Passing binären Blob durch einen Content-Provider
https://stackoverflow.com/questions/3034575
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27-09-2019 - |
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Ich habe einen Content-Provider, die benutzerdefinierten meine Reihe von Android-Anwendungen ist, und eines der Dinge, braucht es zu belichten ist ein kleiner (20-30 KiB) Byte-Array. Der URI für diese Blobs sieht aus wie:
content://my.authority/blob/#
Dabei gilt # die Zeilennummer ist; die resultierenden Cursor haben die Standard _id Säule und eine Datenspalte. Ich bin mit einem MatrixCursor in dem query() Methode des Anbieters:
byte[] byteData = getMyByteData();
MatrixCursor mc = new MatrixCursor(COLUMNS);
mc.addRow(new Object[] { id, byteData });
Später, in der Anwendung die Daten raubend, das tue ich:
Cursor c = managedQuery(uri, null, null, null, null);
c.moveToFirst();
byte[] data = c.getBlob(c.getColumnIndexOrThrow("data"));
Allerdings sind die Daten nicht den Inhalt meiner ursprünglichen Byte-Array enthalten; vielmehr enthält es so etwas wie [B@435cc518, die mehr wie die Adresse des Arrays als der Inhalt aussieht. Ich habe versucht, den Byte-Array in einer Implementierung von java.sql.Blob Einwickeln, herauszufinden, dass es für das könnte zu suchen, da das Content-Provider-Subsystem geschrieben wurde leicht mit SQLite zu verwenden sein, aber es hat nicht geholfen.
Hat jemand bekommen dies funktioniert? Wenn die Daten im Dateisystem waren, gibt es Methoden, in ContentProvider, dass ich einen Marshalled InputStream an den Kunden zu schaffen, verwenden könnte, aber die Daten Ich versuche, in den Inhalte-Anbietern APK Leben als Ressource zurück zu senden.
Lösung
Sie werden nicht in der Lage sein, eine MatrixCursor zu verwenden, um den Byte-Array zu senden. Dies liegt daran, es auf AbstractCursor#fillWindow Methode abhängt, die die CursorWindow mit Object#toString füllt. Also, was passiert ist, dass die Byte-Array toString Methode aufgerufen wird, und es ist, dass anstelle des Inhalts des Byte-Array zu speichern, die ist, was Sie wollen. Der einzige Weg, um dies ich sehen kann, ist Ihre eigene Cursor zu implementieren, die die CursorWindow in geeigneter Weise für einen Byte-Array füllen.
Andere Tipps
Holen Sie sich das MatrixCursor von Ice Cream Sandwich Quellen. Es implementiert getBlob richtig.
Modifizierte Quellcode ist unten, wenn Sie es verwenden möchten. Sie können es in 1.6+ Projekte Android verwenden.
/*
* Copyright (C) 2007 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package yuku.androidsdk.android.database.icsmatrixcursor;
import android.database.*;
import java.util.*;
/**
* A mutable cursor implementation backed by an array of {@code Object}s. Use
* {@link #newRow()} to add rows. Automatically expands internal capacity
* as needed.
*/
public class MatrixCursor extends AbstractCursor {
private final String[] columnNames;
private Object[] data;
private int rowCount = 0;
private final int columnCount;
/**
* Constructs a new cursor with the given initial capacity.
*
* @param columnNames names of the columns, the ordering of which
* determines column ordering elsewhere in this cursor
* @param initialCapacity in rows
*/
public MatrixCursor(String[] columnNames, int initialCapacity) {
this.columnNames = columnNames;
this.columnCount = columnNames.length;
if (initialCapacity < 1) {
initialCapacity = 1;
}
this.data = new Object[columnCount * initialCapacity];
}
/**
* Constructs a new cursor.
*
* @param columnNames names of the columns, the ordering of which
* determines column ordering elsewhere in this cursor
*/
public MatrixCursor(String[] columnNames) {
this(columnNames, 16);
}
/**
* Gets value at the given column for the current row.
*/
private Object get(int column) {
if (column < 0 || column >= columnCount) {
throw new CursorIndexOutOfBoundsException("Requested column: "
+ column + ", # of columns: " + columnCount);
}
if (mPos < 0) {
throw new CursorIndexOutOfBoundsException("Before first row.");
}
if (mPos >= rowCount) {
throw new CursorIndexOutOfBoundsException("After last row.");
}
return data[mPos * columnCount + column];
}
/**
* Adds a new row to the end and returns a builder for that row. Not safe
* for concurrent use.
*
* @return builder which can be used to set the column values for the new
* row
*/
public RowBuilder newRow() {
rowCount++;
int endIndex = rowCount * columnCount;
ensureCapacity(endIndex);
int start = endIndex - columnCount;
return new RowBuilder(start, endIndex);
}
/**
* Adds a new row to the end with the given column values. Not safe
* for concurrent use.
