Android 如何在文件系统中写入映像的内容

我正在尝试写图片的内容，我从图库或相机中选择，但是，在一个文件系统中，它没有写任何东西，我不知道为什么，请有人帮助我

  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;
    });
  }

列出字节；
未来获取\u本地路径异步{
最终目录=等待getApplicationDocumentsDirectory（）；
打印（directory.path）；
返回directory.path；
}
未来获取\u本地文件异步{
最终路径=等待_localPath；
打印（路径）；
返回文件（“$path/image.png”）；
}
未来写计数器（变量字节）异步{
final file=wait\u localFile；
打印（文件）；
//写这个文件。
返回文件.writeAsBytes（字节）；
}
Future readCounter（）异步{
试一试{
final file=wait\u localFile；
//读取文件。
List contents=wait file.readAsBytes（）；
返回int.parse（contents.toString（））；
}捕获（e）{
//如果遇到错误，则返回0。
返回0；
}
}
Future pickImage（）异步{
tempStore=wait ImagePicker.pickImage（源：ImageSource.gallery）；
bytes=等待tempStore.readAsBytes（）；
//encoded1=base64.encode（字节）；
写计数器（字节）；
var val=等待读取计数器（）；
打印（val）；
//打印（编码D1）；
设置状态（）{
pickedImage=tempStore；
isImageLoaded=true；
});
}

1。打开图像文件 对于打开图像，实际上可以将可变内容设置为文件

try {
  final file = await _localFile;

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

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

所以稍后，我们可以使用这个小部件轻松地渲染它

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，您实际上可以更改此设置

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

及

这一个

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

3.完整示例 幸运的是，我在这里构建了完整的工作示例，我发现如果我们将更多的业务逻辑分离到其他文件中，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;
  }
}

  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;
    });
  }

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

文件：lib/screen/openImage.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;
  }
}

  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;
    });
  }

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