add bezier3

Author: linsir6

Android自定义View/三阶贝塞尔曲线.md

@@ -0,0 +1,126 @@
+# 三阶贝塞尔曲线
+
+如果您对贝塞尔曲线还不是很了解的话，可以看一下[二阶贝塞尔曲线](https://github.com/linsir6/AndroidNote/blob/master/Android%E8%87%AA%E5%AE%9A%E4%B9%89View/%E4%BA%8C%E9%98%B6%E8%B4%9D%E5%A1%9E%E5%B0%94%E6%9B%B2%E7%BA%BF.md)，下面我们看一下三阶曲线的效果图：
+
+
+
+![bezier3](https://ws4.sinaimg.cn/large/006tKfTcly1fgwiac2u2qg308u0gm7nz.gif)
+
+
+
+
+
+实现的思路和二阶的几乎一样，只是换了个函数，加了个控制点。
+
+
+
+代码：
+
+
+
+```java
+public class Bezier3 extends View {
+
+
+    private Paint mPaint;
+    private int centerX, centerY;
+
+    private PointF start, end, control1, control2;
+    private boolean mode = true;
+
+    public Bezier3(Context context) {
+        this(context, null);
+
+    }
+
+    public Bezier3(Context context, AttributeSet attrs) {
+        super(context, attrs);
+
+        mPaint = new Paint();
+        mPaint.setColor(Color.BLACK);
+        mPaint.setStrokeWidth(8);
+        mPaint.setStyle(Paint.Style.STROKE);
+        mPaint.setTextSize(60);
+
+        start = new PointF(0, 0);
+        end = new PointF(0, 0);
+        control1 = new PointF(0, 0);
+        control2 = new PointF(0, 0);
+    }
+
+    public void setMode(boolean mode) {
+        this.mode = mode;
+    }
+
+    @Override
+    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
+        super.onSizeChanged(w, h, oldw, oldh);
+        centerX = w / 2;
+        centerY = h / 2;
+
+        // 初始化数据点和控制点的位置
+        start.x = centerX - 200;
+        start.y = centerY;
+        end.x = centerX + 200;
+        end.y = centerY;
+        control1.x = centerX;
+        control1.y = centerY - 100;
+        control2.x = centerX;
+        control2.y = centerY - 100;
+
+    }
+
+    @Override
+    public boolean onTouchEvent(MotionEvent event) {
+        // 根据触摸位置更新控制点，并提示重绘
+        if (mode) {
+            control1.x = event.getX();
+            control1.y = event.getY();
+        } else {
+            control2.x = event.getX();
+            control2.y = event.getY();
+        }
+        invalidate();
+        return true;
+    }
+
+    @Override
+    protected void onDraw(Canvas canvas) {
+        super.onDraw(canvas);
+        //drawCoordinateSystem(canvas);
+
+        // 绘制数据点和控制点
+        mPaint.setColor(Color.GRAY);
+        mPaint.setStrokeWidth(20);
+        canvas.drawPoint(start.x, start.y, mPaint);
+        canvas.drawPoint(end.x, end.y, mPaint);
+        canvas.drawPoint(control1.x, control1.y, mPaint);
+        canvas.drawPoint(control2.x, control2.y, mPaint);
+
+        // 绘制辅助线
+        mPaint.setStrokeWidth(4);
+        canvas.drawLine(start.x, start.y, control1.x, control1.y, mPaint);
+        canvas.drawLine(control1.x, control1.y, control2.x, control2.y, mPaint);
+        canvas.drawLine(control2.x, control2.y, end.x, end.y, mPaint);
+
+        // 绘制贝塞尔曲线
+        mPaint.setColor(Color.RED);
+        mPaint.setStrokeWidth(8);
+
+        Path path = new Path();
+
+        path.moveTo(start.x, start.y);
+        path.cubicTo(control1.x, control1.y, control2.x, control2.y, end.x, end.y);
+
+        canvas.drawPath(path, mPaint);
+    }
+
+
+}
+
+```
+
+
+[代码地址](https://github.com/linsir6/mCustomView/tree/master/Bezier3)：https://github.com/linsir6/mCustomView/tree/master/Bezier3
+
+

README.md

@@ -43,6 +43,7 @@ Android-Note里面记录了有关Android的常用基础知识、面试中经常
 - [PieView](/Android自定义View/自定义View——PieView.md)
 - [SlideslipListView](/Android自定义View/自定义view——sideslipListView.md)
 - [二阶贝塞尔曲线](/Android自定义View/二阶贝塞尔曲线.md)
+- [三阶贝塞尔曲线](/Android自定义View/三阶贝塞尔曲线.md)
 
 
 ### 面试题