camera上flash的常亮

本文介绍了一种在Samsung手机上实现手电筒模式的方法,并提供了一个CameraHelper类来控制手电筒的开关。此外,针对Samsung手机关闭手电筒模式的问题,提出了一种解决方案。

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I'm finding that torch mode is generally working fine on 2.1 but I had the same problem with the Samsung Epic and found a hack around it.

Looking at the params returned by Camera.getParameters() when run on the Samsung Epic, I noticed that the flash-modes it claims to support are: flash-mode-values=off,on,auto;

torch-mode is not listed, implying it's not supported.

However, I found that this model would still accept that mode and WOULD turn the LED on! The bad news was that when later setting the flash-mode back to auto or off left the LED still lit! It will not turn off until you call Camera.release().

I guess that's why Samsung dont include it in the list of supported!?!

So...the method I use to toggle torch in a CameraHelper class is...

/***
 * Attempts to set camera flash torch/flashlight mode on/off
 * @param isOn true = on, false = off
 * @return boolean whether or not we were able to set it
 */
public boolean setFlashlight(boolean isOn)
{
    if (mCamera == null)
    {
        return false;
    }
    Camera.Parameters params = mCamera.getParameters();
    String value;
    if (isOn) // we are being ask to turn it on
    {
        value = Camera.Parameters.FLASH_MODE_TORCH;
    }
    else  // we are being asked to turn it off
    {
        value =  Camera.Parameters.FLASH_MODE_AUTO;
    }

    try{    
        params.setFlashMode(value);
        mCamera.setParameters(params);

        String nowMode = mCamera.getParameters().getFlashMode();

        if (isOn && nowMode.equals(Camera.Parameters.FLASH_MODE_TORCH))
        {
            return true;
        }
        if (! isOn && nowMode.equals(Camera.Parameters.FLASH_MODE_AUTO))
        {
            return true;
        }
        return false;
    }
    catch (Exception ex)
    {
        MyLog.e(mLOG_TAG, this.getClass().getSimpleName() +  " error setting flash mode to: "+ value + " " + ex.toString());
    }
}

The activities that use this call it as follows...

private void toggleFlashLight()
{
    mIsFlashlightOn = ! mIsFlashlightOn;

    /**
     * hack to fix an issue where the Samsung Galaxy will turn torch on,
     * even though it says it doesnt support torch mode,
     * but then will NOT turn it off via this param.
     */
    if (! mIsFlashlightOn && Build.MANUFACTURER.equalsIgnoreCase("Samsung"))
    {
        this.releaseCameraResources();
        this.initCamera();
    }
    else
    {
        boolean result = mCamHelper.setFlashlight(mIsFlashlightOn);
        if (! result)
        {
            alertFlashlightNotSupported();
        }
    }
}

The magic that makes this work in releaseCameraResources() is that it calls Camera.release()....and then I have to reinitialize all my camera stuff for Samsung devices.

Not pretty but seems to be working for plenty of users.

Note that I do have a report of torch mode not working at all with this code on Nexus one but have been able to dig into it. It definitely works on HTC EVO and Samsung Epic.

Hope this helps.

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### 使用 Android Camera2 API 实现带闪光灯的拍照功能 为了实现带有闪光灯功能的照片拍摄,可以按照以下方法操作: #### 初始化相机管理器并获取特性列表 首先,在初始化 `CameraManager` 后,通过查询设备上的可用摄像机ID列表来确认所选摄像头是否支持闪光灯。这一步骤非常重要,因为并非所有的摄像头都具备此硬件能力。 ```java // 获取CameraManager实例 CameraManager manager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE); String[] cameraIds; try { cameraIds = manager.getCameraIdList(); } catch (CameraAccessException e) { throw new RuntimeException(e); } for (String id : cameraIds){ try { // 查询特定摄像头的能力特征集 StreamConfigurationMap map = manager.getCameraCharacteristics(id).get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP); Integer flashAvailability = manager.getCameraCharacteristics(id). get(CameraCharacteristics.FLASH_INFO_AVAILABLE); if(Boolean.TRUE.equals(flashAvailability)){ Log.d(TAG,"This device has a flash unit."); }else{ Log.w(TAG,"No flash available on this device"); } }catch(Exception ex){ continue; // 如果访问失败则跳过该摄像头 } } ``` #### 设置捕获请求中的闪光灯参数 当准备构建用于预览或捕捉图像的实际 `CaptureRequest.Builder` 时,应根据需求配置相应的闪光灯模式。这里提供了几种常见的选项供选择: - **自动** (`FLASH_MODE_AUTO`):让系统决定何时开启闪光灯。 - **始终开启** (`FLASH_MODE_TORCH`):保持常亮状态作为手电筒用途。 - **强制启用** (`FLASH_MODE_ON`):每次拍摄照片前都会触发一次强光照射。 - **关闭** (`FLASH_MODE_OFF`):完全禁用闪光灯效果。 ```java if (flashSupported && isTorchOn()) { previewBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_ALWAYS_FLASH); }else{ previewBuilder.set(CaptureRequest.CONTROL_AE_MODE,CaptureRequest.CONTROL_AE_MODE_ON); } previewBuilder.set(CaptureRequest.FLASH_MODE, mode); //mode为上述四种之一 ``` #### 控制按钮事件处理逻辑 针对UI界面上用来切换闪光灯开关状态的控件绑定点击监听器,并在此处更新内部标志位变量以反映最新的用户偏好设定。每当检测到交互动作发生后,重新提交修改后的 `CaptureRequest` 给会话对象即可完成即时生效的目的[^1]。 ```java private boolean mIsFlashlightEnabled; public void toggleFlashlight(View view) { mIsFlashlightEnabled = !mIsFlashlightEnabled; updatePreview(); // 更新预览界面显示 if(mSession != null){ try { captureStillPicture(); } catch (Exception e) { Toast.makeText(context,e.getMessage(),Toast.LENGTH_SHORT).show(); } } } ``` 以上就是利用 Android Camera2 API 来控制闪光灯的具体做法概述。需要注意的是不同品牌型号之间可能存在细微差异,因此建议开发者们仔细阅读官方文档并参照样例项目来进行调试优化工作。
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