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Android原生绘图之一起画个表

零、前言

前几天介绍了一大堆Android的Canvas,Paint,Path的API,接下来将是灵活地使用他们
今天带来的是一个手表的绘制,经过本篇的洗礼,相信你会对Canvas的图层概念有更深刻的理解
至于表的美丑不是本文的重点,本文只有一个目的,就是理清Canvas的save和restore的意义

表.gif


一、准备工作

1.新建类继承View
public class TolyClockView extends View {

    public TolyClockView(Context context) {
        this(context, null);
    }

    public TolyClockView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);

        init();
    }

    private void init() {
        //TODO 初始化
    }
    
       @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //TODO 绘制
    }
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2.分析一下

一般我们都会这样去自定义一个View,但很少人会有图层这个概念,毕竟咱都是敲代码的
如下图,一开始是一个x,y轴在顶点的图层,如果你不用save(),那你始终都在这个图层,图层栈始终只有一个

开始绘制时.png


3.下面在这个界面上绘制本人专用坐标系:(已封装成工具,附在文尾)

网格和坐标系属于辅助性的工具,绘制起来比较多,所以使用Picture录制,在init()里初始化
Picture在onDraw里绘制高效些,区别就像准备一车砖盖房子和造一块才砖盖一下房子

//成员变量
private Picture mPictureGrid;//网格Canvas元件
private Point mCoo = new Point(500, 800);//坐标系原点
private Picture mPictureCoo;//坐标系Canvas元件

//init()中
mPictureGrid = HelpDraw.getGrid(getContext());
mPictureCoo = HelpDraw.getCoo(getContext(), mCoo);
//初始化画笔
mMainPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mMainPaint.setStyle(Paint.Style.STROKE);
mMainPaint.setStrokeCap(Paint.Cap.ROUND);

//onDraw里
canvas.drawPicture(mPictureGrid);
canvas.drawPicture(mPictureCoo);
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正如API字面上的意思,在canvas上将网格和坐标系两张图片绘制出来,如下图:

绘制坐标系时.png


二、绘制逻辑

准备工作做好了,下面要到正题了

1.onDraw里
canvas.save();//保存先前状态(相当于在另一个图层操作)
canvas.translate(mCoo.x, mCoo.y);//将画布定点平移到绘制的坐标系中心
canvas.restore();//合并到root图层
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2.看一下这两句翻译在图上是什么意思:

一旦canvas.save(),相当于新建了一个图层(黑色虚线所示),
然后canvas.translate(mCoo.x, mCoo.y)将新建的图层向右和向下移动
新建的图层的好处:只有栈顶的图层才能操作(如Canvas移动时,root图层并没有动,这正是我们想要的)

save和translate.png

3.绘制外圈破碎的圆:drawBreakCircle(canvas)
 /**
 * 绘制破碎的圆
 * @param canvas
 */
private void drawBreakCircle(Canvas canvas) {
    for (int i = 0; i < 4; i++) {
        canvas.save();//保存先前状态(相当于在另一个图层操作)
        canvas.rotate(90 * i);
        mMainPaint.setStrokeWidth(8);
        mMainPaint.setColor(Color.parseColor("#D5D5D5"));
        //在-350, -350, 350, 350的矩形区域,从10°扫70°绘制圆弧
        canvas.drawArc(
                -350, -350, 350, 350,
                10, 70, false, mMainPaint);
        canvas.restore();//恢复先前状态(相当于将图层和前一图层合并)
    }
}     
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先看i=0时:
由于save了,前面的图层被锁定,相当于在另一个图层操作

绘制碎圆.png

canvas.restore()调用后,
图层2将它的结果给了图层1,挥挥衣袖,不带走一片云彩,出栈了

绘制碎圆2.png

先看i=1时:
由于save了,前面的图层被锁定,相当于在另一个图层操作
这里canvas.rotate(90 * 1)相当于当前图层转了90°,如图:
注意:我只将坐标轴的第一象限涂色,canvas图层是一个无限的面,canvas宽高只是限制显示,
旋转、平移、缩放等的关键在于坐标轴的变换,旋转90°相当于坐标轴转了90°

