Uploading images from your gallery it not an easy task on Android. This tutorial will illuminate the argument under several aspects.
On our web server, we create a new, empty script, for example: upload-image.php. Instead, you may also use our online script.
We open the file in our preferred editor and add the following code.
The settings allow to define parameters used in the script.
In Android Studio we create a new project.
In the application gradle, we add Picasso, which is an external library for viewing images.
Let’s use this specific version, which runs with API 28.
In the app window we add an image view, and 2 buttons.
Upon window creation, we add 2 event handlers.
The first button will allow us to choose an image from the gallery.
The second button will allow us to upload the image.
We now will create the respective functions.
This piece of code selects an image from the gallery.
Then, we override the activity result event with our code.
In order to make this feature work properly, we ask permission to access the gallery, and add later the storage read permission to the manifest.
We add this function, which retrieves the physical file name of the image. It is pretty complex, because the possible file locations are many, and there are no real standards for storing files.
We read then the raw contents of the image and save them in memory. It could also be moved to the upload button, but if in the mean time the image is deleted, the function will return an error.
Further on, we view the image on our window and store the raw data in a local variable.
The upload function calls an asynchronous task, which natively leaks a bit of memory. It is however of temporary nature, and we can safely ignore it.
In this function, the upload happens. We set the parameters accordingly.
There are many ways to pass parameters, some of which work, other’s not.
The boundary is ideally a random string. It is used to separate blocks of information.
In order to make this feature work properly, we add the internet permission to the manifest. This permission does not require user interaction.
Let’s try what we get so far.
The app asks us permission to access the gallery. Some phone will grant the gallery application always to access, other’s not. We ask permission in any case and leave the decision to the operating system.
We attempt to upload the file. It fails, because the key parameter can’t be read.
For this kind of conversation, we need to create a POST block for the key parameter.
Now, the upload succeeded.
We select the upload URL and paste it in our browser. Together with the filename, we view the uploaded image.
We try another image.
This is the code so far.
Now, we see some of the advanced features.
The application may lose the image, when the phone is moved around.
To avoid data loss, we can block the view, or let the system save the data while switching view. Let’s see how this works.
That’s all for today. Thank you for watching!
Android Studio 3 – Work Manager
A few days ago, Android has added a new and more efficient way to run background services. We will explore here the main features.
We create a new, empty project. As always, the name is at our personal discretion.
We open also the application build configuration and its manifest file.
In the manifest file, we add an action, which allows Google to harvest information, once the application is added to the app store.
Before the application tag, we add a few permissions, in order to allow Internet access and interrogate the network status.
Then, we add the permission to react on the boot status. Essentially, this permission registers the application at system level, because it will receive a notification when the system is ready to use.
Under the application tag, we add a broadcast receiver for this system event. We give it a significant name. Then we add an intent filter and the respective action.
Then, we click on the broadcast name, and choose to create a new class. Within the class, we add the required functions. This class has no user interface.
In the function which receives the event, we add for now a log entry.
If we use this broadcast receiver also for other notifications, we additionally have to filter the actions.
In order to add the work-in-progress addition, we go to the application configuration and add the following line.
Now, we add a worker class, which is called every time from the system, when our programmed event occurs.
We may create as many worker classes as needed, for every background task we want to perform. Each class should be as small as possible, since the work manager allows to call all tasks with very powerful features, which give us full control over the code flow. In other words, it is not advisable to pack as many as possible features into a single procedure, because the new features allow us to gain better control over predefined steps.
We create now the respective function, and we make it public to the package and static. A public static function becomes available to all other classes of our project.
Now we can start our application and run one worker instance at each button press. We filter our log entries with our tag. The first message informs us about the request, and shortly after, we are informed about the execution of the background task.
To automate the button press, we can add the creation of a new task from within the task itself. We would do that, if our events happen more frequently than every 15 minutes. We also disable or hide the button, to avoid a second manual start.
If we now press the button, the function is called once manually and then by the background task.
How can we tell it is background? Well, stop your application and see! As long as your device is running, the task starts itself over and over.
I add the same command in the broadcast receiver.
Now, I will run the application on my real phone and reboot. After the device becomes available again, the system calls the background task without my direct intervention.
The background task continues after a short pause, even when I force to stop the application. This behaviour eventually is a bug, but right now it is a feature, which makes workers much more attractive than a service.
That’s all for today. Thank you for watching!
Channel: Exploding Computers
Published: 2018-08-29 17:10:27
Goth •Special• Sculpted Acrylic Nails 🗡️
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Channel: Nail Career Education
Published: 2018-10-11 03:32:22
School Days: PT Period | The Timeliners
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Channel: The Timeliners
Published: 2018-10-07 07:57:00
Why Did Scientists Create Zombie Dogs?
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Published: 2018-10-08 19:36:39
ఈమహిళా IAS ఇచ్చిన సమాదానంవిని సీనియర్స్ షాక్ | IAS Lady Shocking Answers In Civil Interview
Published: 2018-10-08 13:23:00