android原生SQLite数据库的使用
sqlite作为android内置的轻量级数据库 有诸多有点… 也有缺点…
1, 创建一个Openhelper
package com.diandou.demo39_androidsqlite.sql;
import android.content.Context;
import android.database.DatabaseErrorHandler;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
/**
* Created by baiya on 2018/2/7.
*/
public class DemoSQLiteOpenHelper extends SQLiteOpenHelper{
private static final String TAG = "DemoSQLiteOpenHelper";
public DemoSQLiteOpenHelper(Context context) {
/**
* 参数说明:
*
* 第一个参数: 上下文
* 第二个参数: 数据库文件名称
* 第三个参数: null代表默认的游标工厂
* 第四个参数: 数据库的版本号 (数据库版本号只增不减)
*
*/
super(context, "demo.db", null, 2);
Log.d(TAG,"DemoSQLiteOpenHelper");
}
/**
* 数据库创建时调用
*
* 只有在app第一次安装时才会调用这个方法
* @param db
*/
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(
"create table contactinfo (" +
"id integer primary key autoincrement, " +
"name varchar(20), " +
"phone varchar(20))"
);
Log.d(TAG,"onCreate");
}
/**
* 数据库升级时调用
*
* 只有在上面super执行的时候才会执行这个方法
*
* @param db
* @param oldVersion
* @param newVersion
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.d(TAG,"onUpgrade + oldVersion: " + oldVersion + "newVersion: " + newVersion);
switch (oldVersion) {
case 2:
db.execSQL(
"create table contactinfo2 (" +
"id integer primary key autoincrement, " +
"name varchar(20), " +
"phone varchar(20))"
); // 判断版本号.如果是老版本, 走upgrade逻辑,创建新的表
break;
case 3:
db.execSQL("alter table contactinfo add category_id integer");
default:
}
}
}2,创建一个dao
package com.diandou.demo39_androidsqlite.sql;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
/**
* Created by baiya on 2018/2/7.
*/
public class DemoDao {
private DemoSQLiteOpenHelper helper;
public DemoDao(Context context) {
helper = new DemoSQLiteOpenHelper(context);
}
/**
* 添加一条记录
* @param name 联系人姓名
* @param phone 联系人电话
* @return 返回的是添加后在数据库的行号 -1代表添加失败
*/
public long add(String name, String phone, String category_id){
SQLiteDatabase db = helper.getWritableDatabase();
//db.execSQL("insert into contactinfo (name,phone) values (?,?)", new Object[]{name,phone});
ContentValues values = new ContentValues();
values.put("name", name);
values.put("phone", phone);
values.put("category_id", category_id);
//内部是组拼sql语句实现的.
long rowid = db.insert("contactinfo", null, values);
//记得释放数据库资源
db.close();
return rowid;
}
/**
* 根据姓名删除一条记录
* @param name 要删除的联系人的姓名
* @return 返回0代表的是没有删除任何的记录 返回整数int值代表删除了几条数据
*/
public int delete(String name){
//判断这个数据是否存在.
