Скроллинг увеличенного изображения - Программирование Android - Ответ 4634931

public class ScrollImageView extends View {
    private final int DEFAULT_PADDING = 10;
    private Display mDisplay;
    private Bitmap mImage;
 
    /* Current x and y of the touch */
    private float mCurrentX = 0;
    private float mCurrentY = 0;
 
    private float mTotalX = 0;
    private float mTotalY = 0;
    /* The touch distance change from the current touch */
    private float mDeltaX = 0;
    private float mDeltaY = 0;
 
    private float scaleFactor = 2.0f;
 
    int mDisplayWidth;
    int mDisplayHeight;
    int mPadding;
 
public ScrollImageView(Context context, int widthD, int heightD) {
    super(context);
    this.mDisplayWidth = widthD ;
    this.mDisplayHeight =heightD ;
    initScrollImageView(context);
    this.mImage = BitmapFactory.decodeResource(getResources(), R.drawable.img) ;
}
public ScrollImageView(Context context, AttributeSet attributeSet) {
    super(context);
    initScrollImageView(context);
}
 
private void initScrollImageView(Context context) {
    mDisplay = ((WindowManager)context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay();
    mPadding = DEFAULT_PADDING;
}
 
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    int width = this.mDisplayWidth ;
    int height = this.mDisplayHeight ;
    setMeasuredDimension(width, height);
}
 
private int measureDim(int measureSpec, int size) {
        int result = 0;
        int specMode = MeasureSpec.getMode(measureSpec);
        int specSize = MeasureSpec.getSize(measureSpec);
 
        if (specMode == MeasureSpec.EXACTLY) {
            result = specSize;
        } else {
            result = size;
            if (specMode == MeasureSpec.AT_MOST) {
               result = Math.min(result, specSize);
            }
        }
        return result;
    }
 
public Bitmap getImage() {
    return mImage;
}
 
public void setImage(Bitmap image) {
    mImage = image;
}
 
public int getPadding() {
    return mPadding;
}
 
public void setPadding(int padding) {
    this.mPadding = padding;
}
 
@Override
public boolean onTouchEvent(MotionEvent event) {
    if (event.getAction() == MotionEvent.ACTION_DOWN) {
        mCurrentX = event.getRawX();
        mCurrentY = event.getRawY();
    } 
    else if (event.getAction() == MotionEvent.ACTION_MOVE) {
        float x = event.getRawX();
        float y = event.getRawY();
 
        // Update how much the touch moved
        mDeltaX = x - mCurrentX;
        mDeltaY = y - mCurrentY;
 
        mCurrentX = x;
        mCurrentY = y;
 
        invalidate();
    }
    // Consume event
    return true;
}
 
@Override
protected void onDraw(Canvas canvas) {
    if (mImage == null) {
        return;
}
 
    float newTotalX = mTotalX + mDeltaX;
    // Don't scroll off the left or right edges of the bitmap.
    if (mPadding > newTotalX && newTotalX > getMeasuredWidth() - mImage.getWidth() - mPadding)
        mTotalX += mDeltaX;
 
    float newTotalY = mTotalY + mDeltaY;
    // Don't scroll off the top or bottom edges of the bitmap.
    if (mPadding > newTotalY && newTotalY > getMeasuredHeight() - mImage.getHeight() - mPadding)
        mTotalY += mDeltaY;
 
    Paint paint = new Paint();
    canvas.scale(scaleFactor, scaleFactor);
    canvas.drawBitmap(mImage, mTotalX, mTotalY, paint);
}
}