public class MyView extends View {
    private String TAG="MyView";    private Paint mPaint;   //畫筆
private RectF oval;
    public MyView(Context context) {
        super(context);
        init();
    }

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init();
    }
    public 
 
MyView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    /**
     * 初始化
*/
private void init() {
        mPaint=new Paint();
        // 設定Paint為無鋸齒
mPaint.setAntiAlias(true);
        oval=new RectF();
    }

    //測量
@Override
 
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int widthMode=MeasureSpec.getMode(widthMeasureSpec);
        int widthSize=MeasureSpec.getSize(widthMeasureSpec);
        int heightMode=MeasureSpec.getMode(heightMeasureSpec);
        int 
 
heightSize=MeasureSpec.getSize(heightMeasureSpec);
        switch (widthMode){
            case MeasureSpec.AT_MOST:
                //子容器可以是宣告大小內的任意大小.
break;
            case MeasureSpec.EXACTLY:
                //父容器已經為子容器設定了尺寸,子容器應當服從這些邊界,不論子容器想要多大的空間.
break;
            case MeasureSpec.UNSPECIFIED:
                //父容器對於子容器沒有任何限制,子容器想要多大就多大.
break;

        }
        Log.e(TAG, "onMeasure--widthSize-->" + widthSize);
        Log.e(TAG, "onMeasure--heightMode-->" + heightMode);
        Log.e(TAG, "onMeasure--heightSize-->" + heightSize);
    }
    //畫的位置
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        super.onLayout(changed, left, top, right, bottom);
        Log.e(TAG, "onLayout");
    }

    @Override
protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        mPaint.setColor(Color.BLUE);
        int with=getWidth();
        int height=getHeight();
        mPaint.setStyle(Paint.Style.FILL);
        // 畫一個正放形 前面兩個是左上角座標 後面兩個是右下角座標
canvas.drawRect(0,20,30,50,mPaint);

    }