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 stream in a view

Answer 1

https://github.com/pinguo-yuyidong/Camera2/blob/master/app/src/main/java/us/yydcdut/androidltest/otheractivity/FlashActivity.java
here，you don't need the preview to open the flash.

Answer 2

Just use following class to turn on/off FlashLight in Android L,

public class FlashLightUtilForL {
    private CameraCaptureSession mSession;
    private CaptureRequest.Builder mBuilder;
    private CameraDevice mCameraDevice;
    private CameraManager mCameraManager;

    public FlashLightUtilForL(Context context) {
        try {
            mCameraManager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
            //here to judge if flash is available
            CameraCharacteristics cameraCharacteristics = mCameraManager.getCameraCharacteristics("0");
            boolean flashAvailable = cameraCharacteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);
            if (flashAvailable) {
                mCameraManager.openCamera("0", new MyCameraDeviceStateCallback(), null);
            } else {
                //todo: throw Exception
            }
            //mCameraManager.openCamera("0", new MyCameraDeviceStateCallback(), null);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    class MyCameraDeviceStateCallback extends CameraDevice.StateCallback {

        @Override
        public void onOpened(CameraDevice camera) {
            mCameraDevice = camera;
            //get builder
            try {
                mBuilder = camera.createCaptureRequest(CameraDevice.TEMPLATE_MANUAL);
                //flash on, default is on
                mBuilder.set(CaptureRequest.CONTROL_AE_MODE, CameraMetadata.CONTROL_AF_MODE_AUTO);
                mBuilder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_TORCH);
                List<Surface> list = new ArrayList<Surface>();
                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 = mCameraManager.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;
    }

    /**
     * session callback
     */
    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;
    }
}

Answer 3

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<Surface> list = new ArrayList<Surface>();
                                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

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="com.camera2.MainActivity">

    <Button
        android:onClick="click"
        android:id="@+id/on"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="On" />

    <Button
        android:onClick="click"
        android:id="@+id/off"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Off" />
</LinearLayout>

manifest

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.camera2">


    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.FLASHLIGHT" />

    <uses-feature android:name="android.hardware.camera" />
    <uses-feature android:name="android.hardware.camera.autofocus" />
    <uses-feature android:name="android.hardware.camera.flash" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

use close() to close camera settings