在Android画布上旋转RectF

Question

我一直在四处搜寻，似乎找不到此问题的解决方法。我试图显示一个在画布上空格的枪（作为一个RectF），它使用tick方法自动旋转。我正在保存画布，按照枪角旋转画布，然后绘制矩形，然后在画笔内部恢复画布...但它只是旋转一次。任何人都有如何让它不断旋转的想法？谢谢！

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如果有人正在寻找类似的东西，那么在下面的评论中回答了这个问题。

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

您发布的代码中没有任何内容正在递增（或递减）angleOfGun。

如果这是真的，那么只有“看到”它第一次旋转1度然后粘在那里才有意义。你需要在你的打勾方法的末尾添加这样一行：

angleOfGun = (angleOfGun + 1) % 360;