绘制碎圆3.png

canvas.restore()调用后,
图层2将它的结果给了图层1,挥挥衣袖,不带走一片云彩,出栈了

绘制碎圆4.png

经过这两个图层的演示,想必你应该明白图层的作用了吧。
最后画完之后,图层全合并到root

绘制碎圆5.png


4.绘制小点

画60个点(小线),每逢5变长,也就是画直线,每次将画布旋转360/60=6°

    private void drawDot(Canvas canvas) {
        for (int i = 0; i < 60; i++) {
            if (i % 5 == 0) {
                canvas.save();
                canvas.rotate(30 * i);
                mMainPaint.setStrokeWidth(8);
                mMainPaint.setColor(ColUtils.randomRGB());
                canvas.drawLine(250, 0, 300, 0, mMainPaint);

                mMainPaint.setStrokeWidth(10);
                mMainPaint.setColor(Color.BLACK);
                canvas.drawPoint(250, 0, mMainPaint);
                canvas.restore();
            } else {
                canvas.save();
                canvas.rotate(6 * i);
                mMainPaint.setStrokeWidth(4);
                mMainPaint.setColor(Color.BLUE);
                canvas.drawLine(280, 0, 300, 0, mMainPaint);
                canvas.restore();
            }
        }
    }
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点绘制.png


5.绘制时针:
 /**
     * 绘制时针
     *
     * @param canvas
     */
    private void drawH(Canvas canvas) {

        canvas.save();
        canvas.rotate(40);
        mMainPaint.setColor(Color.parseColor("#8FC552"));
        mMainPaint.setStrokeCap(Paint.Cap.ROUND);
        mMainPaint.setStrokeWidth(8);
        canvas.drawLine(0, 0, 150, 0, mMainPaint);
        canvas.restore();
    }
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6.绘制分针:
    /**
     * 绘制分针
     * @param canvas
     * @param deg
     */
    private void drawM(Canvas canvas) {
        canvas.save();
        canvas.rotate(120);
        mMainPaint.setColor(Color.parseColor("#87B953"));
        mMainPaint.setStrokeWidth(8);
        canvas.drawLine(0, 0, 200, 0, mMainPaint);
        mMainPaint.setColor(Color.GRAY);
        mMainPaint.setStrokeWidth(30);
        canvas.drawPoint(0, 0, mMainPaint);
        canvas.restore();
    }
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7.绘制秒针
    /**
     * 绘制秒针
     *
     * @param canvas
     * @param deg
     */
    private void drawS(Canvas canvas, float deg) {
        mMainPaint.setStyle(Paint.Style.STROKE);
        mMainPaint.setColor(Color.parseColor("#6B6B6B"));
        mMainPaint.setStrokeWidth(8);
        mMainPaint.setStrokeCap(Paint.Cap.SQUARE);

        canvas.save();
        canvas.rotate(deg);

        canvas.save();
        canvas.rotate(45);
        //使用path绘制:在init里初始化一下就行了
        mMainPath.addArc(-25, -25, 25, 25, 0, 240);
        canvas.drawPath(mMainPath, mMainPaint);
        canvas.restore();

        mMainPaint.setStrokeCap(Paint.Cap.ROUND);
        canvas.drawLine(-25, 0, -50, 0, mMainPaint);

        mMainPaint.setStrokeWidth(2);
        mMainPaint.setColor(Color.BLACK);
        canvas.drawLine(0, 0, 320, 0, mMainPaint);

        mMainPaint.setStrokeWidth(15);
        mMainPaint.setColor(Color.parseColor("#8FC552"));
        canvas.drawPoint(0, 0, mMainPaint);
        canvas.restore();
    }

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时针.png


8.添加文字
/**
 * 添加文字
 * @param canvas
 */
private void drawText(Canvas canvas) {
    mMainPaint.setTextSize(60);
    mMainPaint.setStrokeWidth(5);
    mMainPaint.setStyle(Paint.Style.FILL);
    mMainPaint.setTextAlign(Paint.Align.CENTER);
    mMainPaint.setColor(Color.BLUE);
    canvas.drawText("Ⅲ", 350, 30, mMainPaint);
    canvas.drawText("Ⅵ", 0, 350 + 30, mMainPaint);
    canvas.drawText("Ⅸ", -350, 30, mMainPaint);
    canvas.drawText("Ⅻ", 0, -350 + 30, mMainPaint);
    //使用外置字体放在assets目录下
    Typeface myFont = Typeface.createFromAsset(getContext().getAssets(), "CHOPS.TTF");
    mMainPaint.setTypeface(myFont);
    mMainPaint.setTextSize(70);
    canvas.drawText("Toly", 0, -150, mMainPaint);
}
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效果.png

好了,静态效果实现了,现在让它动起来吧


三、让表动起来

1.显示当前时间:

表的旋转角度由每个针绘制是的canvas.rotate(XXX);决定,
那么动态改变旋转的角度不就行了吗! 看下面一道数学题:

