如何连续从下到上移动图像？

Question

我一直在研究http://obviam.net/index.php/a-very-basic-the-game-loop-for-android/上的例子.在这里我想做一些改变.

Speed.java

public class Speed {

    public static final int DIRECTION_RIGHT = 1;
    public static final int DIRECTION_LEFT  = -1;
    public static final int DIRECTION_UP    = -1;
    public static final int DIRECTION_DOWN  = 1;

    private float xv = 1;   // velocity value on the X axis
    private float yv = 1;   // velocity value on the Y axis

    private int xDirection = DIRECTION_RIGHT;
    private int yDirection = DIRECTION_DOWN;

    public Speed() {
        this.xv = 1;
        this.yv = 1;
    }

    public Speed(float xv, float yv) {
        this.xv = xv;
        this.yv = yv;
    }

    public float getXv() {
        return xv;
    }
    public void setXv(float xv) {
        this.xv = xv;
    }
    public float getYv() {
        return yv;
    }
    public void setYv(float yv) {
        this.yv = yv;
    }

    public int getxDirection() {
        return xDirection;
    }
    public void setxDirection(int xDirection) {
        this.xDirection = xDirection;
    }
    public int getyDirection() {
        return yDirection;
    }
    public void setyDirection(int yDirection) {
        this.yDirection = yDirection;
    }

    // changes the direction on the X axis
    public void toggleXDirection() {
        xDirection = xDirection * -1;
    }

    // changes the direction on the Y axis
    public void toggleYDirection() {
        yDirection = yDirection * -1;
    }

}

使用此功能,图像可以向各个方向移动.现在我只想限制这种从下到上的运动.onclick的功能是,我们可以单击并将图像拖动到所需位置.我想替换它只是让图像消失或去另一个活动.请帮我改变这段代码.提前致谢.

Answer 1

如果您使用过 SurfaceView 那么在onDraw(Canvas canvas)方法中用于从下到上移动图像的代码是这样的。

canvas.drawBitmap(bitmap,xPoint,yPoint,paint);

其中 bitmap 是图像（要移动的位图），xPoint 是 x 坐标，yPoint 是 y 坐标，paint 是 Paint，也可以为 null。

对于从下到上的移动只需更新

yPoint = yPoint - 1;

在调用之前的任何线程中onDraw()。

愿这对你有帮助。