我需要将服务中的Cursor(SQLiteCursor)传递给API 10 上的应用程序，并且很难找到一个不错的(快速的)解决方案。
我看过CursorWindow类。这是Parcelable，但我无法在API 10上实例化该类以使用SQLiteCursor.fillWindow()，因为它没有有效的构造函数。不推荐使用CursorWindow(boolean)。
即使我得到了一个CursorWindow实例，其中包含来自SQLiteCursor的数据，如何将该窗口复制到新的Cursor中？我应该为此使用哪种Cursor实现？我看不到可扩展的Cursor的可用AbstractWindowedCursor。
谢谢你的时间!
最佳答案
我实现了一个ParcelableCursor类，该类实现了CrossProcessCursor和Parcelable接口(interface)。如果有人感兴趣，我会发布它。尚不支持/实现某些操作，以及使用自定义BijectiveMap(这很容易实现)。
/**
* Prefer ParcelableCursorForIntent instead.<br/>
* Cursor for IPC. Takes a CursorWindow as data buffer and the number of columns
* that CursorWindow has.<br/>
* <br/>
* <b>NOTE: this Cursor cannot be parceled when sending by intents due to <a
* href="http://code.google.com/p/android/issues/detail?id=4470">an Android
* bug</a>. Please use ParcelableCursorForIntent instead.</b>
*
* @author [email protected]
*
*/
public class ParcelableCursor implements Parcelable, CrossProcessCursor {
/** Cursor data window */
protected CursorWindow window = CursorHelper.getCursorWindowInstance();
/** How many columns we have */
protected int numColumns = 0;
/** Column names */
protected BijectiveMap<String, Integer> colNames = new BijectiveHashMap<String, Integer>();
/** Current row */
protected int curRow = -1;
/** Is this cursor closed? */
protected boolean closed = false;
/** CREATOR for Parcelable */
public static final Parcelable.Creator<ParcelableCursor> CREATOR = new Parcelable.Creator<ParcelableCursor>() { // NOPMD
// AM
@Override
public ParcelableCursor createFromParcel(final Parcel in) {
return new ParcelableCursor(in);
}
@Override
public ParcelableCursor[] newArray(final int size) {
return new ParcelableCursor[size];
}
};
/**
* Creates an empty ParcelableCursor. Please consider to use
* {@link #setFromCursor(AbstractWindowedCursor)} or
* {@link #setFromWindow(CursorWindow)} to initialize it.
*/
public ParcelableCursor() {
// Empty ParcelableCursor, don't forget to use #setFromCursor
}
/** Constructor for Parcelable */
public ParcelableCursor(final Parcel in) {
readFromParcel(in); // NOPMD by yasin on 12/7/12 11:55 AM - Android's
// Parceleble
}
/**
* Adds a new column at the end and assigns it this name. This will make
* this cursor to lose all its data, so you have to add all the columns
* before adding any row.
*/
private void addColumn(final String name) {
this.numColumns++;
this.curRow = -1;
this.colNames.put(name, this.numColumns - 1);
}
@Override
public void close() {
this.window.close();
this.closed = true;
}
@Override
public void copyStringToBuffer(final int columnIndex,
final CharArrayBuffer buffer) {
// TODO: what does this do?