*
* @throws IllegalArgumentException if {@code columnValues.length !=
* columnNames.length}
* @param columnValues in the same order as the the column names specified
* at cursor construction time
*/
public void addRow(Object[] columnValues) {
if (columnValues.length != columnCount) {
throw new IllegalArgumentException("columnNames.length = "
+ columnCount + ", columnValues.length = "
+ columnValues.length);
}
int start = rowCount++ * columnCount;
ensureCapacity(start + columnCount);
System.arraycopy(columnValues, 0, data, start, columnCount);
}
/**
* Adds a new row to the end with the given column values. Not safe
* for concurrent use.
*
* @throws IllegalArgumentException if {@code columnValues.size() !=
* columnNames.length}
* @param columnValues in the same order as the the column names specified
* at cursor construction time
*/
public void addRow(Iterable<?> columnValues) {
int start = rowCount * columnCount;
int end = start + columnCount;
ensureCapacity(end);
if (columnValues instanceof ArrayList<?>) {
addRow((ArrayList<?>) columnValues, start);
return;
}
int current = start;
Object[] localData = data;
for (Object columnValue : columnValues) {
if (current == end) {
// TODO: null out row?
throw new IllegalArgumentException(
"columnValues.size() > columnNames.length");
}
localData[current++] = columnValue;
}
if (current != end) {
// TODO: null out row?
throw new IllegalArgumentException(
"columnValues.size() < columnNames.length");
}
// Increase row count here in case we encounter an exception.
rowCount++;
}
/** Optimization for {@link ArrayList}. */
private void addRow(ArrayList<?> columnValues, int start) {
int size = columnValues.size();
if (size != columnCount) {
throw new IllegalArgumentException("columnNames.length = "
+ columnCount + ", columnValues.size() = " + size);
}
rowCount++;
Object[] localData = data;
for (int i = 0; i < size; i++) {
localData[start + i] = columnValues.get(i);
}
}
/** Ensures that this cursor has enough capacity. */
private void ensureCapacity(int size) {
if (size > data.length) {
Object[] oldData = this.data;
int newSize = data.length * 2;
if (newSize < size) {
newSize = size;
}
this.data = new Object[newSize];
System.arraycopy(oldData, 0, this.data, 0, oldData.length);
}
}
/**
* Builds a row, starting from the left-most column and adding one column
* value at a time. Follows the same ordering as the column names specified
* at cursor construction time.
*/
public class RowBuilder {
private int index;
private final int endIndex;
RowBuilder(int index, int endIndex) {
this.index = index;
this.endIndex = endIndex;
}
/**
* Sets the next column value in this row.
*
* @throws CursorIndexOutOfBoundsException if you try to add too many
* values
* @return this builder to support chaining
*/
public RowBuilder add(Object columnValue) {
if (index == endIndex) {
throw new CursorIndexOutOfBoundsException(
"No more columns left.");
}
data[index++] = columnValue;
return this;
}
}
// AbstractCursor implementation.
@Override
public int getCount() {
return rowCount;
}
@Override
public String[] getColumnNames() {
return columnNames;
}
@Override
public String getString(int column) {
Object value = get(column);
if (value == null) return null;
return value.toString();
}
@Override
public short getShort(int column) {
Object value = get(column);
if (value == null) return 0;
if (value instanceof Number) return ((Number) value).shortValue();
return Short.parseShort(value.toString());
}
@Override
public int getInt(int column) {
Object value = get(column);
if (value == null) return 0;
if (value instanceof Number) return ((Number) value).intValue();
return Integer.parseInt(value.toString());
}
@Override
public long getLong(int column) {
Object value = get(column);
if (value == null) return 0;
if (value instanceof Number) return ((Number) value).longValue();
return Long.parseLong(value.toString());
}
@Override
public float getFloat(int column) {
Object value = get(column);
if (value == null) return 0.0f;
if (value instanceof Number) return ((Number) value).floatValue();
return Float.parseFloat(value.toString());
}
@Override
public double getDouble(int column) {
Object value = get(column);
if (value == null) return 0.0d;
if (value instanceof Number) return ((Number) value).doubleValue();
return Double.parseDouble(value.toString());
}
@Override
public byte[] getBlob(int column) {
Object value = get(column);
return (byte[]) value;
}
@Override
public boolean isNull(int column) {
return get(column) == null;
}
}
Sie müssen FillWindow in Ihrer AbstractCursor Implementierung außer Kraft zu setzen. Hier ist eine, die von JUST BLOBS
auf einen Content-Provider arbeitet public void fillWindow(int position, CursorWindow window) {
if (position < 0 || position >= getCount()) {
return;
}
window.acquireReference();
try {
int oldpos = mPos;
mPos = position - 1;
window.clear();
window.setStartPosition(position);
int columnNum = getColumnCount();
window.setNumColumns(columnNum);
while (moveToNext() && window.allocRow()) {
for (int i = 0; i < columnNum; i++) {
byte [] field = getBlob(i);
if (field != null) {
if (!window.putBlob(field, mPos, i)) {
window.freeLastRow();
break;
}
} else {
if (!window.putNull(mPos, i)) {
window.freeLastRow();
break;
}
}
}
}
mPos = oldpos;
} catch (IllegalStateException e){
// simply ignore it
} finally {
window.releaseReference();
}
}
