Question

android开发 BaseAdapter中getView()里的ViewGroup是什么意思

public View getView(int position,View converView,ViewGroup parent){}
中的ViewGroup parent是什么
为什么每次使用是定义成null也能照常用？

Answer 1

应该去看下源码，parent是item的view的父视图，调整item宽高用的，你自定义一个viewGroup的时候除了通常要重写onLayout onMeasure等方法，计算子view的宽高，如果有了这个parent参数，并且后面的attachToRoot值为否，则会从parent中提取layout_width和layout_height组成LayoutParams，设给convertView。

源码：
ViewGroup.LayoutParams params = null;

if (root != null) {
if (DEBUG) {
System.out.println("Creating params from root: " +
root);
}
// Create layout params that match root, if supplied
params = root.generateLayoutParams(attrs);
if (!attachToRoot) {
// Set the layout params for temp if we are not
// attaching. (If we are, we use addView, below)
temp.setLayoutParams(params);
}
}

if (root != null && attachToRoot) {
root.addView(temp, params);
}

// Decide whether to return the root that was passed in or the
// top view found in xml.
if (root == null || !attachToRoot) {
result = temp;
}