Android绘图：一个可交互的Android绘制曲线的demo

一个可交互的Android绘制曲线的demo：

package com.ray.demo;
 
import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.Path;
import android.graphics.Point;
import android.graphics.RectF;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
 
public class LineFunActivity extends Activity {
     
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(new SampleView(this));
    }
     
    private class SampleView extends View{
        public static final int RECT_SIZE = 8;
        private Point mSelectedPoint = null;
 
        public static final int POINT_ARRAY_SIZE = 7;
        public static final int C_START = 0;
        public static final int C_END = 1;
        public static final int C_CONTROL_1 = 2;
        public static final int C_CONTROL_2 = 3;
        public static final int Q_START = 4;
        public static final int Q_END = 5;
        public static final int Q_CONTROL = 6;
 
        private Point\[\] mPoints = new Point\[POINT_ARRAY_SIZE\];
         
        public SampleView(Context context) {
            super(context);
            mPoints\[C_START\] = new Point(100,100);
            mPoints\[C_END\] = new Point(200,200);
            mPoints\[C_CONTROL_1\] = new Point (150,100);
            mPoints\[C_CONTROL_2\] = new Point(150,200);
             
            mPoints\[Q_START\] = new Point(100,300);
            mPoints\[Q_END\] = new Point(150,400);
            mPoints\[Q_CONTROL\] = new Point(200,350);
        }
 
        @Override
        protected void onDraw(Canvas canvas) {
            super.onDraw(canvas);
            canvas.drawColor(Color.WHITE);
 
            // set up paint
            Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
            paint.setColor(Color.BLACK);
 
            // draw the cubic line
            Path path = new Path();
            path.moveTo(mPoints\[C_START\].x,mPoints\[C_START\].y);
            path.cubicTo(mPoints\[C_CONTROL_1\].x, mPoints\[C_CONTROL_1\].y, 
                    mPoints\[C_CONTROL_2\].x, mPoints\[C_CONTROL_2\].y, 
                    mPoints\[C_END\].x, mPoints\[C_END\].y);
            paint.setStrokeWidth(2);
            paint.setStyle(Style.STROKE);
            canvas.drawPath(path, paint);
            canvas.drawLine(mPoints\[C_START\].x,mPoints\[C_START\].y, 
                    mPoints\[C_CONTROL_1\].x, mPoints\[C_CONTROL_1\].y, paint);
            canvas.drawLine(mPoints\[C_END\].x, mPoints\[C_END\].y, 
                    mPoints\[C_CONTROL_2\].x, mPoints\[C_CONTROL_2\].y, paint);
             
            // draw the quad line
            paint.setColor(Color.BLACK);
            paint.setStyle(Style.FILL);
            paint.setStrokeWidth(2);
            path.reset();
            path.moveTo(mPoints\[Q_START\].x, mPoints\[Q_START\].y);
            path.quadTo(mPoints\[Q_CONTROL\].x, mPoints\[Q_CONTROL\].y, 
                    mPoints\[Q_END\].x, mPoints\[Q_END\].y);
            canvas.drawPath(path, paint);
            canvas.drawLine(mPoints\[Q_START\].x, mPoints\[Q_START\].y, 
                    mPoints\[Q_CONTROL\].x, mPoints\[Q_CONTROL\].y, paint);
            canvas.drawLine(mPoints\[Q_END\].x, mPoints\[Q_END\].y, 
                    mPoints\[Q_CONTROL\].x, mPoints\[Q_CONTROL\].y, paint);
             
            // draw control points
            paint.setColor(Color.RED);
            paint.setStyle(Style.FILL);
            for (int i=0; i<POINT_ARRAY_SIZE; i++){
                canvas.drawRect(pointToRect(mPoints\[i\]),paint);
            }
        }
 
        @Override
        public boolean onTouchEvent(MotionEvent event) {
            switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                for (int i=0; i<POINT_ARRAY_SIZE; i++){
                    if (pointToRect(mPoints\[i\]).contains(event.getX(),event.getY())){
                        mSelectedPoint = mPoints\[i\];
                    }
                }
                break;
            case MotionEvent.ACTION_MOVE:
                if ( null != mSelectedPoint){           
                    mSelectedPoint.x = (int) event.getX();
                    mSelectedPoint.y = (int) event.getY();
                    invalidate();
                }
                break;
            case MotionEvent.ACTION_UP:
                mSelectedPoint = null;
                break;
            default:
                break;
            }       
            return true;
             
        }
         
        private RectF pointToRect(Point p){
            return new RectF(p.x -RECT_SIZE/2, p.y - RECT_SIZE/2,
                    p.x + RECT_SIZE/2, p.y + RECT_SIZE/2);
        }
    }
}

demo下载：

• LineFun.zip(56.5 KB)