AsyncTask 异步任务 的用法（并且使用ORMlite关系数据库）；

 package com.lixu.asynctask;

 import com.j256.ormlite.field.DatabaseField;
 import com.j256.ormlite.table.DatabaseTable;

 @DatabaseTable(tableName = "users")
 public class User {
     public User() {

     }

     @Override
     public String toString() {
         return "id" + user_id + "," + ",姓名：" + name + ",年龄：" + age + ",性别：" + sex+",班级是："+aclass;
     }

     public int getUser_id() {
         return user_id;
     }

     public void setUser_id(int user_id) {
         this.user_id = user_id;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public int getAge() {
         return age;
     }

     public void setAge(int age) {
         this.age = age;
     }

     public String getSex() {
         return sex;
     }

     public void setSex(String sex) {
         this.sex = sex;
     }

     public AClass getAclass() {
         return aclass;
     }

     public void setAclass(AClass aclass) {
         this.aclass = aclass;
     }

     public User(int user_id, String name, int age, String sex, AClass aclass) {
         super();
         this.user_id = user_id;
         this.name = name;
         this.age = age;
         this.sex = sex;
         this.aclass = aclass;
     }

     @DatabaseField(id=true,columnName = "user_id")
     public int user_id;

     @DatabaseField(columnName = "name")
     public String name;

     @DatabaseField(columnName = "age")
     public int age;
     @DatabaseField(columnName = "sex")
     public String sex;
     @DatabaseField(canBeNull = false, foreign = true, foreignAutoRefresh = true)
     public AClass aclass;

 }

 package com.lixu.asynctask;

 import com.j256.ormlite.dao.ForeignCollection;
 import com.j256.ormlite.field.DataType;
 import com.j256.ormlite.field.DatabaseField;
 import com.j256.ormlite.field.ForeignCollectionField;
 import com.j256.ormlite.table.DatabaseTable;

 @DatabaseTable(tableName = "classes")
 public class AClass {

     public AClass(long id, String name, ForeignCollection<User> user) {
         super();
         this.id = id;
         this.name = name;
         this.user = user;
     }

     @Override
     public String toString() {
         return "id" + id + "班级名：" + name;
     }

     public long getId() {
         return id;
     }

     public void setId(long id) {
         this.id = id;
     }

     public String getName() {
         return name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public ForeignCollection<User> getUser() {
         return user;
     }

     public void setUser(ForeignCollection<User> user) {
         this.user = user;
     }

     @DatabaseField(id = true)
     public long id;

     @DatabaseField(dataType = DataType.STRING)
     public String name;

     @ForeignCollectionField(eager = false)
     public ForeignCollection<User> user = null;

     public AClass() {

     }

 }

 package com.lixu.asynctask;

 import com.j256.ormlite.android.apptools.OrmLiteSqliteOpenHelper;
 import com.j256.ormlite.dao.Dao;
 import com.j256.ormlite.support.ConnectionSource;
 import com.j256.ormlite.table.TableUtils;
 import android.content.Context;
 import android.database.sqlite.SQLiteDatabase;
 import android.database.sqlite.SQLiteDatabase.CursorFactory;
 import android.util.Log;

 public class MyORMlite extends OrmLiteSqliteOpenHelper {
     private static String DATABASENAME = "lixu.db";
     private static int DATABASEVERSION = 1;

     private static MyORMlite mMyORMlite = null;
     private Dao<User, Integer> muserDao = null;
     private Dao<AClass, Integer> mclassDao = null;

     public MyORMlite(Context context, String databaseName, CursorFactory factory, int databaseVersion) {
         super(context, databaseName, factory, databaseVersion);
     }

     public static MyORMlite getInstance(Context context) {
         if (mMyORMlite == null) {
             mMyORMlite = new MyORMlite(context, DATABASENAME, null, DATABASEVERSION);
         }
         return mMyORMlite;