11:12:45秒,时针、分针、秒针的指针各与中心水平线的夹角?
答:
秒针:45 / 60.f * 360 - 90
分针:12 / 60.f * 360 - 90 + 45 / 60.f * 1
时针:11 / 12.f * 360 - 90 + 12 / 60.f * 30 + 45 / 3600.f * 30
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2.动态更新角度:绘制指针的三个函数,加角度参数
Calendar calendar = Calendar.getInstance();
int hour = calendar.get(Calendar.HOUR_OF_DAY);
int min = calendar.get(Calendar.MINUTE);
int sec = calendar.get(Calendar.SECOND);

drawS(canvas, sec / 60.f * 360 - 90);
drawM(canvas, min / 60.f * 360 - 90 + sec / 60.f);
drawH(canvas, hour / 12.f * 360 - 90 + min / 60.f * 30 + sec / 3600.f * 30);
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时间.png


3.现在每次进来,都会更新时间了,怎么自动更新呢?

循环的黄金搭档:Handler + Timer

public class ClockActivity extends AppCompatActivity {

    /**
     * 新建Handler
     */
    Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            mView.invalidate();//处理:刷新视图
        }
    };

    private View mView;
    private Timer timer = new Timer();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_toly_clock);
        ButterKnife.bind(this);

        mView = findViewById(R.id.id_toly_clock);

        TimerTask timerTask = new TimerTask() {
            @Override
            public void run() {
                mHandler.sendEmptyMessage(0);//发送消息
            }
        };
        //定时任务
        timer.schedule(timerTask, 0, 1000);
    }
}
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表.gif

ok,完结散花(分析图画的真要命...)


后记:捷文规范

1.本文成长记录及勘误表
项目源码 日期 备注
V0.1--github 2018-11-8 Android原生绘图之一起画个表
2.更多关于我
笔名 QQ 微信 爱好
张风捷特烈 1981462002 zdl1994328 语言
我的github 我的简书 我的CSDN 个人网站
3.声明

1----本文由张风捷特烈原创,转载请注明
2----欢迎广大编程爱好者共同交流
3----个人能力有限,如有不正之处欢迎大家批评指证,必定虚心改正
4----看到这里,我在此感谢你的喜欢与支持


icon_wx_200.png

附录:网格+坐标系绘制工具:

1.HelpDraw
/**
 * 作者:张风捷特烈<br/>
 * 时间:2018/11/5 0005:8:43<br/>
 * 邮箱:1981462002@qq.com<br/>
 * 说明:辅助画布
 */
public class HelpDraw {

    /**
     * 获取屏幕尺寸
     */
    public static Point getWinSize(Context context) {
        Point point = new Point();
        Utils.loadWinSize(context, point);
        return point;
    }

    /**
     * 绘制网格
     */
    public static Picture getGrid(Context context) {
        return getGrid(getWinSize(context));
    }

    /**
     * 绘制坐标系
     */
    public static Picture getCoo(Context context, Point coo) {
        return getCoo(coo, getWinSize(context));
    }


    /**
     * 绘制网格
     *
     * @param winSize 屏幕尺寸
     */
    private static Picture getGrid(Point winSize) {

        Picture picture = new Picture();
        Canvas recording = picture.beginRecording(winSize.x, winSize.y);
        //初始化网格画笔
        Paint paint = new Paint();
        paint.setStrokeWidth(2);
        paint.setColor(Color.GRAY);
        paint.setStyle(Paint.Style.STROKE);
        //设置虚线效果new float[]{可见长度, 不可见长度},偏移值
        paint.setPathEffect(new DashPathEffect(new float[]{10, 5}, 0));
        recording.drawPath(HelpPath.gridPath(50, winSize), paint);
        return picture;

    }

    /**
     * 绘制坐标系
     *
     * @param coo     坐标系原点
     * @param winSize 屏幕尺寸
     */
    private static Picture getCoo(Point coo, Point winSize) {
        Picture picture = new Picture();
        Canvas recording = picture.beginRecording(winSize.x, winSize.y);
        //初始化网格画笔
        Paint paint = new Paint();
        paint.setStrokeWidth(4);
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.STROKE);
        //设置虚线效果new float[]{可见长度, 不可见长度},偏移值
        paint.setPathEffect(null);

        //绘制直线
        recording.drawPath(HelpPath.cooPath(coo, winSize), paint);
        //左箭头
        recording.drawLine(winSize.x, coo.y, winSize.x - 40, coo.y - 20, paint);
        recording.drawLine(winSize.x, coo.y, winSize.x - 40, coo.y + 20, paint);
        //下箭头
        recording.drawLine(coo.x, winSize.y, coo.x - 20, winSize.y - 40, paint);
        recording.drawLine(coo.x, winSize.y, coo.x + 20, winSize.y - 40, paint);
        //为坐标系绘制文字
        drawText4Coo(recording, coo, winSize, paint);
        return picture;
    }

