How can I show a CameraPreview widget Immediately,instead of inited with a black block？

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huang

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Jul 9, 2018, 6:38:31 AM7/9/18

to Flutter Dev

import 'package:camera/camera.dart';
import 'dart:async';
import 'package:flutter/material.dart';

class CameraMgr{
  CameraMgr._();
  CameraController _cameraCtrl;

  Future<CameraController> openCamera() async {
    CameraDescription cameraDescription;
    List<CameraDescription> cameras = await availableCameras();
    for (CameraDescription xx in cameras){
      if(xx.lensDirection==CameraLensDirection.front){
        cameraDescription = xx;
        break;
      }
    }
    if(cameraDescription==null){
      return null;
    }
    if (_cameraCtrl != null) {
      await _cameraCtrl.dispose();
    }
    _cameraCtrl = new CameraController(cameraDescription, ResolutionPreset.low)..addListener(() {
      if (_cameraCtrl.value.hasError) {
        print("");
      }
    });

    try {
      await _cameraCtrl.initialize();
    } on CameraException catch (e) {
      print(e);
    }
    return _cameraCtrl;
  }
  close()async {
    if (_cameraCtrl != null) {
      await _cameraCtrl.dispose();
    }
    _cameraCtrl = null;
  }
}
CameraMgr myCameraMgr = new CameraMgr._();

class TestCamera extends StatefulWidget{
  @override
  State<StatefulWidget> createState() {
    return new _TestCameraState();
  }
}
class _TestCameraState extends State<TestCamera>{
  @override
  void initState() {
    super.initState();
    myCameraMgr.openCamera();
  }
  @override
  void dispose(){
    super.dispose();
    myCameraMgr.close();
  }
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        backgroundColor: Colors.blueAccent,
        body: new Center(
          child: new LayoutBuilder(
            builder: (BuildContext ctx,BoxConstraints bcts){
              return new GestureDetector(
                child: new Container(
                  height: 80.0,
                  color: Colors.red[100],
                  child: new Text("touch to show dialog"),
                ),
                onTap: ()async{
                  CameraController ctrl = await myCameraMgr.openCamera();
                  showDialog(
                    context: ctx,
                    builder: (BuildContext _){
                      return new Container(
                        height: bcts.maxHeight,
                        width: bcts.maxWidth,
                        child: new DialogCamera(ctrl),
                      );
                    }
                  );
                },
              );
            },
          )
        ),
      ),
    );
  }
}

class DialogCamera extends StatelessWidget{
  DialogCamera(this.ctrl);
  final CameraController ctrl;
  @override
  Widget build(BuildContext context) {
    return new Container(
      margin: new EdgeInsets.all(150.0),
      child: new Center(
        child: new CameraPreview(this.ctrl),
      ),
    );
  }
}

void main() {
  runApp(new TestCamera());
}

There is my test case above. In my app,I need show and take photo by CameraPreview frequently,but the Initialization of the widget is too slow.

I have tried to cache the CameraController,but it change nothing.

Is there some ways to rending the widget in advance？or other ways to solve this problem？

Thank you very much!

huang

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Jul 9, 2018, 9:57:58 PM7/9/18

to Flutter Dev

Sorry，it's my fault，I made a mistake.

if(_cameraCtrl!=null){
  return _cameraCtrl;
}