我正在尝试从我的SQLite数据库中提取数据并将其显示在列表视图中，这是我到目前为止所做的，但它只将第一条记录放在listview中。 我认为“while（mCursor.moveToNext（））{”位需要改变但不确定如何。原始代码每次都将文本视图中的每条记录放在一个新行上。
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
我已经改变了，所以只有这个代码在onCreate方法中，但同样的事情发生了，当数据库中有多个东西时会显示一个项目。
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)
答案 0 :(得分：2)
看起来您想要在ListView中显示表中的数据，因此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大多数代码都不会执行您要执行的操作。）
您有一些逻辑错误。
1）如果对象是null，则无法引用其任何方法：
if (mCursor == null){
/* mCursor.close(); This will throw an NullPointerException! */
Log.w("cursor", "null cursor");
return;
}
2）通过在读取行之前调用moveToFirst() 和 moveToNext()，您可以跳过第一条记录。此外，您在阅读记录之间两次调用moveToNext()，因此您只阅读其他记录。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getString()或getInt()之类的方法：
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。您只是一遍又一遍地使用相同的值覆盖s：
while (mCursor.moveToNext()){
s = new String[] { foodNameColumn, proteinColumn, fatColumn, carbsColumn };
}
如果此循环执行一次或一千次并不重要，s将始终相同。
答案 1 :(得分：0)
应该是这样的
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);
即使您的mCursor为空，它仍然可以，只是列表中没有显示任何项目。