}
@Override
public void deactivate() {
// Deprecated, does nothing
}
@Override
public int describeContents() {
// Nothing to do here
return 0;
}
@Override
public void fillWindow(final int position, final CursorWindow window) {
CursorHelper.copyCursorWindow(position, this.window, window);
}
@Override
public byte[] getBlob(final int columnIndex) {
return this.window.getBlob(this.curRow, columnIndex);
}
@Override
public int getColumnCount() {
return this.numColumns;
}
@Override
public int getColumnIndex(final String columnName) {
int ret = -1;
final Integer col = this.colNames.get(columnName);
if (col != null) {
ret = col;
}
return ret;
}
@Override
public int getColumnIndexOrThrow(final String columnName)
throws IllegalArgumentException {
final Integer col = this.colNames.get(columnName);
if (col == null) {
throw new IllegalArgumentException();
}
return col;
}
@Override
public String getColumnName(final int columnIndex) {
return this.colNames.getKey(columnIndex);
}
@Override
public String[] getColumnNames() {
if (DebugConfig.DEBUG) {
Log.d("PARCELCURSOR.getColumnNames()---", "===GETTING COLNAMES===");
}
final Set<Entry<String, Integer>> set = this.colNames.entrySet();
final String[] colArray = new String[set.size()];
for (final String colName : this.colNames.keySet()) {
if (DebugConfig.DEBUG) {
Log.d("-------------PARCELCURSOR.getColumnNames()", colName);
}
final int pos = this.colNames.get(colName);
colArray[pos] = colName;
}
return colArray;
}
@Override
public int getCount() {
return this.window.getNumRows();
}
@Override
public double getDouble(final int columnIndex) {
return this.window.getDouble(this.curRow, columnIndex);
}
@Override
public Bundle getExtras() {
// Does not support Extras
return null;
}
@Override
public float getFloat(final int columnIndex) {
return this.window.getFloat(this.curRow, columnIndex);
}
@Override
public int getInt(final int columnIndex) {
return this.window.getInt(this.curRow, columnIndex);
}
@Override
public long getLong(final int columnIndex) {
return this.window.getLong(this.curRow, columnIndex);
}
@Override
public int getPosition() {
return this.curRow;
}
@Override
public short getShort(final int columnIndex) { // NOPMD by yasin on 12/7/12
// 11:57 AM - Override
return this.window.getShort(this.curRow, columnIndex);
}
@Override
public String getString(final int columnIndex) {
return this.window.getString(this.curRow, columnIndex);
}
@SuppressLint("NewApi")
@Override
public int getType(final int columnIndex) {
final int currentapiVersion = android.os.Build.VERSION.SDK_INT;
int result = 0;
if (currentapiVersion >= android.os.Build.VERSION_CODES.HONEYCOMB) {
result = this.window.getType(this.curRow, columnIndex);
} else {
if (this.window.isNull(this.curRow, columnIndex)) {
result = 0; // FIELD_TYPE_NULL;
} else if (this.window.isFloat(this.curRow, columnIndex)) {
result = 2; // FIELD_TYPE_FLOAT;
} else if (this.window.isLong(this.curRow, columnIndex)) {
result = 1; // FIELD_TYPE_INTEGER;
} else if (this.window.isString(this.curRow, columnIndex)) {
result = 3; // FIELD_TYPE_STRING;
} else if (this.window.isBlob(this.curRow, columnIndex)) {
result = 4; // FIELD_TYPE_BLOB;
}
}
return result;
}
@Override
public boolean getWantsAllOnMoveCalls() {
return false;
}
@Override
public CursorWindow getWindow() {
final CursorWindow ret = CursorHelper.getCursorWindowInstance();
fillWindow(0, ret);
return ret;
}
@Override
public boolean isAfterLast() {
return (this.curRow >= this.window.getNumRows());
}
@Override
public boolean isBeforeFirst() {
return (this.curRow < 0);
}
@Override
public boolean isClosed() {
return this.closed;
}
@Override
public boolean isFirst() {
return (this.curRow == 0);
}
@Override
public boolean isLast() {
return (this.curRow == this.window.getNumRows() - 1);
}
@Override
public boolean isNull(final int columnIndex) {
return this.getType(columnIndex) == FIELD_TYPE_NULL;
}
@Override
public boolean move(final int offset) {
final int oldPos = this.curRow;
this.curRow += offset;
if (this.curRow < -1) {
this.curRow = -1;
return false;
} else if (this.curRow > this.window.getNumRows() - 1) {
