如何在Android中绘制填充多边形？
答案 0 :(得分：105)
Android没有类似Java的方便drawPolygon(x_array, y_array, numberofpoints)操作。您必须逐步制作Path对象。例如，要为3D地牢墙制作填充的梯形形状，您可以将所有点放在x和y数组中，然后编码如下：
Paint wallpaint = new Paint();
wallpaint.setColor(Color.GRAY);
wallpaint.setStyle(Style.FILL);
Path wallpath = new Path();
wallpath.reset(); // only needed when reusing this path for a new build
wallpath.moveTo(x[0], y[0]); // used for first point
wallpath.lineTo(x[1], y[1]);
wallpath.lineTo(x[2], y[2]);
wallpath.lineTo(x[3], y[3]);
wallpath.lineTo(x[0], y[0]); // there is a setLastPoint action but i found it not to work as expected
canvas.drawPath(wallpath, wallpaint);
要为某个深度添加常量线性渐变，您可以按如下方式编码。注意y [0]使用两次以使梯度保持水平：
wallPaint.reset(); // precaution when resusing Paint object, here shader replaces solid GRAY anyway
wallPaint.setShader(new LinearGradient(x[0], y[0], x[1], y[0], Color.GRAY, Color.DKGRAY,TileMode.CLAMP));
canvas.drawPath(wallpath, wallpaint);
答案 1 :(得分：41)
您需要将绘画对象设置为FILL
Paint paint = new Paint();
paint.setStyle(Paint.Style.FILL);
然后你可以画任何你想要的东西，它就会被填满。
canvas.drawCircle(20, 20, 15, paint);
canvas.drawRectangle(60, 20, 15, paint);
等
对于更复杂的形状，您需要使用PATH object。
答案 2 :(得分：12)
我喜欢分三步完成......
步骤1.创建一个尖类; - ）
/**
* Simple point
*/
private class Point {
public float x = 0;
public float y = 0;
public Point(float x, float y) {
this.x = x;
this.y = y;
}
}
步骤2.添加绘图方法/功能
/**
* Draw polygon
*
* @param canvas The canvas to draw on
* @param color Integer representing a fill color (see http://developer.android.com/reference/android/graphics/Color.html)
* @param points Polygon corner points
*/
private void drawPoly(Canvas canvas, int color, Point[] points) {
// line at minimum...
if (points.length < 2) {
return;
}
// paint
Paint polyPaint = new Paint();
polyPaint.setColor(color);
polyPaint.setStyle(Style.FILL);
// path
Path polyPath = new Path();
polyPath.moveTo(points[0].x, points[0].y);
int i, len;
len = points.length;
for (i = 0; i < len; i++) {
polyPath.lineTo(points[i].x, points[i].y);
}
polyPath.lineTo(points[0].x, points[0].y);
// draw
canvas.drawPath(polyPath, polyPaint);
}
第3步。绘制
drawPoly(canvas, 0xFF5555ee,
new Point[]{
new Point(10, 10),
new Point(15, 10),
new Point(15, 20)
});
是的，你可以更有效地做到这一点，但可能没那么可读： - ）。
答案 3 :(得分：4)
使用x边和自定义半径绘制多边形：
private void drawPolygon(Canvas mCanvas, float x, float y, float radius, float sides, float startAngle, boolean anticlockwise, Paint paint) {
if (sides < 3) { return; }
float a = ((float) Math.PI *2) / sides * (anticlockwise ? -1 : 1);
mCanvas.save();
mCanvas.translate(x, y);
mCanvas.rotate(startAngle);
Path path = new Path();
path.moveTo(radius, 0);
for(int i = 1; i < sides; i++) {
path.lineTo(radius * (float) Math.cos(a * i), radius * (float) Math.sin(a * i));
}
path.close();
mCanvas.drawPath(path, paint);
mCanvas.restore();
}
答案 4 :(得分：2)
BTW - 我发现一旦你开始创建你的路径，路径中的任何moveTo命令都意味着形状没有填充。
当您考虑它时，Android / Java会使形状不填充，因为moveTo将代表多边形中断。
但是我看过一些像How to draw a filled triangle in android canvas?
