RotateAnimation旋转两次，而不是旋转一次

Question

I was trying to implement a feature where a user can rotate a picture. I thought of using the RotateAnimation for it like so:

rotateRight.setOnClickListener(new OnClickListener(){

    @Override
    public void onClick(View v) {

    //create a new bitmap that is rotated 90 deg
    Matrix mat = new Matrix();
    mat.postRotate(90);//90 degree rotation right
    Bitmap bMapRotate = Bitmap.createBitmap(bmp, 0, 0, bmp.getWidth(), bmp.getHeight(), mat, true);//create a new bitmap with the rotated angle
    bmp = bMapRotate; //save the rotated bitmap as the bitmap that will be uploaded

    RotateAnimation rotateAnim = new RotateAnimation(0f, 90f, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
    rotateAnim.setDuration((long)100);
    rotateAnim.setRepeatCount(0);
    rotateAnim.setFillAfter(true);//maintains the rotation
    previewImage.startAnimation(rotateAnim);

    previewImage.setImageBitmap(bmp);//set the bitmap to the rotated one (if I don't do this, the animation will always start from the initial position


    }

});

However, when I do this the picture rotates two times the first time the button is clicked. Every time after that the picture rotates properly. Another thing to note is that the picture saved in bmp has the right rotation is 90deg off what the ImageView ( previewImage ) is showing

Let me know if I can give you guys any further details.

Answer 1

I'm sorry, but I don't know very well what you are looking for, but if you want to rotate something an image, I suggest that you use a BufferedImage, together with AffineTransform to rotate it.

First you call the resource at the beggining of the program (if you have an image to call).

BufferedImage image = null;
try {
    image = ImageIO.read( MyClass.class.getResourceAsStream( "scr/someimage.png" ) );
}
catch ( java.io.IOException iOException ) { 
    JOptionPane.showMessageDialog( null, "It was not possible to load the dot cursor." );
    System.exit( 0 );
}

After that, if you wish to rotate, just do:

BufferedImage rotatedImage = new BufferedImage( image.getWidth(), image.getHeight(), BufferedImage.TYPE_INT_ARGB );

AffineTransform rotate = AffineTransform.getRotateInstance( Math.PI/2 );
//Must be in radian. Math.PI/2 = 90º
BufferedImageOp buffIOP = new AffineTransformOp( rotate, null );

Graphics2D g2 = rotatedImage.createGraphics();
g2.drawImage( image, buffIOP, 0, 0 );
g2.dispose();

I don't know if this is usefull for you, but I hope I helped in some way.