查了很多资料，其他博客大多都是介绍以前的的方案，基于9.0系统的基本没有找到，要么就不全，特别是获取手电筒状态的资料，下面就大致介绍一下：

打开和关闭的方法是：toggleLight

获取手电筒状态的通过回调方法：mTorchCallback(这就是为什么进入页面就需要注册该回调)

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);

}

});

//获取CameraManager

if(mCameraManager == null){

mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

}

mCameraManager.registerTorchCallback(mTorchCallback, null);

}

//callback成员变量初始化

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 {

//获取当前手机所有摄像头设备ID

String[] ids = mCameraManager.getCameraIdList();

for (String id : ids) {

CameraCharacteristics c = mCameraManager.getCameraCharacteristics(id);

//查询该摄像头组件是否包含闪光灯

Boolean flashAvailable = c.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);

/*

* 获取相机面对的方向

* CameraCharacteristics.LENS_FACING_FRONT 前置摄像头

* CameraCharacteristics.LENS_FACING_BACK 后只摄像头

* CameraCharacteristics.LENS_FACING_EXTERNAL 外部的摄像头

*/

Integer lensFacing = c.get(CameraCharacteristics.LENS_FACING);

if (flashAvailable != null && flashAvailable

&& lensFacing != null && lensFacing == CameraCharacteristics.LENS_FACING_BACK) {

//打开或关闭手电筒

mCameraManager.setTorchMode(id, OPEN);

break;

}

}

} catch (CameraAccessException e) {

e.printStackTrace();

}

}

@Override

protected void onDestroy() {

super.onDestroy();

if(mCameraManager != null && mTorchCallback != null){

mCameraManager.unregisterTorchCallback(mTorchCallback);

}

}