     }

     @Override
     public void onCreate(SQLiteDatabase arg0, ConnectionSource arg1) {

         try {
             TableUtils.createTableIfNotExists(arg1, User.class);
             TableUtils.createTableIfNotExists(arg1, AClass.class);
             Log.d("MyORMlite", "被创建");
         } catch (Exception e) {
             e.printStackTrace();
         }
     }

     public Dao<User, Integer> getuserDao() {
         if (muserDao == null) {
             try {
                 muserDao = getDao(User.class);
             } catch (Exception e) {
                 e.printStackTrace();
             }
         }
         return muserDao;
     }

     public Dao<AClass, Integer> getclassDao() {
         if (mclassDao == null) {
             try {
                 mclassDao = getDao(AClass.class);
             } catch (Exception e) {
                 e.printStackTrace();
             }
         }
         return mclassDao;
     }

     @Override
     public void close() {
         super.close();
         muserDao = null;
         mclassDao = null;

     }

     @Override
     public void onUpgrade(SQLiteDatabase arg0, ConnectionSource arg1, int arg2, int arg3) {

     }

 }

 package com.lixu.asynctask;

 import java.sql.SQLException;
 import java.util.List;

 import com.j256.ormlite.dao.Dao;
 import com.lixu.asynctask.AClass;
 import com.lixu.asynctask.User;
 import com.lixu.asynctask.MyORMlite;

 import android.app.Activity;
 import android.os.AsyncTask;
 import android.os.Bundle;
 import android.text.method.ScrollingMovementMethod;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.widget.Button;
 import android.widget.TextView;
 import android.widget.Toast;

 public class MainActivity extends Activity {
     private Dao<User, Integer> muserDao = null;
     private Dao<AClass, Integer> mclassDao = null;
     TextView tv;
     StringBuffer sb = null;

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

         MyORMlite mMyORMlite = MyORMlite.getInstance(this);
         muserDao = mMyORMlite.getuserDao();
         mclassDao = mMyORMlite.getclassDao();

         tv = (TextView) findViewById(R.id.tv);
         tv.setMovementMethod(ScrollingMovementMethod.getInstance());

         Button btn = (Button) findViewById(R.id.button1);
         btn.setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {
                 MyTask mMyTask = new MyTask();
                 mMyTask.execute();
             }
         });
     }

     // 用一个类继承AsyncTask
     private class MyTask extends AsyncTask {
         // 先执行这个方法 可以处理一些初始化的事件等。
         @Override
         protected void onPreExecute() {
             sb = new StringBuffer();
             super.onPreExecute();
         }

         // 这个方法可以处理相对耗时较长的任务，这个方法里面不可以执行ui任务。
         @Override
         protected Object doInBackground(Object... params) {
             add();
             List<User> list = chaxun();
             for (User n : list) {
                 sb.append("姓名是：" + n.getName() + ",性别是：" + n.getSex() + ",班级是：" + n.getAclass().getName() + "\n");
             }
             return sb;
         }

         // 可以将上一个方法处理的结果传到这个方法中，并且这个方法里面可以处理ui任务。
         @Override
         protected void onPostExecute(Object params) {
             super.onPostExecute(params);
             tv.setText(params.toString());
             Toast.makeText(MainActivity.this, "显示成功", 0).show();
         }
     }

     public List<User> chaxun() {
         List<User> list = null;
         try {
             list = muserDao.queryForAll();

         } catch (SQLException e) {
             e.printStackTrace();
         }
         return list;

     }

     public void add() {

         for (int j = 1; j <= 3; j++) {
             AClass classes = null;
             classes = new AClass();
             classes.setName("大三" + j + "班");
             classes.setId(j);
             try {
                 mclassDao.createIfNotExists(classes);
             } catch (SQLException e) {
                 e.printStackTrace();
             }
             for (int i = 10 * (j - 1) + 1; i <= 10 * j; i++) {
                 User user = new User();
                 user.setName("张三" + i);
                 user.setAge(20 + i);
                 user.setUser_id(i);
                 user.setSex("男");
                 user.setAclass(classes);// 挂载到class
                 try {
                     muserDao.createIfNotExists(user);
                 } catch (SQLException e) {
                     e.printStackTrace();
                 }

             }
         }

     }
 }