Android onMeasure(widthSpec, heightSpec)

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每個View中都有一個測量繪製控制項大小的方法onMeasure(int widthMeasureSpec, int heightMeasureSpec) ，該方法用於初始化控制項所佔的地區：

摘自SlidingDrawer.java，僅作參考說明onMeasure(int widthMeasureSpec, int heightMeasureSpec)方法

@Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        //onMeasure方法傳入的兩個參數widthMeasureSpec, heightMeasureSpec，其單位為dp或dip            int widthSpecMode = MeasureSpec.getMode(widthMeasureSpec);    //這裡判斷單位是dp或dip，有或者其他的單位類型        int widthSpecSize =  MeasureSpec.getSize(widthMeasureSpec); //將單位轉為px        int heightSpecMode = MeasureSpec.getMode(heightMeasureSpec);        int heightSpecSize =  MeasureSpec.getSize(heightMeasureSpec);        if (widthSpecMode == MeasureSpec.UNSPECIFIED || heightSpecMode == MeasureSpec.UNSPECIFIED) {            throw new RuntimeException("SlidingDrawer cannot have UNSPECIFIED dimensions");        }        //        final View handle = mHandle;        measureChild(handle, widthMeasureSpec, heightMeasureSpec);        if (mVertical) {            int height = heightSpecSize - handle.getMeasuredHeight() - mTopOffset;            mContent.measure(MeasureSpec.makeMeasureSpec(widthSpecSize, MeasureSpec.EXACTLY),                    MeasureSpec.makeMeasureSpec(height, MeasureSpec.EXACTLY));        } else {            int width = widthSpecSize - handle.getMeasuredWidth() - mTopOffset;            mContent.measure(MeasureSpec.makeMeasureSpec(width, MeasureSpec.EXACTLY),                    MeasureSpec.makeMeasureSpec(heightSpecSize, MeasureSpec.EXACTLY));        }        //最後繪製父控制項的大小        setMeasuredDimension(widthSpecSize, heightSpecSize);        //super.onMeasure(widthMeasureSpec, heightMeasureSpec)原型則是下面這樣寫的:        //setMeasuredDimension(getDefaultSize(getSuggestedMinimumWidth(), widthMeasureSpec),        //        getDefaultSize(getSuggestedMinimumHeight(), heightMeasureSpec));    }

 

   

Android onMeasure(widthSpec, heightSpec)