在画布上绘图时自定义路径线样式

Question

我目前正在处理地图叠加，它突出显示沿指定点的路线，我需要实现某些线条样式（类似于屏幕截图）

我正在尝试做的是用透明线和两侧的黑色笔划线来突出显示路线

到目前为止，使用不同的填充样式和绘画设置并没有让我找到任何解决方案。

有人知道我需要寻找什么方向吗？

目前我只画了实线，但这不是我想要的：

油漆设置：

mPaint.setStyle(Paint.Style.STROKE);
mPaint.setColor(COLOR_DEFAULT);
mPaint.setPathEffect(new CornerPathEffect(10));
mPaint.setStrokeWidth(6);
mPaint.setAntiAlias(true);

绘图程序

canvas.drawPath(mPath, mPaint);

Answer 1

我使用 PathDashPathEffect 获得了非常好的结果，它使用了一个“破折号”，它是两个非常薄的矩形和 MORPH 样式选项。在此处查看最后一行和第三行：

这是通过修改来自 SDK 的 ApiDemos 中的 PathEffects 示例绘制的：

package com.example.android.apis.graphics;

import android.content.Context;
import android.graphics.*;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;

public class PathEffects extends GraphicsActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new SampleView(this));
    }

    private static class SampleView extends View {
        private Paint mPaint;
        private Path mPath;
        private PathEffect[] mEffects;
        private int[] mColors;
        private float mPhase = 3;

        private static void makeEffects(PathEffect[] e, float phase) {
            e[0] = null;     // no effect
            e[1] = new CornerPathEffect(10);
            e[2] = new DashPathEffect(new float[] {10, 5, 5, 5}, phase);
            e[3] = new PathDashPathEffect(makePathDash(), 12, phase,
                                          PathDashPathEffect.Style.MORPH);
            e[4] = new ComposePathEffect(e[2], e[1]);
            e[5] = new ComposePathEffect(e[3], e[1]);
        }

        public SampleView(Context context) {
            super(context);
            setFocusable(true);
            setFocusableInTouchMode(true);

            mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
            mPaint.setStyle(Paint.Style.STROKE);
            mPaint.setStrokeWidth(6);

            mPath = makeFollowPath();

            mEffects = new PathEffect[6];

            mColors = new int[] { Color.BLACK, Color.RED, Color.BLUE,
                                  Color.GREEN, Color.MAGENTA, Color.BLACK
                                };
        }

        @Override protected void onDraw(Canvas canvas) {
            canvas.drawColor(Color.WHITE);

            RectF bounds = new RectF();
            mPath.computeBounds(bounds, false);
            canvas.translate(10 - bounds.left, 10 - bounds.top);

            makeEffects(mEffects, mPhase);
            invalidate();

            for (int i = 0; i < mEffects.length; i++) {
                mPaint.setPathEffect(mEffects[i]);
                mPaint.setColor(mColors[i]);
                canvas.drawPath(mPath, mPaint);
                canvas.translate(0, 28);
            }
        }

        @Override public boolean onKeyDown(int keyCode, KeyEvent event) {
            switch (keyCode) {
                case KeyEvent.KEYCODE_DPAD_CENTER:
                    mPath = makeFollowPath();
                    return true;
            }
            return super.onKeyDown(keyCode, event);
        }

        private static Path makeFollowPath() {
            Path p = new Path();
            p.moveTo(0, 0);
            for (int i = 1; i <= 15; i++) {
                p.lineTo(i*20, (float)Math.random() * 35);
            }
            return p;
        }

        private static Path makePathDash() {
            Path p = new Path();
            p.moveTo(-6, 4);
            p.lineTo(6,4);
            p.lineTo(6,3);
            p.lineTo(-6, 3);
            p.close();
            p.moveTo(-6, -4);
            p.lineTo(6,-4);
            p.lineTo(6,-3);
            p.lineTo(-6, -3);
            return p;
        }
    }
}

Answer 2

我设法为我的问题找到了更好的解决方案。 所以我摆脱了我的自定义路径效果并开始使用通常的笔触。所以我基本上画了2次我的路径：首先我画黑线，然后我画更细的透明线以清除之前黑线的中心。

这种方法的唯一技巧是我需要在单独的位图中绘制我的路径（使用临时画布），并且当路径位图准备好时 - 将其渲染到主画布。

希望这对其他人有帮助

@Override
public void draw(Canvas canvas, final MapView mapView, boolean shadow)
{
    //Generate new bitmap if old bitmap doesn't equal to the screen size (f.i. when screen orientation changes)
    if(pathBitmap == null || pathBitmap.isRecycled() || pathBitmap.getWidth()!=canvas.getWidth() || pathBitmap.getHeight()!=canvas.getHeight())
    {
        if(pathBitmap != null)
        {        
            pathBitmap.recycle();
        }
        pathBitmap = Bitmap.createBitmap(canvas.getWidth(), canvas.getHeight(), Config.ARGB_8888);
        tempCanvas.setBitmap(pathBitmap);
    }

    //Render routes to the temporary bitmap
    renderPathBitmap();

    //Render temporary bitmap onto main canvas
    canvas.drawBitmap(pathBitmap, 0, 0, null);
    }
}

private void renderPath(Path path, Canvas canvas)
{
    routePaint.setStrokeWidth(ROUTE_LINE_WIDTH);
    routePaint.setColor(OUTER_COLOR);
    routePaint.setXfermode(null);

    canvas.drawPath(path, routePaint); //render outer line

    routePaint.setStrokeWidth(ROUTE_LINE_WIDTH/1.7f);
    routePaint.setColor(Color.TRANSPARENT);
    routePaint.setXfermode(new PorterDuffXfermode(Mode.CLEAR));

    canvas.drawPath(path, routePaint); //render inner line
}

所以结果看起来像：