Android 5, camera2 use only flash

Question

I need to use only the flash with the API camera2 (Android 5, API level 21), like torch applications. But all the examples that I found requires the display of camera strea

Answer 1

here is the complete demo check this.

package com.camera2;

import android.content.Context;
import android.graphics.SurfaceTexture;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CameraMetadata;
import android.hardware.camera2.CaptureRequest;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Size;
import android.view.Surface;
import android.view.View;
import android.widget.Button;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity
    {
        private CameraManager cameraManager;
        private CameraCharacteristics cameraCharacteristics;

        private CameraDevice mCameraDevice;
        private CameraCaptureSession mSession;

        private CaptureRequest.Builder mBuilder;

        private Button on;
        private Button off;


        @Override
        protected void onCreate(Bundle savedInstanceState)
            {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.activity_main);

                on = (Button) findViewById(R.id.on);
                off = (Button) findViewById(R.id.off);

                initCamera();
            }

        public void click(View v)
            {
                switch (v.getId())
                    {
                    case R.id.on:
                        try
                            {
                                turnOnFlashLight(); 
                            }
                        catch (Exception e)
                            {
                                e.printStackTrace();
                            }
                        break;
                    case R.id.off:
                        turnOffFlashLight();
                        break;
                    }
            }

        private void initCamera()
            {
                cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
                try
                    {
                        String[] id = cameraManager.getCameraIdList();
                        if (id != null && id.length > 0)
                            {
                                cameraCharacteristics = cameraManager.getCameraCharacteristics(id[0]);
                                boolean isFlash = cameraCharacteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);
                                if (isFlash)
                                    {
                                        cameraManager.openCamera(id[0], new MyCameraDeviceStateCallback(), null);               
                                    }
                            }
                    }
                catch (CameraAccessException e)
                    {
                        e.printStackTrace();
                    }
            }

        class MyCameraDeviceStateCallback extends CameraDevice.StateCallback
            {

                @Override
                public void onOpened(CameraDevice camera)
                    {
                        mCameraDevice = camera;
                        // get builder
                        try
                            {
                                mBuilder = camera.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
                                List list = new ArrayList();
                                SurfaceTexture mSurfaceTexture = new SurfaceTexture(1);
                                Size size = getSmallestSize(mCameraDevice.getId());
                                mSurfaceTexture.setDefaultBufferSize(size.getWidth(), size.getHeight());
                                Surface mSurface = new Surface(mSurfaceTexture);
                                list.add(mSurface);
                                mBuilder.addTarget(mSurface);
                                camera.createCaptureSession(list, new MyCameraCaptureSessionStateCallback(), null);
                            }
                        catch (CameraAccessException e)
                            {
                                e.printStackTrace();
                            }
                    }

                @Override
                public void onDisconnected(CameraDevice camera)
                    {

                    }

                @Override
                public void onError(CameraDevice camera, int error)
                    {

                    }
            }

        private Size getSmallestSize(String cameraId) throws CameraAccessException
            {
                Size[] outputSizes = cameraManager.getCameraCharacteristics(cameraId).get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP).getOutputSizes(SurfaceTexture.class);
                if (outputSizes == null || outputSizes.length == 0)
                    {
                        throw new IllegalStateException("Camera " + cameraId + "doesn't support any outputSize.");
                    }
                Size chosen = outputSizes[0];
                for (Size s : outputSizes)
                    {
                        if (chosen.getWidth() >= s.getWidth() && chosen.getHeight() >= s.getHeight())
                            {
                                chosen = s;
                            }
                    }
                return chosen;
            }

        class MyCameraCaptureSessionStateCallback extends CameraCaptureSession.StateCallback
            {
                @Override
                public void onConfigured(CameraCaptureSession session)
                    {
                        mSession = session;
                        try
                            {
                                mSession.setRepeatingRequest(mBuilder.build(), null, null);
                            }
                        catch (CameraAccessException e)
                            {
                                e.printStackTrace();
                            }
                    }

                @Override
                public void onConfigureFailed(CameraCaptureSession session)
                    {

                    }
            }

        public void turnOnFlashLight()
            {
                try
                    {
                        mBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_TORCH);
                        mSession.setRepeatingRequest(mBuilder.build(), null, null);
                    }
                catch (Exception e)
                    {
                        e.printStackTrace();
                    }
            }

        public void turnOffFlashLight()
            {
                try
                    {
                        mBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_OFF);
                        mSession.setRepeatingRequest(mBuilder.build(), null, null);
                    }
                catch (Exception e)
                    {
                        e.printStackTrace();
                    }
            }

        private void close()
            {
                if (mCameraDevice == null || mSession == null)
                    {
                        return;
                    }
                mSession.close();
                mCameraDevice.close();
                mCameraDevice = null;
                mSession = null;
            }
    }

xml

manifest

use close() to close camera settings