Sqlite基础（四）

打开数据库读取数据

private MyDatabaseHelper dbHelper;

dbHelper=new MyDatabaseHelper(this,"List.db",null,1);
dbHelper.getWritableDatabase();
SQLiteDatabase db=dbHelper.getWritableDatabase();

Cursor cursor=db.query("List",null,null,null, null,null,null);//读取数据库里面专业是所有信息
if(cursor.moveToFirst()){
     do{
         String inorout=cursor.getString(cursor.getColumnIndex("收支"));//根据key值读取信息
         String num=cursor.getString(cursor.getColumnIndex("金额"));
         String kind=cursor.getString(cursor.getColumnIndex("分类"));
         String txt=cursor.getString(cursor.getColumnIndex("备注"));
         String date=cursor.getString(cursor.getColumnIndex("日期"));
         str+=""+inorout+";"+ ""+num+";"+ ""+kind+";"+ ""+txt+";"+date+"
";//将数据库信息存到str中并换行
     }while (cursor.moveToNext());
 }
 cursor.close();
 txt.setText(str);//打印信息

MyDatabaseHelper.java

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.widget.Toast;

public class MyDatabaseHelper extends SQLiteOpenHelper {
    public static final String CREATE_LIST="create table List("
            +"id integer primary key autoincrement,"
            +"收支 text,"
            +"金额 text,"
            +"分类 text,"
            +"备注 text,"
            +"日期 text)";
    private Context mContext;

    public MyDatabaseHelper(Context context, String name,
                            SQLiteDatabase.CursorFactory factory, int version){
        super(context,name,factory,version);
        Log.v("Log","创建数据库");
        mContext=context;
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_LIST);
        Log.v("Log","创建成功");
        Toast.makeText(mContext, "创建成功", Toast.LENGTH_SHORT).show();
    }
    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }
}