1 /* 2 * Copyright (C) 2006 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.database; 18 19 import android.content.ContentResolver; 20 import android.net.Uri; 21 import android.os.Bundle; 22 23 import java.util.Map; 24 25 /** 26 * This interface provides random read-write access to the result set returned 27 * by a database query. 28 * 29 * Cursor implementations are not required to be synchronized so code using a Cursor from multiple 30 * threads should perform its own synchronization when using the Cursor. 31 */ 32 public interface Cursor { 33 /** 34 * Returns the numbers of rows in the cursor. 35 * 36 * @return the number of rows in the cursor. 37 */ 38 int getCount(); 39 40 /** 41 * Returns the current position of the cursor in the row set. 42 * The value is zero-based. When the row set is first returned the cursor 43 * will be at positon -1, which is before the first row. After the 44 * last row is returned another call to next() will leave the cursor past 45 * the last entry, at a position of count(). 46 * 47 * @return the current cursor position. 48 */ 49 int getPosition(); 50 51 /** 52 * Move the cursor by a relative amount, forward or backward, from the 53 * current position. Positive offsets move forwards, negative offsets move 54 * backwards. If the final position is outside of the bounds of the result 55 * set then the resultant position will be pinned to -1 or count() depending 56 * on whether the value is off the front or end of the set, respectively. 57 * 58 * <p>This method will return true if the requested destination was 59 * reachable, otherwise, it returns false. For example, if the cursor is at 60 * currently on the second entry in the result set and move(-5) is called, 61 * the position will be pinned at -1, and false will be returned. 62 * 63 * @param offset the offset to be applied from the current position. 64 * @return whether the requested move fully succeeded. 65 */ 66 boolean move(int offset); 67 68 /** 69 * Move the cursor to an absolute position. The valid 70 * range of values is -1 <= position <= count. 71 * 72 * <p>This method will return true if the request destination was reachable, 73 * otherwise, it returns false. 74 * 75 * @param position the zero-based position to move to. 76 * @return whether the requested move fully succeeded. 77 */ 78 boolean moveToPosition(int position); 79 80 /** 81 * Move the cursor to the first row. 82 * 83 * <p>This method will return false if the cursor is empty. 84 * 85 * @return whether the move succeeded. 86 */ 87 boolean moveToFirst(); 88 89 /** 90 * Move the cursor to the last row. 91 * 92 * <p>This method will return false if the cursor is empty. 93 * 94 * @return whether the move succeeded. 95 */ 96 boolean moveToLast(); 97 98 /** 99 * Move the cursor to the next row. 100 * 101 * <p>This method will return false if the cursor is already past the 102 * last entry in the result set. 103 * 104 * @return whether the move succeeded. 105 */ 106 boolean moveToNext(); 107 108 /** 109 * Move the cursor to the previous row. 110 * 111 * <p>This method will return false if the cursor is already before the 112 * first entry in the result set. 113 * 114 * @return whether the move succeeded. 115 */ 116 boolean moveToPrevious(); 117 118 /** 119 * Returns whether the cursor is pointing to the first row. 120 * 121 * @return whether the cursor is pointing at the first entry. 122 */ 123 boolean isFirst(); 124 125 /** 126 * Returns whether the cursor is pointing to the last row. 127 * 128 * @return whether the cursor is pointing at the last entry. 129 */ 130 boolean isLast(); 131 132 /** 133 * Returns whether the cursor is pointing to the position before the first 134 * row. 135 * 136 * @return whether the cursor is before the first result. 137 */ 138 boolean isBeforeFirst(); 139 140 /** 141 * Returns whether the cursor is pointing to the position after the last 142 * row. 143 * 144 * @return whether the cursor is after the last result. 145 */ 146 boolean isAfterLast(); 147 148 /** 149 * Removes the row at the current cursor position from the underlying data 150 * store. After this method returns the cursor will be pointing to the row 151 * after the row that is deleted. This has the side effect of decrementing 152 * the result of count() by one. 153 * <p> 154 * The query must have the row ID column in its selection, otherwise this 155 * call will fail. 156 * 157 * @hide 158 * @return whether the record was successfully deleted. 159 * @deprecated use {@link ContentResolver#delete(Uri, String, String[])} 160 */ 161 @Deprecated 162 boolean deleteRow(); 163 164 /** 165 * Returns the zero-based index for the given column name, or -1 if the column doesn't exist. 166 * If you expect the column to exist use {@link #getColumnIndexOrThrow(String)} instead, which 167 * will make the error more clear. 168 * 169 * @param columnName the name of the target column. 170 * @return the zero-based column index for the given column name, or -1 if 171 * the column name does not exist. 