今天对比了一下内存映射文件的性能和普通文件的测试，不比不知道，一比吓一跳啊。差距太大了。

public class FileTest {

	static int length = 0x8000000; // 128 Mb

	public void doMemTest() {
		try {
			long start = System.currentTimeMillis();
			FileChannel fc = new RandomAccessFile("e:/test/test.dat", "rw").getChannel();
			MappedByteBuffer out = fc.map(FileChannel.MapMode.READ_WRITE, 0, length);
			for (int i = 0; i < length; i++) {  
	            out.put((byte) 'x');  
	        } 
			long end = System.currentTimeMillis();
			fc.close();
			System.out.println(end - start);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public void doGeneralTest() {
		try {
			long start = System.currentTimeMillis();
			RandomAccessFile fc = new RandomAccessFile("e:/test/test.dat", "rw");
			for (int i = 0; i < length; i++) {  
	            fc.write((byte) 'x');
	        } 
			long end = System.currentTimeMillis();
			
			System.out.println(end - start);
			fc.close();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	public static void main(String[] args) throws Exception {
		FileTest t = new FileTest();
//		t.doMemTest();
		t.doGeneralTest();
	}
}

doMemtest这个方法，1000多毫秒的样子，doGeneralTest这个基本就没跑完过。

有时候我们想在listView上分类，或者呢 有时候一行显示两列内容，有时候需要三列内容 ，那怎么实现呢，这里呢就要使用

class Section {  
        String caption;  
        Adapter adapter;  
          
        Section(String caption, Adapter adapter) {  
            this.caption=caption;  
            this.adapter=adapter;  
        }  
    }  

自定义一个类，这个类呢包含多个adapter就可以了，想用那种就用那种。

abstract public class SectionedAdapter extends BaseAdapter {  
    abstract protected View getHeaderView(String caption,int index,View convertView,ViewGroup parent);  
      
    private List<Section> sections=new ArrayList<Section>();  
    private static int TYPE_SECTION_HEADER=0;  
  
    public SectionedAdapter() {  
        super();  
    }  
  
    public void addSection(String caption, Adapter adapter) {  
        sections.add(new Section(caption, adapter));  
    }  
  
    public Object getItem(int position) {  
        for (Section section : this.sections) {  
            if (position==0) {  
                return(section);  
            }  
              
            int size=section.adapter.getCount()+1;  
  
            if (position<size) {  
                return(section.adapter.getItem(position-1));  
            }  
  
            position-=size;  
        }  
          
        return(null);  
    }  
  
    public int getCount() {  
        int total=0;  
          
        for (Section section : this.sections) {  
            total+=section.adapter.getCount()+1; // add one for header  
        }  
          
        return(total);  
    }  
  
    public int getViewTypeCount() {  
        int total=1;    // one for the header, plus those from sections  
          
        for (Section section : this.sections) {  
            total+=section.adapter.getViewTypeCount();  
        }  
          
        return(total);  
    }  
  
    public int getItemViewType(int position) {  
        int typeOffset=TYPE_SECTION_HEADER+1;   // start counting from here  
          
        for (Section section : this.sections) {  
            if (position==0) {  
                return(TYPE_SECTION_HEADER);  
            }  
              
            int size=section.adapter.getCount()+1;  
  
            if (position<size) {  
                return(typeOffset+section.adapter.getItemViewType(position-1));  
            }  
  
            position-=size;  
            typeOffset+=section.adapter.getViewTypeCount();  
        }  
          
        return(-1);  
    }  
  
    public boolean areAllItemsSelectable() {  
        return(false);  
    }  
  
    public boolean isEnabled(int position) {  
        return(getItemViewType(position)!=TYPE_SECTION_HEADER);  
    }  
  
    @Override  
    public View getView(int position, View convertView,  
                                            ViewGroup parent) {  
        int sectionIndex=0;  
          
        for (Section section : this.sections) {  
            if (position==0) {  
                return(getHeaderView(section.caption, sectionIndex,convertView, parent));  
            }  
  
            int size=section.adapter.getCount()+1;  
  
            if (position<size) {  
                return(section.adapter.getView(position-1,  convertView,parent));  
            }  
  
            position-=size;  
            sectionIndex++;  
        }  
          
        return(null);  
    }  
  
    @Override  
    public long getItemId(int position) {  
        return(position);  
    }  
  
    class Section {  
        String caption;  
        Adapter adapter;  
          
        Section(String caption, Adapter adapter) {  
            this.caption=caption;  
            this.adapter=adapter;  
        }  
    }  
} 

然后主类就是

public class SectionedDemo extends ListActivity {  
    private static String[] items={"lorem", "ipsum", "dolor","purus"};  
      
    @Override  
    public void onCreate(Bundle icicle) {  
        super.onCreate(icicle);  
        setContentView(R.layout.main);  
          
        adapter.addSection("Original",new ArrayAdapter<String>(this,  
                                                    android.R.layout.simple_list_item_1,  
                                                    items));  
          
        List<String> list=Arrays.asList(items);  
          
        Collections.shuffle(list);  
  
        adapter.addSection("Shuffled",new ArrayAdapter<String>(this,  
                                                    android.R.layout.simple_list_item_1,  
                                                    list));  
          
        list=Arrays.asList(items);  
          
        Collections.shuffle(list);  
  
        adapter.addSection("Re-shuffled",new ArrayAdapter<String>(this,  
                                                    android.R.layout.simple_list_item_1,  
                                                    list));  
          
        setListAdapter(adapter);  
    }  
      
    SectionedAdapter adapter=new SectionedAdapter() {  
        protected View getHeaderView(String caption, int index,View convertView,ViewGroup parent) {  
            TextView result=(TextView)convertView;  
              
            if (convertView==null) {  
                result=(TextView)getLayoutInflater().inflate(R.layout.header, null);  
            }  
              
            result.setText(caption);  
              
            return(result);  
        }  
    };  
} 

其他的就需要你自己变化了，我这里只是吧内容打乱。

有些东西我只是简单调解没有源码或者我认为很简单的就不提供了。

对于复杂一些或者很难说清的 本人表达能力有限会把源码发上的