SQLiteDatabase db = helper.getWritableDatabase();
//db.execSQL("delete from contactinfo where name=?", new Object[]{name});
int rowcount = db.delete("contactinfo", "name=?", new String[]{name});
db.close();
//再从数据库里面查询一遍,看name是否还在
return rowcount;
}
/**
* 修改联系人电话号码
* @param newphone 新的电话号码
* @param name 要修改的联系人姓名
* @return 0代表一行也没有更新成功, >0 整数代表的是更新了多少行记录
*/
public int update(String newphone , String name){
//根据姓名修改电话号码
SQLiteDatabase db = helper.getWritableDatabase();
//db.execSQL("update contactinfo set phone =? where name=?", new Object[]{newphone,name});
ContentValues values = new ContentValues();
values.put("phone", newphone);
int rowcount = db.update("contactinfo", values, "name=?", new String[]{name});
db.close();
return rowcount;
}
/**
* 查询联系人的电话号码
* @param name 要查询的联系人
* @return 电话号码
*/
public String getPhoneNumber(String name){
String phone = null;
SQLiteDatabase db = helper.getReadableDatabase();
//Cursor cursor = db.rawQuery("select phone from contactinfo where name=?", new String[]{name});
Cursor cursor = db.query("contactinfo", new String[]{"phone"}, "name=?", new String[]{name}, null, null, null);
if(cursor.moveToNext()){//如果光标可以移动到下一位,代表就是查询到了数据
phone = cursor.getString(0);
}
cursor.close();//关闭掉游标,释放资源
db.close();//关闭数据库,释放资源
return phone;
}
/**
* 获取所有数据
* @return
*/
public String getAll(){
String all = "";
SQLiteDatabase db = helper.getReadableDatabase();
Cursor cursor = db.query("contactinfo", new String[]{"phone", "name", "category_id"}, null, null, null, null, null);
while (cursor.moveToNext()){//如果光标可以移动到下一位,代表就是查询到了数据
all += cursor.getString(0)+"..."+cursor.getString(1)+"..."+cursor.getString(2)+"///";
}
cursor.close();//关闭掉游标,释放资源
db.close();//关闭数据库,释放资源
return all;
}
/**
* 查询所有表名
* @return
*/
public String updateField(){
String allTable = "";
SQLiteDatabase db = helper.getReadableDatabase();
Cursor cursor = db.rawQuery("select name from sqlite_master where type='table' order by name", null);
while(cursor.moveToNext()){
//遍历出表名
String name = cursor.getString(0);
allTable += name+"....";
}
return allTable;
}
}
3, App启动入口记得初始化一次,别忘了配置
package com.diandou.demo39_androidsqlite;
import android.app.Application;
import com.diandou.demo39_androidsqlite.sql.DemoSQLiteOpenHelper;
/**
* Created by baiya on 2018/2/22.
*/
public class App extends Application {
@Override
public void onCreate() {
super.onCreate();
initSqlite();
}
/**
* 初始化数据库
*/
private void initSqlite() {
DemoSQLiteOpenHelper openHelper = new DemoSQLiteOpenHelper(this);
}
}
4,在activity中测试
package com.diandou.demo39_androidsqlite;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import com.diandou.demo39_androidsqlite.sql.DemoDao;
public class MainActivity extends AppCompatActivity {
private DemoDao demoDao;
private EditText mEtName;
private EditText mEtPhone;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mEtName = (EditText) findViewById(R.id.mEtName);
mEtPhone = (EditText) findViewById(R.id.mEtPhone);
demoDao = new DemoDao(this);
}
public void add(View view){
String name = mEtName.getText().toString();
String phone = mEtPhone.getText().toString();
String category_id = "fdfdfd";
long add = demoDao.add(name, phone,category_id);
if (add != -1){
Toast.makeText(this, "添加成功" + add, 0).show();
}
}
public void delete(View view){
String name = mEtName.getText().toString();
int delete = demoDao.delete(name);
if (delete != 0){
Toast.makeText(this, "删除成功" + delete, 0).show();
}
}
public void update(View view){
String name = mEtName.getText().toString();
String phone = mEtPhone.getText().toString();
//根据phone更新name
int update = demoDao.update(phone, name);
if (update != 0){
Toast.makeText(this, "更新成功" + update, 0).show();
}
}
public void query(View view){
// String name = mEtName.getText().toString();
// String phoneNumber = demoDao.getPhoneNumber(name);
// String phoneNumber_1 = demoDao.getPhoneNumber(name);
// if (!TextUtils.isEmpty(phoneNumber_1)) {
// Toast.makeText(this, "查询成功" + phoneNumber_1, 0).show();
// }
String all = demoDao.getAll();
if (!TextUtils.isEmpty(all)) {
Toast.makeText(this, "查询成功--" + all, 0).show();
}
}
public void allTableName(View view) {
String all = demoDao.updateField();
if (!TextUtils.isEmpty(all)) {
Toast.makeText(this, "查询成功--" + all, 0).show();
}
}
}
sqlite表的字段不可以更改, 但是可以添加
update方法中就是升级用的, onCreate方法只是在app第一次安装到手机上会调用一次, 创建完表之后就不会在走了
所以, 如果是在update中创建表, 或是增加字段的话, 记得在onCreate中也写一份