如何在文件系统中写入图像的内容

Question

我正在尝试从图库或照相机中选择要写入的图像内容，但是它没有写任何我不知道为什么的文件系统，请有人帮我

  List<int> bytes;
 Future<String> get _localPath async {
    final directory = await getApplicationDocumentsDirectory();
    print(directory.path);
    return directory.path;
  }

  Future<File> get _localFile async {
    final path = await _localPath;
    print(path);
    return File('$path/image.png');
  }
  Future<File> writeCounter(var bytes) async {
    final file = await _localFile;
    print(file);
    // Write the file.
    return file.writeAsBytes(bytes);
  }

  Future<int> readCounter() async {
    try {
      final file = await _localFile;

      // Read the file.
      List<int> contents = await file.readAsBytes();

      return int.parse(contents.toString());
    } catch (e) {
      // If encountering an error, return 0.
      return 0;
    }
  }

  Future pickImage() async {
    tempStore = await ImagePicker.pickImage(source: ImageSource.gallery);
    bytes = await tempStore.readAsBytes();
   // encoded1 = base64.encode(bytes);
      writeCounter(bytes);
      var val = await readCounter();
      print(val);
    //print(encoded1);
    setState(() {
      pickedImage = tempStore;
      isImageLoaded = true;
    });
  }

Answer 1

1。打开图像文件

要打开图像，实际上您可以将变量内容设置为“文件”。

try {
  final file = await _localFile;

  // Read the file.
  List<int> contents = await file.readAsBytes();

  return int.parse(contents.toString());
}

将其变成

try {
  File file = await _localFile;
  return file;
} 

所以稍后，我们可以使用此小部件轻松渲染它

class DisplayImage extends StatelessWidget {
  DisplayImage({
    @required this.imageData,
  });
  final File imageData;

  @override
  Widget build(BuildContext context) {
    return Image.file(imageData);
  }
}

2。保存图像文件

另一方面，为了保存图像，您实际上可以更改

codetempStore = await ImagePicker.pickImage(source: ImageSource.gallery);
bytes = await tempStore.readAsBytes();
// encoded1 = base64.encode(bytes);
writeCounter(bytes);

和

final file = await _localFile;
print(file);
// Write the file.
return file.writeAsBytes(bytes);

进入这个

final file = await _localFile;
File result = await file.writeAsBytes(imageData.readAsBytesSync());
return result;

3。完整示例

幸运的是，我在此Github Repo中建立了完整的工作示例，发现如果我们将更多的业务逻辑与其他文件分开，它将变得更易于管理。

演示

文件： lib / services / localStorage.dart

import 'dart:async';
import 'dart:io';
import 'package:path_provider/path_provider.dart';

class LocalStorage {
  String getFileExt(File imageData) {
    String fullFilename = imageData.uri.pathSegments.last;
    String extension = fullFilename.split(".").last;
    return extension;
  }

  Future<File> _getLocalFile({String filename}) async {
    var dir = await getApplicationDocumentsDirectory();
    return File('${dir.path}/$filename');
  }

  // Loading Image File
  Future<File> loadImageLocal({String imageFilename}) async {
      final file = await _getLocalFile(filename: imageFilename);
      if (!file.existsSync()){
        throw FormatException("does not exist");
      }
      return file;
  }

  // Saving Image File
  Future<File> saveImageLocal({File imageData, String newFilename}) async {
    final file = await _getLocalFile(filename: newFilename);
    File result = await file.writeAsBytes(imageData.readAsBytesSync());
    return result;
  }
}

文件： lib / screen / saveImage.dart

  Future saveImage() async {
    if (_formKey.currentState.validate()) {
      _formKey.currentState.save();
      await LocalStorage().saveImageLocal(
        imageData: imageData,
        newFilename: newFilename,
      );
      _scaffoldKey.currentState.showSnackBar(SnackBar(
        content: Text('$newFilename saved successfully'),
        duration: Duration(seconds: 3),
      ));
    }
  }

  Future getImage() async {
    File image = await ImagePicker.pickImage(source: ImageSource.gallery);
    setState(() {
      imageData = image;
    });
  }

文件： lib / screen / openImage.dart

  Future loadImage() async {
    if (_formKey.currentState.validate()) {
      _formKey.currentState.save();
      try {
        File result = await LocalStorage().loadImageLocal(
          imageFilename: imageFilename,
        );
        setState(() {
          loadedImage = result;
        });
      } 
    }
  }