如何使矩形在Android中绘制onTouchEvent？

Question

I have been working on game which simply creates a rectangle when user touches screen, I don't know how to get the X coordinates and Y coordinates of touchEvent to be the "float" of my rects, every time I put a float number in the X,Y coordinates it says "There is no applicable constructor in (float, float, int, int)". Which I don't know what that means.

    public class GameBoard extends View {

    private ArrayList<Rect> rectangles = new ArrayList<Rect>();

    public GameBoard(Context context) {
        super(context);

    }
    @Override
    public boolean onTouchEvent (MotionEvent event) {
        float xCoor = event.getX();
        float yCoor = event.getY();

        switch (event.getAction()){
            case MotionEvent.ACTION_DOWN:
                rectangles.add(new Rect(xCoor, yCoor, 10, 40));
                break;
        }
        return true;
    }
    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint = new Paint();
        paint.setColor(Color.BLUE);
        for (Rect rect : rectangles) {
            canvas.drawRect(rect, paint);
        }
    }
}

Answer 1

You are using Rect for int values ,

Instead you can use RectF for the float values

new RectF(xCoor, yCoor, 10, 40)

Answer 2

see the Constructor of Rect

 public Rect(int,int,int,int);

is expecting all parameters to be int

You need to typecast x and y values from float to int

    int xCoor = (int)event.getX();
    int yCoor = (int)event.getY();

Answer 3

try to use this ::->     


 DrawingImage = (ImageView) this.findViewById(R.id.DrawingImageView1);

        Bitmap bitmap = Bitmap.createBitmap((int) getWindowManager()
            .getDefaultDisplay().getWidth(), (int) getWindowManager()
            .getDefaultDisplay().getHeight(), Bitmap.Config.ARGB_8888);

        Canvas canvas = new Canvas(bitmap);
        DrawingImage.setImageBitmap(bitmap);

        // Draw Rectangle

        Paint paint = new Paint();
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.FILL_AND_STROKE);
        paint.setStrokeWidth(10);

        float left = 20;
        float top = 20;
        float right = 50;
        float bottom = 100;

        canvas.drawRect(left, top, right, bottom, paint);

Answer 4

You are adding a new Rect to your ArrayList by calling the constructor Rect. new Rect tells Java to create a new Rect object.

A constructor is like a method, except it has the same name as the Class it's in. It just so happens that the Rect class does not have a constructor with floats as its parameters.

So you have to convert your floats to integer before passing them to the Rect constructor.

int xCoor = (int) event.getX();
int yCoor = (int) event.getY();

Notice also that when you cast (casting is converting from one type to another) that the value in only ever rounded down to the nearest integer. In fact anything after the decimal point is simply discarded.

I think if your going to make a success of your Android developments you would be best served getting a good textbook on Object Oriented programming in Java.