我正在尝试用我的 android 应用程序做一些非常不同的事情：我需要以定时间隔（每 2 秒左右）将相机的图像作为位图抓取。我不希望它是实时的，因为一旦我拥有它，我需要在位图上运行几个繁重的进程，而且为了提高效率，我不想每秒运行几十次。我也不需要将它保存为文件，我只需要它在 currentBitmap 中。
这是我尝试实现的代码：
public class MainActivity extends Activity {
private Camera camera;
private CameraPreview camPreview;
private FrameLayout camLayout;
// The app will process the camera frame on intervals instead of constantly
private static final long PROCESS_TIME = 2000; //(in milliseconds)
private static final long START_TIME = 2000;
private Timer timer;
// I want the bitmap in this instance
private Bitmap currentBitmap;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
camLayout = (FrameLayout) findViewById(R.id.camera_preview);
setupCameraPreview();
// Set up the timer
timer = new Timer();
timer.schedule(new TimerTask() {
@Override
public void run() {
TimerMethod();
}
}, START_TIME, PROCESS_TIME);
}
private void TimerMethod()
{ // Run Timer_Action on the same thread as the UI
this.runOnUiThread(Timer_Action);
}
private Runnable Timer_Action = new Runnable() {
public void run() {
// Process each bitmap here
try {
camera.takePicture(null, null, pictureCallback);
} catch (NullPointerException e) {
e.printStackTrace();
}
Toast.makeText(getApplicationContext(),
"Photo capture attempted", Toast.LENGTH_SHORT).show();
}
};
private Camera.PictureCallback pictureCallback = new Camera.PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
try {
currentBitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
Toast.makeText(getApplicationContext(),
"Photo capture successful", Toast.LENGTH_SHORT).show();
} catch (NullPointerException e) {
e.printStackTrace();
}
}
};
private void setupCameraPreview() {
try { // Try to initialize the camera
camera = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT);
camPreview = new CameraPreview(this, camera);
camLayout.addView(camPreview);
} catch (Exception e) {
e.printStackTrace();
camera = null;
camPreview = null;
}
}
当我跑步时会发生什么，相机预览和计时器似乎运行良好。但是 pictureCallback、data[] 和 currentBitmap 都保持为空，因此 try 块抛出它们的异常并且应用程序继续运行。我的猜测是 pictureCallback 没有从相机获取数据，但我该如何解决呢？如果这不是问题，那是什么？
非常感谢所有帮助。