Android:将数据从数据库绑定(bind)到 ListView

Question

我试图从我的 SQLite 数据库中提取我的数据并将其显示在 ListView 中，这是我目前所拥有的，但它只将第一条记录放在 ListView 中。我认为“while (mCursor.moveToNext()){”位需要更改但不确定如何更改。原始代码每次都将每条记录放在新行的 TextView 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:

我已经更改了它，所以只有这段代码在 onCreate 方法中，但是同样的事情发生了，当数据库中有多个东西时显示一个项目。

            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 类

    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) {

    }

}

错误

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

看起来你想在 ListView 中显示表格中的数据，所以只需创建一个适配器:

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);

(单独使用此代码，您不需要使用下面的任何其他代码，但您应该阅读它以了解为什么您的大部分代码不会执行您尝试执行的操作。)

---

你有一些逻辑错误。

1) 如果一个对象是null，你不能引用它的任何方法:

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

2) 在读取一行之前调用moveToFirst() 和 moveToNext() 可以跳过第一条记录。此外，您在两次读取记录之间调用了 moveToNext()，因此您只是每隔一个读取一次。试试这个:

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

3) 现在要手动从 Cursor 读取实际值，您必须使用类似 getString() 或 getInt() 的方法:

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

4) 在原始循环中，您没有向 s 添加任何数据。您只是用相同的值一遍又一遍地覆盖 s:

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

不管这个循环执行一次还是一千次，s 总是一样的。