MarginLayoutParams

创建及使用MarginLayoutParmas

MarginLayoutParams是继承自ViewGroup.LayoutParmas,创建时直接new一个对象即可;但一般我们可以这么做:

先获取View本身的LayoutParams对象,检测是否属于一个MarginLayoutParmas对象,如果是直接修改属性值即可;如果不是,需要以原有布局参数对象为基础,创建一个新的MarginLayoutParams对象,再进行属性设置

ViewGroup.LayoutParams params = view.getLayoutParams();
 ViewGroup.MarginLayoutParams marginParams = null;
 //获取view的margin设置参数
 if (params instanceof ViewGroup.MarginLayoutParams) {
     marginParams = (ViewGroup.MarginLayoutParams) params;
 } else {
     //不存在时创建一个新的参数
     //基于View本身原有的布局参数对象
     marginParams = new ViewGroup.MarginLayoutParams(params);
 }

创建一个MarginLayoutParams时,需要以View本身的布局参数对象为基础,否则可能丢失一些原本的布局属性.

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通用的设置margin属性的方法

/**
 * 设置某个View的margin
 *
 * @param view   需要设置的view
 * @param isDp   需要设置的数值是否为DP
 * @param left   左边距
 * @param right  右边距
 * @param top    上边距
 * @param bottom 下边距
 * @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;
    //获取view的margin设置参数
    if (params instanceof ViewGroup.MarginLayoutParams) {
        marginParams = (ViewGroup.MarginLayoutParams) params;
    } else {
        //不存在时创建一个新的参数
        marginParams = new ViewGroup.MarginLayoutParams(params);
    }

    //根据DP与PX转换计算值
    if (isDp) {
        leftPx = getPxFromDpi(left);
        rightPx = getPxFromDpi(right);
        topPx = getPxFromDpi(top);
        bottomPx = getPxFromDpi(bottom);
    }
    //设置margin
    marginParams.setMargins(leftPx, topPx, rightPx, bottomPx);
    view.setLayoutParams(marginParams);
    return marginParams;
}

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转载自MarginLayoutParams–一个可以在代码中直接设置margin的方法