我想在android中使用4个可拖动的点创建一个不规则的四边形，如下图所示。
这样，用户可以手动拖动一个一个的点，并把创建四边形，因为他们希望使用4点我已经尝试了以下。
import java.util.ArrayList;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.drawable.BitmapDrawable;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
/**
* DrawView class holds corner objects and handle them by drawing
* overlay.
*
* @author Chintan Rathod (http://chintanrathod.com)
*/
public class DrawView2 extends View {
Point point1, point3;
Point point2, point4;
/**
* point1 and point 3 are of same group and same as point 2 and point4
*/
int groupId = -1;
private ArrayList < ColorBall > colorballs = new ArrayList < ColorBall > ();
// array that holds the balls
private int balID = 0;
// variable to know what ball is being dragged
Paint paint;
Canvas canvas;
public DrawView2(Context context) {
super(context);
paint = new Paint();
setFocusable(true); // necessary for getting the touch events
canvas = new Canvas();
// setting the start point for the balls
point1 = new Point();
point1.x = 50;
point1.y = 20;
point2 = new Point();
point2.x = 150;
point2.y = 20;
point3 = new Point();
point3.x = 150;
point3.y = 120;
point4 = new Point();
point4.x = 50;
point4.y = 120;
// declare each ball with the ColorBall class
colorballs.add(new ColorBall(context, R.drawable.ic_cancel, point1));
colorballs.add(new ColorBall(context, R.drawable.ic_cancel, point2));
colorballs.add(new ColorBall(context, R.drawable.ic_cancel, point3));
colorballs.add(new ColorBall(context, R.drawable.ic_cancel, point4));
}
public DrawView2(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public DrawView2(Context context, AttributeSet attrs) {
super(context, attrs);
paint = new Paint();
setFocusable(true); // necessary for getting the touch events
canvas = new Canvas();
// setting the start point for the balls
point1 = new Point();
point1.x = 50;
point1.y = 20;
point2 = new Point();
point2.x = 150;
point2.y = 20;
point3 = new Point();
point3.x = 150;
point3.y = 120;
point4 = new Point();
point4.x = 50;
point4.y = 120;
// declare each ball with the ColorBall class
colorballs.add(new ColorBall(context, R.drawable.ic_cancel, point1));
colorballs.add(new ColorBall(context, R.drawable.ic_cancel, point2));
colorballs.add(new ColorBall(context, R.drawable.ic_cancel, point3));
colorballs.add(new ColorBall(context, R.drawable.ic_cancel, point4));
}
// the method that draws the balls
@Override
protected void onDraw(Canvas canvas) {
// canvas.drawColor(0xFFCCCCCC); //if you want another background color
// paint.setAntiAlias(true);
// paint.setDither(true);
paint.setColor(Color.parseColor("#55000000"));
paint.setStyle(Paint.Style.FILL);
paint.setStrokeJoin(Paint.Join.ROUND);
// mPaint.setStrokeCap(Paint.Cap.ROUND);
paint.setStrokeWidth(5);
canvas.drawPaint(paint);
paint.setColor(Color.parseColor("#55FFFFFF"));
if (groupId == 1) {
canvas.drawLine(point1.x + colorballs.get(0).getWidthOfBall() ,
point3.y + colorballs.get(2).getWidthOfBall() , point3.x + colorballs.get(2).getWidthOfBall() ,
point1.y + colorballs.get(0).getWidthOfBall() , paint);
} else if(groupId == 2){
canvas.drawLine(point2.x + colorballs.get(1).getWidthOfBall() ,
point1.y + colorballs.get(0).getWidthOfBall() , point1.x + colorballs.get(0).getWidthOfBall(),
point2.y + colorballs.get(1).getWidthOfBall() , paint);
} else if(groupId ==3){
canvas.drawLine(point2.x + colorballs.get(1).getWidthOfBall() ,
point4.y + colorballs.get(3).getWidthOfBall() , point4.x + colorballs.get(3).getWidthOfBall(),
point2.y + colorballs.get(1).getWidthOfBall() , paint);
} else {
