RotatableImageView in Android

RotatableImageView in Android

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Matrix;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;

public class RotatableImageView extends ImageView {

    private float mRotationDegrees = 0f;
    private float mFocusX = 0f;
    private float mFocusY = 0f;
    private Matrix mMatrix = new Matrix();
    private Matrix mSavedMatrix = new Matrix();
    private boolean mIsRotating = false;

    public RotatableImageView(Context context) {
        super(context);
        init();
    }

    public RotatableImageView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public RotatableImageView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        setScaleType(ScaleType.MATRIX);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mIsRotating = false;
                mSavedMatrix.set(mMatrix);
                mFocusX = event.getX();
                mFocusY = event.getY();
                break;

            case MotionEvent.ACTION_MOVE:
                float dx = event.getX() - mFocusX;
                float dy = event.getY() - mFocusY;
                if (!mIsRotating) {
                    if (Math.abs(dx) > 10 || Math.abs(dy) > 10) {
                        mIsRotating = true;
                    }
                }
                if (mIsRotating) {
                    mMatrix.set(mSavedMatrix);
                    float degrees = (float) Math.toDegrees(Math.atan2(dy, dx));
                    mMatrix.postRotate(degrees - mRotationDegrees, getMeasuredWidth() / 2f, getMeasuredHeight() / 2f);
                    setImageMatrix(mMatrix);
                }
                break;

            case MotionEvent.ACTION_UP:
                if (mIsRotating) {
                    mRotationDegrees = (mRotationDegrees + 360f) % 360f;
                }
                break;
        }
        return true;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        canvas.save();
        canvas.rotate(mRotationDegrees, getMeasuredWidth() / 2f, getMeasuredHeight() / 2f);
        super.onDraw(canvas);
        canvas.restore();
    }

    public void rotate(float degrees) {
        mMatrix.postRotate(degrees, getMeasuredWidth() / 2f, getMeasuredHeight() / 2f);
        setImageMatrix(mMatrix);
    }

    public void setRotationDegrees(float degrees) {
        mMatrix.postRotate(degrees - mRotationDegrees, getMeasuredWidth() / 2f, getMeasuredHeight() / 2f);
        mRotationDegrees = degrees;
        setImageMatrix(mMatrix);
    }

    public float getRotationDegrees() {
        return mRotationDegrees;
    }

}