@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ViewCompat.setBackground(findViewById(R.id.text_view),
createCircleRect(
5, Color.RED,
30));
}
public ShapeDrawable
createCircleRect(
final int strokeWidth,
final int strokeColor,
final int radius) {
Shape shape =
new Shape() {
@Override
public void draw(Canvas canvas, Paint paint) {
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(strokeWidth);
paint.setColor(strokeColor);
RectF rectf=
new RectF(
0,
0, getWidth(), getHeight());
canvas.drawRoundRect(rectf, radius, radius, paint);
}
};
return new ShapeDrawable(shape);
}
使用以上代码绘制TextView的背景Shape，会发现，四个圆角的线宽要大于四边直线线宽。如图：
出现这种问题的原因是，使用Style.Stroke绘制粗线，基准线在中线，stroke边由中线向内外扩展。以上代码直接以矩形的最外一圈作为基准线，导致直线边只能绘制向里的一半线宽。所以Shape中的draw方法应该做如下修改：
Shape shape =
new Shape() {
@Override
public void draw(Canvas canvas, Paint paint) {
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(strokeWidth);
paint.setColor(strokeColor);
int d = strokeWidth /
2;
RectF rectF=
new RectF(d, d, getWidth()- d, getHeight()- d);
canvas.drawRoundRect(rectF, radius, radius, paint);
}
};
这样显示的圆角矩形就正常了：
感谢文章：Android中Canvas绘图基础详解（附源码下载）给我的提示。
