如何画点之间的线，拉这些点？(How to draw a lines between points

2019-06-25 02:15发布

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我想提请在视图点之间的线，再拉这些点高达期望的位置，甚至形状会发生变化。

我知道如何绘制两个点之间的线canvas.drawLine(10, 10, 90, 10, paint); 通过使用此我可以绘制点之间的线。

EDIT ：我在这里附上图像清晰的解释，从保罗的回答，现在我能够绘制线条点之间，仍然有拉动点的问题...

Answer 1:

下面是它是如何做。 假设你有你的观点，让这些全球性的： 

PointF topLeft = new PointF(10,10);
PointF topRight = new PointF(90,10);
PointF bottomLeft = new PointF(10,90);
PointF bottomRight = new PointF(90,90);

什么，你需要做的是让每个点周围一RectF。 在该RectF越大，该点的更大的触摸面积。 

float sizeOfRect = 5f;
RectF topLeftTouchArea = new RectF(topLeft.x - sizeOfRect, topLeft.y - sizeOfRect, topLeft.x + sizeOfRect, topLeft.y + sizeOfRect);
//Do this for the other points too

定义一些全局变量，以跟踪哪些用户在onTouch做。 一个int是被触碰的角落​​里，和其他四是角落标识符。 

private final int NONE = -1, TOUCH_TOP_LEFT = 0, TOUCH_TOP_RIGHT = 1, TOUCH_BOT_LEFT = 2, TOUCH_BOT_RIGHT = 3;
int currentTouch = NONE;

现在，在onTouch事件，您可以检查哪些点你的用户像这样感人的： 

@Override
public boolean onTouchEvent(MotionEvent event) {
    switch (event.getAction()) {
    //The user just put their finger down.
    //We check to see which corner the user is touching
    //And set our global, currentTouch, to the appropriate constant.
    case MotionEvent.ACTION_DOWN:
        if (topLeftTouchArea.contains(event.getX(), event.getY()) {
            currentTouch = TOUCH_TOP_LEFT;
        } else if (topRightTouchArea.contains(event.getX(),event.getY()) {
            currentTouch = TOUCH_TOP_RIGHT;
        } else if (botLeftTouchArea.contains(event.getX(),event.getY()) {
            currentTouch = TOUCH_BOT_LEFT;
        } else if (botRightTouchArea.contains(event.getX(), event.getY()) {
            currentTouch = TOUCH_BOT_RIGHT;
        } else {
            return false; //Return false if user touches none of the corners
        }
        return true; //Return true if the user touches one of the corners
    //Now we know which corner the user is touching.
    //When the user moves their finger, we update the point to the user position and invalidate.
    case MotionEvent.ACTION_MOVE:
        switch (currentTouch) {
        case TOUCH_TOP_LEFT:
             topLeft.x = event.getX();
             topLeft.y = event.getY();
             //The bottom left x position has to move with the top left corner
             bottomLeft.x = topLeft.x;
             //The top right y position has to move with the top left corner
             topRight.y = topLeft.y;
             invalidate();
             return true;
        case TOUCH_TOP_RIGHT:
             topRight.x = event.getX();
             topRight.y = event.getY();
             //The top left y position has to move with the top right corner
             topLeft.y = topRight.y;
             //The bottom right x position has to move with the top right corner
             bottomRight.x = topRight.x;
             invalidate();
             return true;
        case TOUCH_BOT_LEFT:
             bottomLeft.x = event.getX();
             bottomLeft.y = event.getY();
             bottomRight.y = bottomLeft.y;
             topLeft.x = bottomLeft.x;
             invalidate();
             return true;
        case TOUCH_BOT_RIGHT:
             bottomRight.x = event.getX();
             bottomRight.y = event.getY();
             topRight.x = bottomRight.x;
             bottomLeft.y = bottomRight.y;
             invalidate();
             return true;
        }
        //We returned true for all of the above cases, because we used the event
        return false; //If currentTouch is none of the above cases, return false

    //Here the user lifts up their finger.
    //We update the points one last time, and set currentTouch to NONE.
    case MotionEvent.ACTION_UP:
        switch (currentTouch) {
        case TOUCH_TOP_LEFT:
             topLeft.x = event.getX();
             topLeft.y = event.getY();
             //The bottom left x position has to move with the top left corner
             bottomLeft.x = topLeft.x;
             //The top right y position has to move with the top left corner
             topRight.y = topLeft.y;
             invalidate();
             currentTouch = NONE;
             return true;
        case TOUCH_TOP_RIGHT:
             topRight.x = event.getX();
             topRight.y = event.getY();
             //The top left y position has to move with the top right corner
             topLeft.y = topRight.y;
             //The bottom right x position has to move with the top right corner
             bottomRight.x = topRight.x;
             invalidate();
             currentTouch = NONE;
             return true;
        case TOUCH_BOT_LEFT:
             bottomLeft.x = event.getX();
             bottomLeft.y = event.getY();
             bottomRight.y = bottomLeft.y;
             topLeft.x = bottomLeft.x;
             invalidate();
             currentTouch = NONE;
             return true;
        case TOUCH_BOT_RIGHT:
             bottomRight.x = event.getX();
             bottomRight.y = event.getY();
             topRight.x = bottomRight.x;
             bottomLeft.y = bottomRight.y;
             invalidate();
             currentTouch = NONE;
             return true;
        }
        return false;
    }
}

