動態計算Gridview的高度，寬度，將GridView居中

/**
 * 設置GridView居中
 * 當父目錄是RelativeLayout  需要在GridView設置   android:layout_centerHorizontal="true"
 * 當父目錄是LinearLayout    需要在父目錄設置  android:gravity="center_horizontal"
 * @param gridView
 */
public static void calGridViewSumWH(GridView gridView) {
    int numColumns;
    int horizontalSpacing;
    try {
        numColumns = getFieldValue("mRequestedNumColumns", gridView);
        if (numColumns < 1) return;
        horizontalSpacing = getFieldValue("mRequestedHorizontalSpacing", gridView);

        ListAdapter listAdapter = gridView.getAdapter();
        if (listAdapter == null) return;

        int totalHeight = 0;
        int totalWidth = 0;
        int len = listAdapter.getCount();
        for (int i = 0; i < len; i++) {
            View listItem = listAdapter.getView(i, null, gridView);
            listItem.measure(0, 0);
            if (i < numColumns)
                totalWidth+= listItem.getMeasuredWidth();

            if ((i + 1) % numColumns == 0 && (i + 1) != len) {
                if (Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN) {
                    totalHeight += listItem.getMeasuredHeight() + gridView.getVerticalSpacing();
                } else {
                    totalHeight += listItem.getMeasuredHeight();
                }
            }
            if ((i + 1) == len) {
                totalHeight += listItem.getMeasuredHeight();
            }
        }
        if (len < numColumns) {
            gridView.setNumColumns(len);
        }
        if (Build.VERSION.SDK_INT > Build.VERSION_CODES.JELLY_BEAN) {
            totalWidth = totalWidth + horizontalSpacing * (numColumns - 1);
        }

        ViewGroup.LayoutParams params = gridView.getLayoutParams();
        params.height = totalHeight;
        params.width = totalWidth;
        gridView.setLayoutParams(params);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

/**
 * 動態獲取屬性值
 * @param attributeName
 * @param gridView
 * @return
 */
public static int getFieldValue(String attributeName, GridView gridView) {
    try {
        Field field = GridView.class.getDeclaredField(attributeName);
        field.setAccessible(true);
        return Integer.parseInt(field.get(gridView).toString());
    } catch (Exception e) {
        e.printStackTrace();
    }
    return 0;
}

然後xml在設置的時候，需要如下設置

<RelativeLayout
    android:layout_width="130dp"
    android:layout_height="130dp">
        <ImageView
            android:id="@+id/iv_img"
            android:layout_centerInParent="true"
            android:maxHeight="130dp"
            android:maxWidth="130dp"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
</RelativeLayout>

因爲上述代碼測量得到的寬高會受到圖片大小的影響，一旦圖片大於父容器中設置的130dp，那樣子測量得到的寬高也會變動，導致最後展示的效果會有所偏差。

<RelativeLayout
    android:paddingTop="25dp"
    android:paddingBottom="25dp"
    android:background="@android:color/white"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <GridView
        android:id="@+id/ahgv_qualification"
        android:verticalSpacing="25dp"
        android:horizontalSpacing="25dp"
        android:numColumns="2"
        android:layout_centerHorizontal="true"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
</RelativeLayout>