如何在两点之间画直线？

Question

我正在尝试在我的代码中实现名为first 的一点，以使用从first 指向second 的手指移动加入第二点second，无论如何，线都应该是直的 em> ，如果 first 点没有到达 second 点，线应该在 ACTION_UP 上消失。

我的灵感来自： https://play.google.com/store/apps/details?id=nf.co.sumwu.dropdot&hl=en

我正在尝试通过使用 CustomView 的 onDraw 方法来实现它

这是我的尝试：

public class MyGFX extends View{

// setup initial color
  private final int paintColor = Color.BLACK;
  // defines paint and canvas
  private Paint drawPaint;

  Point first , second;

  private Path path = new Path();

public MyGFX(Context context,AttributeSet attrs) {
    super(context, attrs);
    setupPaint(); // same as before
    first = new Point(100,100);
    second = new Point(200,100);
}

// Get x and y and append them to the path
public boolean onTouchEvent(MotionEvent event) {
    float pointX = event.getX();
    float pointY = event.getY();
    // Checks for the event that occurs
    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        boolean insideCircle = 
                (2*((int)pointX - (first.x + 2))) + (2*((int)pointY - (first.y + 2))) <= (2 * 2);

        if(insideCircle){
            // Starts a new line in the path
            path.moveTo(first.x,first.y);
            Toast.makeText(getContext(), "path.moveto is called \n first.x = "
            +first.x+" first.y = "+first.y+" px ="+pointX+"  py ="+pointY, 
                    Toast.LENGTH_SHORT).show();
        }

        break;
    case MotionEvent.ACTION_MOVE:
        boolean insideCircle2 = 
        (2*(pointX - (second.x + 2))) + (2*(pointY - (second.y + 2))) <= (2 * 2);

        if(insideCircle2){
            // Starts a new line in the path
            path.moveTo(pointX, pointY);
        }
        // Draws line between last point and this point
        path.lineTo(pointX, pointY);
        postInvalidate(); // Indicate view should be redrawn

        break;
    case MotionEvent.ACTION_UP:
        path.close();
        break;
    default:
        return false;
   }

   return true; // Indicate we've consumed the touch
}

 // Setup paint with color and stroke styles
  private void setupPaint() {
    drawPaint = new Paint();
    drawPaint.setColor(paintColor);
    drawPaint.setAntiAlias(true);
    drawPaint.setStrokeWidth(5);
    drawPaint.setStyle(Paint.Style.STROKE);
    drawPaint.setStrokeJoin(Paint.Join.ROUND);
    drawPaint.setStrokeCap(Paint.Cap.ROUND);
  }

// Draws the path created during the touch events
  @Override
  protected void onDraw(Canvas canvas) {
      canvas.drawCircle(first.x, first.y, 2, drawPaint);
      canvas.drawCircle(second.x, second.y, 2, drawPaint);

      if(!path.isEmpty())
          canvas.drawPath(path, drawPaint);


  }


}

Answer 1

试试这个......

layout.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"      android:layout_width="match_parent"
        android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
        android:paddingRight="@dimen/activity_horizontal_margin"
        android:paddingTop="@dimen/activity_vertical_margin"
        android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

        <play.decisio.com.myapplication.ConnectDotsView
            android:layout_width="match_parent"
            android:id="@+id/dot"
            android:layout_height="match_parent" />

    </RelativeLayout>

MainActivity.java

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        view=(ConnectDotsView)findViewById(R.id.dot);
        List<Point> point=new ArrayList<Point>();
        for(int i=0;i<5;i++){
            point.add(new Point(i*100+100, i*100+10));
        }
        view.setPoints(point);
    }

Answer 2

使用Canvas.drawLine()。

drawLine(float startX, float startY, float stopX, float stopY, Paint paint)

所以

canvas.drawLine(10.0, 5.0, 11.0, 12.6,...);