圈屏幕

Question

我想提請圈在屏幕的中心不匹配，但我發現了這樣的事情：

我使用這個代碼來繪製此圈。

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); 
} 

我不明白爲什麼它在兩邊切即使我使用的屏幕尺寸繪製的，所以它應該完全適合它。

Answer 1

您沒有考慮線的粗細（strokeWidth）。假設它的厚度爲0，你畫了一個圓圈，所以「實際」圓圈接觸到屏幕的邊緣，但是由於你使用了厚厚的畫筆，有些油漆從邊緣泄漏。

在半徑 StrokeWidth

Answer 2

帳戶：

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

Answer 3

你應該減少厚度/ 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); 
    }