android SQLite数据库的基本操作

 1 package barry.android.db;
 2 
 3 import android.content.ContentValues;
 4 import android.content.Context;
 5 import android.database.Cursor;
 6 import android.database.sqlite.SQLiteDatabase;
 7 import android.database.sqlite.SQLiteOpenHelper;
 8 
 9 public class DBUtil extends SQLiteOpenHelper {
10 
11     private final static String DATABASE_NAME = "db2004";
12     private final static int DATABASE_VERSION = 1;
13     private static final String TABLE_NAME ="students";
14     private static final String FILED_1 = "name";
15     private static final String FILED_2 = "password";
16 
17     public DBUtil(Context context){
18         super(context, DATABASE_NAME,null,DATABASE_VERSION);
19         System.out.println("new DBUtil");
20     }
21 
22     @Override
23     public void onCreate(SQLiteDatabase db) {
24         String sql = "CREATE TABLE "+TABLE_NAME+" ( "+FILED_1 +" TEXT, "+ FILED_2 +" TEXT );";
25         db.execSQL(sql);
26         System.out.println("oncreate创建表");
27     }
28 
29     @Override
30     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
31         db.execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
32         System.out.println("onUpgrade删除表");
33         this.onCreate(db);
34     }
35     
36     /**
37      * 查询表中所有的数据
38      * @return
39      */
40     public Cursor select(){
41         return this.getReadableDatabase()
42             .query(TABLE_NAME, null, null, null, null, null, null);        
43     }
44 
45     /**
46      * 插入一条数据到表中
47      * @param name 字段一的值
48      * @param password 字段二的值
49      */
50     public void insert(String name ,String password){
51         ContentValues cv = new ContentValues();
52         cv.put(FILED_1, name);
53         cv.put(FILED_2, password);        
54         this.getWritableDatabase().insert(TABLE_NAME, null, cv);
55         this.getWritableDatabase().close();//关闭数据库对象 
56     }    
57     
58     /**
59      * 删除表中的若干条数据
60      * @param name 一个包含所有要删除数据的"name"字段的数组
61      */
62     public void delete(String[] name){
63         String where = FILED_1+" = ?";
64         String[] whereValues = name; 
65         this.getWritableDatabase().delete(TABLE_NAME, where, whereValues);
66         this.getWritableDatabase().close();
67     }
68     
69     /**
70      * 更新表中的数据(修改字段二"password")
71      * @param name 要更新的数据"name"字段值
72      * @param newPassword 新的"password"字段
73      */
74     public void update(String name,String newPassword){        
75         ContentValues cv = new ContentValues();
76         cv.put(FILED_2, newPassword);        
77         String where =FILED_1+" = ?";
78         String[] whereValues= {name};        
79         this.getWritableDatabase().update(TABLE_NAME, cv, where, whereValues);
80         this.getWritableDatabase().close();
81     }    
82     
83     /**
84      * 清空表中的数据
85      */
86     public void clean (){
87         this.getWritableDatabase().execSQL("DROP TABLE IF EXISTS "+TABLE_NAME);
88         System.out.println("clean删除表");
89         this.onCreate(this.getWritableDatabase());
90         this.getWritableDatabase().close();
91     }
92 }

 1 package barry.android.db;
 2 
 3 import android.app.Activity;
 4 import android.database.Cursor;
 5 import android.os.Bundle;
 6 
 7 public class Demo04_helperActivity extends Activity {
 8     /** Called when the activity is first created. */
 9     @Override
10     public void onCreate(Bundle savedInstanceState) {
11         super.onCreate(savedInstanceState);
12         setContentView(R.layout.main);
13         
14         
15         DBUtil dbUtil = new DBUtil(this);
16         dbUtil.insert("周杰伦", "jaychou");
17         dbUtil.insert("韩寒", "twocolds");
18         dbUtil.insert("郭德纲", "yunhejiuxiao");        
19         
20         System.out.println("***********************************全部数据息");
21         printData(dbUtil);        
22         
23         dbUtil.delete(new String[]{"周杰伦"});
24         
25         System.out.println("***********************************删除‘周杰伦‘之后数据");
26         printData(dbUtil); 
27         
28         dbUtil.update("郭德纲", "longtengsihai");;
29         System.out.println("***********************************修改‘郭德纲’的密码为‘longtengsihai‘");
30         printData(dbUtil); 
31         
32         dbUtil.clean();
33         
34     }
35 
36     private void printData(DBUtil dbUtil) {
37         Cursor cursor = dbUtil.select();        
38         if(cursor.moveToFirst()){
39             System.out.println("当前表中的数据条数："+cursor.getCount());
40             do{
41                 System.out.println(cursor.getString(0)+cursor.getString(1));                
42             }while(cursor.moveToNext());
43         }
44         cursor.close();
45     }
46 }