canvas.drawLine(point3.x + colorballs.get(2).getWidthOfBall() ,
point4.y + colorballs.get(3).getWidthOfBall() , point4.x + colorballs.get(3).getWidthOfBall(),
point3.y + colorballs.get(2).getWidthOfBall() , paint);
}
BitmapDrawable mBitmap;
mBitmap = new BitmapDrawable();
// draw the balls on the canvas
for (ColorBall ball: colorballs) {
canvas.drawBitmap(ball.getBitmap(), ball.getX(), ball.getY(),
new Paint());
}
}
// events when touching the screen
public boolean onTouchEvent(MotionEvent event) {
int eventaction = event.getAction();
int X = (int) event.getX();
int Y = (int) event.getY();
switch (eventaction) {
case MotionEvent.ACTION_DOWN:
// touch down so check if the finger is on
// a ball
balID = -1;
groupId = -1;
for (ColorBall ball: colorballs) {
// check if inside the bounds of the ball (circle)
// get the center for the ball
int centerX = ball.getX() + ball.getWidthOfBall();
int centerY = ball.getY() + ball.getHeightOfBall();
paint.setColor(Color.CYAN);
// calculate the radius from the touch to the center of the ball
double radCircle = Math.sqrt((double)(((centerX - X) * (centerX - X)) + (centerY - Y) * (centerY - Y)));
if (radCircle < ball.getWidthOfBall()) {
balID = ball.getID();
if (balID == 1 ) {
groupId = 1;
canvas.drawLine(point1.x, point3.y, point3.x, point1.y,
paint);
} else if(balID == 2){
groupId = 2;
canvas.drawLine(point1.x, point2.y, point2.x, point1.y,
paint);
} else if(balID == 3){
groupId = 3;
canvas.drawLine(point4.x, point2.y, point4.x, point2.y,
paint);
} else {
groupId = 4;
canvas.drawLine(point4.x, point3.y, point3.x, point4.y,
paint);
}
invalidate();
break;
}
invalidate();
}
break;
case MotionEvent.ACTION_MOVE:
// touch drag with the ball
// move the balls the same as the finger
if (balID > -1) {
colorballs.get(balID).setX(X);
colorballs.get(balID).setY(Y);
paint.setColor(Color.CYAN);
if (groupId == 1) {
colorballs.get(0).setX(colorballs.get(0).getX());
colorballs.get(0).setY(colorballs.get(0).getY());
colorballs.get(2).setX(colorballs.get(2).getX());
colorballs.get(2).setY(colorballs.get(2).getY());
canvas.drawLine(point3.x, point1.y, point3.x, point1.y,
paint);
} else if(groupId == 2){
colorballs.get(1).setX(colorballs.get(1).getX());
colorballs.get(1).setY(colorballs.get(1).getY());
colorballs.get(3).setX(colorballs.get(3).getX());
colorballs.get(3).setY(colorballs.get(3).getY());
canvas.drawLine(point4.x, point2.y, point4.x, point2.y,
paint);
}
invalidate();
}
break;
case MotionEvent.ACTION_UP:
// touch drop - just do things here after dropping
break;
}
// redraw the canvas
invalidate();
return true;
}
}
我面临的问题是，当我试图拖动一个点，它也拖动另一个点，但任何人都可以请让我帮助这个。我的代码输出如下，这不是我想要的东西。我得到的形状
好吧，我能够解决这个问题
canvas.drawLine(point2.x + colorballs.get(1).getWidthOfBall() / 2,
point2.y + colorballs.get(1).getWidthOfBall() / 2,
point1.x + colorballs.get(0).getWidthOfBall() / 2, point1.y + colorballs.get(0).getWidthOfBall() / 2, paint);
canvas.drawLine(point4.x + colorballs.get(3).getWidthOfBall() / 2,
point4.y + colorballs.get(3).getWidthOfBall() / 2,
point1.x + colorballs.get(0).getWidthOfBall() / 2, point1.y + colorballs.get(0).getWidthOfBall() / 2, paint);
canvas.drawLine(point3.x + colorballs.get(2).getWidthOfBall() / 2,
point3.y + colorballs.get(2).getWidthOfBall() / 2,
point2.x + colorballs.get(1).getWidthOfBall() / 2, point2.y + colorballs.get(1).getWidthOfBall() / 2, paint);
canvas.drawLine(point3.x + colorballs.get(2).getWidthOfBall() / 2,
point3.y + colorballs.get(2).getWidthOfBall() / 2,
point4.x + colorballs.get(3).getWidthOfBall() / 2, point4.y + colorballs.get(3).getWidthOfBall() / 2, paint);