释放摄像头：＆QUOT;方法发布之后被称为（）＆QUOT;例外 [英] Releasing the camera: "Method called after release()" exception

问题描述

我想纳入我的应用程序的一些相机相关的功能。我手动打开摄像头，并获得与集previewCallback 和启动preVIEW 。我做的不的使用面显示preVIEW，但我将它设置为符合照相机API文档。这是我打开摄像头：

I'm trying to incorporate some camera-related features in my app. I open the camera manually and get the preview stream with setPreviewCallback and startPreview. I do not use the surface for displaying preview, but I do set it to comply with the Camera API docs. This is how I open the camera:

public Camera openCamera(int id)
{
    m_openedCamera = Camera.open(id);
    m_surfaceHolder = new SurfaceView(MyApplication.instance().getApplicationContext()).getHolder();
    Assert.assertNotNull(m_openedCamera);
    m_openedCamera.setPreviewDisplay(m_surfaceHolder);
    m_openedCameraFacing = facing;
    if (m_openedCamera != null)
        m_openedCamera.setPreviewCallback(this);
    m_openedCamera.startPreview();
}

这是我释放它，没有什么花哨这里：

And this is how I release it, nothing fancy here:

public void releaseCamera()
{
    if (m_openedCamera != null)
    {
        m_openedCamera.stopPreview();
        m_openedCamera.release();
        m_openedCamera = null;
    }
}

这有点儿工作在第一，但我松开相机，我得到一个异常（）方法释放后，被称为。
为了澄清：我做的不的调用任何相机的方法相机已被释放之后。在调试器，我没有双重和三重检查。我觉得这里有同步和异步调用引起该问题的混合。

It kinda works at first, but as I release the camera, I get an exception "Method called after release()". To clarify: I do not call any camera methods after the camera has been released. Double and triple-checked under debugger that I don't. I think there's a mix of synchronous and asynchronous calls here that causes the problem.

推荐答案

在preVIEW回调可能会导致此异常。 上previewFrame（）不是synchroneous，它收到的相机参数，它可能会变得无效时，相机。发布（）执行。这可能即使回调不使用一个单独的线程发生（强烈推荐）。

The preview callback could cause this exception. onPreviewFrame() is not synchroneous, and it receives a Camera parameter that may become invalid when Camera.release() is performed. This could happen even if callbacks are not using a separate thread (highly recommended).

在发布（），电话集previewCallback（空），并保持一个全球性的标志丢弃回调相机发布之后。

Before release(), call setPreviewCallback(null), and keep a global flag to discard callbacks after the camera is released.

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