在 Android 画布上旋转 RectF

Question

我一直在四处寻找，似乎无法找到解决此问题的方法。我正在尝试在画布上的空间中显示一把枪（作为 RectF），它使用 tick 方法自动旋转。我正在保存画布，将其旋转枪角，然后绘制矩形，然后在 tick 方法中恢复画布......但它只旋转枪一次。有人知道如何让它连续旋转吗？谢谢！

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如果有人在寻找类似的东西，这个问题在下面的 cmets 中得到了回答。

    public class SpaceAnimator implements Animator {

// constants
private static final int FRAME_INTERVAL = 60; // animation-frame interval, in milliseconds
private static final int BACKGROUND_COLOR = Color.BLACK; // background color

// paint objects
private Paint whitePaint;
private Paint yellowPaint;
private Paint bluePaint;

//random number generator
Random randomGen = new Random();

//PointF array to hold star positions 
ArrayList<PointF> stars = new ArrayList<PointF>();

//Number of stars
int numberOfStars = 100;

//PointFs for center of the sun and angle of gun
PointF centerOfSun1 = new PointF(300,200);
float angleOfGun = 1;


// constructor
public SpaceAnimator() {

    //Create a white paint object
    whitePaint = new Paint();
    whitePaint.setColor(Color.WHITE);

    //Create a yellow paint object
    yellowPaint = new Paint();
    yellowPaint.setColor(Color.YELLOW); 

    //create a blue paint object
    bluePaint = new Paint();
    bluePaint.setColor(Color.BLUE);

    //Set position of the stars
    for(int i = 0; i < numberOfStars; i++)
    {
        int randStarX = randomGen.nextInt(100); //random X initial position
        int randStarY = randomGen.nextInt(100); //random Y initial position
        stars.add(new PointF(randStarX, randStarY)); //set X and Y positions
    }

}

/**
 * Interval between animation frames
 * 
 * @return the time interval between frames, in milliseconds.
 */
public int interval() {
    return FRAME_INTERVAL;
}

/**
 * The background color.
 * 
 * @return the background color onto which we will draw the image.
 */
public int backgroundColor() {
    // create/return the background color
    return BACKGROUND_COLOR;
}

/**
 * Action to perform on clock tick
 * 
 * @param g the canvas object on which to draw
 */
public void tick(Canvas g) {

    int height = g.getHeight();
    int width = g.getWidth();

    //draw the stars
    for(int i = 0; i < numberOfStars; i++)
    {
        g.drawCircle(stars.get(i).x/100 * width, stars.get(i).y/100 * height, randomGen.nextInt(2), whitePaint);
    }

    //draw the first sun
    g.drawCircle(centerOfSun1.x, centerOfSun1.y, 40, yellowPaint);

    //rotate/draw the gun
    g.save();
    g.rotate(angleOfGun);
    g.drawRect(new RectF(width/2 - 20, height/2 - 20, width/2 + 20, height/2 + 20), bluePaint);
    g.restore();
}

Answer 1

您发布的代码中的任何内容都没有增加（或减少）angleOfGun。

如果这是真的，那么您只会“看到”它第一次旋转 1 度然后停留在那里是有道理的。您需要在 tick 方法的末尾添加这样的一行：

angleOfGun = (angleOfGun + 1) % 360;