package com.example.bezier;

import java.util.ArrayList;

import java.util.List;

import android.app.Activity;

import android.content.Context;

import android.graphics.Canvas;

import android.graphics.Color;

import android.graphics.Paint;

import android.graphics.PathMeasure;

import android.graphics.Paint.Style;

import android.graphics.Path;

import android.os.Bundle;

import android.view.View;

import android.view.Window;

import android.view.WindowManager;

public class MainActivity extends Activity {

	@Override

	public void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		requestWindowFeature(Window.FEATURE_NO_TITLE);

		getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);

		setContentView(new BezierView(this));

	}

}

class BezierView extends View {

	/**

	 *

	 * @author liqiongwei

	 * @param context

	 *

	 */

	public BezierView(Context context) {

		super(context);

	}

	protected void onDraw(Canvas canvas) {

		List<Float> points = new ArrayList<Float>();

		Paint paint = new Paint();

		// 添加第一个点(118.0, 294.0),

		points.add((float) 118.0);// X轴

		points.add((float) 294.0);// Y轴

		// 添加第二个点

		points.add((float) 206.0);

		points.add((float) 294.0);

		// 添加第三个点

		points.add((float) 294.0);

		points.add((float) 118.0);

		// 添加第四个点

		points.add((float) 382.0);

		points.add((float) 206.0);

		points.add((float) 470.0);

		points.add((float) 118.0);

		// 通过画折线和贝塞尔曲线可以知道，点得位置是不一样的。

		// 画折线

		for (int i = 0; i < points.size() - 2; i = i + 2) {

			canvas.drawLine(points.get(i), points.get(i + 1), points.get(i + 2), points.get(i + 3), paint);

			canvas.drawCircle(points.get(i), points.get(i + 1), 3, paint);

		}

		canvas.drawCircle(points.get(points.size() - 2), points.get(points.size() - 1), 3, paint);

		// 贝塞尔曲线

		paint.setColor(Color.BLUE);

		Path p = new Path();

		Point p1 = new Point();

		Point p2 = new Point();

		Point p3 = new Point();

		float xp = points.get(0);

		float yp = points.get(1);

		// 设置第一个点开始

		p.moveTo(xp, yp);

		int length = points.size();

		// 设置第一个控制点33%的距离

		float mFirstMultiplier = 0.3f;

		// 设置第二个控制点为66%的距离

		float mSecondMultiplier = 1 - mFirstMultiplier;

		for (int b = 0; b < length; b += 2) {

			int nextIndex = b + 2 < length ? b + 2 : b;

			int nextNextIndex = b + 4 < length ? b + 4 : nextIndex;

			// 设置第一个控制点

			calc(points, p1, b, nextIndex, mSecondMultiplier);

			// 设置第二个控制点

			p2.setX(points.get(nextIndex));

			p2.setY(points.get(nextIndex + 1));

			// 设置第二个控制点

			calc(points, p3, nextIndex, nextNextIndex, mFirstMultiplier);

			// 最后一个点就是赛贝尔曲线上的点

			p.cubicTo(p1.getX(), p1.getY(), p2.getX(), p2.getY(), p3.getX(), p3.getY());

			// 画点

		}

		PathMeasure mPathMeasure;

		 mPathMeasure = new PathMeasure(p, false);

		// 设置为线

		paint.setStyle(Style.STROKE);

		reSetPointWithPath(mPathMeasure, points);

		for (int k = 0; k < points.size()-1; k +=2) {

			canvas.drawCircle(points.get(k), points.get(k+1), 5, paint);

		}

		canvas.drawPath(p, paint);

		invalidate();

	}

	/**

	 * 计算控制点

	 * @param points

	 * @param result

	 * @param index1

	 * @param index2

	 * @param multiplier

	 */

	private void calc(List<Float> points, Point result, int index1, int index2, final float multiplier) {

		float p1x = points.get(index1);

		float p1y = points.get(index1 + 1);

		float p2x = points.get(index2);

		float p2y = points.get(index2 + 1);

		float diffX = p2x - p1x;

		float diffY = p2y - p1y;

		result.setX(p1x + (diffX * multiplier));

		result.setY(p1y + (diffY * multiplier));

	}

	/**

	 * 重新设置点的位置，为曲线上的位置

	 * @param mPathMeasure

	 * @param pointsList

	 */

	public void reSetPointWithPath(PathMeasure mPathMeasure, List<Float> pointsList){

        int length = (int) mPathMeasure.getLength();

        int pointsLength = pointsList.size();

        float[] coords = new float[2];

        for (int b = 0; b < length; b++) {

          mPathMeasure.getPosTan(b, coords, null);

          double prevDiff = Double.MAX_VALUE;

          boolean ok = true;

          for (int j = 0; j < pointsLength && ok; j += 2) {

            double diff = Math.abs(pointsList.get(j) - coords[0]);

            if (diff < 1) {

              pointsList.set(j + 1, coords[1]);

              prevDiff = diff;

            }

            ok = prevDiff > diff;

          }

        }

	}

}

package com.example.bezier;

import java.io.Serializable;

/**

 * 点的类，来源于Achartengine

 */

public final class Point implements Serializable {

  private float mX;

  private float mY;

  public Point() {

  }

  public Point(float x, float y) {

    mX = x;

    mY = y;

  }

  public float getX() {

    return mX;

  }

  public float getY() {

    return mY;

  }

  public void setX(float x) {

    mX = x;

  }

  public void setY(float y) {

    mY = y;

  }

}