Android：從數據庫綁定數據到列表視圖

Question

我想從我的SQLite數據庫拉我的數據，並顯示它在一個列表視圖，這是我迄今爲止，但它只放在列表視圖中的第一條記錄。 我認爲「while（mCursor.moveToNext（））{」位需要改變，但不知道如何。原始代碼每次將每條記錄放入一個新行中的文本視圖中。

if (mCursor == null){ 
     mCursor.close(); 
     Log.w("cursor", "null cursor"); 
    }  

     mCursor.moveToFirst(); 
    String[] s = null; 


    while (mCursor.moveToNext()){ 

     s = new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn }; 

     mCursor.moveToNext(); 
    } 


    SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
      R.layout.aa_four_column, 
      mCursor, 
      s, 
      new int[] { R.id.txtCol1, R.id.txtCol2, R.id.txtCol3, R.id.txtCol4 }, 0); 

    lvDB.setAdapter(adapter); 

更新：

我已經改變了它，僅此代碼是在onCreate方法，但同樣的事情發生，一個項目時顯示有在DB多的東西。

  mCursor = dataBase.select("SELECT * FROM " + TABLE_NAME); 

     SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
        R.layout.aa_four_column, 
        mCursor, 
        new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn }, 
        new int[] { R.id.txtCol1, R.id.txtCol2, R.id.txtCol3, R.id.txtCol4 }, 0); 

     lvDB.setAdapter(adapter); 

aa_column_four.xml 
<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="match_parent" 
    android:layout_height="wrap_content" 
    android:orientation="horizontal" > 

    <TextView 
     android:id="@+id/txtCol1" 
     android:layout_width="181dp" 
     android:layout_height="wrap_content" 
     android:text="Column 1 text will end up here!" /> 

    <TextView 
     android:id="@+id/txtCol2" 
     android:layout_width="63dp" 
     android:layout_height="wrap_content" 
     android:text="Column 2 text will end up here!" /> 

    <TextView 
     android:id="@+id/txtCol3" 
     android:layout_width="96dp" 
     android:layout_height="wrap_content" 
     android:text="Column 3 text will end up here!" /> 

    <TextView 
     android:id="@+id/txtCol4" 
     android:layout_width="104dp" 
     android:layout_height="wrap_content" 
     android:text="Column 4 text will end up here!" /> 

</LinearLayout> 

DatabaseManager類

public class DataBaseManager extends SQLiteOpenHelper { 

    //the MAIN package of your project 
    private static String DB_PATH = "/data/data/com.example.activities/databases/"; 

    //the name of your database 
    private static String DB_NAME = "DB_Nutrition"; 

    private static SQLiteDatabase mDataBase; 

    private static DataBaseManager sInstance = null; 
    // database version 
    private static final int DATABASE_VERSION = 1; 

    /** 
    * Constructor Takes and keeps a reference of the passed context in order to 
    * access to the application assets and resources. 
    */ 
    DataBaseManager() { 
     super(ApplicationContextProvider.getContext(), DB_NAME, null, DATABASE_VERSION); 

     try { 
      createDataBase(); 
      openDataBase(); 
     } catch (IOException e) { 
      e.printStackTrace(); 
     } 

    } 

    /** 
    * Singleton for DataBase 
    * 
    * @return singleton instance 
    */ 
    public static DataBaseManager instance() { 

     if (sInstance == null) { 
      sInstance = new DataBaseManager(); 
     } 
     return sInstance; 
    } 


    /** 
    * Creates a empty database on the system and rewrites it with your own 
    * database. 
    * 
    * @throws java.io.IOException io exception 
    */ 
    private void createDataBase() throws IOException { 

     boolean dbExist = checkDataBase(); 

     if (dbExist) { 
      // do nothing - database already exist 
     } else { 

      // By calling this method an empty database will be created into 
      // the default system path 
      // of your application so we are gonna be able to overwrite that 
      // database with our database. 
      this.getReadableDatabase(); 

      try { 

       copyDataBase(); 

