Flutter plugin that downloads images and movies on the Internet and saves to Photo Library on iOS or specified directory on Android.
This will keep Exif(DateTimeOriginal) and GPS(Latitude, Longitude).

Add the following keys to your Info.plist file, located in /ios/Runner/Info.plist:

• NSPhotoLibraryUsageDescription - Specifies the reason for your app to access the user’s photo library. This is called Privacy - Photo Library Usage Description in the visual editor.
• NSPhotoLibraryAddUsageDescription - Specifies the reason for your app to get write-only access to the user’s photo library. This is called Privacy - Photo Library Additions Usage Description in the visual editor.

Add this permission in AndroidManifest.xml. (If you call AndroidDestinationType#inExternalFilesDir(), This setting is not necessary.)

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

try {
  // Saved with this method.
  var imageId = await ImageDownloader.downloadImage("https://raw.githubusercontent.com/wiki/ko2ic/image_downloader/images/flutter.png");
  if (imageId == null) {
    return;
  }

  // Below is a method of obtaining saved image information.
  var fileName = await ImageDownloader.findName(imageId);
  var path = await ImageDownloader.findPath(imageId);
  var size = await ImageDownloader.findByteSize(imageId);
  var mimeType = await ImageDownloader.findMimeType(imageId);
} on PlatformException catch (error) {
  print(error);
}

The return value is as follows.

• imageId of the saved image if saving succeeded.
• null if not been granted permission.
• Otherwise it is a PlatformException.

You can specify the storage location.
(Currently, external storage is only supported on Android.)

Three directories by default are provided.

• AndroidDestinationType.directoryDownloads -> Environment.DIRECTORY_DOWNLOADS on Android
• AndroidDestinationType.directoryPictures -> Environment.DIRECTORY_PICTURES on Android
• AndroidDestinationType.directoryDCIM -> Environment.DIRECTORY_DCIM on Android
• AndroidDestinationType.directoryMovies -> Environment.DIRECTORY_MOVIES on Android

In addition, there is also custom.

For example, the following sources is stored in /storage/emulated/0/sample/custom/sample.gif.
(Depends on the device.)

await ImageDownloader.downloadImage(url,
                                    destination: AndroidDestinationType.custom('sample')                                  
                                    ..subDirectory("custom/sample.gif"),
        );

For example, the following sources is stored in /storage/emulated/0/Android/data/<applicationId>/files/sample/custom/sample.gifby calling inExternalFilesDir() .
(Depends on the device.)

 await ImageDownloader.downloadImage(url,
                                     destination: AndroidDestinationType.custom('sample')
                                     ..inExternalFilesDir()
                                     ..subDirectory("custom/sample.gif"),
         );

Note: inExternalFilesDir() will not require WRITE_EXTERNAL_STORAGE permission, but downloaded images will also be deleted when uninstalling.

You can get the progress value.
Note: On iOS, onProgressUpdate cannot get imageId.

  @override
  void initState() {
    super.initState();

    ImageDownloader.callback(onProgressUpdate: (String imageId, int progress) {
      setState(() {
        _progress = progress;
      });
    });
  }

You can do it simply by using await .

var list = [
  "https://raw.githubusercontent.com/wiki/ko2ic/image_downloader/images/bigsize.jpg",
  "https://raw.githubusercontent.com/wiki/ko2ic/image_downloader/images/flutter.jpg",
  "https://raw.githubusercontent.com/wiki/ko2ic/image_downloader/images/flutter_transparent.png",
  "https://raw.githubusercontent.com/wiki/ko2ic/flutter_google_ad_manager/images/sample.gif",
  "https://raw.githubusercontent.com/wiki/ko2ic/image_downloader/images/flutter_no.png",
  "https://raw.githubusercontent.com/wiki/ko2ic/image_downloader/images/flutter.png",
];

List<File> files = [];

for (var url in list) {
  try {
    var imageId = await ImageDownloader.downloadImage(url);
    var path = await ImageDownloader.findPath(imageId);
    files.add(File(path));
  } catch (error) {
    print(error);
  }
}
setState(() {
  _mulitpleFiles.addAll(files);
});

There is a open method to be able to immediately preview the download file.
If you call it, in the case of ios, a preview screen using UIDocumentInteractionController is displayed. In case of Android, it is displayed by Intent.

var imageId = await ImageDownloader.downloadImage(url);
var path = await ImageDownloader.findPath(imageId);
await ImageDownloader.open(path);

Note: in the case of android, to use this feature, the following settings are required.

Add the following within <application> tag in AndroidManifest.xml .

        <provider
                android:name="com.ko2ic.imagedownloader.FileProvider"
                android:authorities="${applicationId}.image_downloader.provider"
                android:exported="false"
                android:grantUriPermissions="true">
            <meta-data
                    android:name="android.support.FILE_PROVIDER_PATHS"
                    android:resource="@xml/provider_paths"/>
        </provider>

Add provider_paths.xml in android/app/src/main/res/xml/ .

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="external_files" path="."/>
</paths>

You can determine the type of error with PlatformException#code.

In the case of HTTP status error, the code is stored.
In the case of the file format is not supported, unsupported_file is stored.
There is an important point in the case of unsupported_file.
Even unsupported files are stored in a temporary directory.
It can be retrieved with error.details ["unsupported_file_path"]; .
Note: it will be deleted when you exit the app.

ImageDownloader.downloadImage(url).catchError((error) {
  if (error is PlatformException) {
    var path = "";
    if (error.code == "404") {
      print("Not Found Error.");
    } else if (error.code == "unsupported_file") {
      print("UnSupported FIle Error.");
      path = error.details["unsupported_file_path"];
    }
  }
})

If the file can not be previewed, the preview_error is stored in the code.

  await ImageDownloader.open(_path).catchError((error) {
    if (error is PlatformException) {
      if (error.code == "preview_error") {
        print(error.message);
      }
    }    
  });

https://github.com/ko2ic/image_downloader/wiki#trouble-shooting