查了很多資料，其他博客大多都是介紹以前的的方案，基于9.0系統(tǒng)的基本沒有找到，要么就不全，特別是獲取手電筒狀態(tài)的資料，下面就大致介紹一下：

打開和關(guān)閉的方法是：toggleLight
獲取手電筒狀態(tài)的通過回調(diào)方法：mTorchCallback（這就是為什么進(jìn)入頁面就需要注冊該回調(diào)）

    private CameraManager mCameraManager;
    public void initData() {
    //ivFlashlight是界面上的imageview控件
    ivFlashlight.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                toggleLight(!isFlashLightOn);
            }
        });
        //獲取CameraManager
        if(mCameraManager == null){
            mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        }
        mCameraManager.registerTorchCallback(mTorchCallback, null);
    }
    //callback成員變量初始化
    private CameraManager.TorchCallback mTorchCallback = new CameraManager.TorchCallback() {
        @Override
        public void onTorchModeChanged(@NonNull String cameraId, boolean enabled) {
            super.onTorchModeChanged(cameraId, enabled);
            Log.e(TAG, "onTorchModeChanged cameraId=" + cameraId + ";enabled=" + enabled);
            isFlashLightOn = enabled;
            ivFlashlight.setIcon(enabled ? MaterialDrawableBuilder.IconValue.FLASHLIGHT : MaterialDrawableBuilder.IconValue.FLASHLIGHT_OFF);
        }
    };
    public void toggleLight(boolean OPEN) {
        try {
            //獲取當(dāng)前手機(jī)所有攝像頭設(shè)備ID
            String[] ids = mCameraManager.getCameraIdList();
            for (String id : ids) {
                CameraCharacteristics c = mCameraManager.getCameraCharacteristics(id);
                //查詢該攝像頭組件是否包含閃光燈
                Boolean flashAvailable = c.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);

                /*
                 * 獲取相機(jī)面對的方向
                 * CameraCharacteristics.LENS_FACING_FRONT 前置攝像頭
                 * CameraCharacteristics.LENS_FACING_BACK 后只攝像頭
                 * CameraCharacteristics.LENS_FACING_EXTERNAL 外部的攝像頭
                 */
                Integer lensFacing = c.get(CameraCharacteristics.LENS_FACING);
                if (flashAvailable != null && flashAvailable
                        && lensFacing != null && lensFacing == CameraCharacteristics.LENS_FACING_BACK) {
                    //打開或關(guān)閉手電筒
                    mCameraManager.setTorchMode(id, OPEN);
                    break;
                }
            }
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }
    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(mCameraManager != null && mTorchCallback != null){
            mCameraManager.unregisterTorchCallback(mTorchCallback);
        }
    }