捕获图像后调用 StartPreview() 的最佳方法是什么? [英] What's the best way to call StartPreview() after an image is captured?

问题描述

一旦调用 Camera.takePicture()，我的预览将停止更新，如文档中所述.检测图像捕获过程已完成并调用 startPreview() 使其再次开始更新的最佳方法是什么?

Once a call is made to Camera.takePicture(), my preview will stop updating as described in the docs. What's the best way to detect that the image capture process is finished and call startPreview() to make it start updating again?

根据文档，不能将调用放在传递给 takePicture 的任何回调中，因为它们应该在我调用它之前都已返回.

The call can't be placed in any of the callbacks passed to takePicture, according to the docs, as they should all have returned before I invoke it.

我目前最好的猜测是创建一个处理程序并从 JPEG 回调(或最后定义的要返回的回调中的任何一个)向其发布延迟的 Runnable.

My current best guess is to create a Handler and post a delayed Runnable to it from the JPEG callback (or whichever is the most last defined callback to return).

推荐答案

您应该从 AsyncTask(或线程)中启动 mCamera.takePicture，但是 AsyncTaks 是更简单的选择.

You should start the mCamera.takePicture from within an AsyncTask (or a thread) however AsyncTaks's are the easier option.

一个非常简单的实现(当然可以修改)是:

A really simple implementation (which of course can be modified) is to:

拍照调用的方法

/**
 * Execute the AsyncTask that will handle the preview of the captured photo.
 */
public void takePicture() {
    TakePictureTask takePictureTask = new TakePictureTask();
    takePictureTask.execute();
}

AsyncTask 子类

/**
 * A pretty basic example of an AsyncTask that takes the photo and
 * then sleeps for a defined period of time before finishing. Upon
 * finishing, it will restart the preview - Camera.startPreview().
 */

private class TakePictureTask extends AsyncTask<Void, Void, Void> {

    @Override
    protected void onPostExecute(Void result) {
        // This returns the preview back to the live camera feed
        mCamera.startPreview();
    }

    @Override
    protected Void doInBackground(Void... params) {
        mCamera.takePicture(null, null, mPictureCallback);

        // Sleep for however long, you could store this in a variable and
        // have it updated by a menu item which the user selects.
        try {
            Thread.sleep(3000); // 3 second preview
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;
    }

}

PictureCallback 字段

private PictureCallback mPictureCallback = new PictureCallback() {

    @Override
    public void onPictureTaken(byte[] data, Camera camera) {
        File file = null;

        // Check whether the media is mounted with read/write permission.
        if (Environment.MEDIA_MOUNTED.equals(
                Environment.getExternalStorageState())) {
            file = getOutputMediaFile();
        }

        if (file == null) {
            Log.d(TAG, "Error creating media file, check storage persmissions!");
            return;
        }

        try {
            FileOutputStream fileOutputStream = new FileOutputStream(file);
            fileOutputStream.write(data);
            fileOutputStream.close();
        } catch (FileNotFoundException e) {
            Log.d(TAG, "File not found: " + e.getMessage());
        } catch (IOException e) {
            Log.d(TAG, "Error accessing file: " + e.getMessage());
        }
    }
};

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