NyARToolkit撮影機能の拡張

Question

今、NyARToolkitのsampleSimpleLiteを拡張して、タッチすると写真を撮れるようにしたいと考えています。
getDrawingCacheを使って撮影しようと考えたのですが、どうしてもちゃんと撮れず、真っ黒の画像が保存されます。原因と解決法、または違う方法を知ってたら教えていただきたいです。

public class SimpleLiteActivity extends AndSketch implements AndGLView.IGLFunctionEvent {
	//private Camera camera;
	CameraPreview _camera_preview;
	AndGLView _glv;

	Camera.Size _cap_size;

	/**
	 * ATTENTION: This was auto-generated to implement the App Indexing API.
	 * See https://g.co/AppIndexing/AndroidStudio for more information.
	 */
	private GoogleApiClient client;

	/**
	 * onStartでは、Viewのセットアップをしてください。
	 */
	@Override
	public void onStart() {
		super.onStart();
		// ATTENTION: This was auto-generated to implement the App Indexing API.
		// See https://g.co/AppIndexing/AndroidStudio for more information.
		client.connect();
		FrameLayout fr = ((FrameLayout) this.findViewById(R.id.sketchLayout));
		//カメラの取得
		this._camera_preview = new CameraPreview(this);
		this._cap_size = this._camera_preview.getRecommendPreviewSize(320, 240);
		//画面サイズの計算
		int h = this.getWindowManager().getDefaultDisplay().getHeight();
		int w = this.getWindowManager().getDefaultDisplay().getWidth();
		int screen_w, screen_h;
		screen_w = w;
		screen_h = h;
		//camera
		fr.addView(this._camera_preview, 0, new LayoutParams(screen_w, screen_h));
		//GLview
		this._glv = new AndGLView(this);
		fr.addView(this._glv, 0, new LayoutParams(screen_w, screen_h));
		// ATTENTION: This was auto-generated to implement the App Indexing API.
		// See https://g.co/AppIndexing/AndroidStudio for more information.
		Action viewAction = Action.newAction(
				Action.TYPE_VIEW, // TODO: choose an action type.
				"SimpleLite Page", // TODO: Define a title for the content shown.
				// TODO: If you have web page content that matches this app activity's content,
				// make sure this auto-generated web page URL is correct.
				// Otherwise, set the URL to null.
				Uri.parse("http://host/path"),
				// TODO: Make sure this auto-generated app URL is correct.
				Uri.parse("android-app://jp.nyatla.nyartoolkit.and/http/host/path")
		);
		AppIndex.AppIndexApi.start(client, viewAction);
	}


	NyARAndSensor _ss;
	NyARAndMarkerSystem _ms;
	private int _mid;
	AndGLTextLabel text;
	AndGLBox box;
	AndGLFpsLabel fps;

	public void setupGL(GL10 gl) {
		try {
			AssetManager assetMng = getResources().getAssets();
			//create sensor controller.
			this._ss = new NyARAndSensor(this._camera_preview, this._cap_size.width, this._cap_size.height, 30);
			//create marker system
			this._ms = new NyARAndMarkerSystem(new NyARMarkerSystemConfig(this._cap_size.width, this._cap_size.height));
			this._mid = this._ms.addARMarker(assetMng.open("AR/data/neomoto.pat"), 16, 25, 80);
			this._ss.start();
			//setup openGL Camera Frustum
			gl.glMatrixMode(GL10.GL_PROJECTION);
			gl.glLoadMatrixf(this._ms.getGlProjectionMatrix(), 0);
			this.text = new AndGLTextLabel(this._glv);
			this.box = new AndGLBox(this._glv, 40);
			this._debug = new AndGLDebugDump(this._glv);
			this.fps = new AndGLFpsLabel(this._glv, "MarkerPlaneActivity");
			this.fps.prefix = this._cap_size.width + "x" + this._cap_size.height + ":";

