private void setListViewHeightBasedOnChildren(ListView listView) {
                  ListAdapter listAdapter = listView.getAdapter();
                  if (listAdapter == null) {
                             // pre-condition
                             return;
                  }

                  int totalHeight = 0;
                  for (int i = 0; i < listAdapter.getCount(); i++) {
                             View listItem = listAdapter.getView(i, null, listView);
                             listItem.measure(0, 0);
                             totalHeight += listItem.getMeasuredHeight();
                  }

                  ViewGroup.LayoutParams params = listView.getLayoutParams();
                  params.height = totalHeight
                           + (listView.getDividerHeight() * (listAdapter.getCount() - 1));
                  listView.setLayoutParams(params);
     }

在ListView声明之后调用就可以了。

     看到大家的回复，还有更简单的方法：
     不需要硬着算，只需要自定义ListView，重写下OnMeasured方法就好了，受教了，谢谢

public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
           int mExpandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
           super.onMeasure(widthMeasureSpec, mExpandSpec);

    }