CursorUtil.java
/*
* Copyright (C) 2018 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 androidx.room.util;
import android.database.Cursor;
import android.database.MatrixCursor;
import androidx.annotation.NonNull;
import androidx.annotation.RestrictTo;
/**
* Cursor utilities for Room
*
* @hide
*/
@RestrictTo(RestrictTo.Scope.LIBRARY_GROUP_PREFIX)
public class CursorUtil {
/**
* Copies the given cursor into a in-memory cursor and then closes it.
* <p>
* This is useful for iterating over a cursor multiple times without the cost of JNI while
* reading or IO while filling the window at the expense of memory consumption.
*
* @param c the cursor to copy.
* @return a new cursor containing the same data as the given cursor.
*/
@NonNull
public static Cursor copyAndClose(@NonNull Cursor c) {
final MatrixCursor matrixCursor;
try {
matrixCursor = new MatrixCursor(c.getColumnNames(), c.getCount());
while (c.moveToNext()) {
final Object[] row = new Object[c.getColumnCount()];
for (int i = 0; i < c.getColumnCount(); i++) {
switch (c.getType(i)) {
case Cursor.FIELD_TYPE_NULL:
row[i] = null;
break;
case Cursor.FIELD_TYPE_INTEGER:
row[i] = c.getLong(i);
break;
case Cursor.FIELD_TYPE_FLOAT:
row[i] = c.getDouble(i);
break;
case Cursor.FIELD_TYPE_STRING:
row[i] = c.getString(i);
break;
case Cursor.FIELD_TYPE_BLOB:
row[i] = c.getBlob(i);
break;
default:
throw new IllegalStateException();
}
}
matrixCursor.addRow(row);
}
} finally {
c.close();
}
return matrixCursor;
}
/**
* Patches {@link Cursor#getColumnIndex(String)} to work around issues on older devices.
* If the column is not found, it retries with the specified name surrounded by backticks.
*
* @param c The cursor.
* @param name The name of the target column.
* @return The index of the column, or -1 if not found.
*/
public static int getColumnIndex(@NonNull Cursor c, @NonNull String name) {
final int index = c.getColumnIndex(name);
if (index >= 0) {
return index;
}
return c.getColumnIndex("`" + name + "`");
}
/**
* Patches {@link Cursor#getColumnIndexOrThrow(String)} to work around issues on older devices.
* If the column is not found, it retries with the specified name surrounded by backticks.
*
* @param c The cursor.
* @param name The name of the target column.
* @return The index of the column.
* @throws IllegalArgumentException if the column does not exist.
*/
public static int getColumnIndexOrThrow(@NonNull Cursor c, @NonNull String name) {
final int index = c.getColumnIndex(name);
if (index >= 0) {
return index;
}
return c.getColumnIndexOrThrow("`" + name + "`");
}
private CursorUtil() {
}
}