I have been coding speed for an object. I have made it so the object will move from one end of the screen to another at a speed depending on the screen size, at the monemt I have made it so it will take one second to pass the screen. So i have worked out the speed in code but when I go to assign the speed it tells me to force close and i do not understand why. Here is the code:

MainGame Code:

@Override
protected void onDraw(Canvas canvas) {
    setBlockSpeed(getWidth());
}

private int blockSpeed;
 private void setBlockSpeed(int screenWidth){
Log.d(TAG, "screenWidth " + screenWidth);
 blockSpeed = screenWidth / 100; // 100 is the FPS.. i want it to take 1 second to pass the screen
 Math.round(blockSpeed); // to make it a whole number   
 block.speed = blockSpeed; // if i dont put blockSpeed and put eg 8 it still tells me to force close  
 }

Block.java Code:

public int speed;

public void draw(Canvas canvas) {
    canvas.drawBitmap(bitmap, x - (bitmap.getWidth() / 2), y - (bitmap.getHeight() / 2), null);
    if(dontmove == 0){
        this.x -= speed;


    }
}