Android自己定義View之儀錶盤

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建立項目，建立DashBoardView繼承自View實現OnGlobalLayoutListener介面，並重寫OnDraw方法。
使用OnGlobalLayoutListener介面須要重寫onGlobalLayout方法。在這種方法中我們將擷取View的寬高。

建立例如以下變數：

private Context mContext;    private Paint mCirclePaint,mDegreePaint,mHourPaint,mMinPaint;    private int mViewWidth,mViewHeight;

初始化這些變數：

public void init(Context context){        mContext = context;        mCirclePaint =  new Paint(Paint.ANTI_ALIAS_FLAG);        mDegreePaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mHourPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mMinPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mCirclePaint.setAntiAlias(true);        mCirclePaint.setStrokeWidth(5);        mCirclePaint.setStyle(Paint.Style.STROKE);        mHourPaint.setStrokeWidth(20);        mMinPaint.setStrokeWidth(10);        getViewTreeObserver().addOnGlobalLayoutListener(this);    }

onGlobalLayout中初始化DashBoardView寬高：

@Override    public void onGlobalLayout() {        mViewHeight = getHeight();        mViewWidth = getWidth();    }

在onDraw方法中加入例如以下繪製代碼：

/*        * 畫錶盤圓形        * */        canvas.drawCircle(mViewWidth/2,mViewHeight/2,mViewWidth/2,mCirclePaint);        /*        * 畫刻度        * */        for (int i=0;i<24;i++){            if(i==0 || i==6 || i==12 || i==18){                /*                * 畫整點刻度                * */                mDegreePaint.setStrokeWidth(5);                mDegreePaint.setTextSize(30);                canvas.drawLine(mViewWidth/2,mViewHeight/2-mViewWidth/2,mViewWidth/2,mViewHeight/2-mViewWidth/2+60,mDegreePaint);                String degree = String.valueOf(i);                canvas.drawText(degree,mViewWidth/2-mDegreePaint.measureText(degree)/2,mViewHeight/2-mViewWidth/2+90,mDegreePaint);            }else{                mDegreePaint.setStrokeWidth(3);                mDegreePaint.setTextSize(15);                canvas.drawLine(mViewWidth/2,mViewHeight/2-mViewWidth/2,mViewWidth/2,mViewHeight/2-mViewWidth/2+30,mDegreePaint);                String degree = String.valueOf(i);                canvas.drawText(degree,mViewWidth/2-mDegreePaint.measureText(degree)/2,mViewHeight/2-mViewWidth/2+90,mDegreePaint);            }            /*            * 通過旋轉畫布來畫好全部的刻度            * */            canvas.rotate(15,mViewWidth/2,mViewHeight/2);        }        /*        * 畫指標        * */        mHourPaint.setStrokeWidth(20);        mMinPaint.setStrokeWidth(10);        canvas.save();        canvas.translate(mViewWidth/2,mViewHeight/2);        canvas.drawLine(0,0,100,100,mHourPaint);        canvas.drawLine(0,0,100,200,mMinPaint);        canvas.restore();

至此我們就完畢了一個儀錶盤的繪製。例如以下：

完整代碼下載：完整項目

Android自己定義View之儀錶盤