172 * @see #getColumnIndexOrThrow(String) 173 */ 174 int getColumnIndex(String columnName); 175 176 /** 177 * Returns the zero-based index for the given column name, or throws 178 * {@link IllegalArgumentException} if the column doesn't exist. If you're not sure if 179 * a column will exist or not use {@link #getColumnIndex(String)} and check for -1, which 180 * is more efficient than catching the exceptions. 181 * 182 * @param columnName the name of the target column. 183 * @return the zero-based column index for the given column name 184 * @see #getColumnIndex(String) 185 * @throws IllegalArgumentException if the column does not exist 186 */ 187 int getColumnIndexOrThrow(String columnName) throws IllegalArgumentException; 188 189 /** 190 * Returns the column name at the given zero-based column index. 191 * 192 * @param columnIndex the zero-based index of the target column. 193 * @return the column name for the given column index. 194 */ 195 String getColumnName(int columnIndex); 196 197 /** 198 * Returns a string array holding the names of all of the columns in the 199 * result set in the order in which they were listed in the result. 200 * 201 * @return the names of the columns returned in this query. 202 */ 203 String[] getColumnNames(); 204 205 /** 206 * Return total number of columns 207 * @return number of columns 208 */ 209 int getColumnCount(); 210 211 /** 212 * Returns the value of the requested column as a byte array. 213 * 214 * <p>If the native content of that column is not blob exception may throw 215 * 216 * @param columnIndex the zero-based index of the target column. 217 * @return the value of that column as a byte array. 218 */ 219 byte[] getBlob(int columnIndex); 220 221 /** 222 * Returns the value of the requested column as a String. 223 * 224 * <p>If the native content of that column is not text the result will be 225 * the result of passing the column value to String.valueOf(x). 226 * 227 * @param columnIndex the zero-based index of the target column. 228 * @return the value of that column as a String. 229 */ 230 String getString(int columnIndex); 231 232 /** 233 * Retrieves the requested column text and stores it in the buffer provided. 234 * If the buffer size is not sufficient, a new char buffer will be allocated 235 * and assigned to CharArrayBuffer.data 236 * @param columnIndex the zero-based index of the target column. 237 * if the target column is null, return buffer 238 * @param buffer the buffer to copy the text into. 239 */ 240 void copyStringToBuffer(int columnIndex, CharArrayBuffer buffer); 241 242 /** 243 * Returns the value of the requested column as a short. 244 * 245 * <p>If the native content of that column is not numeric the result will be 246 * the result of passing the column value to Short.valueOf(x). 247 * 248 * @param columnIndex the zero-based index of the target column. 249 * @return the value of that column as a short. 250 */ 251 short getShort(int columnIndex); 252 253 /** 254 * Returns the value of the requested column as an int. 255 * 256 * <p>If the native content of that column is not numeric the result will be 257 * the result of passing the column value to Integer.valueOf(x). 258 * 259 * @param columnIndex the zero-based index of the target column. 260 * @return the value of that column as an int. 261 */ 262 int getInt(int columnIndex); 263 264 /** 265 * Returns the value of the requested column as a long. 266 * 267 * <p>If the native content of that column is not numeric the result will be 268 * the result of passing the column value to Long.valueOf(x). 269 * 270 * @param columnIndex the zero-based index of the target column. 271 * @return the value of that column as a long. 272 */ 273 long getLong(int columnIndex); 274 275 /** 276 * Returns the value of the requested column as a float. 277 * 278 * <p>If the native content of that column is not numeric the result will be 279 * the result of passing the column value to Float.valueOf(x). 280 * 281 * @param columnIndex the zero-based index of the target column. 282 * @return the value of that column as a float. 283 */ 284 float getFloat(int columnIndex); 285 286 /** 287 * Returns the value of the requested column as a double. 288 * 289 * <p>If the native content of that column is not numeric the result will be 290 * the result of passing the column value to Double.valueOf(x). 291 * 292 * @param columnIndex the zero-based index of the target column. 293 * @return the value of that column as a double. 294 */ 295 double getDouble(int columnIndex); 296 297 /** 298 * Returns <code>true</code> if the value in the indicated column is null. 299 * 300 * @param columnIndex the zero-based index of the target column. 301 * @return whether the column value is null. 302 */ 303 boolean isNull(int columnIndex); 304 305 /** 306 * Returns <code>true</code> if the cursor supports updates. 307 * 308 * @return whether the cursor supports updates. 