本文详述了android抽奖程序的实现方法，程序为一个抽奖大转盘代码，里面定义了很多图形方法和动画。
实现主要功能的SlyderView.java源代码如下：
import android.app.Activity; import android.content.Context; import android.graphics.BlurMaskFilter; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.ColorMatrixColorFilter; import android.graphics.EmbossMaskFilter; import android.graphics.MaskFilter; import android.graphics.Paint; import android.graphics.PorterDuffXfermode; import android.graphics.Paint.Style; import android.graphics.PorterDuff.Mode; import android.graphics.Path; import android.graphics.RadialGradient; import android.graphics.RectF; import android.graphics.Shader.TileMode; import android.util.AttributeSet; import android.util.TypedValue; import android.view.View; public class SlyderView extends View{ public SlyderView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); init(context); } public SlyderView(Context context, AttributeSet attrs) { super(context, attrs); init(context); } public SlyderView(Context context) { super(context); init(context); } /** * 屏幕宽度 */ private int screenW; /** * 屏幕的高度 */ private int screenH; /** * 分割的度数 */ private int [] drgrees = {20,50,40,90,70,40,50}; /*** * 分割的文字 */ private String [] strs = {"level1","level2","level3","level4","level5","level6","level7"}; /** * 分割的颜色 */ private int [] colos = new int[] { 0xfed9c960, 0xfe57c8c8, 0xfe9fe558, 0xfef6b000, 0xfef46212, 0xfecf2911, 0xfe9d3011 }; /** * 画笔 */ private Paint paint; /** * 文字的大小 */ private float textSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 15, getResources().getDisplayMetrics()); /** * 文字的颜色 */ private int textcolor = Color.WHITE; /** * 园的半径 */ private float radius = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 100, getResources().getDisplayMetrics()); /** * 画文字的距离 */ private float textdis = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 80, getResources().getDisplayMetrics()); /** * 画箭头的大小 */ private float roketSize = TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP, 10, getResources().getDisplayMetrics()); private float initDegress = 0; /** * 圆心 */ private float centerX; /** * 圆心 */ private float centerY; /** * 立体边缘 */ private MaskFilter filter = new EmbossMaskFilter(new float[] { 1, 1, 1 },0.4f, 6, 3.5f); private MaskFilter outerFilter = new BlurMaskFilter(10, BlurMaskFilter.Blur.OUTER); private MaskFilter innerFilter = new BlurMaskFilter(10, BlurMaskFilter.Blur.INNER); @SuppressWarnings("deprecation") private void init(Context context){ paint = new Paint(); paint.setAntiAlias(true); paint.setStyle(Style.FILL); paint.setColor(Color.WHITE); screenW = ((Activity)context).getWindowManager().getDefaultDisplay().getWidth(); screenH = ((Activity)context).getWindowManager().getDefaultDisplay().getHeight(); int[] colores = new int[3]; colores[0] = Color.rgb(0xfF, 0x99, 0x00); colores[1] = Color.rgb(0xff, 0xff, 0x00); colores[2] = Color.rgb(0xff, 0x99, 0x00); float[] positions = new float[3]; positions[0] = 0.0f; positions[1] = 0.5f; positions[2] = 1.0f; gradient = new RadialGradient(centerX, centerY, radius/5, colores, positions, TileMode.CLAMP); } /** * 绘制三角箭头 */ private Path path = new Path(); /** * 绘制矩形框 */ private RectF oval; /** * 外圆内阴影矩阵 */ private ColorMatrixColorFilter colorFilter = new ColorMatrixColorFilter(new float[]{ 1,0,0,0,0, 0,1,0,0,0, 0,0,1,0,0, 0,0,0,-1,255 }); @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); centerX = screenW/2; centerY = screenH/2; oval = new RectF(centerX-radius,centerY-radius,centerX+radius,centerY+radius); float start = 0; paint.setColor(Color.rgb(0xdd, 0xdd, 0xdd)); paint.setAlpha(127); canvas.drawCircle(centerX, centerY, radius+10, paint); paint.setAlpha(255); //画扇形 paint.setAntiAlias(true); for(int i=0;i<drgrees.length;i++){ float sweepAngle = drgrees[i]; float startAngle = start; paint.setColor(colos[i%colos.length]); canvas.drawArc(oval, startAngle, sweepAngle, true, paint); start += drgrees[i]; } //画文字 paint.setColor(textcolor); paint.setAntiAlias(true); paint.setTextSize(textSize); paint.setTextAlign(Paint.Align.RIGHT); start = 0; for(int i=0;i<drgrees.length;i++){ canvas.save(); canvas.rotate(start+drgrees[i]/2, centerX, centerY); canvas.drawText(strs[i], centerX+textdis, centerY, paint); canvas.restore(); start += drgrees[i]; } int saveCount = canvas.save(); //画外层立体效果 paint.setColorFilter(colorFilter); canvas.saveLayer(oval,paint,Canvas.ALL_SAVE_FLAG); paint.setColorFilter(null); canvas.drawARGB(255, 0, 0, 0); paint.setXfermode(new PorterDuffXfermode(Mode.CLEAR)); canvas.drawCircle(centerX, centerY, radius, paint); paint.setXfermode(null); paint.setMaskFilter(innerFilter); paint.setColor(Color.argb(0xff, 0, 0, 0)); canvas.drawCircle(centerX, centerY, radius, paint); paint.setMaskFilter(null); canvas.restoreToCount(saveCount); //画内圆和内园效果 canvas.save(); paint.setColor(Color.argb(0xff, 0, 0, 0)); paint.setAntiAlias(true); paint.setMaskFilter(outerFilter); canvas.rotate(initDegress, centerX, centerY); canvas.drawCircle(centerX, centerY, radius/3, paint); paint.setMaskFilter(null); paint.setColor(Color.WHITE); canvas.drawCircle(centerX, centerY, radius/3, paint); //画三角型叠加当箭头 path.moveTo(centerX-radius/3, centerY); path.lineTo(centerX, centerY-radius/3-roketSize); path.lineTo(centerX+radius/3, centerY); path.close(); canvas.drawPath(path, paint); canvas.restore(); paint.setMaskFilter(filter); paint.setColor(Color.GREEN); paint.setShader(gradient); canvas.drawCircle(centerX, centerY, radius/5, paint); paint.setMaskFilter(null); paint.setShader(null); //重绘调整三角的指向达到滚动的效果，现实项目中可不能这样用的，效率太低下了，拆分View用动画完成滚动才是王道 if(isRunning){ if(initDegress>=360){ initDegress = 0; } initDegress +=4; invalidate(); } if(isStoping){ if(initDegress<=360){ initDegress+=4; invalidate(); }else{ if(initDegress-360<stop_degress){ initDegress+=2; invalidate(); } } } } private boolean isRunning = false; private boolean isStoping = false; private int stop_degress =90; /** * 渐变 */ private RadialGradient gradient; public void play(){ isRunning = true; invalidate(); } public void stop(int count){ for(int i =0;i<=count;i++){ if(i == count){ stop_degress +=drgrees[i]/2; }else{ stop_degress +=drgrees[i]; } } isStoping = true; isRunning = false; invalidate(); } }