用于从sdcard加载图像的android进度条

Question

下面显示的是从SD卡读取图像并将其转换为灰色图像的代码。它没有进度条实现，效果很好。然而，在我实现进度条之后，我无法获得任何图像。

public class MainActivity extends AppCompatActivity {
    ProgressDialog barProgressDialog;
    Handler updateBarHandler;
    public static final int REQUEST_CODE = 10;  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        rawImage = (ImageView) findViewById(R.id.rawImage);
        updateBarHandler = new Handler();
    }
    public void rawImageClicked(View v) {
        Intent rawIntent = new Intent(Intent.ACTION_PICK);
        File pictureDirectory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM);

        String pictureDirectoryPath = pictureDirectory.getPath();
        Uri data=Uri.parse(pictureDirectoryPath);
        rawIntent.setDataAndType(data, "image/*");
        startActivityForResult(rawIntent, REQUEST_CODE);
    }

    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (resultCode==RESULT_OK){
            if(requestCode==REQUEST_CODE){
                final float red = (float) 0.299;
                final float green = (float) 0.587;
                final float blue = (float) 0.114;

                final Uri imagef = data.getData();
                final InputStream[] streamI = new InputStream[1];
                //InputStream streamI;

                final ProgressDialog ringProgressDialog =ProgressDialog.show(MainActivity.this, "Wait", "Downloading Image ...", true);
                ringProgressDialog.setCancelable(true);
                new Thread(new Runnable() {
                    @Override
                    public void run() {
                        try {
                            streamI[0] = getContentResolver().openInputStream(imagef);
                            //Create bitmap from selected image
                            Bitmap imgb = BitmapFactory.decodeStream(streamI[0]);
                            //Define rows and columns of selected image
                            int rows = imgb.getHeight();
                            int cols = imgb.getWidth();

                            operation =Bitmap.createBitmap(cols, rows, imgb.getConfig());
                            //Convert original image to Gray Image
                            for (int i=0;i<cols;i++){
                                for(int j=0;j<rows;j++) {
                                    int p = imgb.getPixel(i, j);
                                    int r = Color.red(p);
                                    int g = Color.green(p);
                                    int b = Color.blue(p);
                                    r = (int) (red * r);
                                    g = (int) (green * g);
                                    b = (int) (blue * b);
                                    int gray = (int) (r * 0.299 + g * 0.587 + b * 0.114);
                                    operation.setPixel(i, j, Color.argb(Color.alpha(p), gray, gray, gray));
                                }
                            }
                            rawImage.setImageBitmap(operation);
                            Thread.sleep(100);
                        }catch (Exception e) {
                            e.printStackTrace();
                        }ringProgressDialog.dismiss();
                    }
                }).start();
            }
        }
}        

下面显示的是工作代码：

    Uri imagef = data.getData();
    InputStream streamI;
            try{
                streamI = getContentResolver().openInputStream(imagef);
                //Create bitmap from selected image
                Bitmap imgb = BitmapFactory.decodeStream(streamI);
                //Define rows and columns of selected image
                int rows = imgb.getHeight();
                int cols = imgb.getWidth();
                Log.d("rows",Integer.toString(rows)+ "  "+Integer.toString(cols));
                operation =Bitmap.createBitmap(cols, rows, imgb.getConfig());
                //Convert original image to Gray Image
                for (int i=0;i<cols;i++){
                    for(int j=0;j<rows;j++){
                        int p = imgb.getPixel(i,j);
                        int r = Color.red(p);
                        int g = Color.green(p);
                        int b = Color.blue(p);
                        r = (int) (red*r);
                        g = (int) (green*g);
                        b = (int) (blue*b);
                        int gray = (int) (r*0.299+g*0.587+b*0.114);
                        operation.setPixel(i, j, Color.argb(Color.alpha(p), gray, gray, gray));
                    }
                }
                rawImage.setImageBitmap(operation);
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }