How can I move an image from one point to another

问题:

I'm developing a game, and in this game I have to move an image on a Canvas from one point to another in any direction, not just vertical or horizontal.

How can I move that image in this manner?

回答1:

I couldn't understand what you actually want but here's something I've tried.

    interface coordinateListener
{
    public void currentPosition(float x,float y);
}

public class ImageView extends View{
    int width;
    int height;
    RectF rect = new RectF();
    float x=0f,y=0f;
    float dX,dY;
    float mStartX,mStartY;
    float mEndX,mEndY;
    Paint paint = new Paint();
    Bitmap mBitmap;
    TranslateAnimation anim;
    View view;
    coordinateListener mListener;
    public ImageView(Context context) {
        super(context);
        init();
    }

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

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

public void init()
{
    view = this;
}
@Override
protected void onMeasure(int widthMeasureSpec,int heightMeasureSpec)
{
    super.onMeasure(widthMeasureSpec,heightMeasureSpec);
    width = getMeasuredWidth();
    height = getMeasuredHeight();
    rect.set(0,0,width,height);
}

@Override
protected void onDraw(Canvas canvas)
{
    super.onDraw(canvas);
    if(mBitmap!=null) {
        canvas.drawBitmap(mBitmap,0,0,paint);
    }
}

@Override
public boolean onTouchEvent(MotionEvent event)
{
    int action = event.getAction() & MotionEvent.ACTION_MASK;

    switch (action)
    {
        case MotionEvent.ACTION_DOWN:
            dX = this.getX() - event.getRawX();
            dY = this.getY() - event.getRawY();
            break;
        case MotionEvent.ACTION_MOVE:
            y = event.getRawY();
            x = event.getRawX();
            y += dY;
            x+=dX;

            this.setY(y);
            this.setX(x);

            mListener = (coordinateListener)getContext(); 
            mListener.currentPosition(x,y);

            invalidate();
            break;
    }
    return true;
}

public void startCoordinates(float x,float y)
{
    mStartX = x;
    mStartY = y;
}

public void endCoordinates(float x,float y)
{
    mEndX = x;
    mEndY = y;
}

public void startTranslation(long duration)
{
    anim = new TranslateAnimation(mStartX,mEndX,mStartY,mEndY);
    anim.setDuration(duration);
    anim.setFillAfter(true);

    anim.setAnimationListener(new Animation.AnimationListener() {
        @Override
        public void onAnimationStart(Animation animation) {

        }

        @Override
        public void onAnimationEnd(Animation animation) {
            view.setX((int)mEndX);
            view.setY((int)mEndY);
            animation.setFillAfter(false);
        }

        @Override
        public void onAnimationRepeat(Animation animation) {

        }
    });

    this.startAnimation(anim);
}

}

You can either drag it from one position to another or you can use Translate to move it...like this,

view.startCoordinates(0f,0f);
view.endCoordinates(500f,0f);
view.startTranslation(3000);

回答2:

Take a look into this library. It should help you with moving, and I think dragging objects like image, etc - PhysicsLayout. Here you can see moving with Two directions - X, Y. If you want to move including Z, there is only single way to implement it, you should use simple scaling.

If you want something more, there are a lot of powerful and pretty nice Frameworks, Environment.

回答3:

After getting a math lecture, it turns out that this is easy to solve. First, we need to get the angle which the target will be moving at.

float deltaX = targetX - startX;
float deltaY = targetY - startY;
float angle = Math.atan2( deltaY, deltaX );

startX/Y can be current X/Y.

Now that we have calculated the angle, we can apply it to the current coordinates:

currentX += speed * Math.cos(angle);//Using cos
currentY += speed * Math.sin(angle);//or sin

to handle the calculations of how much X and Y will be increased by. Using speed as a custom variable if you need to have a custom speed set as well. If you don't need more speed, remove the variable.

And to move the object, apply X/Y to the object:

c.drawBitmap(bm, x, y, null);

Example:

int speed = 10;
int x, y;
int targetX = 100, targetY = 600;
int startX = 900, startY = 100;
public void render(Canvas c){
    super.draw(c);
    float deltaX = targetX - startX;
    float deltaY = targetY - startY;
    float angle = Math.atan2( deltaY, deltaX );
    x += speed * Math.cos(angle);//Using cos
    y += speed * Math.sin(angle);//or sin
    c.drawBitmap(bm, x, y, null);
   (...)
}