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很多童鞋说我的代码运行后,点击home或者back后会程序异常,如果你也这样遇到过,那么你肯定没有仔细读完Himi的博文,第十九篇Himi专门写了关于这些错误的原因和解决方法,这里我在博客都补充说明下,省的童鞋们总疑惑这一块;请点击下面联系进入阅读:
首先对于《赛贝尔曲线》不是很了解的童鞋,请自觉白度百科、google等等...
为了方便偷懒的童鞋,这里给个《贝赛尔曲线》百科地址,以及一段话简述《贝赛尔曲线》:
《贝赛尔曲线》白度百科快速地址:
贝塞尔曲线又称贝兹曲线或贝济埃曲线,一般的矢量图形软件通过它来精确画出曲线,贝兹曲线由线段与节点组成,节点是可拖动的支点,线段像可伸缩的皮筋;
上面这一段话其实就“线段像可伸缩的皮筋”这一句比较重要,也很容易理解;
至于贝赛尔曲线的实现,在Android中极其的简单,因为它是Android封装的一个方法,这个能不简单么。。。。。。只不过它隐藏的比较深,它隐藏于Path类中,方法如下:
android.graphics..quadTo(float x1, float y1, float x2, float y2)
Since:
此方参数解释:
第一个参数:操作点的x坐标
第二个参数:操作点的y坐标
第三个参数:结束点的x坐标
第四个参数:结束点的y坐标
从API中看出,赛贝尔曲线从API-1就开始支持了;
熟悉方法后,下面就来实现:
SurfaceView框架不多讲,看过我博客的都应该知道的;
直接看MySurfaceView类,此类继承SurfaceView ,是游戏的主视图
这里为了更清晰的讲解:这里部分代码先不贴出来了,最后会整体贴出,当然源码也是免费在最后提供~
首先是定义相关的成员变量:
-
- private int startX, startY, controlX, controlY, endX, endY;
-
- private Path path;
-
- private Paint paintQ;
-
- private Random random;
本类构造函数:
-
-
-
- public MySurfaceView(Context context) {
- super(context);
- ...
-
- path = new Path();
- paintQ = new Paint();
- paintQ.setAntiAlias(true);
- paintQ.setStyle(Style.STROKE);
- paintQ.setStrokeWidth(5);
- paintQ.setColor(Color.WHITE);
- random = new Random();
- ...
- }
接着我把绘制贝赛尔曲线封装一个方法了,函数如下:
-
-
-
-
-
- public void drawQpath(Canvas canvas) {
- path.reset();
-
- path.moveTo(startX, startY);
-
- path.quadTo(controlX, controlY, endX, endY);
-
- canvas.drawPath(path, paintQ);
- }
最后是用户触屏监听函数以及逻辑函数:
-
-
-
- @Override
- public boolean onTouchEvent(MotionEvent event) {
- endX = (int) event.getX();
- endY = (int) event.getY();
- return true;
- }
-
-
-
- private void logic() {
- if (endX != 0 && endY != 0) {
-
- controlX = random.nextInt((endX - startX) / 2);
- controlY = random.nextInt((endY - startY) / 2);
- }
- }
整个代码很easy~主要是贝赛尔函数的参数,尤其是操作点,操作点的各种不同可以实现不同的效果,这里我简单的统一的讲操作点设置成用户触屏点的x,y的一半,呵呵偷懒了~嘻嘻~
我把贝赛尔的操作点写在了逻辑logic()函数中,不断的执行,并且每次利用nextInt函数得到随机的操作点,主要为了让其曲线不断的变化从而形成一个震动的曲线运动轨迹;
ok,效果接图如下:
这里可能由于图片是静止的效果看起来不是很明显,大家可以运行源码来观察 ,好了~本节就这样吧;下面贴出整个MySurfaceView的源码:(最后有本项目的源码下载地址)
- package com.qpath;
- import java.util.Random;
- 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.view.KeyEvent;
- import android.view.MotionEvent;
- import android.view.SurfaceHolder;
- import android.view.SurfaceHolder.Callback;
- import android.view.SurfaceView;
-
-
-
-
-
- public class MySurfaceView extends SurfaceView implements Callback, Runnable {
- private SurfaceHolder sfh;
- private Paint paint;
- private Thread th;
- private boolean flag;
- private Canvas canvas;
- public static int screenW, screenH;
-
-
- private int startX, startY, controlX, controlY, endX, endY;
-
- private Path path;
-
- private Paint paintQ;
-
- private Random random;
-
-
-
- public MySurfaceView(Context context) {
- super(context);
- sfh = this.getHolder();
- sfh.addCallback(this);
- paint = new Paint();
- paint.setColor(Color.WHITE);
- paint.setAntiAlias(true);
- setFocusable(true);
-
-
- path = new Path();
- paintQ = new Paint();
- paintQ.setAntiAlias(true);
- paintQ.setStyle(Style.STROKE);
- paintQ.setStrokeWidth(5);
- paintQ.setColor(Color.WHITE);
- random = new Random();
- }
-
-
-
- public void surfaceCreated(SurfaceHolder holder) {
- screenW = this.getWidth();
- screenH = this.getHeight();
- flag = true;
-
- th = new Thread(this);
-
- th.start();
-
- }
-
-
-
- public void myDraw() {
- try {
- canvas = sfh.lockCanvas();
- if (canvas != null) {
- canvas.drawColor(Color.BLACK);
-
- drawQpath(canvas);
- }
- } catch (Exception e) {
-
- } finally {
- if (canvas != null)
- sfh.unlockCanvasAndPost(canvas);
- }
- }
-
-
-
-
-
- public void drawQpath(Canvas canvas) {
- path.reset();
-
- path.moveTo(startX, startY);
-
- path.quadTo(controlX, controlY, endX, endY);
-
- canvas.drawPath(path, paintQ);
- }
-
-
-
- @Override
- public boolean onTouchEvent(MotionEvent event) {
- endX = (int) event.getX();
- endY = (int) event.getY();
- return true;
- }
-
-
-
- private void logic() {
- if (endX != 0 && endY != 0) {
-
- controlX = random.nextInt((endX - startX) / 2);
- controlY = random.nextInt((endY - startY) / 2);
- }
- }
-
-
-
- @Override
- public boolean onKeyDown(int keyCode, KeyEvent event) {
- return super.onKeyDown(keyCode, event);
- }
- public void run() {
- while (flag) {
- long start = System.currentTimeMillis();
- myDraw();
- logic();
- long end = System.currentTimeMillis();
- try {
- if (end - start < 50) {
- Thread.sleep(50 - (end - start));
- }
- } catch (InterruptedException e) {
- e.printStackTrace();
- }
- }
- }
-
-
-
- public void surfaceChanged(SurfaceHolder holder, int format, int width,
- int height) {
- }
-
-
-
- public void surfaceDestroyed(SurfaceHolder holder) {
- flag = false;
- }
- }
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