Android: Rotate Image in Imageview by an Angle

Android: Rotate image in imageview by an angle

Another simple way to rotate an ImageView:

UPDATE:

Required imports:

import android.graphics.Matrix;
import android.widget.ImageView;

Code: (Assuming imageView, angle, pivotX & pivotY are already defined)

Matrix matrix = new Matrix();
imageView.setScaleType(ImageView.ScaleType.MATRIX);   //required
matrix.postRotate((float) angle, pivotX, pivotY);
imageView.setImageMatrix(matrix);

This method does not require creating a new bitmap each time.

NOTE: To rotate an ImageView on ontouch at runtime you can
set onTouchListener on ImageView & rotate it by adding last two
lines(i.e. postRotate matrix & set it on imageView) in above code
section in your touch listener ACTION_MOVE part.

Android: Rotate image in ImageView by 90degrees but without delay

I also tried to do it once and couldn't find any other solution but using animation. Here how I'd do.

private void rotate(float degree) {
    final RotateAnimation rotateAnim = new RotateAnimation(0.0f, degree,
            RotateAnimation.RELATIVE_TO_SELF, 0.5f,
            RotateAnimation.RELATIVE_TO_SELF, 0.5f);

    rotateAnim.setDuration(0);
    rotateAnim.setFillAfter(true);
    imgview.startAnimation(rotateAnim);
}

Android: Rotate image by dragging a specific part of it

In OnTouchListener's onTouchEvent method, you can utilize the ACTION_DOWN event to check, if a TouchEvent starts inside the little outer circles. If this is true, set a boolean to true. In the ACTION_MOVE event, you just have to check the boolean and only rotate if it is set to true. Then, use ACTION_UP and ACTION_CANCEL to set the boolean to false again.

@Override
public boolean onTouchEvent(MotionEvent event) {
    int x = (int)event.getX();
    int y = (int)event.getY();
    boolean rightPosition = false;
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            // When the event is in the little circles rightPosition=true
            break;
        case MotionEvent.ACTION_MOVE:
            if(rightPosition) yourRotationCode();
            break;
        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
            rightPosition = false;
    }
return false;
}

How do you know, if the drag starts in the little circles?

Tl;dr: Keep track of the polar coordinates of the little circles and compare them with the ACTION_DOWN event's coordinates.

To determine, if the ACTION_DOWN event occurs inside the little circles, keep track of the angle, your ImageView is rotated from it's 'zero position'. In the beginning, the little circles are at 45° and 125°. Offset them against the current rotation of your ImageView, get the angle between 12 o'clock and the ACTION_DOWN event and compare them. Also take into account the distance between the point of rotation and the event. As you already calculate the needed rotation, I think you know how to determine these angles.

The right distance from the point of rotation should be calculated from the ImageView's height and width, so you remain density independent. This needs some pixel counting and calculating the ratio, based on the original image resource, done by hand. This ratio can then be hard coded to a constant value.

As the position of an TouchEvent is precise to one pixel, you should add some offset around the calculated center of the little circles. I would recommend a square around the little circle. Its side length has again to be calculated in aspect to the ImageView's height and width. Again you can determine the ratio of your 'valid area' to the size of the ImageView by hand and provide it as a constant. Then you just have to check if the starting point's coordinates are within +/-(side length / 2) of the center of the little circles.

How to rotate image in imageview on button click each time?

Change your onClick() method to

@Override
public void onClick(View v)
{                  
    imageView.setRotation(imageView.getRotation() + 90);
}

Notice, what the docs say

Sets the degrees that the view is rotated around the pivot point. Increasing values result in clockwise rotation.

I'd like to update my answer to show how to use RotateAnimation to achieve the same effect in case you're also targeting Android devices running Gingerbread (v10) or below.

private int mCurrRotation = 0; // takes the place of getRotation()

Introduce an instance field to track the rotation degrees as above and use it as:

mCurrRotation %= 360;
float fromRotation = mCurrRotation;
float toRotation = mCurrRotation += 90;

final RotateAnimation rotateAnim = new RotateAnimation(
        fromRotation, toRotation, imageview.getWidth()/2, imageView.getHeight()/2);

rotateAnim.setDuration(1000); // Use 0 ms to rotate instantly 
rotateAnim.setFillAfter(true); // Must be true or the animation will reset

imageView.startAnimation(rotateAnim);

Usually one can setup such View animations through XML as well. But, since you have to specify absolute degree values in there, successive rotations will repeat themselves instead of building upon the previous one to complete a full circle. Hence, I chose to show how to do it in code above.

Android Rotatable ImageView

You can rotate a ImageView by using setRotation(int);

// rotate imageView 45 around center pivot point
imageView.setPivotX(imageView.getWidth()/2);
imageView.setPivotY(imageView.getHeight()/2);
imageView.setRotation(45);

Reference: http://goo.gl/WhhGM
Edit: I had to shorten the link because of a ) in the url, some browsers don't like that.

RotateAnimation Get Current angle of image

For Rotation Animation, Yes There is as shown below:

RotateAnimation rotateAnimation = new RotateAnimation();rotateAnimation.setAnimationListener(new Animation.AnimationListener() {  @Override  public void onAnimationStart(Animation animation) {
  }
  @Override  public void onAnimationEnd(Animation animation) {
  }
  @Override  public void onAnimationRepeat(Animation animation) {
  }});