Select all text inside TextField when it gets focus - flutter

Question

On TextField foucus I want to select all text so that when the user starts typing the existing text gets deleted.
This will be alternative of : android:selectAllOnFocus="true" in Android.
How to achive this?

Answer 1

Pass a controller and focusNode explicitly, then you have full control:
final _controller = TextEditingController();
final _focusNode = FocusNode();
initState() {
super.initState();
_focusNode.addListener(() {
if(_focusNode.hasFocus) {
_controller.selection = TextSelection(baseOffset: 0, extentOffset: _controller.text.length);
}
});
}
build() => TextField(controller: _controller, focusNode: _focusNode);
Update
from https://github.com/flutter/flutter/issues/28307#issuecomment-467952074 to prevent endless loop:
_controller.addListener(() {
final newText = _controller.text.toLowerCase();
_controller.value = _controller.value.copyWith(
text: newText,
selection: TextSelection(baseOffset: newText.length, extentOffset: newText.length),
composing: TextRange.empty,
);
});

Answer 2

It's also possible to set the selection in onTap event. Like this:
TextField(
controller: _controller,
onTap: () => _controller.selection = TextSelection(baseOffset: 0, extentOffset: _controller.value.text.length),
)

Answer 3

It's actually much easier than the accepted answer.
First initialize a TextEditingController.
final _controller = TextEditingController();
Then, somewhere within your build method (probably within your edit text logic), set the text and the selection props like so.
_controller.text = textValue;
_controller.selection = TextSelection(
baseOffset: 0,
extentOffset: textValue.length,
);
In the TextFormField, make sure to assign the controller and set autofocus to true.
TextFormField(
controller: _controller,
autofocus: true,
//...more properties
That's it!

Answer 4

For a cleaner, reusable experience an Extension class method (see note below) is handy.
extension TextEditingControllerExt on TextEditingController {
void selectAll() {
if (text.isEmpty) return;
selection = TextSelection(baseOffset: 0, extentOffset: text.length);
}
}
On the field:
TextField(
controller: myController,
onTap: myController.selectAll
)
Example
On Dartpad:
https://dartpad.dev/?id=271737b109637f90a2fe5ea55ea2ac43
Note
In extension classes, this can be omitted.
text is assumed to be: this.text i.e. <this instance of controller>.text
Same with selection being actually this.selection.

Answer 5

As of Dart 2:
controller1.selection = TextSelection(baseOffset:0, extentOffset:controller1.text.length);