Android 貝塞爾曲線 折線圖

1、貝塞爾曲線：http://baike.baidu.com/view/60154.htm，在這里理解什么是貝塞爾曲線

2、直接上圖：

 

3、100多行代碼就可以畫出貝塞爾曲線，直接上代碼

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();
		// 添加第一個點(118.0, 294.0),
		points.add((float) 118.0);// X軸
		points.add((float) 294.0);// Y軸
		// 添加第二個點
		points.add((float) 206.0);
		points.add((float) 294.0);
		// 添加第三個點
		points.add((float) 294.0);
		points.add((float) 118.0);
		// 添加第四個點
		points.add((float) 382.0);
		points.add((float) 206.0);

		points.add((float) 470.0);
		points.add((float) 118.0);

		// 通過畫折線和貝塞爾曲線可以知道，點得位置是不一樣的。
		// 畫折線
		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);

		// 貝塞爾曲線
		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);
		// 設置第一個點開始
		p.moveTo(xp, yp);
		int length = points.size();
		// 設置第一個控制點33%的距離
		float mFirstMultiplier = 0.3f;
		// 設置第二個控制點為66%的距離
		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;
			// 設置第一個控制點
			calc(points, p1, b, nextIndex, mSecondMultiplier);
			// 設置第二個控制點
			p2.setX(points.get(nextIndex));
			p2.setY(points.get(nextIndex + 1));
			// 設置第二個控制點
			calc(points, p3, nextIndex, nextNextIndex, mFirstMultiplier);
			// 最后一個點就是賽貝爾曲線上的點
			p.cubicTo(p1.getX(), p1.getY(), p2.getX(), p2.getY(), p3.getX(), p3.getY());
			// 畫點
		}
		PathMeasure mPathMeasure;
		 mPathMeasure = new PathMeasure(p, false);
		// 設置為線
		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();
	}

	/**
	 * 計算控制點
	 * @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));
	}
	
	/**
	 * 重新設置點的位置，為曲線上的位置
	 * @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;
          }
        }
	}
}

4、定義點的類

package com.example.bezier;

import java.io.Serializable;

/**
 * 點的類，來源於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;
  }
}

5、下載地址：http://files.cnblogs.com/liqw/Bezier.zip

本文來源於：http://www.cnblogs.com/liqw/p/3631137.html

有問題，請提問，大家一起研究！