这样做是让周围的点的矩形。 想象一下，在图像绘制在你点框。 这些都是“触摸板”，由矩形对象创建。 该矩形的尺寸是由sizeOfRect设置。 在的onTouchEvent，它检查每个矩形对象，以确定用户的触摸是在矩形内，信令的用户试图触摸该点。



Answer 2:

我想你可能会寻找的路径类：

路径类封装化合物（多轮廓）由直线段，二次曲线，和三次曲线的几何路径。 它可以与canvas.drawPath（路径，油漆），或者填充或抚摸（基于油漆的风格）绘制，也可用于裁剪或在路径上绘制文本。

请参见本教程的例子canvas.drawPath



Answer 3:

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.PointF;
import android.view.MotionEvent;
import android.view.View;

public class TestView extends View
{

    private Paint paint;
    private PointF startPoint, endPoint;
    private boolean isDrawing;

    public TestView(Context context)
    {
        super(context);
        init();
    }

    private void init()
    {
        paint = new Paint();
        paint.setColor(Color.RED);
        paint.setStyle(Style.STROKE);
        paint.setStrokeWidth(2);
        paint.setAntiAlias(true);
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        if(isDrawing)
        {
            canvas.drawLine(startPoint.x, startPoint.y, endPoint.x, endPoint.y, paint);
        }
    }


    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        switch (event.getAction())
        {
            case MotionEvent.ACTION_DOWN:
                startPoint = new PointF(event.getX(), event.getY());
                endPoint = new PointF();
                isDrawing = true;
                break;
            case MotionEvent.ACTION_MOVE:
                if(isDrawing)
                {
                    endPoint.x = event.getX();
                    endPoint.y = event.getY();
                    invalidate();
                }
                break;
            case MotionEvent.ACTION_UP:
                if(isDrawing)
                {
                    endPoint.x = event.getX();
                    endPoint.y = event.getY();
                    isDrawing = false;
                    invalidate();
                }
                break;
            default:
                break;
        }
        return true;
    }
}


Answer 4:

编辑：

事实上，你需要使用路径类机器人。 抱歉，我不能拿出一个代码段。 但这里的东西让你开始了。

当你画一条线- canvas.drawLine(x1, y1, x2, y2, paint); 你的出发点是(x1,y1) 现在，如果你需要从任何终端拉行了，你需要首先解决的另一端。 假设你从拉(x2,y2) 所以(x1,y1)变为恒定的并且你从另一端拉。 当使用Path类，首先调用moveTo()这个定位点。 它所做的是它提供了点关于该线已被移动。 然后，你可以使用lineTo()上的触摸事件调用相应拉长线。 将需要大量的调整的。 但是，这是可以让你开始的。 抱歉，我不能拿出一个片断，时间有点短。 见Path类的文档。 您可能会发现一些更有用的东西。

编辑：

关于添加触摸听众几点：

假设你有从线(x1,y1)到(x2,y2)

我们得到一个点触控监听器，你可以将onTouchListener添加到您的整体视图。 

final View touchView = findViewById(R.id.touchView);
    touchView.setOnTouchListener(new View.OnTouchListener() {
        @Override
        public boolean onTouch(View v, MotionEvent event) {
               if(event.getX() == x2 && event.getY() == y2)
               {
                  //you know that you have clicked on the rear end of the line,so now you can do your dragging stuff.
                  if(event.getAction() == MotionEvent.ACTION_DOWN){
                       //you know user has clicked in order to draw
                       //redraw the existing line with black color to remove it
                       paint.setColor(Color.BLACK);
                       canvas.drawLine(x1, y1, x2, y2, paint);
                       //reset the paint object
                       paint.setColor(Color.WHITE); 
                       //now use moveTo() and lineTo() to attain the functionality of dragging on your Path object
                       path.moveTo(x1,y1);
                       path.lineTo(event.getX(),event.getY());
                  }else if(event.getAction() == MotionEvent.ACTION_MOVE){
                       path.lineTo(event.getX(),event.getY());
                  }else if(event.getAction() == MotionEvent.ACTION_UP){
                  }
       }  
               return true;
        }
    });

这只是一个想法，我依然没有得到机会来测试它。 我希望它能帮助。



文章来源: How to draw a lines between points and pull those points?
标签： android drawing points
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