A few seconds delay when trying to turn on the power of the LED flash

Question

I am trying to turn on the LED flash, but the LED flash turns on after a delay of a few seconds.

I have a built-in torch in my phone, and when I click on it, the flash immediately turns on.

What is the problem?

Here is my code:

private void processOnClick() { if (manuName.contains("motorola")) { DroidLED led; try { led = new DroidLED(); led.enable(true); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } else { if (mCamera == null) { try { mCamera = Camera.open(); } catch (Exception e) { e.printStackTrace(); } } try { mCamera = Camera.open(); } catch (Exception e) { e.printStackTrace(); } if (mCamera != null) { final Parameters params = mCamera.getParameters(); List<String> flashModes = params.getSupportedFlashModes(); if (flashModes == null) { return; } else { if (count == 0) { params.setFlashMode(Parameters.FLASH_MODE_OFF); mCamera.setParameters(params); mCamera.startPreview(); } String flashMode = params.getFlashMode(); if (!Parameters.FLASH_MODE_TORCH.equals(flashMode)) { if (flashModes.contains(Parameters.FLASH_MODE_TORCH)) { params.setFlashMode(Parameters.FLASH_MODE_TORCH); mCamera.setParameters(params); } else { // Toast.makeText(this, // "Flash mode (torch) not supported",Toast.LENGTH_LONG).show(); params.setFlashMode(Parameters.FLASH_MODE_ON); mCamera.setParameters(params); try { mCamera.autoFocus(new AutoFocusCallback() { public void onAutoFocus(boolean success, Camera camera) { count = 1; } }); } catch (Exception e) { e.printStackTrace(); } } } } } } if (mCamera == null) { return; } } private void processOffClick() { if (manuName.contains("motorola")) { DroidLED led; try { led = new DroidLED(); led.enable(false); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } } else { if (mCamera != null) { mCamera.stopPreview(); mCamera.release(); } } } 

DroidLED Class:

 import java.lang.reflect.Method; import android.os.IBinder; class DroidLED { private Object svc = null; private Method getFlashlightEnabled = null; private Method setFlashlightEnabled = null; @SuppressWarnings("unchecked") public DroidLED() throws Exception { try { // call ServiceManager.getService("hardware") to get an IBinder for the service. // this appears to be totally undocumented and not exposed in the SDK whatsoever. Class sm = Class.forName("android.os.ServiceManager"); Object hwBinder = sm.getMethod("getService", String.class).invoke(null, "hardware"); // get the hardware service stub. this seems to just get us one step closer to the proxy Class hwsstub = Class.forName("android.os.IHardwareService$Stub"); Method asInterface = hwsstub.getMethod("asInterface", android.os.IBinder.class); svc = asInterface.invoke(null, (IBinder) hwBinder); // grab the class (android.os.IHardwareService$Stub$Proxy) so we can reflect on its methods Class proxy = svc.getClass(); // save methods getFlashlightEnabled = proxy.getMethod("getFlashlightEnabled"); setFlashlightEnabled = proxy.getMethod("setFlashlightEnabled", boolean.class); } catch(Exception e) { throw new Exception("LED could not be initialized"); } } public boolean isEnabled() { try { return getFlashlightEnabled.invoke(svc).equals(true); } catch(Exception e) { return false; } } public void enable(boolean tf) { try { setFlashlightEnabled.invoke(svc, tf); } catch(Exception e) {} } } 

I took this code from some answer around stackoverflow.

Thanks for your help!

Answer 1

Do you get big delays with the motor system?

This is just an assumption, but the DroidLED constructor calls for expensive system initializations. Could you do this?

 public class MyWidgetClickHandler { private DroidLED = null; public MyWidgetClickHandler(string ManuName) { // This is slow. It will run once at initialization. if (ManuName != null && ManuName.toLowerCase().contains("motorola")) DroidLED = new DroidLED(); } public void processOnClick() { if (DroidLED != null) DroidLED.enable(true); else ; // ... TODO } public void processOffClick() { if (DroidLED != null) DroidLED.enable(false); else ; // ... TODO } } 

There could be a lot more. For example, you can create an LED interface with enable and isEnabled and have two implementations for it. One of them will be DroidLED , and the other is CommonCameraLED . In this case, it looks like this:

 public class LEDFactory { public static LED createLED(string ManuName) { if (ManuName != null && ManuName.toLowerCase().contains("motorola")) return new DroidLED(); else return new CommonCameraLED(); } } public class MyWidgetClickHandler { private LED myLed = null; public MyWidgetClickHandler(string ManuName) { myLed = LEDFactory.createLED(ManuName); } public void processOnClick() { myLed.enable(true); // NOTHING TO DO } public void processOffClick() { myLed.enable(false); // NOTHING TO DO } } 

You can also create Thread to initialize so that the phone does not start slowly.

Answer 2

I ran into the same problem and found a solution, but I ran the tests using the Samsung Galaxy S2. This code should work on every device.

Profiling each of the functions, I found that some of the calls required to configure the camera have a delay of up to 500 ms , which makes the strobe effect impossible.

My solution was to move all these functions to a separate function, which I call when I want to get the camera, and reduce the “enable” code only until Camera.setParameters() called. By doing this, the delay decreased to 4 ms .

For example (the given code is only for confirming the point):

 // First get the camera for your app (Keep this variables as class members so the live between functions) private void acquireCamera() { try { // Get camera cam = Camera.open(); // This is not on your code but you should do it for compatibility mSurfaceTexture = new SurfaceTexture(0); cam.setPreviewTexture(mSurfaceTexture); cam.startPreview(); camParams = cam.getParameters(); } catch(IOException e) { /*...*/ } } // Then turn on / off as many times you want. private void setTorch(boolean on) { camParams.setFlashMode(on? Camera.Parameters.FLASH_MODE_TORCH : Camera.Parameters.FLASH_MODE_OFF); cam.setParameters(camParams); } // Finally release the camera when you`re done private void releaseCamera { camParams = null; cam.stopPreview(); mSurfaceTexture = null; cam.release(); }