正在学习android sprite，但我的位图出现错误

我正在学习如何在android上制作精灵

我的位图有问题

public class Sprite {
Bitmap b;
BoardGame bg;
int x,y;
int xSpeed,ySpeed;
int height,width;
int direction;

public Sprite(BoardGame BoardGame, Bitmap blob) {
    b = blob;
    bg = BoardGame;
    height = b.getHeight();
    width = b.getWidth();
    x = 0;
    y = 0;
    xSpeed = 5;
    ySpeed = 0;
    direction = 0;
}


private void update()
{
    if (x > bg.getWidth() - width - xSpeed)
    {
        xSpeed = 0;
        ySpeed = 5;
        direction = 1;
    }
    if (y > bg.getHeight() - height - xSpeed) {
        xSpeed = -5;
        ySpeed = 0;
        direction = 2;
    }
    if (x + xSpeed < 0)
    {
        x = 0;
        xSpeed = 5;
        ySpeed = 0;
        direction = 3;
    }

    x+=xSpeed;
    y+=ySpeed;
}

public void onDraw(Canvas canvas) {
    update();
    Rect src = new Rect(0,0,width,height);
    Rect dst = new Rect(x,y,x+width,y+height);
    canvas.drawBitmap(b,x,y,null);
}

}

由于某种原因，“getHeight（）”不起作用

传递给

Sprite

构造函数的参数

Bitmap blob

为null。您尝试取消对空对象的引用

首先创建

Sprite

，然后再创建

blob

。这是在创建

BoardGame

时，在这里初始化

Sprite

，

blob

为空

BoardGame BoardGame = new BoardGame(this);//here you create it, but blob is null!
//first here you initialize blob
blob = BitmapFactory.decodeResource(getResources(),R.drawable.monkey);
blob = Bitmap.createScaledBitmap(ball,170,170,false);

一个可能的解决方案是调整

main活动
的
onCreate
方法中的执行顺序：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ball = BitmapFactory.decodeResource(getResources(), R.drawable.aqua_ball_green);
    ball = Bitmap.createScaledBitmap(ball,170,170,false);
    blob = BitmapFactory.decodeResource(getResources(),R.drawable.monkey);
    blob = Bitmap.createScaledBitmap(ball,170,170,false);
    //Put BoardGame here:
    BoardGame BoardGame = new BoardGame(this);
    setContentView(BoardGame);
}

这样，当
blob
也已初始化时，您就可以初始化
BoardGame

希望这能澄清问题
 您能否发布您的
main活动
代码，在那里您可以创建
Sprite
，并且
位图
也是如此？@user8完成，这是唯一的活动。
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ball = BitmapFactory.decodeResource(getResources(), R.drawable.aqua_ball_green);
    ball = Bitmap.createScaledBitmap(ball,170,170,false);
    blob = BitmapFactory.decodeResource(getResources(),R.drawable.monkey);
    blob = Bitmap.createScaledBitmap(ball,170,170,false);
    //Put BoardGame here:
    BoardGame BoardGame = new BoardGame(this);
    setContentView(BoardGame);
}