如何在Android中使用Seekbar旋转图像360度？

Question

I am creating an Android App to rotate an image by 360 degrees. When I track the Seek bar the image should Rotate.

Could you please help me how to achieve this?

Imageview selectedimage;
final int width = selectedimage.width;
final int height = selectedimage.height;      

final Bitmap scaledBitmap = Bitmap.createScaledBitmap(selectedimage,width, height, true); 
selectedimage.setImageBitmap(getRotatedBitmap(scaledBitmap));

seekbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() { 
  @Override
      public void onStopTrackingTouch(SeekBar seekBar) {
          // TODO Auto-generated method stub
      }

 @Override
      public void onStartTrackingTouch(SeekBar seekBar) {
          // TODO Auto-generated method stub
      }

 @Override
     public void onProgressChanged(SeekBar seekBar, int progress,
                            boolean fromUser) {
            // TODO Auto-generated method stub

             rotation += 90;
             rotation %= 360;
             Bitmap bitmap = getRotatedBitmap(scaledBitmap);
             selectedImage.setImageBitmap(bitmap);
     }
   });     

private Bitmap getRotatedBitmap(Bitmap bitmap) {
    if (rotation % 360 == 0) {
        return bitmap;
    }
    Matrix matrix = new Matrix();
    matrix.postRotate(rotation, bitmap.getWidth() / 2,
                      bitmap.getHeight() / 2);

    return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
                        bitmap.getHeight() / 2, matrix, true);
}

I don't know how to calculate Rotation value and apply to seek bar when track forward in which case the seek bar that image should rotate gradually and when track backward it should rotate gradually reverse.

Answer 1

You can try this. I have used drawable image and get bitmap from it.

 seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            int progress = 0;

            @Override
            public void onProgressChanged(SeekBar seekBar, int progresValue, boolean fromUser) {
                progress = progresValue;

                Bitmap bMap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);
                Matrix mat = new Matrix();
                mat.postRotate(progresValue);
                Bitmap bMapRotate = Bitmap.createBitmap(bMap, 0, 0, bMap.getWidth(), bMap.getHeight(), mat, true);
                imageView.setImageBitmap(bMapRotate);
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                Toast.makeText(getApplicationContext(), "Started tracking seekbar", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });

Answer 2

No need of creating new bitmap everytime. Use just matrix instead of

float pivX=imageView.getDrawable().getBounds().width()/2;
float pivY=imageView.getDrawable().getBounds().height()/2;
Matrix matrix = new Matrix();
imageView.setScaleType(ScaleType.MATRIX);   
matrix.postRotate((float) angle, pivX, pivY);
imageView.setImageMatrix(matrix);

if APK Level >=11

imageView.setRotation(angle);

Answer 3

seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        int progress = 0;

        @Override
        public void onProgressChanged(SeekBar seekBar, int progresValue, boolean fromUser) {
            mat.postRotate(progresValue, centerX, centerY);
            imageView.setImageMatrix(mat);
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {
            Toast.makeText(getApplicationContext(), "Started tracking seekbar", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {

        }
    });

Bitmap bMap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);

Matrix mat = new Matrix();

create your Bitmap and matrix. You should be avoid to create bitmap every time. Instead of that one you use matrix.