问题:
我正在制作一款需要从相机快速响应的Android应用程序,但是我注意到应用程序表现缓慢。经过测量时间,我发现函数startPreview()是问题的根源。
代码预览:
这是与问题相关的代码必要部分。
PreviewGoogle类(自定义预览): 在应用程序启动时调用surfaceChanged,我设置了一些相机参数,然后调用了startPreview
public class PreviewGoogle extends ViewGroup implements SurfaceHolder.Callback {
private final String TAG = "myapp1";
Camera mCamera;
public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {
try
{
// Now that the size is known, set up the camera parameters and begin
// the preview.
Camera.Parameters parameters = mCamera.getParameters();
parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
parameters.setFocusMode(Camera.Parameters.FOCUS_MODE_INFINITY);
parameters.setWhiteBalance(Camera.Parameters.WHITE_BALANCE_AUTO);
parameters.setSceneMode(Camera.Parameters.SCENE_MODE_AUTO);
parameters.setJpegQuality(100);
parameters.setPictureSize(Globals.CAMERA_WIDTH, Globals.CAMERA_HEIGHT);
requestLayout();
mCamera.setParameters(parameters);
long before = System.currentTimeMillis();
mCamera.startPreview();
long after = System.currentTimeMillis();
Log.d(TAG, "PreviewGoogle, surfaceChanged: startPreview took " + (after - before) + " ms");
}
catch (Exception e) {
Log.d(TAG, "PreviewGoogle, surfaceChanged: " + e.getMessage());
}
}
}
PhotoShootActivity类:在这个类中,我调用了rawImageCallback的startPreview方法,因为我在jpegCallback中使用了BitmapFactory(不是必要的事情)
public class PhotoShootActivity extends Activity
{
private static final String TAG = "myapp1";
PreviewGoogle preview;
// Handles data for raw picture
PictureCallback rawCallback = new PictureCallback()
{
public void onPictureTaken(byte[] data, Camera camera)
{
try
{
long before = System.currentTimeMillis();
preview.getCamera().startPreview();
long after = System.currentTimeMillis();
Log.d(PhotoShootActivity.TAG, "PhotoShootActivity, rawCallback: preview started in " + (after - before) + " ms");
}
catch(Exception e)
{
Log.e(TAG, "PhotoShootActivity, rawCallback: " + e.getMessage());
}
}
};
}
计时器的数字应该是这样的:
09-09 10:58:42.336: DEBUG/myapp1(21958): PhotoShootActivity, onCreate
**09-09 10:58:44.396: DEBUG/myapp1(21958): PreviewGoogle, surfaceChanged: startPreview took 1457 ms**
09-09 10:58:48.438: DEBUG/myapp1(21958): PhotoShootActivity, buttonCapture: Picture taken in 65ms
09-09 10:58:48.496: DEBUG/myapp1(21958): PhotoShootActivity, shutterCallback: Empty
**09-09 10:58:49.790: DEBUG/myapp1(21958): PhotoShootActivity, rawCallback: preview started in 662 ms**
第一次startPreview花费了约1500毫秒,而第二次只花费了662毫秒!!!
解决方案:
我正在寻找的问题不是完整的代码(只是给我提示:)),我认为在预览中可能会漏掉某些内容,考虑在这种情况下使用线程,但我还不熟悉Android SDK(我开始学习Android编程才4天)。
顺祝安康...