一、SurfaceView认识及的应用的思路
- SurfaceView继承自（extends）View，View是在UI线程中进行绘制；
- 而SurfaceView是在一个子线程中对自己进行绘制，优势：避免造成UI线程阻塞；
- SurfaceView中包含一个专门用于绘制的Surface，Surface中包含一个Canvas;
- 获得Canvas:可以从SurfaceView中方法的getHolder()获得SurfaceHolder,从holder获得Canvas;
- holder还管理着SurfaceView的生命周期：
①surfaceCreated()创建子线程，子线程的run()方法中开启SurfaceView的绘制。
②surfaceChanged()。
③surfaceDestoryed()中关闭子线程。
二、SurfaceView的一般写法
package com.example.luckypan; import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceHolder.Callback;
import android.view.SurfaceView; public class SurfaceViewTemplate extends SurfaceView implements Callback, Runnable { private SurfaceHolder mHolder;
private Canvas mCanvas;
/**
* 用于绘制线程
*/
private Thread thread;
/**
* 线程的控制开关
*/
private boolean isRunning;
public SurfaceViewTemplate(Context context) {
this(context, null);
}
public SurfaceViewTemplate(Context context, AttributeSet attrs) {
super(context, attrs);
mHolder=getHolder();
mHolder.addCallback(this);
//可获得焦点
setFocusable(true);
setFocusableInTouchMode(true);
//设置常量
setKeepScreenOn(true);
}
public void surfaceCreated(SurfaceHolder holder) {
isRunning=true;
thread=new Thread(this);
thread.start(); }
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub }
public void surfaceDestroyed(SurfaceHolder holder) {
isRunning=false; }
public void run() {
//不断进行绘制
while (isRunning)
{
draw();
}
}
private void draw() {
try {
mCanvas=mHolder.lockCanvas();
if (mCanvas!=null) {
//
}
}
catch (Exception e) { }
finally
{
if (mCanvas!=null) {
mHolder.unlockCanvasAndPost(mCanvas);
}
}
} }
SurfaceViewTemplate
三、代码编写
- 绘制抽奖转盘的盘快
-
绘制背景：drawBg(), Canvas的两个方法：drawColor(color the color to draw onto the canvas)，这里我设置背景色为白色0xFFFFFFFF、drawBitmap(Bitmap bitmap, Rect src, Rect dst, Paint paint),这个bitmap是背景图片，背景是一个矩形new Rect(),其他参数设置为null。
private void drawBg() {
mCanvas.drawColor(0xFFFFFFFF);
mCanvas.drawBitmap(mBgBitmap, null, new Rect(mPadding/2, mPadding/2, getMeasuredWidth()-mPadding/2, getMeasuredHeight()-mPadding/2), null);
}drawBg
- 绘制盘快：
//绘制盘快
float tmpAngle=mStartAngle;
float sweepAngle=360/mItemCount;
for (int i = 0; i < mItemCount; i++) {
mArcPaint.setColor(mColor[i]);
//绘制盘快
mCanvas.drawArc(mRange, tmpAngle, sweepAngle,true, mArcPaint);
- 绘制抽奖转盘的奖项文字
/**
* 绘制每个盘快的文本
* @param tmpAngle
* @param sweepAngle
* @param string
*/
private void drawText(float tmpAngle, float sweepAngle, String string) {
Path path=new Path();
path.addArc(mRange, tmpAngle, sweepAngle);
//利用水平偏移量让文字居中
float textWidth=mTextPaint.measureText(string);
int hOffset=(int) (mRadius*Math.PI/mItemCount/2-textWidth/2);
int vOffset=mRadius/2/6;//垂直偏移量
mCanvas.drawTextOnPath(string, path, hOffset, vOffset, mTextPaint);
}
drawText
- 绘制抽奖转盘的图片
/**
* 绘制图片
* @param tmpAngle
* @param bitmap
*/
private void drawIcon(float tmpAngle, Bitmap bitmap) {
//设置图片的宽度为直径的1/8
int imgWidth=mRadius/8;
float angle=(float) ((tmpAngle+360/mItemCount/2)*Math.PI/180);
int x=(int) (mCenter+mRadius/2/2*Math.cos(angle));
int y=(int) (mCenter+mRadius/2/2*Math.sin(angle));
//确定图片位置
Rect rect=new Rect(x-imgWidth/2, y-imgWidth/2, x+imgWidth/2, y+imgWidth/2);
mCanvas.drawBitmap(bitmap, null, rect,null);
}
drawIcon
- 转盘滚动及设置停止的指向
private void draw() {
try {
mCanvas=mHolder.lockCanvas();
if (mCanvas!=null) {
//绘制背景
drawBg();
//绘制盘快
float tmpAngle=mStartAngle;
float sweepAngle=360/mItemCount;
for (int i = 0; i < mItemCount; i++) {
mArcPaint.setColor(mColor[i]);
//绘制盘快
mCanvas.drawArc(mRange, tmpAngle, sweepAngle,true, mArcPaint);
//绘制文本
drawText(tmpAngle,sweepAngle,mStrings[i]);
//绘制图片
drawIcon(tmpAngle,mImagBitmaps[i]);
tmpAngle+=sweepAngle;
}
mStartAngle+=mSpeed;
//判断是否点击停止按钮
if (isShouldEnd) {
mSpeed-=1;
}
if (mSpeed<=0)
{
mSpeed=0;
isShouldEnd=false;
}
}
}
catch (Exception e) {
}
finally
{
if (mCanvas!=null) {
mHolder.unlockCanvasAndPost(mCanvas);
}
}
}
draw
四、抽奖转盘的秘密
/**
* 电机启动旋转
* 控制指定盘快停止范围
* @param index
*/
public void luckyStart(int index)
{
//计算每一项的角度
float angle=360/mItemCount;
//计算每一项的中奖范围
//1->150~210
//0->210~270
float from=270-(index+1)*angle;
float end=from+angle;
// 设置停下来需要旋转的距离
float targetFrom=4*360+from;
float targetEnd=4*360+end;
/**
* <pre>
* v1->0 且每次-1
* (v1+0)*(v1+1)/2=targetFrom 等差数列求和公式;
* v1*v1+v1-2*targetFrom=0;
* v1=(-1+Math.sqrt(1+8*targetFrom))/2 一元二次方程求根公式
* </pre>
*/
float v1=(float) ((-1+Math.sqrt(1+8*targetFrom))/2);
float v2=(float) ((-1+Math.sqrt(1+8*targetEnd))/2);
mSpeed=v1+Math.random()*(v2-v1);
// mSpeed=v2;
isShouldEnd=false;
}
luckyStart