圈屏幕

Question

我想提请圈在屏幕的中心不匹配，但我发现了这样的事情：

我使用这个代码来绘制此圈。

public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 

    Display display = getWindowManager().getDefaultDisplay(); 
    int width = display.getWidth(); 
    int height = display.getHeight(); 

    Bitmap bmp = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_4444); 

    Canvas c = new Canvas(bmp); 

    RectF rect = new RectF(0,0,width,width); 
    drawCircle(rect, c, width, height); 
    ImageView img = (ImageView) findViewById(R.id.imageView1); 
    img.setImageBitmap(bmp); 
    img.setScaleType(ScaleType.FIT_CENTER); 


} 

private void drawCircle(RectF rect, Canvas c, int width, int height) { 
    Paint paint = new Paint(); 
    paint.setARGB(255, 255 , 10, 21); 
    paint.setStrokeWidth(10); 
    paint.setAntiAlias(true); 
    paint.setStrokeCap(Paint.Cap.BUTT); 
    paint.setStyle(Paint.Style.STROKE); 
    int radius; 
    if(width < height) 
     radius = width/2; 
    else 
     radius = height/2; 
    c.drawCircle(width/2, height/2, radius, paint); 
} 

我不明白为什么它在两边切即使我使用的屏幕尺寸绘制的，所以它应该完全适合它。

Answer 1

您没有考虑线的粗细（strokeWidth）。假设它的厚度为0，你画了一个圆圈，所以“实际”圆圈接触到屏幕的边缘，但是由于你使用了厚厚的画笔，有些油漆从边缘泄漏。

在半径 StrokeWidth

Answer 2

帐户：

// Substract stroke width. 
radius -= paint.getStrokeWidth()/2; 
c.drawCircle(width/2, height/2, radius, paint); 

Answer 3

你应该减少厚度/ 2。

private void drawCircle(RectF rect, Canvas c, int width, int height) { 
     Paint paint = new Paint(); 
     paint.setARGB(255, 255 , 10, 21); 
     paint.setStrokeWidth(10); 
     paint.setAntiAlias(true); 
     paint.setStrokeCap(Paint.Cap.BUTT); 
     paint.setStyle(Paint.Style.STROKE); 
     int radius; 
     if(width < height) 
      radius = width/2; 
     else 
      radius = height/2; 

//this is the new line: 
     radius-= 5; 
     c.drawCircle(width/2, height/2, radius, paint); 
    }