    /**
     * 为坐标系绘制文字
     *
     * @param canvas  画布
     * @param coo     坐标系原点
     * @param winSize 屏幕尺寸
     * @param paint   画笔
     */
    private static void drawText4Coo(Canvas canvas, Point coo, Point winSize, Paint paint) {
        //绘制文字
        paint.setTextSize(50);
        canvas.drawText("x", winSize.x - 60, coo.y - 40, paint);
        canvas.drawText("y", coo.x - 40, winSize.y - 60, paint);
        paint.setTextSize(25);
        //X正轴文字
        for (int i = 1; i < (winSize.x - coo.x) / 50; i++) {
            paint.setStrokeWidth(2);
            canvas.drawText(100 * i + "", coo.x - 20 + 100 * i, coo.y + 40, paint);
            paint.setStrokeWidth(5);
            canvas.drawLine(coo.x + 100 * i, coo.y, coo.x + 100 * i, coo.y - 10, paint);
        }

        //X负轴文字
        for (int i = 1; i < coo.x / 50; i++) {
            paint.setStrokeWidth(2);
            canvas.drawText(-100 * i + "", coo.x - 20 - 100 * i, coo.y + 40, paint);
            paint.setStrokeWidth(5);
            canvas.drawLine(coo.x - 100 * i, coo.y, coo.x - 100 * i, coo.y - 10, paint);
        }

        //y正轴文字
        for (int i = 1; i < (winSize.y - coo.y) / 50; i++) {
            paint.setStrokeWidth(2);
            canvas.drawText(100 * i + "", coo.x + 20, coo.y + 10 + 100 * i, paint);
            paint.setStrokeWidth(5);
            canvas.drawLine(coo.x, coo.y + 100 * i, coo.x + 10, coo.y + 100 * i, paint);
        }

        //y负轴文字
        for (int i = 1; i < coo.y / 50; i++) {
            paint.setStrokeWidth(2);
            canvas.drawText(-100 * i + "", coo.x + 20, coo.y + 10 - 100 * i, paint);
            paint.setStrokeWidth(5);
            canvas.drawLine(coo.x, coo.y - 100 * i, coo.x + 10, coo.y - 100 * i, paint);
        }
    }
}
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2.HelpPath
/**
 * 作者:张风捷特烈<br/>
 * 时间:2018/11/5 0005:8:05<br/>
 * 邮箱:1981462002@qq.com<br/>
 * 说明:辅助分析路径
 */
public class HelpPath {

    /**
     * 绘制网格:注意只有用path才能绘制虚线
     *
     * @param step    小正方形边长
     * @param winSize 屏幕尺寸
     */
    public static Path gridPath(int step, Point winSize) {

        Path path = new Path();

        for (int i = 0; i < winSize.y / step + 1; i++) {
            path.moveTo(0, step * i);
            path.lineTo(winSize.x, step * i);
        }

        for (int i = 0; i < winSize.x / step + 1; i++) {
            path.moveTo(step * i, 0);
            path.lineTo(step * i, winSize.y);
        }
        return path;
    }

    /**
     * 坐标系路径
     *
     * @param coo     坐标点
     * @param winSize 屏幕尺寸
     * @return 坐标系路径
     */
    public static Path cooPath(Point coo, Point winSize) {
        Path path = new Path();
        //x正半轴线
        path.moveTo(coo.x, coo.y);
        path.lineTo(winSize.x, coo.y);
        //x负半轴线
        path.moveTo(coo.x, coo.y);
        path.lineTo(coo.x - winSize.x, coo.y);
        //y负半轴线
        path.moveTo(coo.x, coo.y);
        path.lineTo(coo.x, coo.y - winSize.y);
        //y负半轴线
        path.moveTo(coo.x, coo.y);
        path.lineTo(coo.x, winSize.y);
        return path;
    }
}
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3.Utils
public class Utils {
    /**
     * 获得屏幕高度
     *
     * @param ctx 上下文
     * @param winSize 屏幕尺寸
     */
    public static void loadWinSize(Context ctx, Point winSize) {
        WindowManager wm = (WindowManager) ctx.getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics outMetrics = new DisplayMetrics();
        if (wm != null) {
            wm.getDefaultDisplay().getMetrics(outMetrics);
        }
        winSize.x = outMetrics.widthPixels;
        winSize.y = outMetrics.heightPixels;
    }

}

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