Codename One：連接並填充SQLite數據庫的下拉菜單

Question

我想將SQLite數據庫文件連接到一個選擇器組件（接受字符串）。這應該類似於下拉菜單。我試圖按照以前的建議和例子，但沒有成功。

如前一篇文章所述，我已將數據庫文件保存在應用程序的源文件夾中。 View of the source folder where I have saved the database file (highlighted).

我用來實現我的應用程序的代碼如下面的佈局。

// -----------------------

數據庫代碼

// --------- --------------

public class MyApplication { 

private Form current; 
private Resources theme; 

public void init(Object context) { 
    theme = UIManager.initFirstTheme("/theme"); 

    // Pro only feature, uncomment if you have a pro subscription 
    // Log.bindCrashProtection(true); 
} 

private Container Home() { 
    Container home = new Container(new BoxLayout(BoxLayout.Y_AXIS)); 
    return home; 
} 

private Container AddItem() { 
    Container addItem = new Container(new BoxLayout(BoxLayout.Y_AXIS)); 

    TextArea item = new TextArea("Add Item"); 
    addItem.addComponent(item); 
    Picker selectItem = new Picker(); 
    selectItem.setType(Display.PICKER_TYPE_STRINGS); 

//----------------------------------------------------------------------------------   

Database db = null; 
Cursor cur = null; 
try { 
    db = Display.getInstance().openOrCreate("FoodAndBeverage.db"); 
    if(selectItem.getText().startsWith("Still Water")) { 
     cur = db.executeQuery(selectItem.getText()); 
     int columns = cur.getColumnCount(); 
     addItem.removeAll(); 
     if(columns > 0) { 
      boolean next = cur.next(); 
      if(next) { 
       ArrayList<String[]> data = new ArrayList<>(); 
       String[] columnNames = new String[columns]; 
       for(int iter = 0 ; iter < columns ; iter++) { 
        columnNames[iter] = cur.getColumnName(iter); 
       } 
       while(next) { 
        Row currentRow = cur.getRow(); 
        String[] currentRowArray = new String[columns]; 
        for(int iter = 0 ; iter < columns ; iter++) { 
         currentRowArray[iter] = currentRow.getString(iter); 
        } 
        data.add(currentRowArray); 
        next = cur.next(); 
       } 
       Object[][] arr = new Object[data.size()][]; 
       data.toArray(arr); 
       addItem.add(BorderLayout.CENTER, new Table(new DefaultTableModel(columnNames, arr))); 
      } else { 
       addItem.add(BorderLayout.CENTER, "Query returned no results"); 
      } 
     } else { 
      addItem.add(BorderLayout.CENTER, "Query returned no results"); 
     } 
    } else { 
     db.execute(selectItem.getText()); 
     addItem.add(BorderLayout.CENTER, "Query completed successfully"); 
    } 
    addItem.revalidate(); 
} catch(IOException err) { 
    Log.e(err); 
    addItem.removeAll(); 
    addItem.add(BorderLayout.CENTER, "Error: " + err); 
    addItem.revalidate(); 
} finally { 
    Util.cleanup(db); 
    Util.cleanup(cur); 
} 

//--------------------------------------------------------------------------------------------- 

    addItem.addComponent(selectItem); 
    TextField quantity = new TextField("", "Quantity (ml or g)", 4, TextArea.NUMERIC); 
    addItem.addComponent(quantity); 
    Button add = new Button("Add"); 
    addItem.addComponent(add); 
    TextArea results = new TextArea("Results"); 
    addItem.addComponent(results); 
    return addItem; 
} 

private Container Settings() { 
    Container settings = new Container(new BoxLayout(BoxLayout.Y_AXIS));  
    TextArea nutrients = new TextArea("Target"); 
    settings.addComponent(nutrients); 
    TextField volume = new TextField("", "Volume (ml)", 4, TextArea.NUMERIC); 
    settings.addComponent(volume); 
    TextArea duration = new TextArea("Hydration Duration"); 
    settings.addComponent(duration); 
    settings.add("Start:"); 
    Picker start = new Picker(); 
    start.setType(Display.PICKER_TYPE_TIME); 
    settings.addComponent(start); 
    settings.add("End:"); 
    Picker end = new Picker(); 
    end.setType(Display.PICKER_TYPE_TIME); 
    settings.addComponent(end);  
    Button save = new Button("Save"); 
    settings.addComponent(save); 
    return settings; 
} 

public void start() { 
    if(current != null) 
    { 
     current.show(); 
     return; 
    } 

    Form home = new Form("Hydrate", new BorderLayout()); 
    Tabs t = new Tabs(); 
    t.addTab("Home", Home()); 
    t.addTab("Intake", AddItem()); 
    t.addTab("Settings", Settings()); 
    home.add(BorderLayout.NORTH, t); 
    home.show(); 

} 

public void stop() { 
    current = Display.getInstance().getCurrent(); 
} 

public void destroy() { 
} 

} 

因此，我將不勝感激正是我錯了，如何實現我的代碼修改建議的任何意見和指導。

Answer 1

我假設src下的文件確實以擴展db結尾，因爲Windows隱藏的擴展無意義已打開。

此代碼將不打開文件放在src分貝：

db = Display.getInstance().openOrCreate("FoodAndBeverage.db"); 

你需要做的是這樣的隱式初始化DB首次安裝該應用程式：

String path = Display.getInstance().getDatabasePath("FoodAndBeverage.db"); 
FileSystemStorage fs = FileSystemStorage.getInstance(); 
if(!fs.exists(path)) { 
    try (InputStream is = Display.getInstance().getResourceAsStream(getClass(), "/FoodAndBeverage.db"); 
      OutputStream os = fs.openOutputStream(path)) { 
     Util.copy(is, os); 
    } catch(IOException err) { 
      Log.e(err); 
    } 
} 
db = Display.getInstance().openOrCreate("FoodAndBeverage.db"); 

請注意，上面的代碼不檢查數據庫的更新，因此假設數據庫是隻讀的，您可能想要使用應用程序更新來更新/合併數據庫。

Answer 2

上面的代碼不適用於Android設備，這隻適用於模擬器。我已經測試了多次在Android設備。在真正的Android設備，數據庫完全不加載，顯示SQL異常錯誤

「沒有這樣的表SQL異常」。

貌似.db的文件從來沒有真實的Android設備測試預裝sqlite的。