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[英]Drag a circle drawn on Canvas to follow user drag on screen (android)
[英]Circle drawn on canvas doesn't match the screen
我想在屏幕中心畫圓圈,但我得到的是這樣的東西:
我正在使用此代碼繪制此圓圈。
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);
}
我不明白為什么它會在側面切割,即使我使用屏幕尺寸來繪制它,所以它應該完全適合它。
您沒有考慮線條的粗細(strokeWidth)。 假設它有0厚度,你畫了一個圓圈,所以“實際”圓圈觸及屏幕的邊緣,但由於你使用了厚厚的畫筆,一些油漆漏過了邊緣。
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);
}
考慮半徑中的StrokeWidth
:
// Substract stroke width.
radius -= paint.getStrokeWidth() / 2;
c.drawCircle(width/2, height/2, radius, paint);
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