转载 ListView动态更新数据

ListView就是可以显示一行行Item的控件，有时候数据非常多，通常需要分页显示，但为了减少用户的输入，我们可以动态更新ListView，把下一页要显示的数据的添加到当前ListView中。

先看看效果：


    需要注意的是在什么时候去更新数据 ，listVIew的setOnScrollListener监听是否滚到了最后一条记录，

    取到的数据加到list中，最后记得调用adapter的notifyDataSetChanged，通知listview改变。

    不废话，上代码。

    主文件：
    view plain

        import java.util.ArrayList;  
        import java.util.List;  
          
        import android.app.Activity;  
        import android.os.AsyncTask;  
        import android.os.Bundle;  
        import android.widget.AbsListView;  
        import android.widget.AbsListView.OnScrollListener;  
        import android.widget.ListView;  
        import android.widget.Toast;  
          
        public class ListViewActivity extends Activity {  
            private ListView listView;  
            //定义适配器  
            private ListItemAdapter listadpter;  
            //定义每一页显示行数  
            private int VIEW_COUNT = 20;  
            //定义的页数  
            private int index = 0;  
            //当前页  
            private int currentPage = 1;  
            //所以数据的条数  
            private int totalCount;  
            //每次取的数据，只要最后一次可能不一样。  
            private int maxResult;  
            //泛型集合ArrayList  
            private ArrayList<Students> arrayList = new ArrayList<Students>();  
            //数据操作的dao类  
            StudentsDAO dao = new StudentsDAO(ListViewActivity.this);  
            //实体bean  
            Students students = new Students();  
            // 标记：上次的ID  
              
            private boolean isUpdating = false;  
            /** Called when the activity is first created. */  
            @Override  
            public void onCreate(Bundle savedInstanceState) {  
                super.onCreate(savedInstanceState);  
                setContentView(R.layout.main);  
                //初始化界面  
                initView();  
                //插入100条记录。  
                dao.insert();  
                totalCount  = dao.getCount();  
                maxResult = getMaxResult();  
                //调用dao里面的selectAll()方法  
                arrayList = dao.getAllItems(index, maxResult);  
                //实例化适配器  
                System.out.println("arrlist-->"+arrayList.size());  
                listadpter = new ListItemAdapter(ListViewActivity.this,arrayList);  
                //填充适配器  
                listView.setAdapter(listadpter);  
                          
                listView.setOnScrollListener(new OnScrollListener() {  
                      
                    @Override  
                    public void onScrollStateChanged(AbsListView view, int scrollState) {  
                          
                    }  
                      
                    @Override  
                    public void onScroll(AbsListView view, int firstVisibleItem,  
                            int visibleItemCount, int totalItemCount) {  
                        if(firstVisibleItem + visibleItemCount == totalItemCount && !isUpdating){  
                            if(totalItemCount<totalCount){ //防止最后一次取数据进入死循环。  
                                Toast.makeText(ListViewActivity.this, "正在取第"+(++currentPage)+"的数据", Toast.LENGTH_LONG).show();  
                            AsyncUpdateDatasTask asyncUpdateWeiBoDatasTask = new AsyncUpdateDatasTask();  
                            asyncUpdateWeiBoDatasTask.execute();  
                            }  
                            System.out.println("begin update-------------");  
                        }  
                    }  
                });  
            }  
            //初始化界面方法  
            private void initView() {  
                // TODO Auto-generated method stub  
                listView = (ListView) findViewById(R.id.list);  
            }  
            class AsyncUpdateDatasTask  extends AsyncTask<Void, Void, List<Students>> {  
          
                @Override  
                protected List<Students> doInBackground(Void... params) {  
                    // TODO Auto-generated method stub  
                    isUpdating = true;  
                    index += VIEW_COUNT;  
                    List<Students> list =new ArrayList<Students>();  
                    list = dao.getAllItems(index, maxResult);  
                    return list;  
                }  
                @Override  
                protected void onPostExecute(List<Students> result) {  
                    // TODO Auto-generated method stub  
                    super.onPostExecute(result);  
                    arrayList.addAll(result);  
                    listadpter.notifyDataSetChanged();  
                    isUpdating = false;  
                    System.out.println("end update--------------");  
                }  
            }  
           private int getMaxResult(){  
               int totalPage = (totalCount+VIEW_COUNT-1)/VIEW_COUNT;  
                  return  totalCount-(totalPage-1)*VIEW_COUNT;  
           }  
        }  