309 * @hide 310 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 311 * update methods 312 */ 313 @Deprecated 314 boolean supportsUpdates(); 315 316 /** 317 * Returns <code>true</code> if there are pending updates that have not yet been committed. 318 * 319 * @return <code>true</code> if there are pending updates that have not yet been committed. 320 * @hide 321 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 322 * update methods 323 */ 324 @Deprecated 325 boolean hasUpdates(); 326 327 /** 328 * Updates the value for the given column in the row the cursor is 329 * currently pointing at. Updates are not committed to the backing store 330 * until {@link #commitUpdates()} is called. 331 * 332 * @param columnIndex the zero-based index of the target column. 333 * @param value the new value. 334 * @return whether the operation succeeded. 335 * @hide 336 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 337 * update methods 338 */ 339 @Deprecated 340 boolean updateBlob(int columnIndex, byte[] value); 341 342 /** 343 * Updates the value for the given column in the row the cursor is 344 * currently pointing at. Updates are not committed to the backing store 345 * until {@link #commitUpdates()} is called. 346 * 347 * @param columnIndex the zero-based index of the target column. 348 * @param value the new value. 349 * @return whether the operation succeeded. 350 * @hide 351 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 352 * update methods 353 */ 354 @Deprecated 355 boolean updateString(int columnIndex, String value); 356 357 /** 358 * Updates the value for the given column in the row the cursor is 359 * currently pointing at. Updates are not committed to the backing store 360 * until {@link #commitUpdates()} is called. 361 * 362 * @param columnIndex the zero-based index of the target column. 363 * @param value the new value. 364 * @return whether the operation succeeded. 365 * @hide 366 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 367 * update methods 368 */ 369 @Deprecated 370 boolean updateShort(int columnIndex, short value); 371 372 /** 373 * Updates the value for the given column in the row the cursor is 374 * currently pointing at. Updates are not committed to the backing store 375 * until {@link #commitUpdates()} is called. 376 * 377 * @param columnIndex the zero-based index of the target column. 378 * @param value the new value. 379 * @return whether the operation succeeded. 380 * @hide 381 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 382 * update methods 383 */ 384 @Deprecated 385 boolean updateInt(int columnIndex, int value); 386 387 /** 388 * Updates the value for the given column in the row the cursor is 389 * currently pointing at. Updates are not committed to the backing store 390 * until {@link #commitUpdates()} is called. 391 * 392 * @param columnIndex the zero-based index of the target column. 393 * @param value the new value. 394 * @return whether the operation succeeded. 395 * @hide 396 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 397 * update methods 398 */ 399 @Deprecated 400 boolean updateLong(int columnIndex, long value); 401 402 /** 403 * Updates the value for the given column in the row the cursor is 404 * currently pointing at. Updates are not committed to the backing store 405 * until {@link #commitUpdates()} is called. 406 * 407 * @param columnIndex the zero-based index of the target column. 408 * @param value the new value. 409 * @return whether the operation succeeded. 410 * @hide 411 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 412 * update methods 413 */ 414 @Deprecated 415 boolean updateFloat(int columnIndex, float value); 416 417 /** 418 * Updates the value for the given column in the row the cursor is 419 * currently pointing at. Updates are not committed to the backing store 420 * until {@link #commitUpdates()} is called. 421 * 422 * @param columnIndex the zero-based index of the target column. 423 * @param value the new value. 424 * @return whether the operation succeeded. 425 * @hide 426 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 427 * update methods 428 */ 429 @Deprecated 430 boolean updateDouble(int columnIndex, double value); 431 432 /** 433 * Removes the value for the given column in the row the cursor is 434 * currently pointing at. Updates are not committed to the backing store 435 * until {@link #commitUpdates()} is called. 436 * 437 * @param columnIndex the zero-based index of the target column. 438 * @return whether the operation succeeded. 439 * @hide 440 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 441 * update methods 442 */ 443 @Deprecated 444 boolean updateToNull(int columnIndex); 445 446 /** 447 * Atomically commits all updates to the backing store. After completion, 448 * this method leaves the data in an inconsistent state and you should call 449 * {@link #requery} before reading data from the cursor again. 450 * 451 * @return whether the operation succeeded. 