Android原生繪圖之一起畫個表

零、前言

前幾天介紹了一大堆Android的Canvas，Paint,Path的API，接下來將是靈活地使用他們
今天帶來的是一個手錶的繪製，經過本篇的洗禮，相信你會對Canvas的圖層概念有更深刻的理解
至於表的美醜不是本文的重點，本文只有一個目的，就是理清Canvas的save和restore的意義

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一、準備工作

1.新建類繼承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 繪製
    }
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2.分析一下

一般我們都會這樣去自定義一個View,但很少人會有圖層這個概念，畢竟我們都是敲程式碼的
如下圖，一開始是一個x,y軸在頂點的圖層,如果你不用save(),那你始終都在這個圖層，圖層棧始終只有一個

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3.下面在這個介面上繪製本人專用座標系:(已封裝成工具，附在文尾)

網格和座標系屬於輔助性的工具，繪製起來比較多,所以使用Picture錄製，在init()裡初始化
Picture在onDraw裡繪製高效些，區別就像準備一車磚蓋房子和造一塊才磚蓋一下房子

//成員變數
private Picture mPictureGrid;//網格Canvas元件
private Point mCoo = new Point(500, 800);//座標系原點
private Picture mPictureCoo;//座標系Canvas元件

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

//onDraw裡
canvas.drawPicture(mPictureGrid);
canvas.drawPicture(mPictureCoo);
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正如API字面上的意思，在canvas上將網格和座標系兩張圖片繪製出來,如下圖：

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二、繪製邏輯

準備工作做好了，下面要到正題了

1.onDraw裡

canvas.save();//儲存先前狀態(相當於在另一個圖層操作)
canvas.translate(mCoo.x, mCoo.y);//將畫布定點平移到繪製的座標系中心
canvas.restore();//合併到root圖層
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2.看一下這兩句翻譯在圖上是什麼意思：

一旦canvas.save()，相當於新建了一個圖層(黑色虛線所示),
然後canvas.translate(mCoo.x, mCoo.y)將新建的圖層向右和向下移動
新建的圖層的好處:只有棧頂的圖層才能操作(如Canvas移動時，root圖層並沒有動，這正是我們想要的)

3.繪製外圈破碎的圓:drawBreakCircle(canvas)

 /**
 * 繪製破碎的圓
 * @param canvas
 */
private void drawBreakCircle(Canvas canvas) {
    for (int i = 0; i < 4; i++) {
        canvas.save();//儲存先前狀態(相當於在另一個圖層操作)
        canvas.rotate(90 * i);
        mMainPaint.setStrokeWidth(8);
        mMainPaint.setColor(Color.parseColor("#D5D5D5"));
        //在-350, -350, 350, 350的矩形區域,從10°掃70°繪製圓弧
        canvas.drawArc(
                -350, -350, 350, 350,
                10, 70, false, mMainPaint);
        canvas.restore();//恢復先前狀態(相當於將圖層和前一圖層合併)
    }
}     
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先看i=0時：
由於save了，前面的圖層被鎖定，相當於在另一個圖層操作

canvas.restore()呼叫後，
圖層2將它的結果給了圖層1，揮揮衣袖，不帶走一片雲彩，出棧了

先看i=1時：
由於save了，前面的圖層被鎖定，相當於在另一個圖層操作
這裡canvas.rotate(90 * 1)相當於當前圖層轉了90°，如圖：
注意:我只將座標軸的第一象限塗色,canvas圖層是一個無限的面，canvas寬高只是限制顯示，
旋轉、平移、縮放等的關鍵在於座標軸的變換，旋轉90°相當於座標軸轉了90°

canvas.restore()呼叫後，
圖層2將它的結果給了圖層1，揮揮衣袖，不帶走一片雲彩，出棧了

經過這兩個圖層的演示，想必你應該明白圖層的作用了吧。
最後畫完之後，圖層全合併到root

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4.繪製小點

畫60個點(小線)，每逢5變長，也就是畫直線，每次將畫布旋轉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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5.繪製時針：

 /**
     * 繪製時針
     *
     * @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.繪製分針：

    /**
     * 繪製分針
     * @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.繪製秒針

    /**
     * 繪製秒針
     *
     * @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繪製：在init裡初始化一下就行了
        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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8.新增文字

/**
 * 新增文字
 * @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);
    //使用外接字型放在assets目錄下
    Typeface myFont = Typeface.createFromAsset(getContext().getAssets(), "CHOPS.TTF");
    mMainPaint.setTypeface(myFont);
    mMainPaint.setTextSize(70);
    canvas.drawText("Toly", 0, -150, mMainPaint);
}
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好了，靜態效果實現了，現在讓它動起來吧

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三、讓表動起來

1.顯示當前時間：

表的旋轉角度由每個針繪製是的canvas.rotate(XXX);決定，
那麼動態改變旋轉的角度不就行了嗎! 看下面一道數學題:

11:12:45秒，時針、分針、秒針的指標各與中心水平線的夾角?
答：
秒針：45 / 60.f * 360 - 90
分針：12 / 60.f * 360 - 90 + 45 / 60.f * 1
時針：11 / 12.f * 360 - 90 + 12 / 60.f * 30 + 45 / 3600.f * 30
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2.動態更新角度：繪製指標的三個函式,加角度引數

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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3.現在每次進來，都會更新時間了,怎麼自動更新呢?

