手动创立RelativeLayout

为何要手动创立RelativeLayout?

-->总有原因的，如果实在没有原因，那最好还是通过xml文件来建立；

要点：要为每一个child view生成一个LayoutParams.

实施：

RelativeLayout root_layout = new RelativeLayout(context);

ImageView img_view          = new ImageView(context);

RelativeLayout.LayoutParams img_lp = new RelativeLayout.LayoutParams(img_width, img_height);

img_lp.topMargin = img_top_margin;

img_lp.leftMargin= img_left_margin;

root_layout.addView(img_view, img_lp);

TextView text_view = new TextView(context);

RelativeLayout.LayoutPrams text_lp = new RelativeLayout.LayoutParams(text_width, text_height);

text_lp.topMargin = text_top_margin;

text_lp.leftMargin = text_left_margin;

root_layout.addView(text_view, text_lp);

错误的方式：使用同一个LayoutParams设置多个View. 最后生成root_layout时的LayoutParams只采用最后一次设置的数值，将导致错误的布局。

RelativeLayout root_layout = new RelativeLayout(context);

ImageView img_view          = new ImageView(context);

RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(img_width, img_height);

img_lp.topMargin = img_top_margin;

img_lp.leftMargin= img_left_margin;

root_layout.addView(img_view, lp);

TextView text_view = new TextView(context);

lp.height = text_height;

lp.width  = text_width;

lp.topMargin = text_top_margin;

lp.leftMargin = text_left_margin;

root_layout.addView(text_view, lp);

---->Wrong layout..

其他的LayoutParams设置：

切以为使用MarginLayout中的数值即可满足布局的要求，要充分发挥RelativeLayout.LayoutParams的功效还可以通过addRule()来设置相对布局，前提是在生成view的时候设置其id(setId)，具体请参考：http://www.mergeconflict.net/2010/08/manually-positioning-views-in.html