452 * @hide 453 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 454 * update methods 455 */ 456 @Deprecated 457 boolean commitUpdates(); 458 459 /** 460 * Atomically commits all updates to the backing store, as well as the 461 * updates included in values. After completion, 462 * this method leaves the data in an inconsistent state and you should call 463 * {@link #requery} before reading data from the cursor again. 464 * 465 * @param values A map from row IDs to Maps associating column names with 466 * updated values. A null value indicates the field should be 467 removed. 468 * @return whether the operation succeeded. 469 * @hide 470 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 471 * update methods 472 */ 473 @Deprecated 474 boolean commitUpdates(Map<? extends Long, 475 ? extends Map<String,Object>> values); 476 477 /** 478 * Reverts all updates made to the cursor since the last call to 479 * commitUpdates. 480 * @hide 481 * @deprecated use the {@link ContentResolver} update methods instead of the Cursor 482 * update methods 483 */ 484 @Deprecated 485 void abortUpdates(); 486 487 /** 488 * Deactivates the Cursor, making all calls on it fail until {@link #requery} is called. 489 * Inactive Cursors use fewer resources than active Cursors. 490 * Calling {@link #requery} will make the cursor active again. 491 */ 492 void deactivate(); 493 494 /** 495 * Performs the query that created the cursor again, refreshing its 496 * contents. This may be done at any time, including after a call to {@link 497 * #deactivate}. 498 * 499 * @return true if the requery succeeded, false if not, in which case the 500 * cursor becomes invalid. 501 */ 502 boolean requery(); 503 504 /** 505 * Closes the Cursor, releasing all of its resources and making it completely invalid. 506 * Unlike {@link #deactivate()} a call to {@link #requery()} will not make the Cursor valid 507 * again. 508 */ 509 void close(); 510 511 /** 512 * return true if the cursor is closed 513 * @return true if the cursor is closed. 514 */ 515 boolean isClosed(); 516 517 /** 518 * Register an observer that is called when changes happen to the content backing this cursor. 519 * Typically the data set won't change until {@link #requery()} is called. 520 * 521 * @param observer the object that gets notified when the content backing the cursor changes. 522 * @see #unregisterContentObserver(ContentObserver) 523 */ 524 void registerContentObserver(ContentObserver observer); 525 526 /** 527 * Unregister an observer that has previously been registered with this 528 * cursor via {@link #registerContentObserver}. 529 * 530 * @param observer the object to unregister. 531 * @see #registerContentObserver(ContentObserver) 532 */ 533 void unregisterContentObserver(ContentObserver observer); 534 535 /** 536 * Register an observer that is called when changes happen to the contents 537 * of the this cursors data set, for example, when the data set is changed via 538 * {@link #requery()}, {@link #deactivate()}, or {@link #close()}. 539 * 540 * @param observer the object that gets notified when the cursors data set changes. 541 * @see #unregisterDataSetObserver(DataSetObserver) 542 */ 543 void registerDataSetObserver(DataSetObserver observer); 544 545 /** 546 * Unregister an observer that has previously been registered with this 547 * cursor via {@link #registerContentObserver}. 548 * 549 * @param observer the object to unregister. 550 * @see #registerDataSetObserver(DataSetObserver) 551 */ 552 void unregisterDataSetObserver(DataSetObserver observer); 553 554 /** 555 * Register to watch a content URI for changes. This can be the URI of a specific data row (for 556 * example, "content://my_provider_type/23"), or a a generic URI for a content type. 557 * 558 * @param cr The content resolver from the caller's context. The listener attached to 559 * this resolver will be notified. 560 * @param uri The content URI to watch. 561 */ 562 void setNotificationUri(ContentResolver cr, Uri uri); 563 564 /** 565 * onMove() will only be called across processes if this method returns true. 566 * @return whether all cursor movement should result in a call to onMove(). 567 */ 568 boolean getWantsAllOnMoveCalls(); 569 570 /** 571 * Returns a bundle of extra values. This is an optional way for cursors to provide out-of-band 572 * metadata to their users. One use of this is for reporting on the progress of network requests 573 * that are required to fetch data for the cursor. 574 * 575 * <p>These values may only change when requery is called. 576 * @return cursor-defined values, or Bundle.EMTPY if there are no values. Never null. 577 */ 578 Bundle getExtras(); 579 580 /** 581 * This is an out-of-band way for the the user of a cursor to communicate with the cursor. The 582 * structure of each bundle is entirely defined by the cursor. 583 * 584 * <p>One use of this is to tell a cursor that it should retry its network request after it 585 * reported an error. 586 * @param extras extra values, or Bundle.EMTPY. Never null. 587 * @return extra values, or Bundle.EMTPY. Never null. 588 */ 589 Bundle respond(Bundle extras); 590 } 591