20190109

看看这本书 -《Android游戏编程之从零开始》

Day_2 2019/01/09

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Canvas 画布

画布类Canvas的一些常用函数如下显示

    {
        try
        {
            canvas = holder.lockCanvas();
            if( canvas != null )
            {
                //----利用填充画布，刷屏
                canvas.drawColor( Color.BLUE );
                //----绘制文本
                canvas.drawText( "Game" , 0 , 0 , paint );
                //----绘制像素点
                canvas.drawPoint( 10 , 20 , paint );
                //----绘制多个像素点
                canvas.drawPoints( new float[]{ 10 , 30 , 30 , 30 } , paint );
                //----绘制直线
                canvas.drawLine( 10 , 40 , 50 , 40 , paint );
                //----绘制多条直线
                canvas.drawLines( new float[]{ 10 , 50 , 50 , 50 , 70 , 50 , 110 , 50 } , paint );
                //----绘制矩形
                canvas.drawRect( 10 , 60 , 40 , 100 , paint );
                //----绘制矩形2
                Rect rect = new Rect( 10 , 100 , 60 , 130 );
                canvas.drawRect( rect , paint );
                //----绘制圆角矩形
                RectF rectF = new RectF( 10 , 140 , 60 , 170 );
                canvas.drawRoundRect( rectF , 20 , 20 , paint );
                //----绘制圆形
                canvas.drawCircle( 20 , 200 , 20 , paint );
                //----绘制弧线
                canvas.drawArc( new RectF( 150 , 20 , 200 , 70 ) , 10 , 230 , true , paint );
                //----绘制椭圆
                canvas.drawOval( new RectF( 150 , 80 , 180 , 100 ) , paint );
                //----绘制指定路径图形
                Path path = new Path();
                //设置起点
                path.moveTo( 160 , 150 );
                path.lineTo( 200 , 150 );
                path.lineTo( 180 , 200 );
                //路径结束
                path.close();
                canvas.drawPath( path , paint );
                //----绘制指定路径图形
                Path pathCircle = new Path();
                //添加一个圆形的路径
                pathCircle.addCircle( 130 , 260 , 20 , Path.Direction.CCW );
                //----绘制带圆形的路径文本
                canvas.drawTextOnPath( "PathText" , pathCircle , 10 , 20 , paint );
            }
        }
        catch( Exception e )
        {
            e.printStackTrace();
        }
        finally
        {
            if( canvas != null )
            {
                holder.unlockCanvasAndPost( canvas );
            }
        }
    }

---

Paint 画笔

paint是绘画辅助类，其中包含文字与位图的样式、颜色等属性信息。
使用api如下：

try
        {
            canvas = holder.lockCanvas();
            if( canvas != null )
            {
                canvas.drawColor( Color.WHITE );
                //-----设置画笔无锯齿
                Paint paint1 = new Paint();
                canvas.drawCircle( 40 , 30 , 20 , paint1 );
                paint1.setAntiAlias( true );
                canvas.drawCircle( 100 , 30 , 20 , paint1 );
                //-----设置画笔的透明度
                canvas.drawText( "无透明度" , 100 , 70 , new Paint() );
                Paint paint2 = new Paint();
                paint2.setAlpha( 0x77 );
                canvas.drawText( "半透明度" , 20 , 70 , paint2 );
                //-----设置绘制文本的锚点
                canvas.drawText( "锚点" , 20 , 90 , new Paint() );
                Paint paint3 = new Paint();
                //设置以文本的中心点绘制
                paint3.setTextAlign( Paint.Align.CENTER );
                canvas.drawText( "锚点" , 20 , 105 , paint3 );
                //-----获取文本长度
                Paint paint4 = new Paint();
                float len = paint4.measureText( "文本宽度:" );
                canvas.drawText( "文本长度:" + len , 20 , 130 , new Paint() );
                //-----设置画笔样式
                canvas.drawRect( new Rect( 20 , 140 , 40 , 160 ) , new Paint() );
                Paint paint5 = new Paint();
                //设置画笔不填充
                paint5.setStyle( Paint.Style.STROKE );
                canvas.drawRect( new Rect( 60 , 140 , 80 , 160 ) , paint5 );
                //-----设置画笔颜色
                Paint paint6 = new Paint();
                paint6.setColor( Color.GRAY );
                canvas.drawText( "灰色" , 30 , 180 , paint6 );
                //-----设置画笔粗细程度
                canvas.drawLine( 20 , 200 , 70 , 200 , new Paint() );
                Paint paint7 = new Paint();
                paint7.setStrokeWidth( 7 );
                canvas.drawLine( 20 , 220 , 70 , 220 , paint7 );
                //-----设置画笔绘制文本的字体粗细
                Paint paint8 = new Paint();
                paint8.setTextSize( 20 );
                canvas.drawText( "文字尺寸" , 20 , 260 , paint8 );
                //-----设置画笔的ARGB分量
                Paint paint9 = new Paint();
                paint9.setARGB( 0x77 , 0xff , 0x00 , 0x00 );
                canvas.drawText( "红色半透明" , 20 , 290 , paint9 );
            }
        }
        catch( Exception e )
        {
            e.printStackTrace();
        }
        finally
        {
            if( canvas != null )
            {
                holder.unlockCanvasAndPost( canvas );
            }
        }

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