ImageView旋转而不重新创建位图

Question

I want to rotate an ImageView image. Here is my code:

Matrix mat = new Matrix();
mat.preRotate(90, ivImage.getWidth()/2, ivImage.getHeight()/2);
ivImage.setScaleType(ScaleType.MATRIX);
ivImage.setImageMatrix(mat);

but when I click on the rotate button, not only the image rotates, but it is scaled too, because the bitmap is larger then the ImageView .

I know I can use

b = Bitmap.createBitmap(b, 0, 0, b.getWidth(), b.getHeight(), mat, true);
ivImage.setImageBitmap(b);

but this is noticeably slower, and has some lag.

So my question is: how to rotate the image without being scaled and without recreating the bitmap?

Answer 1

Here is the code that I have used for rotation of image to 90 degrees.

         if(oldAngle == 0){
              newAngle = oldAngle + 90;
            }
            else if(oldAngle == 90)
                newAngle = oldAngle - 90;
              LinearLayout.LayoutParams layoutParams = (LinearLayout.LayoutParams) view.getLayoutParams();
              int centerX = layoutParams.leftMargin + (view.getWidth()/2);
              int centerY = layoutParams.topMargin + (view.getHeight()/2);
              RotateAnimation animation = new RotateAnimation(oldAngle, newAngle, centerX, centerY);
              animation.setDuration(0);
              animation.setRepeatCount(2);
              animation.setFillAfter(true);
              view.startAnimation(animation);

              oldAngle = newAngle;

Hope it will help you...

Answer 2

How about using an XML animation?

<?xml version="1.0" encoding="utf-8"?>
    <rotate
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:fromDegrees="0"
    android:interpolator="@android:anim/linear_interpolator"
    android:toDegrees="360"
    android:pivotX="50%"
    android:pivotY="50%"
    android:duration="1000"
    android:startOffset="0"
    android:repeatCount="infinite"
    />

And then use it with something like;

 rotation = AnimationUtils.loadAnimation(this, R.anim.clockwise_rotation);
 buttonRefresh.startAnimation(rotation);

ps. This infinitely spins around. So needs some adjustments.

Answer 3

use this

final Random generator = new Random();
        int n = 10000;
        n = generator.nextInt(n);
        final Matrix mtx = new Matrix();
        mtx.postRotate(n);
        rotator = Bitmap.createBitmap(all, 0, 0,
                all.getWidth(), all.getHeight(), mtx,
                true);
        view.setImageBitmap(rotator);

this will rotate the image randomly. just change .nextInt(n) to .nextInt(AnyNumberYouLife) its fast :)

Answer 4

I found that for my purpose it was the best solution to use Canvas instead of ImageView . And for the rotating of the image I chose to use another library that can be found here

Answer 5

here's a nice solution for putting a rotated drawable for an imageView:

Drawable getRotateDrawable(final Bitmap b, final float angle) {
    final BitmapDrawable drawable = new BitmapDrawable(getResources(), b) {
        @Override
        public void draw(final Canvas canvas) {
            canvas.save();
            canvas.rotate(angle, b.getWidth() / 2, b.getHeight() / 2);
            super.draw(canvas);
            canvas.restore();
        }
    };
    return drawable;
}

usage:

Bitmap b=...
float angle=...
final Drawable rotatedDrawable = getRotateDrawable(b,angle);
root.setImageDrawable(rotatedDrawable);

another alternative:

private Drawable getRotateDrawable(final Drawable d, final float angle) {
    final Drawable[] arD = { d };
    return new LayerDrawable(arD) {
        @Override
        public void draw(final Canvas canvas) {
            canvas.save();
            canvas.rotate(angle, d.getBounds().width() / 2, d.getBounds().height() / 2);
            super.draw(canvas);
            canvas.restore();
        }
    };
}

also, if you wish to rotate the bitmap, but afraid of OOM, you can use an NDK solution i've made here

Answer 6

I've found the easiest way to rotate an ImageView is to do this:

view.animate().rotationBy(degrees);

Very easy to implement and android handles all the rest

Hope this helps! :)