canvas.drawLine(10, 10, 90, 10, paint);，使用这个方法我可以绘制点之间的线条。编辑：这里我附上了一张图片以便更清楚地解释，从Paul的答案中，我现在能够绘制点之间的线条，但仍有拉动点的问题...
以下是完成方法。假设您有点，将它们设置为全局变量：
PointF topLeft = new PointF(10,10);
PointF topRight = new PointF(90,10);
PointF bottomLeft = new PointF(10,90);
PointF bottomRight = new PointF(90,90);
您需要做的是在每个点周围创建一个RectF。RectF越大，点的触摸区域就越大。
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
private final int NONE = -1, TOUCH_TOP_LEFT = 0, TOUCH_TOP_RIGHT = 1, TOUCH_BOT_LEFT = 2, TOUCH_BOT_RIGHT = 3;
int currentTouch = NONE;
@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;
}
}
我认为您可能正在寻找Path类：
Path类封装了由直线段、二次曲线和三次曲线组成的复合（多轮廓）几何路径。它可以使用canvas.drawPath（path，paint）绘制，可以填充或描边（基于paint的样式），也可以用于剪切或在路径上绘制文本。
请参阅this tutorial，了解canvas.drawPath的示例。
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;
}
}
编辑：
在Android中，确实需要使用Path类。很抱歉我不能提供代码片段。但是这里有一些让您开始的东西。
当您绘制一条线时- canvas.drawLine(x1, y1, x2, y2, paint);，您的起点是(x1,y1)。现在，如果您需要从任何一端拉出该行，则需要先固定另一端。假设您从(x2,y2) 拉取。因此，(x1,y1)变为常量，并且您从另一端拉动。使用Path类时，请首先调用moveTo() 到这个固定点。它所做的是提供一个关于线条必须移动的点。然后，您可以在触摸事件上使用lineTo() 调用来相应地拉伸该线。需要进行大量调整。但这就是可以让您开始的内容。很抱歉我没有想到一个代码片段，时间有点短。请参阅Path类的文档。您可能会找到更多有用的内容。
编辑：
关于将触摸监听器添加到点：
假设您有一条线从(x1,y1)到(x2,y2)。
现在，要为点添加触摸监听器，可以将onTouchListener添加到整个视图。
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，我还没有机会去测试它。希望它有所帮助。