Integración de cámara en Android con Photo Handler y manejo de permisos

Properly integrating the camera into an Android application requires careful handling of two key points: permissions management and local storage of the photos taken. Below we will see how to achieve these goals using an interface called Photo Handler, whose main task will be the efficient and orderly management of the process.

How to manage photo storage with Photo Handler?

First of all, we propose to create a package in the Domain layer called Camera, inside which a vital file called Photo Handler will be established. This interface will define specific activities related to the camera throughSuspend Functions. Among the defined activities are:

• Save Picture Preview: Save the current picture as a file, possibly being null.
• Uncancel Preview: Cancels the existing preview.
• Get Current Preview Photo: Exposes the current preview by means of aFlow that can return a ByteArray or null.
• Clear Photos: Clears all locally saved images.
• Unphoto Preview: Performs an intermediate operation by exposing a ByteArray.

In addition, it provides access to a list of stored photos through a stream that manipulates files directly stored in the system.

What is the general flow for capturing and storing photos?

There is a clearly defined process for capture and storage:

1. When a photo is taken using CameraX, an initial preview (ByteArray) is generated.
2. This preview is exposed through a stream using Get Current Preview Photo.
3. If the photo is accepted by the user, the user runs Save Picture Preview, converting the preview into a permanent file.
4. If it is not accepted, it is allowed to cancel it with Uncancel Preview.
5. The Get Photos method is used to get a complete list of previously stored images.
6. At the end of the process and to free space or resources, Clear Photos is invoked.

Each method has its specific purpose, optimizing the user experience and maintaining an efficient data flow.

How is Photo Handler implemented in the data module?

The actual implementation occurs in the Data module, creating a responsible class called HandlerImplementation that receives the application context as the main dependency. This context allows to easily define a directory called Photos, where effectively the captured images will be stored.

The access to the images is configured with the following logic: - It is verified if the main directory exists, and if it is not created yet, with the mkdirs() function it is automatically generated - Two local variables called CurrentPreviewPhoto (a MutableStateFlow of ByteArray) and a MutableStateFlow list are managed to keep track of all the photos.

To get saved images, it uses specific functions: - loadPhotos(): Loads the saved photos filtering by standard extensions (jpg, jpeg, png) - Sorts the results by modification date to obtain an organized visualization.

The core implementation corresponds to the methods defined in the interface, clarifying what happens with each action performed by the user:

• When an onPhotoPreview is performed, it updates the current photo in the preview.
• With onCancelPreview, it clears the preview reference.
• The getPhotos function returns the stored photos as a state stream.
• clearPhotos handles the safe deletion of files, executing that action in a separate thread via Dispatchers.IO.
• Finally, the safePicturePreview method performs the actual physical file write, adding timestamps for easier management later.

These steps contribute to a robust and efficient integration of camera and storage management in Android applications with good practices and effective resource management.