Network state casting issue in java

Issue

I have been using a network check functionality in-app, but all things are available in Kotlin now the same thing wants to integrate in java facing some issue related to lazy calling.

This is how I can check network state in Kotlin

class MainActivity : AppCompatActivity(), ConnectivityStateListener {

    private lateinit var tv: TextView
    private val provider: ConnectivityProvider by lazy { ConnectivityProvider.createProvider(this) }

    @RequiresApi(Build.VERSION_CODES.M)
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        tv = findViewById(R.id.connectivity_state)
        val button = findViewById<View>(R.id.button)
        val currentState = findViewById<TextView>(R.id.current_state)

        button.setOnClickListener {
            val hasInternet = provider.getNetworkState().hasInternet()
            currentState.text = "Connectivity (synchronously): $hasInternet"
        }
    }

    override fun onStart() {
        super.onStart()
        provider.addListener(this)
    }

    override fun onStop() {
        super.onStop()
        provider.removeListener(this)
    }

    override fun onStateChange(state: NetworkState) {
        val hasInternet = state.hasInternet()
        tv.text = "Connectivity (via callback): $hasInternet"
    }

    private fun NetworkState.hasInternet(): Boolean {
        return (this as? ConnectedState)?.hasInternet == true
  



 }
}

this is how I integrated into Java

@Override
    protected void onStart() {
        super.onStart();
        provider=ConnectivityProvider.createProvider(this);
        provider.addListener(this);
    }


@Override
protected void onStop() {
    super.onStop();

    provider.removeListener(this);
}

  @Override
    public void onStateChange(@NotNull ConnectivityProvider.NetworkState state) {

        Log.d("To ConnectivityProvider-----", state.toString());
        Toast.makeText(LoginActivity.this, "Available", Toast.LENGTH_SHORT).show();
       if( hasInternet(state)){
           Toast.makeText(LoginActivity.this, "Available", Toast.LENGTH_SHORT).show();
       }else{
            Toast.makeText(LoginActivity.this, "No Internet", Toast.LENGTH_SHORT).show();

       }

    }

    private boolean hasInternet(@NotNull ConnectivityProvider.NetworkState state) {

        ConnectivityProvider.NetworkState.ConnectedState var2 = (ConnectivityProvider.NetworkState.ConnectedState)state;
        if (var2.getHasInternet()) {

            return true;
        }
        return false;
    }

java.lang.ClassCastException: com.ro.other.connectivity.base.ConnectivityProvider$NetworkState$NotConnectedState cannot be cast to com.ro.other.connectivity.base.ConnectivityProvider$NetworkState$ConnectedState

gitlink help me to integrate this in java

Solution

The problem here is with type casting, not with lazy calling. The behaviour of the hasInternet methods in the given Kotlin and Java code is different.

Kotlin:

return (this as? ConnectedState)?.hasInternet == true

If the current NetworkState is not a ConnectedState, the typecast this as? ConnectedState will return null, and the method will return false.

Java:

ConnectivityProvider.NetworkState.ConnectedState var2 = (ConnectivityProvider.NetworkState.ConnectedState)state;
if (var2.getHasInternet()) {
    return true;
}
return false;

This code assumes that state is a ConnectedState (instead of checking it), and throws a ClassCastException if it is an instance of a different class.

The correct Java code for hasInternet method would be:

if (!(state instanceof ConnectivityProvider.NetworkState.ConnectedState)) {
    return false;
}
ConnectivityProvider.NetworkState.ConnectedState var2 = (ConnectivityProvider.NetworkState.ConnectedState)state;
if (var2.getHasInternet()) {
    return true;
}
return false;

Answered By - Mikhail Burshteyn