      )
    ],
)),

Hope this scenario may help someone.