Kotlin Android | Flow Api |

Kotlin Android | Flow Api |

Step 1:

Open build.gradle(:app) and add following dependency and rebuild the project.

implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.5.0'
implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.5.0'

# flow{} builder : flow{} | flowOn() | collect{} | catch{}

MainActivity:

public class MainActivity : AppCompatActivity() {
    private val binding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)

        runBlocking {
            getData().catch { e ->
                Log.d("Tag", "" + e.message);
            }.collect {
                Log.d("Tag", "" + it);
            }
        }
    }

    fun getData(): Flow<Int> = flow {
        for (i in 1..5) {
            delay(500)
            emit(i)
        }
    }.flowOn(Dispatchers.IO)

}

Output:

D/Tag: 1
D/Tag: 2
D/Tag: 3
D/Tag: 4
D/Tag: 5

# flowOf()
public class MainActivity : AppCompatActivity() {
    private val binding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)

        val data = flowOf(1, 23, 4, 56, 43).flowOn(Dispatchers.IO)

        runBlocking {
            data.catch { e ->
                Log.d("Tag", "" + e.message);
            }.collect {
                Log.d("Tag", "" + it);
            }
        }
    }
}
Output:
D/Tag: 1
D/Tag: 23
D/Tag: 4
D/Tag: 56
D/Tag: 43
# asFlow()
public class MainActivity : AppCompatActivity() {
    private val binding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)

        val data = listOf(1, 2, 3, 4).asFlow().flowOn(Dispatchers.IO)

        runBlocking {
            data.catch { e ->
                Log.d("Tag", "" + e.message);
            }.collect {
                Log.d("Tag", "" + it);
            }
        }
    }
}
Output:
D/Tag: 1
D/Tag: 2
D/Tag: 3
D/Tag: 4
# map{}
public class MainActivity : AppCompatActivity() {
    private val binding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)

        val data = flowOf(1, 2, 3, 4, 5).flowOn(Dispatchers.IO)

        runBlocking {
            data.map { value ->
                value +1
            }.catch { e ->
                Log.d("Tag", "" + e.message);
            }.collect {
                Log.d("Tag", "" + it);
            }
        }
    }
}
Output:
D/Tag: 2
D/Tag: 3
D/Tag: 4
D/Tag: 5
D/Tag: 6
# filter{}
public class MainActivity : AppCompatActivity() {
    private val binding by lazy {
        ActivityMainBinding.inflate(layoutInflater)
    }
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)

        val data = flowOf(1, 2, 3, 4, 5, 6).flowOn(Dispatchers.IO)

        runBlocking {
            data.filter { value ->
                value%2 == 0
            }.catch { e ->
                Log.d("Tag", "" + e.message);
            }.collect {
                Log.d("Tag", "" + it);
            }
        }
    }
}
Output:
D/Tag: 2
D/Tag: 4
D/Tag: 6