RelativeLayout container = findViewById(R.id.download_container);

? ? DisplayMetrics metrics = new DisplayMetrics();
? ? getWindowManager().getDefaultDisplay().getMetrics(metrics);
? ? deviceWidth = metrics.widthPixels;
? ? deviceHeight = metrics.heightPixels;

? ? Circle circle = new Circle(this, deviceWidth / 2, deviceHeight / 2, deviceWidth / 8);
? ? Line line = new Line(this, deviceWidth / 2, deviceHeight / 2, deviceWidth / 8);
? ? container.addView(line);

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PointF;
import android.view.View;

public class Line extends View {

? ? private Paint mPaint;
? ? private PointF startPointF;
? ? private PointF endPointF;
? ? private PointF controlPointF1, controlPointF2;

? ? private PointF startPointF2;
? ? private PointF endPointF2;
? ? private PointF controlPointF3, controlPointF4;

? ? public Line(Context context, float x, float y, float radius) {
? ? ? ? super(context);
? ? ? ? double d = (2 * Math.sqrt(2) - 1);
? ? ? ? this.startPointF = new PointF(x, y - radius);
? ? ? ? this.endPointF = new PointF(x, y + radius / 10);
? ? ? ? this.controlPointF1 = new PointF(x, (float) (y - d * radius));
? ? ? ? this.controlPointF2 = new PointF((float) (x + d * radius), (float) (y - d * radius));

? ? ? ? this.startPointF2 = new PointF(x, y - radius);
? ? ? ? this.endPointF2 = new PointF(x, y + radius / 10);
? ? ? ? this.controlPointF3 = new PointF(x, (float) (y - d * radius));
? ? ? ? this.controlPointF4 = new PointF((float) (x - d * radius), (float) (y - d * radius));

? ? ? ? this.mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
? ? ? ? this.mPaint.setColor(Color.WHITE);
? ? }

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

? ? ? ? //繪制貝塞爾曲線
? ? ? ? Path path = new Path();

? ? ? ? path.moveTo(startPointF.x, startPointF.y);
? ? ? ? path.cubicTo(controlPointF1.x, controlPointF1.y, controlPointF2.x, controlPointF2.y, endPointF.x, endPointF.y);
? ? ? ? canvas.drawPath(path, mPaint);

? ? ? ? path.moveTo(startPointF2.x, startPointF2.y);
? ? ? ? path.cubicTo(controlPointF3.x, controlPointF3.y, controlPointF4.x, controlPointF4.y, endPointF2.x, endPointF2.y);
? ? ? ? canvas.drawPath(path, mPaint);
? ? }
}