		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			this.finish();
		}
	}

	AndGLDebugDump _debug = null;

	/**
	 * 継承したクラスで表示したいものを実装してください
	 *
	 * @param gl
	 */
	public void drawGL(GL10 gl) {
		try {
			//背景塗り潰し色の指定
			gl.glClearColor(0, 0, 0, 0);
			//背景塗り潰し
			gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT);
			if (ex != null) {
				_debug.draw(ex);
				return;
			}
			fps.draw(0, 0);
			synchronized (this._ss) {
				this._ms.update(this._ss);
				if (this._ms.isExistMarker(this._mid)) {
					this.text.draw("found" + this._ms.getConfidence(this._mid), 0, 16);
					gl.glMatrixMode(GL10.GL_MODELVIEW);
					gl.glLoadMatrixf(this._ms.getGlMarkerMatrix(this._mid), 0);
					this.box.draw(0, 0, 20);
				}
			}
		} catch (Exception e) {
			ex = e;
		}
	}

	Exception ex = null;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		//setContentView(R.layout.main);

		// ATTENTION: This was auto-generated to implement the App Indexing API.
		// See https://g.co/AppIndexing/AndroidStudio for more information.
		client = new GoogleApiClient.Builder(this).addApi(AppIndex.API).build();
	}

	@Override
	public void onStop() {
		super.onStop();

		// ATTENTION: This was auto-generated to implement the App Indexing API.
		// See https://g.co/AppIndexing/AndroidStudio for more information.
		Action viewAction = Action.newAction(
				Action.TYPE_VIEW, // TODO: choose an action type.
				"SimpleLite Page", // TODO: Define a title for the content shown.
				// TODO: If you have web page content that matches this app activity's content,
				// make sure this auto-generated web page URL is correct.
				// Otherwise, set the URL to null.
				Uri.parse("http://host/path"),
				// TODO: Make sure this auto-generated app URL is correct.
				Uri.parse("android-app://jp.nyatla.nyartoolkit.and/http/host/path")
		);
		AppIndex.AppIndexApi.end(client, viewAction);
		client.disconnect();
	}


	@Override
	public boolean onTouchEvent(MotionEvent event) {
		if (event.getAction() == MotionEvent.ACTION_DOWN) {
			// 読み書きするファイル名を指定
			SimpleDateFormat format = new SimpleDateFormat("'IMG'_yyyyMMdd_HHmmss'.jpeg'", Locale.getDefault());
			String fileName = format.format(new Date(System.currentTimeMillis()));

			File file = new File(Environment.getExternalStorageDirectory() + "/"+fileName);
			// 指定したファイル名が無ければ作成する。
			file.getParentFile().mkdir();
			saveCapture(findViewById(android.R.id.content),file);
		}
		return true;
	}

	public void saveCapture(View view, File file) {
		// キャプチャを撮る
		Bitmap capture = getViewCapture(view);
		FileOutputStream fos = null;
		try {
			fos = new FileOutputStream(file, false);
			// 画像のフォーマットと画質と出力先を指定して保存
			capture.compress(Bitmap.CompressFormat.JPEG, 100, fos);
			toast("撮影完了1");
			fos.flush();
		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			if (fos != null) {
				try {
					fos.close();
				} catch (IOException ie) {
					fos = null;
				}
			}
		}
	}


	public Bitmap getViewCapture(View view) {
		view.setDrawingCacheEnabled(false);
		view.setDrawingCacheEnabled(true);
		view.destroyDrawingCache();

		// Viewのキャプチャを取得
		Bitmap cache = view.getDrawingCache();
		if(cache == null){
			toast("null");
			return null;
		}
		Bitmap screenShot = Bitmap.createBitmap(cache);
		view.setDrawingCacheEnabled(false);
		return screenShot;
	}

	private void toast(String s) {
		Toast.makeText(getApplicationContext(), s, Toast.LENGTH_LONG).show();
	}

}