在画布上绘制虚线 [英] Draw dash line on a Canvas

问题描述

如何在画布上绘制虚线。我已经尝试过了：

  Paint dashPaint = new Paint 
 dashPaint.setARGB（255，0，0，0）; 
 dashPaint.setStyle（Paint.Style.STROKE）; 
 dashPaint.setPathEffect（new DashPathEffect（new float [] {5，10，15，20}，0））; 
 canvas.drawLine（0，canvas.getHeight（）/ 2，canvas.getWidth（），canvas.getHeight（）/ 2，dashPaint）; 
  

它给了我一条简单的线条。

  canvas.drawLine ，canvas.getHeight（）/ 2，canvas.getWidth（），canvas.getHeight（）/ 2，dashPaint）
  

$ b b

这将画一行

解决方案

 路径mPath; 
 mPath = new Path（）; 
 mPath.moveTo（0，h / 2）; 
 mPath.quadTo（w / 2，h / 2，w，h / 2）; 
 h和w是屏幕的高度和宽度
 paint mPaint = new Paint（）; 
 mPaint.setARGB（255，0，0，0）; 
 mPaint.setStyle（Paint.Style.STROKE）; 
 mPaint.setPathEffect（new DashPathEffect（new float [] {5，10，15，20}，0））; 
  

在onDraw（）

  canvas.drawPath（mPath，mPaint） 
  

快照

我有背景和虚线。

示例

  public class FingerPaintActivity extends Activity {
 MyView mv; 
 
 @Override 
 protected void onCreate（Bundle savedInstanceState）{
 super.onCreate（savedInstanceState）; 
 mv = new MyView（this）; 
 setContentView（mv）; 
 mPaint = new Paint（）; 
 mPaint.setAntiAlias（true）; 
 mPaint.setDither（true）; 
 mPaint.setColor（0xffFF0000）; 
 mPaint.setARGB（255，0，0，0）; 
 mPaint.setStyle（Paint.Style.STROKE）; 
 mPaint.setPathEffect（new DashPathEffect（new float [] {10，40，}，0））; 
 mPaint.setStrokeWidth（12）; 
} 
 
 private Paint mPaint; 
 
 public class MyView extends View {
 private Bitmap mBitmap; 
 private Canvas mCanvas; 
 private Path mPath; 
 private Paint mBitmapPaint; 
上下文上下文; 
 
 public MyView（Context c）{
 super（c）; 
 context = c; 
 mPath = new Path（）; 
 mBitmapPaint = new Paint（Paint.DITHER_FLAG）; 
} 
 
 @Override 
 protected void onSizeChanged（int w，int h，int oldw，int oldh）{
 super.onSizeChanged（w，h，oldw， oldh）; 
 mBitmap = Bitmap.createBitmap（w，h，Bitmap.Config.ARGB_8888）; 
 mCanvas = new Canvas（mBitmap）; 
 mPath.moveTo（0，h / 2）; 
 mPath.quadTo（w / 2，h / 2，w，h / 2）; 
} 
 
 @Override 
 protected void onDraw（Canvas canvas）{
 super.onDraw（canvas）; 
 canvas.drawBitmap（mBitmap，0，0，mBitmapPaint）; 
 canvas.drawPath（mPath，mPaint） 
} 
} 
} 
  

How can i draw dash line on a canvas. I already tried this:

Paint dashPaint = new Paint();
dashPaint.setARGB(255, 0, 0, 0);
dashPaint.setStyle(Paint.Style.STROKE);
dashPaint.setPathEffect(new DashPathEffect(new float[]{5, 10, 15, 20}, 0));
canvas.drawLine(0, canvas.getHeight() / 2, canvas.getWidth(), canvas.getHeight() / 2, dashPaint);

And it gave me not dash line but a simple one.

解决方案

You are drawing a line

 canvas.drawLine(0, canvas.getHeight() / 2, canvas.getWidth(), canvas.getHeight() / 2, dashPaint) 

This will draw a line

Solution

       private Path    mPath;
       mPath = new Path();
       mPath.moveTo(0, h / 2);
       mPath.quadTo(w/2, h/2, w, h/2); 
       h and w are height and width of the screen  
       Paint mPaint = new Paint();
       mPaint.setARGB(255, 0, 0, 0);
       mPaint.setStyle(Paint.Style.STROKE);
       mPaint.setPathEffect(new DashPathEffect(new float[]{5, 10, 15, 20}, 0));

In onDraw()

       canvas.drawPath(mPath, mPaint); 

Snap shot

I have background and dashed line drew over it.

Example

public class FingerPaintActivity extends Activity {
    MyView mv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        mv = new MyView(this);
        setContentView(mv);
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setDither(true);
        mPaint.setColor(0xFFFF0000);
        mPaint.setARGB(255, 0, 0, 0);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setPathEffect(new DashPathEffect(new float[]{10, 40,}, 0));
        mPaint.setStrokeWidth(12);
    }

    private Paint mPaint;

    public class MyView extends View {
        private Bitmap mBitmap;
        private Canvas mCanvas;
        private Path mPath;
        private Paint mBitmapPaint;
        Context context;

        public MyView(Context c) {
            super(c);
            context = c;
            mPath = new Path();
            mBitmapPaint = new Paint(Paint.DITHER_FLAG);
        }

        @Override
        protected void onSizeChanged(int w, int h, int oldw, int oldh) {
            super.onSizeChanged(w, h, oldw, oldh);
            mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
            mCanvas = new Canvas(mBitmap);
            mPath.moveTo(0, h / 2);
            mPath.quadTo(w / 2, h / 2, w, h / 2);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            canvas.drawBitmap(mBitmap, 0, 0, mBitmapPaint);
            canvas.drawPath(mPath, mPaint);
        }
    }
}

Modify the above according to your needs.

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