迴圈的黃金搭檔：Handler + Timer

public class ClockActivity extends AppCompatActivity {

    /**
     * 新建Handler
     */
    Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            mView.invalidate();//處理：重新整理檢視
        }
    };

    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);//傳送訊息
            }
        };
        //定時任務
        timer.schedule(timerTask, 0, 1000);
    }
}
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ok，完結散花(分析圖畫的真要命...)

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後記：捷文規範

1.本文成長記錄及勘誤表

專案原始碼	日期	備註
V0.1--github	2018-11-8	Android原生繪圖之一起畫個表

2.更多關於我

筆名	QQ	微信	愛好
張風捷特烈	1981462002	zdl1994328	語言
我的github	我的簡書	我的CSDN	個人網站

3.宣告

1----本文由張風捷特烈原創,轉載請註明
2----歡迎廣大程式設計愛好者共同交流
3----個人能力有限，如有不正之處歡迎大家批評指證，必定虛心改正
4----看到這裡，我在此感謝你的喜歡與支援

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附錄：網格+座標系繪製工具：

1.HelpDraw

/**
 * 作者：張風捷特烈<br/>
 * 時間：2018/11/5 0005:8:43<br/>
 * 郵箱：1981462002@qq.com<br/>
 * 說明：輔助畫布
 */
public class HelpDraw {

    /**
     * 獲取螢幕尺寸
     */
    public static Point getWinSize(Context context) {
        Point point = new Point();
        Utils.loadWinSize(context, point);
        return point;
    }

    /**
     * 繪製網格
     */
    public static Picture getGrid(Context context) {
        return getGrid(getWinSize(context));
    }

    /**
     * 繪製座標系
     */
    public static Picture getCoo(Context context, Point coo) {
        return getCoo(coo, getWinSize(context));
    }


    /**
     * 繪製網格
     *
     * @param winSize 螢幕尺寸
     */
    private static Picture getGrid(Point winSize) {

        Picture picture = new Picture();
        Canvas recording = picture.beginRecording(winSize.x, winSize.y);
        //初始化網格畫筆
        Paint paint = new Paint();
        paint.setStrokeWidth(2);
        paint.setColor(Color.GRAY);
        paint.setStyle(Paint.Style.STROKE);
        //設定虛線效果new float[]{可見長度, 不可見長度},偏移值
        paint.setPathEffect(new DashPathEffect(new float[]{10, 5}, 0));
        recording.drawPath(HelpPath.gridPath(50, winSize), paint);
        return picture;

    }

    /**
     * 繪製座標系
     *
     * @param coo     座標系原點
     * @param winSize 螢幕尺寸
     */
    private static Picture getCoo(Point coo, Point winSize) {
        Picture picture = new Picture();
        Canvas recording = picture.beginRecording(winSize.x, winSize.y);
        //初始化網格畫筆
        Paint paint = new Paint();
        paint.setStrokeWidth(4);
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.STROKE);
        //設定虛線效果new float[]{可見長度, 不可見長度},偏移值
        paint.setPathEffect(null);

        //繪製直線
        recording.drawPath(HelpPath.cooPath(coo, winSize), paint);
        //左箭頭
        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);
        //下箭頭
        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);
        //為座標系繪製文字
        drawText4Coo(recording, coo, winSize, paint);
        return picture;
    }

    /**
     * 為座標系繪製文字
     *
     * @param canvas  畫布
     * @param coo     座標系原點
     * @param winSize 螢幕尺寸
     * @param paint   畫筆
     */
    private static void drawText4Coo(Canvas canvas, Point coo, Point winSize, Paint paint) {
        //繪製文字
        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正軸文字
        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負軸文字
        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正軸文字
        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負軸文字
        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：張風捷特烈<br/>
 * 時間：2018/11/5 0005:8:05<br/>
 * 郵箱：1981462002@qq.com<br/>
 * 說明：輔助分析路徑
 */
public class HelpPath {

    /**
     * 繪製網格:注意只有用path才能繪製虛線
     *
     * @param step    小正方形邊長
     * @param winSize 螢幕尺寸
     */
    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;
    }

    /**
     * 座標系路徑
     *
     * @param coo     座標點
     * @param winSize 螢幕尺寸
     * @return 座標系路徑
     */
    public static Path cooPath(Point coo, Point winSize) {
        Path path = new Path();
        //x正半軸線
        path.moveTo(coo.x, coo.y);
        path.lineTo(winSize.x, coo.y);
        //x負半軸線
        path.moveTo(coo.x, coo.y);
        path.lineTo(coo.x - winSize.x, coo.y);
        //y負半軸線
        path.moveTo(coo.x, coo.y);
        path.lineTo(coo.x, coo.y - winSize.y);
        //y負半軸線
        path.moveTo(coo.x, coo.y);
        path.lineTo(coo.x, winSize.y);
        return path;
    }
}
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3.Utils

public class Utils {
    /**
     * 獲得螢幕高度
     *
     * @param ctx 上下文
     * @param winSize 螢幕尺寸
     */
    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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