Question 173307 in Android Studio Question posted in
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How make endless loop between functions using kotlin for java android in android studio?

package com.example.flashlight

import android.content.Context
import android.hardware.camera2.CameraAccessException
import android.hardware.camera2.CameraManager
import android.os.Bundle
import android.os.Handler
import android.os.Looper
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {
    var flashLightStatus: Boolean = false

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        openFlashLight()

        while (true) {
            Handler(Looper.getMainLooper()).postDelayed({
                //Do something after 100ms
                closeFlashLight()
            }, 5000)
            Handler(Looper.getMainLooper()).postDelayed({
                //Do something after 100ms
                openFlashLight()
            }, 5000)
        }
    }

    private fun openFlashLight() {
        val cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager
        val cameraId = cameraManager.cameraIdList[0]
        if (!flashLightStatus) {
            try {
                cameraManager.setTorchMode(cameraId, true)
                flashLightStatus = true

            } catch (e: CameraAccessException) {
            }
        } else {
            try {
                cameraManager.setTorchMode(cameraId, false)
                flashLightStatus = false
            } catch (e: CameraAccessException) {
            }
        }
    }

    private fun closeFlashLight()
    {
        val cameraManager = getSystemService(Context.CAMERA_SERVICE) as CameraManager
        val cameraId = cameraManager.cameraIdList[0]
        if (flashLightStatus) {
            try {
                cameraManager.setTorchMode(cameraId, false)
                flashLightStatus = false

            } catch (e: CameraAccessException) {
            }
        } else {
            try {
                cameraManager.setTorchMode(cameraId, true)
                flashLightStatus = true
            } catch (e: CameraAccessException) {
            }
        }
    }
}

this now just open the flashlight on the phone and the flashlight stay open all the time because the while(true)

while (true) {
            Handler(Looper.getMainLooper()).postDelayed({
                //Do something after 100ms
                closeFlashLight()
            }, 5000)
            Handler(Looper.getMainLooper()).postDelayed({
                //Do something after 100ms
                openFlashLight()
            }, 5000)
        }

but if I’m removing the while true and doing only:

openFlashLight()
        Handler(Looper.getMainLooper()).postDelayed({
            //Do something after 100ms
            closeFlashLight()
        }, 5000)

this will open the flashlight and will wait 5 seconds then will close the flashlight.
but I want to make something endless that it will open the flash light wait 5 seconds close the flashlight wait 5 seconds open the flashlight wait 5 seconds close.

that way nonstop. open/close each 5 seconds nonstop. that’s why I tried to use the while(true) but then the flashlight just keep staying open nonstop.

Tags:

2

Answers


  1. 0

    If you want to repeat the flashlight on/off cycles every 5 seconds you can do something like this:

    1. Keep a boolean flag as a class member:
    var flashLightOn = false
    1. Make a method that start the flashlight
    fun startFlashLight() {
    openFlashlight()
    flashLightOn = true

    val handler = Handler(Looper.getMainLooper())
    handler.postDelayed(object: Runnable() {
        override fun run() {
            if (flashLightOn) {
                closeFlashLight()
            } else {
                openFlashlight()
            }
            
            // Changing the toggle and calling the same Runnable again after 5 seconds
            flashLightOn = !flashLightOn
            handler.postDelayed(this, 5000)
        }
    }, 5000)
}
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  2. 0

    You can achieve this by using kotlin coroutines

      val scope = CoroutineScope(Dispatchers.Main)

    scope.launch {
        while (true) {
            openFlashlight()
            delay(5000)
            closeFlashlight()
            delay(5000)
        }
    }
    runBlocking {
        delay(Long.MAX_VALUE)
    }

    and also add this dependency in the build.gradle module level file

        implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9")

    And if you want to do it using handler you can try this I am not sure if this will work or not.

    val handler = Handler(Looper.getMainLooper())
var isFlashlightOpen = false

val toggleFlashlight = object : Runnable {
    override fun run() {
        if (isFlashlightOpen) {
            closeFlashlight()
            isFlashlightOpen = false
        } else {
            openFlashlight()
            isFlashlightOpen = true
        }
        handler.postDelayed(this, 5000)
    }
}

handler.postDelayed(toggleFlashlight, 5000)
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