这样的教程在每行之后都有moveTo。尽管这可能会导致多边形不间断，但Android假定moveTo表示多边形中断。
答案 5 :(得分：1)
老问题，但对于任何发现此问题的人来说都是一招。如果包含具有所需多边形的字体作为字形，则可以使用drawText函数绘制多边形。
缺点是你必须提前知道你需要什么样的形状。如果您事先知道可以包含一个漂亮的形状库，那么它就是好处。此代码假定您在项目的assets / fonts文件夹中有一个名为shapes的字体。
TypeFace shapesTypeFace = Typeface.createFromAsset(getAssets(), "fonts/shapes.ttf");
Paint stopSignPaint = new Paint();
stopSignPaint.setColor(Color.RED);
//set anti-aliasing so it looks nice
stopSignPaint.setAntiAlias(true);
stopSignPaint.setTextSize(200);
stopSignPaint.setTypeface(shapesTypeFace);
//will show up as a box or question mark since
//the current display font doesn't have this glyph.
//open the shapes font in a tool like Character Map
//to copy and paste the glyph into your IDE
//saving it as a variable makes it much easier to work with
String hexagonGlyph = ""
String triangleGlyph = ""
....whatever code you got...
//arguments: text, x coordinate, y coordinate, paint
canvas.drawText(hexagonGlyph, 200, 100, stopSignPaint);
//make it into a go sign
stopSignPaint.setColor(Color.Green);
canvas.drawText(hexagonGlyph, 200, 100, stopSignPaint);
//make a tiny one
stopSignPaint.setTextSize(20);
stopSignPaint.setColor(Color.RED);
canvas.drawText(hexagonGlyph, 200, 100, stopSignPaint);
//make a triangle
canvas.drawText(triangleGlyph, 200, 100, stopSignPaint);
答案 6 :(得分：0)
试试这个，或see the full demo
Paint paint = new Paint();
paint.setColor(Color.parseColor("#BAB399"));
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
答案 7 :(得分：0)
此类可用于绘制任何种类的多边形。只需在onDraw（）方法中调用drawPolygonPath()。
class PolygonView : View {
constructor(context: Context?) : super(context) {
init()
}
constructor(context: Context?, attrs: AttributeSet?) : super(context, attrs) {
init()
}
constructor(context: Context?, attrs: AttributeSet?, defStyleAttr: Int) : super(
context,
attrs,
defStyleAttr
) {
init()
}
private lateinit var paint: Paint
private fun init() {
paint = Paint().apply {
color = Color.RED
isAntiAlias = true
style = Paint.Style.FILL
strokeWidth = 10f
}
}
override fun onDraw(canvas: Canvas) {
canvas.drawPath(drawPolygonPath(8, 150f), paint)
canvas.drawPath(drawPolygonPath(5, 120f), paint)
}
/**
* @param sides number of polygon sides
* @param radius side length.
* @param cx drawing x start point.
* @param cy drawing y start point.
* */
private fun drawPolygonPath(
sides: Int,
radius: Float,
cx: Float = radius,
cy: Float = radius
): Path {
val path = Path()
val x0 = cx + (radius * cos(0.0).toFloat())
val y0 = cy + (radius * sin(0.0).toFloat())
//2.0 * Math.PI = 2π, which means one circle(360)
//The polygon total angles of the sides must equal 360 degree.
val angle = 2 * Math.PI / sides
path.moveTo(x0, y0)
for (s in 1 until sides) {
path.lineTo(
cx + (radius * cos(angle * s)).toFloat(),
cy + (radius * sin(angle * s)).toFloat()
)
}
path.close()
return path
}
}