java - Android 中 Paint.StrokeWidth = 1 的 drawLine 问题

Question

我想我遇到了一个讨厌的错误。问题是几乎是水平线具有轻微的渐变并使用 StrokeWidth = 1 的 Paint 不是绘制，例如:

public class MyControl extends View {

   public MyControl(Context context) {
           super(context);
           // TODO Auto-generated constructor stub
   }

   @Override
   protected void onDraw(Canvas canvas)
   {
           super.onDraw(canvas);

       Paint pen = new Paint();
       pen.setColor(Color.RED);
       pen.setStrokeWidth(1);
       pen.setStyle(Paint.Style.STROKE);

           canvas.drawLine(100, 100, 200, 90, pen); //not painted
           canvas.drawLine(100, 100, 200, 100, pen);
           canvas.drawLine(100, 100, 200, 110, pen); //not painted
           canvas.drawLine(100, 100, 200, 120, pen); //not painted
           canvas.drawLine(100, 100, 200, 130, pen);

           pen.Color = Color.MAGENTA;
           pen.setStrokeWidth(2);

           canvas.drawLine(100, 200, 200, 190, pen);
           canvas.drawLine(100, 200, 200, 200, pen);
           canvas.drawLine(100, 200, 200, 210, pen);
           canvas.drawLine(100, 200, 200, 220, pen);
           canvas.drawLine(100, 200, 200, 230, pen);
   }

并以这种方式使用 MyControl 类:

public class prova extends Activity {
   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);

           MyControl ctrl = new MyControl(this);
           setContentView(ctrl);
   }

将 StrokeWidth 设置为 0 或 > 1，绘制所有线条。

任何人都可以对此有所了解，还是我应该将此问题提交为 Android Issue ？

提前致谢!

Answer 1

通过将 strokeWidth 设置为 0，您表示 android 以细线宽度(在任何设备上通常为 1px)绘制。如果您将描边宽度设置为 1，则该值将被缩放，即在 ldpi 设备上它将是 0.75 * 1 = 0.75px。所以这条线可能根本不会被渲染。将 ANTI_ALIAS_FLAG 设置为您的绘图设备可能会有所帮助:

Paint pen = new Paint(Paint.ANTI_ALIAS_FLAG);

或者，您可以计算电流密度的笔划宽度:

pen.setStrokeWidth(1 / getResources().getDisplayMetrics().density);