      } catch (IOException e) { 

       throw new Error("Error copying database"); 
      } 
     } 
    } 

    /** 
    * Check if the database already exist to avoid re-copying the file each 
    * time you open the application. 
    * 
    * @return true if it exists, false if it doesn't 
    */ 
    private boolean checkDataBase() { 

     SQLiteDatabase checkDB = null; 

     try { 
      String myPath = DB_PATH + DB_NAME; 
      checkDB = SQLiteDatabase.openDatabase(myPath, null, 
        SQLiteDatabase.OPEN_READONLY); 

     } catch (SQLiteException e) { 

      // database doesn't exist yet. 

     } 

     if (checkDB != null) { 

      checkDB.close(); 

     } 

     return checkDB != null; 
    } 

    /** 
    * Copies your database from your local assets-folder to the just created 
    * empty database in the system folder, from where it can be accessed and 
    * handled. This is done by transfering bytestream. 
    * 
    * @throws java.io.IOException io exception 
    */ 
    public void copyDataBase() throws IOException { 

     // Open your local db as the input stream 
     InputStream myInput = ApplicationContextProvider.getContext().getAssets().open(DB_NAME); 

     // Path to the just created empty db 
     String outFileName = DB_PATH + DB_NAME; 

     // Open the empty db as the output stream 
     OutputStream myOutput = new FileOutputStream(outFileName); 

     // transfer bytes from the inputfile to the outputfile 
     byte[] buffer = new byte[1024]; 
     int length; 
     while ((length = myInput.read(buffer)) > 0) { 
      myOutput.write(buffer, 0, length); 
     } 

     // Close the streams 
     myOutput.flush(); 
     myOutput.close(); 
     myInput.close(); 

    } 

    private void openDataBase() throws SQLException { 

     // Open the database 
     String myPath = DB_PATH + DB_NAME; 
     mDataBase = SQLiteDatabase.openDatabase(myPath, null, 
       SQLiteDatabase.OPEN_READWRITE); 
    } 

    /** 
    * Select method 
    * 
    * @param query select query 
    * @return - Cursor with the results 
    * @throws android.database.SQLException sql exception 
    */ 
    public Cursor select(String query) throws SQLException { 
     return mDataBase.rawQuery(query, null); 
    } 

    /** 
    * Insert method 
    * 
    * @param table - name of the table 
    * @param values values to insert 
    * @throws android.database.SQLException sql exception 
    */ 
    public void insert(String table, ContentValues values) throws SQLException { 
     mDataBase.insert(table, null, values); 
    } 

    /** 
    * Delete method 
    * 
    * @param table - table name 
    * @param where WHERE clause, if pass null, all the rows will be deleted 
    * @throws android.database.SQLException sql exception 
    */ 
    public void delete(String table, String where) throws SQLException { 

     mDataBase.delete(table, where, null); 

    } 

    /** 
    * Update method 
    * 
    * @param table - table name 
    * @param values - values to update 
    * @param where - WHERE clause, if pass null, all rows will be updated 
    */ 
    public void update(String table, ContentValues values, String where) { 

     mDataBase.update(table, values, where, null); 

    } 

    /** 
    * Let you make a raw query 
    * 
    * @param command - the sql comand you want to run 
    */ 
    public void sqlCommand(String command) { 
     mDataBase.execSQL(command); 
    } 

    @Override 
    public synchronized void close() { 

     if (mDataBase != null) 
      mDataBase.close(); 

     super.close(); 

