ListView多选操作模式详解CHOICE_MODE_MULTIPLE与CHOICE_MODE_MULTIPLE_MODAL

这篇文章我们将详细的介绍如何实现ListView的多选操作，文中将会纠正在使用ListViewCHOICE_MODE_MULTIPLE或者CHOICE_MODE_MULTIPLE_MODAL时容易犯的错误，以及

CHOICE_MODE_MULTIPLE与CHOICE_MODE_MULTIPLE_MODAL的区别。最后我们将给出一个demo来演示两种多选操作的实现。

一、在不使用ListView多选模式的情况下

注：我认为这一节可以不看，因为我觉得不使用ListView的多选模式有点愚蠢。

如果我们不知道ListView自带多选模式，那么我们一般是通过维护一个保存被选择position集合来实现多选的，通常情况下这个集合类型我们选择HashSet。

实现的大致框架如下：

Adapter中：

保存被选择的position

1	public HashSet<Long> selectedItems = new HashSet<Long>();

getView中判断当前Position是否在集合中，从而显示不同的外观

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public View getView(int position, View convertView, ViewGroup par) { ......              if (selectedItems.contains((long)position)){                  holder.cBox.setChecked( true );              } else {                  holder.cBox.setChecked( false );              }              if (selectedMode==AppContext.MULTI_SELECTED){                  holder.cBox.setVisibility(View.VISIBLE);                  holder.check_box_wraper.setVisibility(View.VISIBLE);              } else {                  holder.cBox.setVisibility(View.GONE);                  holder.check_box_wraper.setVisibility(View.GONE);              } ..... ｝

Activity中：

主要是处理onItemClick事件，在不同模式下，做不同的处理。

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@Override public void onItemClick(AdapterView<?> a, View v, int position, long id) {      //普通模式 ：直接打开一个activity          if (itemClickActionMode==AppContext.VIEW_NOTE){              Long mId=Long.parseLong(idText.getText().toString());              Uri uri = ContentUris.withAppendedId(getIntent().getData(), mId);              startActivity( new Intent(Intent.ACTION_VIEW, uri));          }          //多选模式：更新adapter中selectedItems 集合的值，同时 让adapter在getView中改变item的外观。         else {              ViewHolder vHollder = (ViewHolder) v.getTag();              if (mAdapter.selectedItems.contains((long)position)){                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    mAdapter.selectedItems.remove((long)position);              } else {                          mAdapter.selectedItems.add((long)position);              }              mAdapter.notifyDataSetChanged();              onItemSelected(getSelectedCount());              }      }

上面的做法其实用的很普遍。但是我们不提倡。

二、使用ListViiew的CHOICE_MODE_MULTIPLE模式

ListView有四种模式：

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/**   * Normal list that does not indicate choices   */ public static final int CHOICE_MODE_NONE = 0; /**   * The list allows up to one choice   */ public static final int CHOICE_MODE_SINGLE = 1; /**   * The list allows multiple choices   */ public static final int CHOICE_MODE_MULTIPLE = 2; /**   * The list allows multiple choices in a modal selection mode   */ public static final int CHOICE_MODE_MULTIPLE_MODAL = 3;

其中CHOICE_MODE_NONE是普通模式，CHOICE_MODE_SINGLE是单选模式，不常用，CHOICE_MODE_MULTIPLE和CHOICE_MODE_MULTIPLE_MODAL都是多选模式，他们的区别稍后我们会讲到。

所以ListView在设计的时候其实是考虑了多选操作的，我们没有必要自己再像第一节描述的那样专门维护一个HashSet来保存被选择的position。实现ListView的多选操作的代码在ListView直接父类AbsListView中，AbsListView已经有一个mCheckStates变量来做了保存被选择的position这个事情。mCheckStates的定义如下：

1	SparseBooleanArray mCheckStates;

AbsListView还定义了如下公共方法：

//判断一个item是否被选中

1	public boolean isItemChecked(int position);

//获得被选中item的总数

1	public int getCheckedItemCount();

//选中一个item

1	public void setItemChecked(int position, boolean value);

//清除选中的item

1	public void clearChoices();

当点击一个item的时候absListView中会调用performItemClick，如果是CHOICE_MODE_MULTIPLE，则该item点击一次，mCheckStates中相应位置的状态变更一次。然后我们就可以通过listView的getCheckedItemCount()方法获取选择了多少个；isItemChecked(int position)方法判断一个item是不是被选中。

有了这些原生sdk的支持，难道还有什么多选操作是不能实现的吗？所以是不是应该考虑放弃第一节中描述的那种方法了呢？遗憾的是很多android开发者即使是用了CHOICE_MODE_MULTIPLE，仍然没有去利用这些ListView自带的功能，估计是根本不知道该CHOICE_MODE_MULTIPLE的 特性吧，这其实也是android程序员与ios程序员真正存在差距的地方。

CHOICE_MODE_MULTIPLE实战

先看看效果图

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