Saving Photos to the Filesystem

We’re now able to take multiple photos and display them in a photo gallery on the second tab of our app. These photos, however, are not currently being stored permanently, so when the app is closed, they will be lost.

Filesystem API

Fortunately, saving them to the filesystem only takes a few steps. Begin by opening the usePhotoGallery hook (src/hooks/usePhotoGallery.ts), and get access to the writeFile method from the Filesystem class:

注記

We will use the writeFile method initially, but we will use the others coming up shortly, so we'll go ahead and import them now.

Next, create a couple of new functions in usePhotoGallery:

export function usePhotoGallery() {
  const savePicture = async (photo: Photo, fileName: string): Promise<UserPhoto> => {
    const base64Data = await base64FromPath(photo.webPath!);
    const savedFile = await Filesystem.writeFile({
      path: fileName,
      data: base64Data,
      directory: Directory.Data,
    });

    // Use webPath to display the new image instead of base64 since it's
    // already loaded into memory
    return {
      filepath: fileName,
      webviewPath: photo.webPath,
    };
  };
}

export async function base64FromPath(path: string): Promise<string> {
  const response = await fetch(path);
  const blob = await response.blob();
  return new Promise((resolve, reject) => {
    const reader = new FileReader();
    reader.onerror = reject;
    reader.onload = () => {
      if (typeof reader.result === 'string') {
        resolve(reader.result);
      } else {
        reject('method did not return a string');
      }
    };
    reader.readAsDataURL(blob);
  });
}

注記

The base64FromPath method is a helper util that downloads a file from the supplied path and returns a base64 representation of that file.

We pass in the photo object, which represents the newly captured device photo, as well as the fileName, which will provide a path for the file to be stored to.

Next we use the Capacitor Filesystem API to save the photo to the filesystem. We start by converting the photo to base64 format, then feed the data to the Filesystem’s writeFile function.

Last, call savePicture and pass in the photo object and filename directly underneath the call to setPhotos in the takePhoto method. Here is the full method:

const takePhoto = async () => {
  const photo = await Camera.getPhoto({
    resultType: CameraResultType.Uri,
    source: CameraSource.Camera,
    quality: 100,
  });

  const fileName = Date.now() + '.jpeg';
  const savedFileImage = await savePicture(photo, fileName);
  const newPhotos = [savedFileImage, ...photos];
  setPhotos(newPhotos);
};

There we go! Each time a new photo is taken, it’s now automatically saved to the filesystem.