本文介绍了一个用于管理学生信息的数据库工具，包括创建、插入、删除、查询和更新学生记录的功能。
DatabaseUtil.java
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001 package com.dbexample;
002
003 import android.content.ContentValues;
004 import android.content.Context;
005 import android.database.Cursor;
006 import android.database.SQLException;
007 import android.database.sqlite.SQLiteDatabase;
008 import android.database.sqlite.SQLiteOpenHelper;
009 import android.util.Log;
010
011 public class DatabaseUtil{
012
013 private static final String TAG = "DatabaseUtil";
014
015 /**
016 * Database Name
017 */
018 private static final String DATABASE_NAME = "student_database";
019
020 /**
021 * Database Version
022 */
023 private static final int DATABASE_VERSION = 1;
024
025 /**
026 * Table Name
027 */
028 private static final String DATABASE_TABLE = "tb_student";
029
030 /**
031 * Table columns
032 */
033 public static final String KEY_NAME = "name";
034 public static final String KEY_GRADE = "grade";
035 public static final String KEY_ROWID = "_id";
036
037 /**
038 * Database creation sql statement
039 */
040 private static final String CREATE_STUDENT_TABLE =
041 "create table " + DATABASE_TABLE + " (" + KEY_ROWID + " integer primary key autoincrement, "
042 + KEY_NAME +" text not null, " + KEY_GRADE + " text not null);";
043
044 /**
045 * Context
046 */
047 private final Context mCtx;
048
049 private DatabaseHelper mDbHelper;
050 private SQLiteDatabase mDb;
051
052 /**
053 * Inner private class. Database Helper class for creating and updating database.
054 */
055 private static class DatabaseHelper extends SQLiteOpenHelper {
056 DatabaseHelper(Context context) {
057 super(context, DATABASE_NAME, null, DATABASE_VERSION);
058 }
059 /**
060 * onCreate method is called for the 1st time when database doesn't exists.
061 */
062 @Override
063 public void onCreate(SQLiteDatabase db) {
064 Log.i(TAG, "Creating DataBase: " + CREATE_STUDENT_TABLE);
065 db.execSQL(CREATE_STUDENT_TABLE);
066 }
067 /**
068 * onUpgrade method is called when database version changes.
069 */
070 @Override
071 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
072 Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
073 + newVersion);
074 }
075 }
076
077 /**
078 * Constructor - takes the context to allow the database to be
079 * opened/created
080 *
081 * @param ctx the Context within which to work
082 */
083 public DatabaseUtil(Context ctx) {
084 this.mCtx = ctx;
085 }
086 /**
087 * This method is used for creating/opening connection
088 * @return instance of DatabaseUtil
089 * @throws SQLException
090 */
091 public DatabaseUtil open() throws SQLException {
092 mDbHelper = new DatabaseHelper(mCtx);
093 mDb = mDbHelper.getWritableDatabase();
094 return this;
095 }
096 /**
097 * This method is used for closing the connection.
098 */
099 public void close() {
100 mDbHelper.close();
101 }
102
103 /**
104 * This method is used to create/insert new record Student record.
105 * @param name
106 * @param grade
107 * @return long
108 */
109 public long createStudent(String name, String grade) {
110 ContentValues initialValues = new ContentValues();
111 initialValues.put(KEY_NAME, name);
112 initialValues.put(KEY_GRADE, grade);
113 return mDb.insert(DATABASE_TABLE, null, initialValues);
114 }
115 /**
116 * This method will delete Student record.
117 * @param rowId
118 * @return boolean
119 */
120 public boolean deleteStudent(long rowId) {
121 return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
122 }
123
124 /**
125 * This method will return Cursor holding all the Student records.
126 * @return Cursor
127 */
128 public Cursor fetchAllStudents() {
129 return mDb.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_NAME,
130 KEY_GRADE}, null, null, null, null, null);
131 }
132
133 /**
134 * This method will return Cursor holding the specific Student record.
135 * @param id
136 * @return Cursor
137 * @throws SQLException
138 */
139 public Cursor fetchStudent(long id) throws SQLException {
140 Cursor mCursor =
141 mDb.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,
142 KEY_NAME, KEY_GRADE}, KEY_ROWID + "=" + id, null,
143 null, null, null, null);
144 if (mCursor != null) {
145 mCursor.moveToFirst();
146 }
147 return mCursor;
148 }
149
150 /**
151 * This method will update Student record.
152 * @param id
153 * @param name
154 * @param standard
155 * @return boolean
156 */
157 public boolean updateStudent(int id, String name, String standard) {
158 ContentValues args = new ContentValues();
159 args.put(KEY_NAME, name);
160 args.put(KEY_GRADE, standard);
161 return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + id, null) > 0;
162 }
163 }
[代码] 使用方法
01 //插入
02 DatabaseUtil dbUtil = new DatabaseUtil(this);
03 dbUtil.open();
04 dbUtil.createStudent("Prashant Thakkar", "10th");
05 dbUtil.close();
06
07 //查询
08 DatabaseUtil dbUtil = new DatabaseUtil(this);
09 dbUtil.open();
10 Cursor cursor = dbUtil.fetchAllStudents();
11 if(cursor != null){
12 while(cursor.moveToNext()){
13 Log.i("Student", "Student Name: " + cursor.getString(1) +
14 " Grade " + cursor.getString(2));
15 }
16 }
17 dbUtil.close();
SQLite 操作封装 —— DatabaseUtil
最新推荐文章于 2021-05-26 23:12:05 发布
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