this.curRow = this.window.getNumRows() - 1;
return false;
}
return onMove(oldPos, this.curRow);
}
@Override
public boolean moveToFirst() {
if (this.window.getNumRows() == 0) {
return false;
}
final int oldPos = this.curRow;
this.curRow = 0;
return onMove(oldPos, this.curRow);
}
@Override
public boolean moveToLast() {
if (this.window.getNumRows() == 0) {
return false;
}
final int oldPos = this.curRow;
this.curRow = this.window.getNumRows() - 1;
return onMove(oldPos, this.curRow);
}
@Override
public boolean moveToNext() {
final int oldPos = this.curRow++;
if (isAfterLast()) {
this.curRow = this.window.getNumRows();
return false;
}
return onMove(oldPos, this.curRow);
}
@Override
public boolean moveToPosition(final int position) {
if (position < -1 && position >= this.window.getNumRows()) {
return false;
}
final int oldPos = this.curRow;
this.curRow = position;
return onMove(oldPos, this.curRow);
}
@Override
public boolean moveToPrevious() {
final int oldPos = this.curRow--;
if (isBeforeFirst()) {
this.curRow = -1;
return false;
}
return onMove(oldPos, this.curRow);
}
@Override
public boolean onMove(final int oldPosition, final int newPosition) {
// Don't forget to set curRow = -1 if this method returns false
return true;
}
/** Restoring this object from a Parcel */
public void readFromParcel(final Parcel in) {
this.numColumns = in.readInt();
this.colNames = in.readParcelable(ClassLoaderHelper.getClassLoader());
this.curRow = in.readInt();
this.closed = (in.readByte() == 1);
// Closes the cursor before create a new cursor.
if (window != null) {
window.close();
}
this.window = CursorWindow.newFromParcel(in);
}
/** Not supported */
@Override
public void registerContentObserver(final ContentObserver observer) {
// Does nothing
}
/** Not supported */
@Override
public void registerDataSetObserver(final DataSetObserver observer) {
// Does nothing
}
/** Deprecated, not supported */
@Override
public boolean requery() {
return false;
}
/** Not supported */
@Override
public Bundle respond(final Bundle extras) {
// Does nothing
return null;
}
/** Sets this cursor from another windowed Cursor */
public void setFromCursor(final AbstractWindowedCursor cursor) throws CursorIndexOutOfBoundsException, IllegalStateException {
// Reset number of columns
this.numColumns = 0;
// Set column names
final String[] colNames = cursor.getColumnNames();
if (colNames != null) {
for (final String col : colNames) {
addColumn(col);
}
}
// Fill window
this.window.clear();
this.window.setNumColumns(this.numColumns);
cursor.fillWindow(0, this.window);
moveToPosition(-1);
}
/** Sets this cursor from another windowed Cursor */
public void setFromCursor(final MatrixCursor cursor) throws CursorIndexOutOfBoundsException ,IllegalStateException{
// Reset number of columns
this.numColumns = 0;
// Set column names
final String[] colNames = cursor.getColumnNames();
if (colNames != null) {
for (final String col : colNames) {
addColumn(col);
}
}
// Fill window
this.window.clear();
this.window.setNumColumns(this.numColumns);
cursor.fillWindow(0, this.window);
moveToPosition(-1);
}
/** Sets this cursor using a CursorWindow data */
public void setFromWindow(final CursorWindow window) {
CursorHelper.copyCursorWindow(0, window, this.window);
this.numColumns = CursorHelper.getCursorWindowNumCols(window);
moveToPosition(-1);
}
/** Not supported */
@Override
public void setNotificationUri(final ContentResolver cr, final Uri uri) {
// Does nothing
}
/** Not supported */
@Override
public void unregisterContentObserver(final ContentObserver observer) {
// Does nothing
}
/** Not supported */
@Override
public void unregisterDataSetObserver(final DataSetObserver observer) {
// Does nothing
}
@Override
public void writeToParcel(final Parcel out, final int flags) {
out.writeInt(this.numColumns);
out.writeParcelable((Parcelable) this.colNames, 0);
out.writeInt(this.curRow);
out.writeByte(this.closed ? (byte) 1 : 0);
this.window.writeToParcel(out, flags);
}
}
仍在寻找更标准的方法来执行此操作。任何信息将不胜感激!
编辑:这通过了很少的测试，所以在使用它之前进行测试。
EDIT2:实际上，这里充满了错误……我将尽快更新一个错误较小的版本。
EDIT3:自一年以来，我们使用的游标已更新。