安卓学习-（数据存储（数据库，原生sql，和原生安卓操作））

使用原生sql操作数据库
新增数据：db.execSQL("insert into Book (name, author, pages, prices) values (?,?,?,?)", new String[] {"love", "guanjia", "520", "25.5"});
更新数据：db.execSQL("update Book set price = ? where name = ?", new String[] {"26.6", "love"});
删除数据：db.execSQL("delete from Book where pages > ", new String[] {"100"});
查询数据：db.rawQuery("select * from Book ", new String[] {"100"});

使用 封装好的东西来操作数据库
package
com.example.databasetest;
import
android.content.Context;
import
android.database.sqlite.SQLiteDatabase;
import
android.database.sqlite.SQLiteOpenHelper;
import
android.widget.Toast;
public class
MyDatabaseHelper
extends
SQLiteOpenHelper {
//这里都是建表语句
public static
final String
CREATE_BOOK
=
"create table Book ("
+
"id integer primary key autoincrement, "
+
"author text, "
+
"price real, "
+
"pages integer, "
+
"name text)";

public static final
String
CREATE_CATEGORY =
"create table Category ("
+
"id integer primary key autoincrement, "
+
"category_name text, "
+
"category_code integer)";
private
Context
mContext;

public
MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory,
int
version) {
super(context,
name, factory, version);
mContext
= context;
}

@Override
//这里的onCreate方法，如果数据库存在，那么就只会执行一次。
public void
onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_BOOK);
db.execSQL(CREATE_CATEGORY);
Toast.makeText(mContext,
"Create succeeded", Toast.LENGTH_SHORT).show();
}

@Override
//这里是在实例化这个dbhelp的时候，最后一个数字表示版本号，如果大于上次设置的版本号，就会执行
public void
onUpgrade(SQLiteDatabase db,
int
oldVersion,
int
newVersion) {
db.execSQL("drop table if exists Book");
db.execSQL("drop table if exists Category");
onCreate(db);
}
}

package
com.example.databasetest;
import
android.content.ContentValues;
import
android.database.Cursor;
import
android.database.sqlite.SQLiteDatabase;
import
android.support.v7.app.AppCompatActivity;
import
android.os.Bundle;
import
android.util.Log;
import
android.view.View;
import
android.widget.Button;
public class
MainActivity
extends
AppCompatActivity {
private
MyDatabaseHelper
dbHelper;
@Override
protected void
onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//调用构造方法，实例化数据库操作对象
dbHelper
=
new
MyDatabaseHelper(this,
"BookStore.db",
null,
1);
Button createDatabase = (Button) findViewById(R.id.create_database);
createDatabase.setOnClickListener(new
View.OnClickListener() {
@Override
public void
onClick(View v) {
//getWritableDatabase() 和 getReadableDatabase() 都可以创建或实例化一个数据库对象
//当数据库不可写入（例如内存满了），getReadableDatabase返回只读对象，但是getWritableDatabase会报错
dbHelper.getWritableDatabase();
}
});
Button addData = (Button) findViewById(R.id.add_data);
//插入数据！！！
addData.setOnClickListener(new
View.OnClickListener() {
@Override
public void
onClick(View v) {
SQLiteDatabase db =
dbHelper.getWritableDatabase();
ContentValues values =
new
ContentValues();
// 开始组装第一条数据
values.put("name",
"The Da Vinci Code");
values.put("author",
"Dan Brown");
values.put("pages",
454);
values.put("price",
16.96);
db.insert("Book",
null, values);
// 插入第一条数据
values.clear();
// 开始组装第二条数据
values.put("name",
"The Lost Symbol");
values.put("author",
"Dan Brown");
values.put("pages",
510);
values.put("price",
19.95);
db.insert("Book",
null, values);
// 插入第二条数据
}
});
//更新数据
Button updateData = (Button) findViewById(R.id.update_data);
updateData.setOnClickListener(new
View.OnClickListener() {
@Override
public void
onClick(View v) {
SQLiteDatabase db =
dbHelper.getWritableDatabase();
ContentValues values =
new
ContentValues();
values.put("price",
10.99);
//数据库名， 新数据， where语句， 后面是条件
db.update("Book",
values, "name = ?",
new
String[] {
"The Da Vinci Code"
});
}
});
//删除数据
Button deleteButton = (Button) findViewById(R.id.delete_data);
deleteButton.setOnClickListener(new
View.OnClickListener() {
@Override
public void
onClick(View v) {
SQLiteDatabase db =
dbHelper.getWritableDatabase();
db.delete("Book",
"pages > ?",
new
String[] {
"500"
});
}
});
//查询数据
Button queryButton = (Button) findViewById(R.id.query_data);
queryButton.setOnClickListener(new
View.OnClickListener() {
@Override
public void
onClick(View v) {
SQLiteDatabase db =
dbHelper.getWritableDatabase();
// 查询Book表中所有的数据，参数分别是是表名，列名， where条件，具体值，
groupby， having， order by
//查询表中所有数据，并循环
Cursor cursor = db.query("Book",
null,
null,
null,
null,
null,
null);
if
(cursor.moveToFirst()) {
do
{
// 遍历Cursor对象，取出数据并打印
String name = cursor.getString(cursor.getColumnIndex("name"));
String author = cursor.getString(cursor.getColumnIndex("author"));
int
pages = cursor.getInt(cursor.getColumnIndex("pages"));
double
price = cursor.getDouble(cursor.getColumnIndex("price"));
Log.d("MainActivity",
"book name is "
+ name);
Log.d("MainActivity",
"book author is "
+ author);
Log.d("MainActivity",
"book pages is "
+ pages);
Log.d("MainActivity",
"book price is "
+ price);
}
while
(cursor.moveToNext());
}
cursor.close();
}
});
}
}