使用角度在画布中绘制箭头答案

【问题标题】：Draw arrow head in canvas using Angle使用角度在画布中绘制箭头
【发布时间】：2020-06-25 12:11:24
【问题描述】：

我尝试使用以下代码，但此代码未按预期工作。这个简单的解决方案其实我很犹豫，但我浪费了很多时间，终于来了。

deltaX = bounds.right - bounds.left;
deltaY = bounds.bottom - bounds.top;

double distance = Math.sqrt(Math.pow(deltaX, 2) + Math.pow(deltaY, 2));
float arrowLength= (float) (distance / 3);
float lineAngle = (float) Math.atan2(deltaY, deltaX);
float angle = (float) Math.toRadians(20);
float sinValue = (float) Math.sin(lineAngle - angle);
point_x_1 = bounds.left - 20 * sinValue;
point_y_1 = (float) (bounds.bottom - 0.5 * arrowLength* Math.cos(lineAngle - angle));
angle = (float) Math.toRadians(60);
sinValue = (float) Math.sin(lineAngle + angle);
point_x_3 = bounds.left + 20 * sinValue;
point_y_3 = (float) (bounds.bottom + arrowLength* Math.cos(lineAngle + angle));

path.moveTo(bounds.right, bounds.top);
path.lineTo(bounds.left, bounds.bottom);
path.moveTo(point_x_1, point_y_1);
path.lineTo(bounds.left, bounds.bottom);
path.lineTo(point_x_3, point_y_3);

注意：我有四个方向，每个方向都会出现在不同的场景中。

enum PathDirection {
    TopLeftToBottomRight,
    TopRightToBottomLeft,
    BottomLeftToTopRight,
    BottomRightToTopLeft
}

上面我为 TopRightToBottomLeft 尝试的代码。

样本输出

图 1： RectF 值：[180.0,560.0][820.0,740.0]

图 2： RectF 值：[240.0,480.0][640.0,980.0]

更新

path.reset();
canvas.save();
canvas.translate(200, 200);
float direction = (float) Math.atan2(400 - 200, 400 - 200);
canvas.rotate(direction);
path.moveTo(0, 0);
float distance = (float) Math.sqrt(200 * 200 + 200 * 200);
path.lineTo(distance, 0);
float x1 = distance - (distance * 20 / 100);
float y1 = -(distance * 15 / 100);
path.moveTo(x1, y1);
path.lineTo(distance, 0);
x1 = distance - (distance * 20 / 100);
y1 = (distance * 15 / 100);
path.lineTo(x1, y1);
canvas.drawPath(path, mPaint);
canvas.restore();

我使用此代码从位置200, 200 到300, 300 画线。但这会从0, 0 到distance 划清界限。

截图

【问题讨论】：

评论不用于扩展讨论；这个对话是moved to chat。

标签： android canvas path

【解决方案1】：

在pskink 的帮助下，我找到了解决方案，示例代码，它用箭头绘制了从200, 200 到400, 400 的线

path.reset();
RectF rectF = new RectF(200, 200, 400, 400);
canvas.save();
canvas.translate(rectF.left, rectF.top);
float direction = (float) Math.atan2(rectF.bottom - rectF.top, rectF.right - rectF.left);
float degree = (float) Math.toDegrees(direction);
canvas.rotate(degree);
canvas.drawColor(Color.parseColor("#E3F2FD"));
path.moveTo(0, 0);
float x = rectF.right - rectF.left;
float y = rectF.bottom - rectF.top;
float distance = (float) Math.sqrt(x * x + y * y);
path.lineTo(distance, 0);
float x1 = distance - (distance * 20 / 100);
float y1 = -(distance * 15 / 100);
path.moveTo(x1, y1);
path.lineTo(distance, 0);
float x2 = distance - (distance * 20 / 100);
float y2 = (distance * 15 / 100);
path.lineTo(x2, y2);
canvas.drawPath(path, mPaint);
canvas.restore();

SC：

注意如果不想旋转画布，可以使用Helder Sepulveda的回答，也能按预期工作。

【讨论】：