Android MVVM + Django rest API practice

Minimalistic app + server for rest api, android MVVM and sync practice.

How to run

Connect android device and PC to same wifi. Find out your PC's IPv4 address. In ubuntu it can be viewed in Network -> see details of the wifi connection. My laptop's IPv4 address is 192.168.0.103, so from terminal in server root directory (where manage.py is located), first to create a new superuser, python3 manage.py createsuperuser (a superuser named shafin with password shafin already exists), then run python3 manage.py runserver 192.168.0.103:8000. Then to create a new user, go to 192.168.0.103:8000/accounts/signup/ or to view or change everything as an admin, go to 192.168.0.103:8000/admin/. View all available server urls in urls.py.

Change API_BASE = "192.168.0.103:8000/api/" in android's LoginActivity.java. Now you should be able to access server from app.

UUID

It's not feasible to use normal incrementing primary key in a distributed system. If same user creates different data from different devices, they may have same primary key in local database, which will cause in collision while syncing.

Biggest mistakes

• Using auto incrementing ID as primary key instead of UUID.
• Forgetting to add django app in settings.py after startapp.
• Forgetting to handle null pointer exception in android many times.

Future guides for starting django rest framework projects

pip3 install pipenv
pipenv shell
pipenv install django djangorestframework django-cors-headers
django-admin startproject backend
cd backend
python3 manage.py startapp api && echo "urlpatterns = []" > api/urls.py

• add path('api/', include('api.urls')), in backend/urls.py

• vscode select python enterpreter: select the pipenv environment.

• in backend/settings.py,

  • make DATABASES = {}
  • add to INSTALLED_APPS:

    'rest_framework',
    'corsheaders',
    'backend',
    'api.apps.ApiConfig',
    

  • prepend 'corsheaders.middleware.CorsMiddleware', to MIDDLEWARE
  • append CORS_ALLOWED_ORIGINS = ['http://localhost']

• add the following in api/admin.py.

  from django.apps import apps
  from django.contrib.admin.sites import AlreadyRegistered
  
  app_models = apps.get_app_config('api').get_models()
  for model in app_models:
      try:
          admin.site.register(model)
      except AlreadyRegistered:
          pass
  

• python3 backend/manage.py migrate

• python3 backend/manage.py createsuperuser

• python3 backend/manage.py runserver

• create new models in api/models.py. Any change in models have to be followed by: python3 backend/manage.py makemigrations && python3 backend/manage.py migrate

• django auto provides User model. We can add attributes to this model by adding models.py in backend & following this. use User in other models by owner = models.ForeignKey(django.contrib.auth.get_user_model(), models.CASCADE).