谷歌眼镜GDK开发指南之Camera

原文链接：http://bbs.seacat.cn/thread-903-1-1.html

你可以使用Glass Camera来拍照、录像和相机预览。



拍照或录像你有两个选择：


1、通过 startActivityForResult()调用内置的相机activity。
2、使用 Android Camera API 构建你自己的逻辑。有如下一些原则：
在Glass上点击相机按钮是拍照，长按是录像；拍照或录像的时候要提示用户。



如果你的Glassware用 Android APIs来访问摄像头，当用户按下物理相机按键时临时释放Camera.




1、在activity中重写Onkeydown（）方法，并拦截 KEYCODE_CAMERA 来处理相机按下。
2、释放camera 并返回false，来表明你没有消耗掉这个事件，以便内置Glass Camera的启动。




注意：如果你在Onkeydown（）方法中返回true，你的activity会消耗了这个事件并且Glass Camera不能启动。只有在你没有办法拦截Camera的使用时才能这样做（例如你在拍摄连续视频）。

1、在你拍照或摄像完后，Glass返回到你的activity，你可以在OnResume（）中回收Camera。

@Override
publicboolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_CAMERA) {
// Stop the preview and release the camera.
// Execute your logic as quickly as possible
// so the capture happens quickly.
returnfalse;
    } else {
returnsuper.onKeyDown(keyCode, event);
    }
}

@Override
protectedvoid onResume() {
super.onResume();
// Re-acquire the camera and start the preview.
}

拍照或摄像

当使用 ACTION_IMAGE_CAPTURE intent来调用拍照时，在onActivityResult回调的时候图片文件可能还没被准备好。为了处理这种情况，你应当使用一个 FileObserver 来监视保存图片文件的父目录，并且要等到图片写入完成才能试图去访问文件。




注意：这些步骤在拍摄视频时不是必须的。

privatestaticfinalint TAKE_PICTURE_REQUEST = 1;

privatevoid takePicture() {
    Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
    startActivityForResult(intent, TAKE_PICTURE_REQUEST);
}

@Override
protectedvoid onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == TAKE_PICTURE_REQUEST && resultCode == RESULT_OK) {
        String picturePath = data.getStringExtra(
                CameraManager.EXTRA_PICTURE_FILE_PATH);
        processPictureWhenReady(picturePath);
    }

super.onActivityResult(requestCode, resultCode, data);
}

privatevoid processPictureWhenReady(final String picturePath) {
final File pictureFile = new File(picturePath);

if (pictureFile.exists()) {
// The picture is ready; process it.
    } else {
// The file does not exist yet. Before starting the file observer, you
// can update your UI to let the user know that the application is
// waiting for the picture (for example, by displaying the thumbnail
// image and a progress indicator).

final File parentDirectory = pictureFile.getParentFile();
        FileObserver observer = new FileObserver(parentDirectory.getPath()) {
// Protect against additional pending events after CLOSE_WRITE is
// handled.
privateboolean isFileWritten;

@Override
publicvoid onEvent(int event, String path) {
if (!isFileWritten) {
// For safety, make sure that the file that was created in
// the directory is actually the one that we're expecting.
                    File affectedFile = new File(parentDirectory, path);
                    isFileWritten = (event == FileObserver.CLOSE_WRITE
                            && affectedFile.equals(pictureFile));

if (isFileWritten) {
                        stopWatching();

// Now that the file is ready, recursively call
// processPictureWhenReady again (on the UI thread).
                        runOnUiThread(new Runnable() {
@Override
publicvoid run() {
                                processPictureWhenReady(picturePath);
                            }
                        });
                    }
                }
            }
        };
        observer.startWatching();
    }
}

可以查看CameraManager 的java文档来了解更多。