SQLite数据库的增删改查

最近在学习关于SQLite的一些基本操作做了一个demo,这是做完的样子



上面是4个按钮，下面是listview用来显示查询到的结果

下面是代码

MainActivity:主要是做几个按钮的点击事件

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
private Context mContext;
private Button add;
private Button del;
private Button update;
private Button query;
private ListView lv_databases;

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

//创建一个帮助类对象
MySqliteOpenHelper mySqliteOpenHelper = new MySqliteOpenHelper(this);
//调用getReadableDatabase方法来初始化数据库的创建
SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

add = (Button) findViewById(R.id.bt_add);
del = (Button) findViewById(R.id.bt_del);
update = (Button) findViewById(R.id.bt_update);
query = (Button) findViewById(R.id.bt_query);
lv_databases = (ListView) findViewById(R.id.lv_databases);
add.setOnClickListener(this);
del.setOnClickListener(this);
update.setOnClickListener(this);
query.setOnClickListener(this);
}

@Override
public void onClick(View v) {

InfoDao infoDao = new InfoDao(mContext); //创建一个dao对象做增删改查
switch (v.getId()) {
case R.id.bt_add:

InfoBean bean = new InfoBean();
bean.name = "张三";
bean.phone = "1387011254215";
boolean result = infoDao.add(bean);
if (result) {
Toast.makeText(mContext, "添加成功", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(mContext, "添加失败", Toast.LENGTH_SHORT).show();
}

break;

case R.id.bt_del:
int del = infoDao.del("张三");
Toast.makeText(mContext, "成功删除了"+del+"行", Toast.LENGTH_SHORT).show();
break;

case R.id.bt_update:
InfoBean bean2 = new InfoBean();
bean2.name = "张三";
bean2.phone = "124555";
int update = infoDao.update(bean2);
Toast.makeText(mContext, "成功修改了"+update+"行", Toast.LENGTH_SHORT).show();
break;

case R.id.bt_query:
ArrayList<InfoBean>  arrayList = infoDao.query("张三");
QueryAdapter queryAdapter = new QueryAdapter(mContext, arrayList);
lv_databases.setAdapter(queryAdapter);
break;
}
}
}

MySqliteOpenHelper:用来创建数据库

public class MySqliteOpenHelper extends SQLiteOpenHelper {
public MySqliteOpenHelper(Context context) {
//context:上下文  name:数据库文件的名称  factory：用来创建curson对象，默认为null  version：数据库的版本号，从1开始，如果发生改变，onUpfrade方法调用
super(context, "info.db", null, 1);
}

//onCreate方法是数据库第一次创建的时候被调用；特别适合做表结构的初始化，需要执行sql语句
@Override
public void onCreate(SQLiteDatabase db) {
//通过SQLiteDatabase执行一个创建表的sql语句
db.execSQL("create table info(_id integer primary key autoincrement,name varchar(20),phone varchar(11))");

}

//数据库版本号发生改变时才会执行；特别适合做表结构的修改
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}
}

QueryAdapter:做listview的适配器

public class QueryAdapter extends BaseAdapter {

private Context mContext;
private ArrayList<InfoBean> arrayList;

public QueryAdapter(Context mContext, ArrayList<InfoBean> arrayList) {
this.mContext = mContext;
this.arrayList = arrayList;
}

@Override
public int getCount() {
return arrayList.size();
}

@Override
public Object getItem(int position) {
return arrayList.get(position);
}

@Override
public long getItemId(int position) {
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

//复用convertView
View view = null;
if (convertView != null) {
view = convertView;
} else {
view = View.inflate(mContext, R.layout.item, null);
}

//找到控件
TextView item_tv_id = (TextView) view.findViewById(R.id.item_tv_id);
TextView item_tv_name = (TextView) view.findViewById(R.id.item_tv_name);
TextView item_tv_phone = (TextView) view.findViewById(R.id.item_tv_phone);

//找到内容
InfoBean bean = arrayList.get(position);

//设置内容
item_tv_id.setText(bean.id);
item_tv_name.setText(bean.name);
item_tv_phone.setText(bean.phone);

return view;
}
}

InfoDao:做数据库增删改查的逻辑

public class InfoDao {
private MySqliteOpenHelper mySqliteOpenHelper;

public InfoDao(Context context) {
//创建一个帮助类对象
mySqliteOpenHelper = new MySqli
adc7
teOpenHelper(context);

}

public boolean add(InfoBean bean) {
//执行sql语句需要sqliteDatabase对象
//调用getReadableDatabase方法来初始化数据库的创建
SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

ContentValues values = new ContentValues();//使用map封装的对象，用来存放值
values.put("name", bean.name);
values.put("phone", bean.phone);

//参数 table：表名  nullColumnHack：可以为空，表示添加一个空行   valuse：数据一行的值   返回值：代表添加这个新行的id，-1表示添加失败
long result = db.insert("info", null, values);
db.close();
return result != -1;
}

public int del(String name) {
SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

//参数  whereClause：删除条件    whereArgs：条件的占位符参数    返回值：成功删除多少行
int result = db.delete("info", "name = ?", new String[]{name});
db.close();

return result;
}

public int update(InfoBean bean) {
SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

ContentValues values = new ContentValues();//使用map封装的对象，用来存放值
values.put("phone", bean.phone);

int result = db.update("info", values, "name=?", new String[]{bean.name});
db.close();

return result;
}

public ArrayList<InfoBean> query(String name) {

ArrayList<InfoBean> list = new ArrayList<>();

//执行sql语句需要SQLiteDatabase对象
SQLiteDatabase db = mySqliteOpenHelper.getReadableDatabase();

//参数 table：表名  columns：查询的列名，如果null则代表查村所有列  selection：查询条件  selectionArgs：条件占位符的参数值
//groupBy：按什么字段分组  having：分组的条件  orderBy：按什么字段排序
Cursor cursor = db.query("info", new String[]{"_id", "name", "phone"}, "name=?", new String[]{name}, null, null, "_id asc");

//解析Cursor中的数据
if (cursor != null && cursor.getCount() > 0) {//判断cursor中是否存在数据

//循环遍历结果集，获取每一行的内容
while (cursor.moveToNext()) {//条件，游标能否定位到下一行
InfoBean bean = new InfoBean();
//获取数据
bean.id = cursor.getInt(0) + "";
bean.name = cursor.getString(1);
bean.phone = cursor.getString(2);

list.add(bean);
}
cursor.close();//关闭结果集

}
db.close();
return list;
}
}

下面是增删改查的sql语句

insert into info(name,phone) values(‘王五’,’13777777’);

delete from info where name=’王五’;

update info set phone=’139999999’where name=’王五’;

select name,phone from info

最后一个封装属性的类

public class InfoBean {

public String id;

public String name;

public String phone;

}