Question

我有扩展View类的MyView类。 MyView应绘制填充三角形。我画了一个三角形，但我不能把它填满。这是我的onDraw（）方法：

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    Paint paint = new Paint();

    paint.setColor(android.graphics.Color.BLACK);
    canvas.drawPaint(paint);

    paint.setStrokeWidth(4);
    paint.setColor(android.graphics.Color.RED);
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setAntiAlias(true);

    Point a = new Point(0, 0);
    Point b = new Point(0, 100);
    Point c = new Point(87, 50);

    Path path = new Path();
    path.setFillType(FillType.EVEN_ODD);
    path.moveTo(a.x, a.y);
    path.lineTo(b.x, b.y);
    path.moveTo(b.x, b.y);
    path.lineTo(c.x, c.y);
    path.moveTo(c.x, c.y);
    path.lineTo(a.x, a.y);
    path.close();

    canvas.drawPath(path, paint);
}

这就是我得到的结果：

enter image description here

Answer 1

我找到了答案

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    Paint paint = new Paint();

    paint.setColor(android.graphics.Color.BLACK);
    canvas.drawPaint(paint);

    paint.setStrokeWidth(4);
    paint.setColor(android.graphics.Color.RED);
    paint.setStyle(Paint.Style.FILL_AND_STROKE);
    paint.setAntiAlias(true);

    Point a = new Point(0, 0);
    Point b = new Point(0, 100);
    Point c = new Point(87, 50);

    Path path = new Path();
    path.setFillType(FillType.EVEN_ODD);
    path.lineTo(b.x, b.y);
    path.lineTo(c.x, c.y);
    path.lineTo(a.x, a.y);
    path.close();

    canvas.drawPath(path, paint);
}

Answer 2

这个答案清楚地说明了@Egis在答案中给出的数字来自何处。（这将绘制一个倒置的等边三角形并用kotlin写成）

@PostMapping(value={"/tesinsert"}, consumes=MediaType.APPLICATION_JSON_VALUE)
@ResponseStatus(HttpStatus.OK)
public ResponseEntity<?> insert(@RequestBody KasusEntity user) throws Exception {
    Map result = new HashMap();
    userService.insertTabel(user);
    return new ResponseEntity<>(result, HttpStatus.CREATED);
}

获取高度函数为Pythagoras' Theorem，并且总是会发现等边三角形的高度为其边长的约87％

Gist可以在这里找到，它包含另一个方向的代码

Answer 3

我最近创建了一个小型演示应用程序，可以绘制各种形状，包括三角形，矩形和螺旋形。这是绘制三角形的代码。有关完整的上下文，请参考项目。在此应用中，用户可以将三角形绘制为单个图形，也可以在滚动时将两个三角形的组合绘制成一个三角形。三角形的增长是通过“三角形相似性”原理完成的，每个较小的三角形最后都类似于较大的三角形。

项目：https://github.com/jdgreene2008/android_custom_views

源摘录：https://github.com/jdgreene2008/android_custom_views/blob/master/CustomUiComponents/app/src/main/java/com/jarvis/dragdropresearch/views/FlashShapeView.java

 private void drawTriangleShape(Canvas canvas, RectF bounds,
            TriangleInterpolator triangleInterpolator, Paint paint) {
        paint.setStyle(Paint.Style.FILL);

        float baseInterpolation = triangleInterpolator
                .getInterpolatedValues()[TriangleInterpolator.INTERPOLATION_VALUES_BASE];
        float altitudeInterpolation = triangleInterpolator
                .getInterpolatedValues()[TriangleInterpolator.INTERPOLATION_VALUES_ALTITUDE];

        // *** Construct the Left Triangle ** //

        // Bottom left vertex
        float bottomLeftX = bounds.left;
        float bottomLeftY = bounds.bottom;

        // Bottom right corner
        float bottomRightX = bottomLeftX + baseInterpolation;
        float bottomRightY = bounds.bottom;

        //Top Vertex
        float topX = bottomRightX;
        float topY = bottomRightY - altitudeInterpolation;

        Path leftTriangle = new Path();
        leftTriangle.lineTo(bottomLeftX, bottomLeftY);
        leftTriangle.lineTo(bottomRightX, bottomRightY);
        leftTriangle.lineTo(topX, topY);
        leftTriangle.lineTo(bottomLeftX, bottomLeftY);

        canvas.drawPath(leftTriangle, paint);

        if (triangleInterpolator.isSymmetric()) {
            // *** Construct the Right Triangle ** //

            bottomLeftX = bounds.right - baseInterpolation;
            bottomLeftY = bounds.bottom;

            bottomRightX = bounds.right;
            bottomRightY = bounds.bottom;

            topX = bottomLeftX;
            topY = bottomRightY - altitudeInterpolation;

            Path rightTriangle = new Path();
            rightTriangle.lineTo(bottomLeftX, bottomLeftY);
            rightTriangle.lineTo(bottomRightX, bottomRightY);
            rightTriangle.lineTo(topX, topY);
            rightTriangle.lineTo(bottomLeftX, bottomLeftY);

            canvas.drawPath(rightTriangle, paint);
        }
    }

Answer 4

这些链接非常有用。

Answer 5

我想指出，你永远不应该从onDraw（）初始化一个对象，因为它被多次调用并导致性能问题。

如何在Android Canvas上绘制填充三角形

5 个答案: