MarginLayoutParams

創建及使用MarginLayoutParmas

MarginLayoutParams是繼承自ViewGroup.LayoutParmas,創建時直接new一個對象即可;但一般我們可以這麼做:

先獲取View本身的LayoutParams對象,檢測是否屬於一個MarginLayoutParmas對象,如果是直接修改屬性值即可;如果不是,需要以原有佈局參數對象爲基礎,創建一個新的MarginLayoutParams對象,再進行屬性設置

ViewGroup.LayoutParams params = view.getLayoutParams();
 ViewGroup.MarginLayoutParams marginParams = null;
 //獲取view的margin設置參數
 if (params instanceof ViewGroup.MarginLayoutParams) {
     marginParams = (ViewGroup.MarginLayoutParams) params;
 } else {
     //不存在時創建一個新的參數
     //基於View本身原有的佈局參數對象
     marginParams = new ViewGroup.MarginLayoutParams(params);
 }

創建一個MarginLayoutParams時,需要以View本身的佈局參數對象爲基礎,否則可能丟失一些原本的佈局屬性.

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通用的設置margin屬性的方法

/**
 * 設置某個View的margin
 *
 * @param view   需要設置的view
 * @param isDp   需要設置的數值是否爲DP
 * @param left   左邊距
 * @param right  右邊距
 * @param top    上邊距
 * @param bottom 下邊距
 * @return
 */
public static ViewGroup.LayoutParams setViewMargin(View view, boolean isDp, int left, int right, int top, int bottom) {
    if (view == null) {
        return null;
    }

    int leftPx = left;
    int rightPx = right;
    int topPx = top;
    int bottomPx = bottom;
    ViewGroup.LayoutParams params = view.getLayoutParams();
    ViewGroup.MarginLayoutParams marginParams = null;
    //獲取view的margin設置參數
    if (params instanceof ViewGroup.MarginLayoutParams) {
        marginParams = (ViewGroup.MarginLayoutParams) params;
    } else {
        //不存在時創建一個新的參數
        marginParams = new ViewGroup.MarginLayoutParams(params);
    }

    //根據DP與PX轉換計算值
    if (isDp) {
        leftPx = getPxFromDpi(left);
        rightPx = getPxFromDpi(right);
        topPx = getPxFromDpi(top);
        bottomPx = getPxFromDpi(bottom);
    }
    //設置margin
    marginParams.setMargins(leftPx, topPx, rightPx, bottomPx);
    view.setLayoutParams(marginParams);
    return marginParams;
}

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轉載自MarginLayoutParams–一個可以在代碼中直接設置margin的方法