Android圆圈跟随触摸和拖动屏幕

Question

我有一个简单的应用程序，当你在屏幕上移动手指时，它会画一条线。

我想改变它，让它不再画在手指后面，而是在你触摸的地方的正下方画一个圆圈。当你在屏幕上移动手指时，圆圈也会随之移动。它不应该留下一条路。

当触摸屏幕时，圆圈应该出现在手指所在的位置，当手指抬起时，圆圈应该消失。

MainActivity:

package com.example.dot2;
import android.app.Activity;
import android.os.Bundle;
public class MainActivity extends Activity {
@Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(new SingleTouchEventListener(this, null));
  }
} 

SingleTouchEventListener:

package com.example.dot2;
import...
public class SingleTouchEventListener extends View {
 private Paint paint = new Paint();
 private Path path = new Path();
 private Paint mPaint;

public SingleTouchEventListener(Context context, AttributeSet attrs) {
super(context, attrs);
paint.setAntiAlias(true);
paint.setStrokeWidth(6f);
paint.setColor(Color.RED);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeJoin(Paint.Join.ROUND);
}
@Override
protected void onDraw(Canvas canvas) {
 canvas.drawPath(path, paint);
}
@Override
public boolean onTouchEvent(MotionEvent event) {
 float eventX = event.getX();
 float eventY = event.getY();
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
  path.moveTo(eventX, eventY);
  return true;
case MotionEvent.ACTION_MOVE:
  path.lineTo(eventX, eventY);
  break;
case MotionEvent.ACTION_UP:
  // nothing to do
  break;
default:
  return false;
}
// Schedules a repaint.
invalidate();
return true;
}
}

谢谢

Answer 1

我实际上找到了我需要的大部分代码，并添加了其余的…

代码如下:

public class drawingView extends View implements OnTouchListener{
static int x,y,r=255,g=255,b=255;
final static int radius=30;
Paint paint;   
public drawingView(Context context)
{
    super(context);
        paint=new Paint();
    paint.setAntiAlias(true);      
    paint.setARGB(255, r, g, b);    
    setFocusable(true);
    this.setOnTouchListener(this);
}
public void onDraw(Canvas canvas)
{
    paint.setARGB(255, r, g, b);
    //drawing the circle
    canvas.drawCircle(x,y,radius,paint);
}
public boolean onTouch(View view,MotionEvent event)
{
    x=(int)event.getX()-(radius/2);      //logic to plot the circle in exact touch place
    y=(int)event.getY()-(radius/2);
      //System.out.println("X,Y:"+"x"+","+y);      
    randColor();  
    invalidate(); 

    if (event.getAction() == MotionEvent.ACTION_UP) {
        paint.setARGB(12, r, g, b);
    }
    return true;
}

public void randColor()
{
    //r=(int)(Math.random()*255);
    //g=(int)(Math.random()*255);
    //b=(int)(Math.random()*255);
    r=1;
    g=2;
    b=3;
    //Toast.makeText(c, "r,g,b="+r+","+g+","+b,Toast.LENGTH_SHORT).show();
}
public void dissColor(){
    r=255;
    g=255;
    b=255;
}
}