    } 

    @Override 
    public void onCreate(SQLiteDatabase db) { 

    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 

    } 

} 

錯誤

03-03 15:42:13.894: E/SQLiteLog(9809): (14) cannot open file at line 30176 of [00bb9c9ce4] 
03-03 15:42:13.894: E/SQLiteLog(9809): (14) os_unix.c:30176: (2) open(/data/data/com.example.activities/databases/DB_Nutrition) - 
03-03 15:42:13.904: E/SQLiteDatabase(9809): Failed to open database '/data/data/com.example.activities/databases/DB_Nutrition'. 
03-03 15:42:13.904: E/SQLiteDatabase(9809): android.database.sqlite.SQLiteCantOpenDatabaseException: unknown error (code 14): Could not open database 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteConnection.nativeOpen(Native Method) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:209) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteConnection.open(SQLiteConnection.java:193) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteConnectionPool.openConnectionLocked(SQLiteConnectionPool.java:463) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:185) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteConnectionPool.open(SQLiteConnectionPool.java:177) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteDatabase.openInner(SQLiteDatabase.java:804) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteDatabase.open(SQLiteDatabase.java:789) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:694) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.database.sqlite.SQLiteDatabase.openDatabase(SQLiteDatabase.java:669) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at com.example.db_food.DataBaseManager.checkDataBase(DataBaseManager.java:228) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at com.example.db_food.DataBaseManager.createDataBase(DataBaseManager.java:193) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at com.example.db_food.DataBaseManager.<init>(DataBaseManager.java:163) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at com.example.db_food.DataBaseManager.instance(DataBaseManager.java:179) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at com.example.db_food.MyActivity.onCreate(MyActivity.java:63) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.app.Activity.performCreate(Activity.java:5104) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.os.Handler.dispatchMessage(Handler.java:99) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.os.Looper.loop(Looper.java:137) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at java.lang.reflect.Method.invokeNative(Native Method) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at java.lang.reflect.Method.invoke(Method.java:511) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
03-03 15:42:13.904: E/SQLiteDatabase(9809):  at dalvik.system.NativeStart.main(Native Method) 

Answer 1

它看起來像你想從一個ListView表中顯示的數據，因此只需創建一個適配器：

SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
     R.layout.aa_four_column, 
     mCursor, 
     new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn }, 
     new int[] { R.id.txtCol1, R.id.txtCol2, R.id.txtCol3, R.id.txtCol4 }, 0); 

lvDB.setAdapter(adapter); 

（使用此代碼本身，您不需要使用下面的任何其他代碼，但您應該閱讀它以瞭解爲什麼大部分代碼不會執行您正在嘗試執行的操作。）

---

你有幾個邏輯錯誤。讀取行跳過第一個記錄之前

if (mCursor == null){ 
    /* mCursor.close(); This will throw an NullPointerException! */ 
    Log.w("cursor", "null cursor"); 
    return; 
}  

2）通過調用moveToFirst()和moveToNext()：

1）如果一個對象是null不能引用其任何方法。在閱讀記錄之間，你也打電話給moveToNext()兩次，所以你只能讀其他的一個。試試這個：

while (mCursor.moveToNext()){ 
    // Do something 
} 

3）我們手動從遊標讀取的實際值，你必須使用的方法類似getString()或getInt()：

List<String> strings = new ArralyList<String>(); 
while (mCursor.moveToNext()){ 
    strings.add(mCursor.getString(mCursor.getColumnIndex(foodNameColumn)) + " " + mCursor.getInt(mCursor.getColumnIndex(proteinColumn))); 
} 

4）在原來的循環，你是不是將任何數據添加到s。你只是用相同的值覆蓋s一遍又一遍：

while (mCursor.moveToNext()){ 
    s = new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn }; 
} 

如果這個循環執行一次或千倍，s永遠是相同不要緊。

Answer 2

它應該是這樣的

s = new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn }; 

SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, 
      R.layout.aa_four_column, 
      mCursor, 
      s, 
      new int[] { R.id.txtCol1, R.id.txtCol2, R.id.txtCol3, R.id.txtCol4 }, 0); 

即使你mCursor爲null，它仍然是好的，只是沒有項目在列表中顯示。