笔记整理1_1：解决在ScrollView中嵌套ListView不能显示全部item的问题

package com.example.scrollview;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;

import com.pb.custom.MyListView;
import com.pb.custom.Utility;

/**
 * 解决在ScrollView中嵌套ListView不能显示全部item的问题  *　　方法一：重写ListView
 *   方法二：人工计算子控件的尺寸；调用Utility（类名，类在后面）.setListViewHeightBasedOnChildren(ListView对象); *　　注意：ScrollView布局下只能有一个子布局(子布局中可以嵌套其他布局，但是ScrollView下只能是一个，这个要注意),还有一个要注意的是 *   使用方法二的话每个item布局的父组件类型必须是LinearLayout

*/

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

//        MyListView myListView= (MyListView) findViewById(R.id.mylist);

        ListView myListView= (ListView) findViewById(R.id.mylist);
        myListView.setAdapter(new MyAdapter());

        Utility.setListViewHeightBasedOnChildren(myListView);

    }

    class MyAdapter extends BaseAdapter{

        @Override
        public int getCount() {
            return 25;
        }

        @Override
        public Object getItem(int i) {
            return null;
        }

        @Override
        public long getItemId(int i) {
            return i;
        }

        @Override
        public View getView(int i, View view, ViewGroup viewGroup) {
            if(view==null)
                view=getLayoutInflater().inflate(R.layout.mylist_item,null);
            return view;
        }
    }

}

package com.pb.custom;

import android.content.Context;
import android.util.AttributeSet;
import android.widget.ListView;

/** *重写ListView组件
 * Created by dmz1024 on 2015/11/3.
 */
public class MyListView extends ListView {
//    public MyListView(Context context) {
//        super(context);
//    }

    public MyListView(Context context, AttributeSet attrs){
         super(context, attrs);
      }

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

}

package com.pb.custom;

import android.view.View;
import android.view.ViewGroup;
import android.widget.ListAdapter;
import android.widget.ListView;

/**
 * Created by dmz1024 on 2015/11/3.
*  方法二：重新计算每个item高度
 */
public class Utility {
    public static void setListViewHeightBasedOnChildren(ListView listView) {
        //获取ListView对应的Adapter
        ListAdapter listAdapter = listView.getAdapter();
        if (listAdapter == null) {
            // pre-condition
            return;
            }

        int totalHeight = 0;
        for (int i = 0, len = listAdapter.getCount(); i < len; i++) { //listAdapter.getCount()返回数据项的数目
            View listItem = listAdapter.getView(i, null, listView);
            listItem.measure(0, 0); //计算子项View 的宽高
            totalHeight += listItem.getMeasuredHeight(); //统计所有子项的总高度
            }

        ViewGroup.LayoutParams params = listView.getLayoutParams();
        params.height = totalHeight + (listView.getDividerHeight() * (listAdapter.getCount() - 1));
        //listView.getDividerHeight()获取子项间分隔符占用的高度
        //params.height最后得到整个ListView完整显示需要的高度
        listView.setLayoutParams(params);
        }
    }