KotlinAndroidApp

Basic COVID-19 STATUS App with RecyclerView

Concepts of Kotlin used in App:

1. Constants:

   • Package Name:
     • package com.example.finalkotlinproject.CustomZoom
   • companion object is used to define constant values for the Class ZoomCenter (companion object for constants: It's singleton object in the class having single instance only)
   • Eg:

     companion object {
       const val sShrinkAmount = 0.15f
       const val sShrinkDistance = 0.9f
     }
     

2. Nullability

   • Package Name:
     • package com.example.finalkotlinproject.Model
     • package com.example.finalkotlinproject.HelpAdapter
     • package com.example.finalkotlinproject.TeamAdapter
   • In all Data Class/Adapter nullability check is added using ? or !! (? - check if the value is not null while using it along with variable) (!! - It's not null operator which convert to non-null type and throws Null Pointer Exception if it's null)

3. Inheritence

   • Activity:
     • MainActivity
     • ExploreTeams
     • PrecautionActivity
     • ExploreHelp
   • All activity extends AppCompatActivity Class and override the functionality of it using override keyword
   • Eg:

     class MainActivity : AppCompatActivity() {
       override fun onCreate(savedInstanceState: Bundle?) {
       	super.onCreate(savedInstanceState)
       	setContentView(R.layout.activity_main)
       	discover_button.setOnClickListener(){
           	val discover_intent = Intent(this,ExploreTeams::class.java)
           	supertartActivity(discover_intent)
       	}
       	precaution_button.setOnClickListener(){
           	val precaution_intent = Intent(this,PrecautionActivity::class.java )
           	startActivity(precaution_intent)
       	}
       	help_button.setOnClickListener(){
           	val help_intent = Intent(this,ExploreHelp::class.java)
           	startActivity(help_intent)
       	}
       }
     }
     

4. Data Class

   • Package Name:
     • package com.example.finalkotlinproject.Model
   • CustomTeams.kt Kotlin file has 2 Data Class : CustomTeams, HelpNumbers
   • Both Data Class is the Object which holds data to be used by TeamAdapter and HelpAdapter Class repectively
   • The Data Class are instantiate using the CustomTeams() and HelpNumbers() which initialise the object holding passed data

5. Compact Functions

   • Package Name:
     • package com.example.finalkotlinproject.HelpAdapter
     • package com.example.finalkotlinproject.TeamAdapter
   • Abstract function "getItemCount()" returns result which is single expression
   • Hence we can avoid the {} and return statement and is used = to return the expression(here it's return the size of ArrayList passed to Adapter)
   • Eg: override fun getItemCount(): Int = teams.size

6. Abtract Class

   • Package Name:
     • package com.example.finalkotlinproject.TeamAdapter
     • package com.example.finalkotlinproject.HelpAdapter
   • Both TeamAdapter and HelpAdapter are subclasses which are implementing the abstract properties of Abstract Class Adapter (methods that has to be implemented by subclasses are onCreateViewHolder(),getItemCount(),onBindViewHolder() as they are abstarct method of Parent Class)

7. Extention Function

   • Package Name:
     • package com.example.finalkotlinproject.TeamAdapter
     • package com.example.finalkotlinproject.HelpAdapter
   • In extention function we can add functionality to the existing function of the Class
   • Here infalting property is added to ViewGroup Class using dot notation i.e ViewGroup.inflate(layoutIdentifier:Int)
   • So in onCreateViewHolder() function , only inflate function need to be called on parent ViewGroup
   • Eg: fun ViewGroup.inflate(layoutR: Int) : View = LayoutInflater.from(context).inflate(layoutR,this,false)

8. filters

   • Package Name:
     • package com.example.finalkotlinproject.TeamAdapter
   • Here in App ,filter is applied on String to filter out only digits part of it
   • Filter condition is added in {} and it refers to each item of String
   • Eg: val totalCase = h.itemView.description1.text.toString().filter { it.isDigit() }

9. Interface

   • Package Name:
     • package com.example.finalkotlinproject.HelpAdapter
   • Here the method onRequestPermissionsResult() of interface 'OnRequestPermissionsResultCallback' from class 'ActivityCompat' is implemented
   • Eg:

   class HelpAdapter(val context: Context, private val helpnumbers:ArrayList<HelpNumbers>,val requestCall: Int) :  RecyclerView.Adapter<RecyclerView.ViewHolder>(),ActivityCompat.OnRequestPermissionsResultCallback
   override fun onRequestPermissionsResult(requestCode: Int, permissions: Array<out String>, grantResults: IntArray)        
   {
      if(requestCode == requestCall) makeCall()
   }
   

10. Annotation

    • Package Name:
      • package com.example.finalkotlinproject.HelpAdapter
    • SuppressLint annotation specifies that for the given function ignore the specified Warnings given in the String form
    • Eg:

      @SuppressLint("MissingPermission")
          private fun makeCall(){
           val callIn = Intent(Intent.ACTION_CALL)
           callIn.data = Uri.parse("tel:" + callNumber)
           mContext.startActivity(callIn)
          }
      

Working of App:

• Name: COVID19-STATUS
• Description:
  • Stats Button:
    • The redirection give the basic stats of total,current,death cases(data is refered and not live data) of countries
    • The status button pop-ups the window showing status is critical or not critical based total cases evaluation (Picasso is used to load images of countries flags though url's, Hence require internet)
  • Precaution Button:
    • The redirection give the list of steps that can be followed to prevent the infection
  • Help Button:
    • The redirection give the list of emergency numbers of different State and Union Territory of India.
    • On clicking to any number of respective State/Union Territory it redirect to make a Phone call