我有一个内容提供程序，它是我的Android应用程序集自定义的，它需要公开的一个东西是一个小的（20-30 KiB）字节数组。这些blob的URI如下所示：
content://my.authority/blob/#
其中#是行号;生成的游标具有标准_id列和数据列。我在提供商的MatrixCursor方法中使用query()：
byte[] byteData = getMyByteData();
MatrixCursor mc = new MatrixCursor(COLUMNS);
mc.addRow(new Object[] { id, byteData });
稍后，在使用数据的应用程序中，我这样做：
Cursor c = managedQuery(uri, null, null, null, null);
c.moveToFirst();
byte[] data = c.getBlob(c.getColumnIndexOrThrow("data"));
但是，数据不包含原始字节数组的内容;相反，它包含类似[B@435cc518的东西，它看起来更像是数组的地址而不是内容。我尝试在java.sql.Blob的实现中包装字节数组，认为它可能正在寻找，因为内容提供者子系统被编写为易于与SQLite一起使用，但它没有帮助。
有没有人让这个工作？如果数据在文件系统中，ContentProvider中有一些方法可以用来为客户端提供编组InputStream，但我尝试发送的数据作为资源存在。内容提供商的APK。
答案 0 :(得分：7)
从Ice Cream Sandwich来源获取MatrixCursor。它正确实现了getBlob。
如果您想使用它，请在下面修改源代码。您可以在Android 1.6+项目中使用它。
/*
* 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;
}
}
答案 1 :(得分：4)
您将无法使用MatrixCursor发送字节数组。这是因为它取决于使用AbstractCursor#fillWindow填充CursorWindow的{{1}}方法。所以正在发生的是调用字节数组Object#toString方法并且它存储的是代替你想要的字节数组的内容。我能看到的唯一方法是实现自己的Cursor，它将适当填充toString字节数组。
答案 2 :(得分：1)
您需要在AbstractCursor实现中覆盖fillWindow。这是一个适用于JUST BLOBS的内容提供商
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();
}
}