android DB on SD Card 新增、查詢（DB 2/2）

android insert value to DB、select value from DB

這篇文章會介紹

如何新增資料到sqllite database，並在database作查詢等動作

上一篇已經介紹如何在sd card新增資料庫

這裡就只略過如何新增資料庫，直接說明新增and查詢的動作

public class db_sample {
 public static final String STR_TABLE_NAME    = "table_name"; //table名稱
 public static final String STR_FIELD_ID     = "field_id";  //欄位名稱 
 public static final String STR_FIELD_NAME    = "field_name"; //欄位名稱
 private static Context context;         
 
 public db_sample(Context context) {
  this.context = context; //new這個class時，一定要傳入context，因為openOrCreateDatabase是由context底下的method
 }
 
 //建立table的method
 public static final void fnCreateDB(){
  //MODE_WORLD_WRITEABLE，只能有寫的權限
  SQLiteDatabase dbwrite 
      = context.openOrCreateDatabase("/sdcard/hi_test.db", context.MODE_WORLD_WRITEABLE, null);
  
  //建立table
  String sql = 
    String.format("CREATE TABLE %s (%s INTEGER primary key autoincrement, %s text )"
        , STR_TABLE_NAME  
        , STR_FIELD_ID    
        , STR_FIELD_NAME   
    ); 
  dbwrite.execSQL(sql);
 }
 
 //新增資料的method
 public static final long fnInsert(String strText){
  SQLiteDatabase dbwrite 
      = context.openOrCreateDatabase("/sdcard/hi_test.db", context.MODE_WORLD_WRITEABLE, null);
  ContentValues cv = new ContentValues();
  cv.put(STR_FIELD_NAME, strText);
  return dbwrite.insert(STR_TABLE_NAME, null, cv);//如果return -1代表有錯誤，否則會return該筆資料在第幾列
 }
 
 //撈資料的method
 public  static final int fnRead(String strText){
  //MODE_WORLD_WRITEABLE，只能有讀取的權限
  SQLiteDatabase dbread 
      = context.openOrCreateDatabase("/sdcard/hi_test.db",context. MODE_WORLD_READABLE, null);
  
  
  Cursor cursor 
    = dbread.rawQuery( 
      "select "+STR_FIELD_ID+" from "+STR_TABLE_NAME+" where "+STR_FIELD_NAME+"=?", 
      new String[] {strText}
    );
  
  if (cursor.moveToFirst()) { 
   return cursor.getInt(0);
  }
  return -1;
 }
 
}

呼叫方法就如下：

public class test extends Activity{
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 db_sample db = new db_sample(this);
 db.fnCreateDB();
 db.fnInsert("HI");
 int iID = db.fnRead("HI");
 }

}