    数据库Dao文件：

    view plain

        package com.shao.list;  
          
          
        import java.util.ArrayList;  
        import java.util.Random;  
          
        import android.content.ContentValues;  
        import android.content.Context;  
        import android.database.Cursor;  
        import android.database.sqlite.SQLiteDatabase;  
        import android.database.sqlite.SQLiteOpenHelper;  
          
        public class StudentsDAO extends SQLiteOpenHelper {  
          
            private final static String AUDIODATABASE_NAME = "student.db";  
            private final static String TABLE = "student";  
            private final static String COLUM_ID = "id";  
            private final static String COLUM_NAME = "name";  
            private final static String COLUM_AGE = "age";  
            private final static int DATABASE_VERSION = 1;  
            private long row;  
            private ArrayList<Students> arrayList;  
          
            public StudentsDAO(Context context) {  
                super(context, AUDIODATABASE_NAME, null, DATABASE_VERSION);  
                // TODO Auto-generated constructor stub  
            }  
          
            @Override  
            public void onCreate(SQLiteDatabase db) {  
                // TODO Auto-generated method stub  
                String sql = "CREATE TABLE " + TABLE + " (" + COLUM_ID  
                        + " INTEGER primary key autoincrement, " + " " + COLUM_NAME  
                        + " text, " + " " + COLUM_AGE + " int)";  
                db.execSQL(sql);  
            }  
          
            @Override  
            public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {  
                // TODO Auto-generated method stub  
                String sql = "DROP TABLE IF EXISTS " + TABLE;  
                db.execSQL(sql);  
            }  
          
            public long insert() {  
                SQLiteDatabase db = getWritableDatabase();  
                ContentValues cv = new ContentValues();  
                Random random = new Random();  
                for(int i=1;i<=100;i++)  
                {  
                    cv.put(COLUM_ID, i);  
                    cv.put(COLUM_NAME, "name"+String.valueOf(i));  
                    cv.put(COLUM_AGE, random.nextInt(100));  
                    row = db.insert(TABLE, null, cv);  
                }  
                db.close();  
                return row;  
            }  
            //查询记录的总数  
                public int getCount() {  
                    SQLiteDatabase db = getWritableDatabase();  
                     String sql = "select count(*) from '"+TABLE+"'";  
                    Cursor c = db.rawQuery(sql, null);  
                    c.moveToFirst();  
                    int length = c.getInt(0);  
                  c.close();  
                 db.close();  
                // System.out.println("length-->"+length);  
                    return length;  
             }  
                public  ArrayList<Students> getAllItems(int firstResult, int maxResult) {  
                       arrayList=new ArrayList<Students>();  
                         SQLiteDatabase db = getWritableDatabase();  
                        String sql = "select * from '"+TABLE+"' limit ?,?";  
                         Cursor cursor = db.rawQuery(sql, new String[]{String.valueOf(firstResult), String.valueOf(maxResult)});  
                         if (cursor != null && cursor.getCount() > 0) {  
                                cursor.moveToFirst();  
                            }  
                            for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {  
                                Students students=new Students();  
                                students.setId(cursor.getInt(0));  
                                students.setName(cursor.getString(1));  
                                students.setAge(cursor.getInt(2));  
                                arrayList.add(students);  
                            }  
                            cursor.close();  
                            db.close();  
                            return arrayList;  
                    }  
                  
            public ArrayList<Students> selectAll() {  
                arrayList=new ArrayList<Students>();  
                SQLiteDatabase db = this.getWritableDatabase();  
                Cursor cursor = db.query(TABLE, null, null, null, null, null, null);  
                if (cursor != null && cursor.getCount() > 0) {  
                    cursor.moveToFirst();  
                }  
                for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {  
                    Students students=new Students();  
                    students.setId(cursor.getInt(0));  
                    students.setName(cursor.getString(1));  
                    students.setAge(cursor.getInt(2));  
                    arrayList.add(students);  
                }  
                cursor.close();  
                db.close();  
                return arrayList;  
                  
            }  
          
        }