画布运动绘制圆 [英] Canvas Motion draw circle
问题描述
我需要根据我的手指移动绘制一个圆，所以我已经写这个代码
I need to draw a circle as per my finger move so i have write this code
package com.sport;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.BlurMaskFilter;
import android.graphics.BlurMaskFilter.Blur;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PorterDuff.Mode;
import android.graphics.PorterDuffXfermode;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;
public class sport extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new TouchView(this));
}
class TouchView extends View {
Bitmap bgr;
Bitmap overlayDefault;
Bitmap overlay;
Paint pTouch;
int X;
int Y;
Canvas c2;
public TouchView(Context context) {
super(context);
bgr = BitmapFactory.decodeResource(getResources(), R.drawable.new1);
overlayDefault = BitmapFactory.decodeResource(getResources(),
R.drawable.original);
overlay = BitmapFactory.decodeResource(getResources(),
R.drawable.new1).copy(Config.ARGB_8888, true);
c2 = new Canvas(overlay);
pTouch = new Paint(Paint.DEV_KERN_TEXT_FLAG);
pTouch.setXfermode(new PorterDuffXfermode(Mode.SRC_IN));
pTouch.setColor(Color.TRANSPARENT);
// pTouch.setMaskFilter(new BlurMaskFilter(15, Blur.NORMAL));
DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
int ht = displaymetrics.heightPixels;
int wt = displaymetrics.widthPixels;
X = wt / 2;
Y = 0;
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN: {
X = (int) ev.getX();
Y = (int) ev.getY();
//invalidate();
break;
}
case MotionEvent.ACTION_MOVE: {
X = (int) ev.getX();
Y = (int) ev.getY();
/* Toast.makeText(getBaseContext(),"x is::"+ X,
Toast.LENGTH_LONG).show();
Toast.makeText(getBaseContext(),"Y is::"+ Y,
Toast.LENGTH_LONG).show();*/
//c2.drawCircle(X, Y, 70, pTouch);
/*System.out.println("x is"+X);
System.out.println("Y is"+Y);*/
invalidate();
break;
}
case MotionEvent.ACTION_UP:
X = (int) ev.getX();
Y = (int) ev.getY();
/*
* Toast.makeText(getBaseContext(),"x is::"+ X,
* Toast.LENGTH_LONG).show();
* Toast.makeText(getBaseContext(),"Y is::"+ Y,
* Toast.LENGTH_LONG).show();
*/
//invalidate();
break;
case MotionEvent.ACTION_POINTER_ID_MASK :
/*X = (int) ev.getX();
Y = (int) ev.getY();
invalidate();*/
break;
}
return true;
}
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
DisplayMetrics displaymetrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
int ht = displaymetrics.heightPixels;
int wt = displaymetrics.widthPixels;
int heightbitmap = bgr.getHeight();
int widthbitmap = bgr.getWidth();
int minus = wt - widthbitmap;
// draw background
canvas.drawBitmap(bgr, minus / 2, 0, null);
// copy the default overlay into temporary overlay and punch a hole
// in it
c2.drawBitmap(overlayDefault, 360, 0, null); // exclude this line to
// show all as you
Bitmap _scratch = BitmapFactory.decodeResource(getResources(), R.drawable.diff_6); // draw
//c2.drawBitmap(_scratch, 10, 10, pTouch);
if(X >= 470 & X <= 522)
{
if(Y >= 255 & Y<= 330)
{
//c2.drawRect(X, Y, 5, 5, pTouch);
double outer_radius = 0.5 * Math.sqrt((_scratch.getWidth()) * (_scratch.getWidth())+ (_scratch.getHeight()) * (_scratch.getHeight()));
float f = (float) outer_radius;
c2.drawCircle(X, Y, f, pTouch);
}
}
// draw the overlay over the background
canvas.drawBitmap(overlay, minus/2, 0, null);
}
}
}
b $ b
问题::
当我触摸屏幕圈子留在我的手指的右侧像这样。
但我需要它的中心我的手指请帮助这个
Problem:: when i touch on screen circle are stay at right side of my finger Like this. but i need it center of my finger please help on this
推荐答案
问题是因为你创建'overlay'相对于x和y cordinates从触摸事件，后来复制到背景与偏移（负/ 2）。假设您的背景图片小于屏幕分辨率，圆圈将总是向右移动，因此看起来圆圈在您的手指的右边。
The problem is because you create 'overlay' with respect to the x and y cordinates from the touch event and later copying this onto the background with an offset (minus/2). Assuming your background image is smaller than the screen resolution the circle will always shift right and hence will look the circle is at the right of your finger.
如果您使用的分辨率与屏幕尺寸相同的背景图片，则会获得正确绘制的圆形，其中心位于触摸点。
If you use a background image which has same resolution as the screen dimensions , you will get properly drawn circle, with its centre at the point of touch.
这篇关于画布运动绘制圆的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
