public class MyCanvas extends View{
private Canvas myCanvas;
private Paint myPaint=new Paint();
public MyCanvas(Context context) {
super(context);
// TODO Auto-generated constructor stub
}
public MyCanvas(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
}
public MyCanvas(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
this.myCanvas=canvas;
drawAL(0, 0, 100, 100);
}
/**
* 设置画笔默认样式
*/
public void setPaintDefaultStyle(){
myPaint.setAntiAlias(true);
myPaint.setColor(Color.RED);
myPaint.setStyle(Paint.Style.STROKE);
myPaint.setStrokeWidth(3);
}
/**
* 画圆
* @param x x坐标
* @param y y坐标
* @param radius 圆的半径
*/
public void drawCircle(float x,float y,float radius){
myCanvas.drawCircle(x, y, radius, myPaint);
invalidate();
}
/**
* 画一条直线
* @param fromX 起点x坐标
* @param fromY 起点Y坐标
* @param toX 终点X坐标
* @param toY 终点Y坐标
*/
public void drawLine(float fromX,float fromY,float toX,float toY){
Path linePath=new Path();
linePath.moveTo(fromX, fromY);
linePath.lineTo(toX, toY);
linePath.close();
myCanvas.drawPath(linePath, myPaint);
invalidate();
}
/**
* 画箭头
* @param sx
* @param sy
* @param ex
* @param ey
*/
public void drawAL(int sx, int sy, int ex, int ey)
{
double H = 8; // 箭头高度
double L = 3.5; // 底边的一半
int x3 = 0;
int y3 = 0;
int x4 = 0;
int y4 = 0;
double awrad = Math.atan(L / H); // 箭头角度
double arraow_len = Math.sqrt(L * L + H * H); // 箭头的长度
double[] arrXY_1 = rotateVec(ex - sx, ey - sy, awrad, true, arraow_len);
double[] arrXY_2 = rotateVec(ex - sx, ey - sy, -awrad, true, arraow_len);
double x_3 = ex - arrXY_1[0]; // (x3,y3)是第一端点
double y_3 = ey - arrXY_1[1];
double x_4 = ex - arrXY_2[0]; // (x4,y4)是第二端点
double y_4 = ey - arrXY_2[1];
Double X3 = new Double(x_3);
x3 = X3.intValue();
Double Y3 = new Double(y_3);
y3 = Y3.intValue();
Double X4 = new Double(x_4);
x4 = X4.intValue();
Double Y4 = new Double(y_4);
y4 = Y4.intValue();
// 画线
myCanvas.drawLine(sx, sy, ex, ey,myPaint);
Path triangle = new Path();
triangle.moveTo(ex, ey);
triangle.lineTo(x3, y3);
triangle.lineTo(x4, y4);
triangle.close();
myCanvas.drawPath(triangle,myPaint);
}
// 计算
public double[] rotateVec(int px, int py, double ang, boolean isChLen, double newLen)
{
double mathstr[] = new double[2];
// 矢量旋转函数，参数含义分别是x分量、y分量、旋转角、是否改变长度、新长度
double vx = px * Math.cos(ang) - py * Math.sin(ang);
double vy = px * Math.sin(ang) + py * Math.cos(ang);
if (isChLen) {
double d = Math.sqrt(vx * vx + vy * vy);
vx = vx / d * newLen;
vy = vy / d * newLen;
mathstr[0] = vx;
mathstr[1] = vy;
}
return mathstr;
}
}
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作者：大雀儿飞飞
来源：****
原文：https://blog.****.net/yxz329130952/article/details/8084412
版权声明：本文为博主原创文章，转载请附上博文链接！