ViewParent.java revision b6ab098bad4b126eaaaa3aaa5a512fefc4e0749b
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 17package android.view; 18 19import android.graphics.Rect; 20import android.os.Bundle; 21import android.view.accessibility.AccessibilityEvent; 22 23/** 24 * Defines the responsibilities for a class that will be a parent of a View. 25 * This is the API that a view sees when it wants to interact with its parent. 26 * 27 */ 28public interface ViewParent { 29 /** 30 * Called when something has changed which has invalidated the layout of a 31 * child of this view parent. This will schedule a layout pass of the view 32 * tree. 33 */ 34 public void requestLayout(); 35 36 /** 37 * Indicates whether layout was requested on this view parent. 38 * 39 * @return true if layout was requested, false otherwise 40 */ 41 public boolean isLayoutRequested(); 42 43 /** 44 * Called when a child wants the view hierarchy to gather and report 45 * transparent regions to the window compositor. Views that "punch" holes in 46 * the view hierarchy, such as SurfaceView can use this API to improve 47 * performance of the system. When no such a view is present in the 48 * hierarchy, this optimization in unnecessary and might slightly reduce the 49 * view hierarchy performance. 50 * 51 * @param child the view requesting the transparent region computation 52 * 53 */ 54 public void requestTransparentRegion(View child); 55 56 /** 57 * All or part of a child is dirty and needs to be redrawn. 58 * 59 * @param child The child which is dirty 60 * @param r The area within the child that is invalid 61 */ 62 public void invalidateChild(View child, Rect r); 63 64 /** 65 * All or part of a child is dirty and needs to be redrawn. 66 * 67 * <p>The location array is an array of two int values which respectively 68 * define the left and the top position of the dirty child.</p> 69 * 70 * <p>This method must return the parent of this ViewParent if the specified 71 * rectangle must be invalidated in the parent. If the specified rectangle 72 * does not require invalidation in the parent or if the parent does not 73 * exist, this method must return null.</p> 74 * 75 * <p>When this method returns a non-null value, the location array must 76 * have been updated with the left and top coordinates of this ViewParent.</p> 77 * 78 * @param location An array of 2 ints containing the left and top 79 * coordinates of the child to invalidate 80 * @param r The area within the child that is invalid 81 * 82 * @return the parent of this ViewParent or null 83 */ 84 public ViewParent invalidateChildInParent(int[] location, Rect r); 85 86 /** 87 * Returns the parent if it exists, or null. 88 * 89 * @return a ViewParent or null if this ViewParent does not have a parent 90 */ 91 public ViewParent getParent(); 92 93 /** 94 * Called when a child of this parent wants focus 95 * 96 * @param child The child of this ViewParent that wants focus. This view 97 * will contain the focused view. It is not necessarily the view that 98 * actually has focus. 99 * @param focused The view that is a descendant of child that actually has 100 * focus 101 */ 102 public void requestChildFocus(View child, View focused); 103 104 /** 105 * Tell view hierarchy that the global view attributes need to be 106 * re-evaluated. 107 * 108 * @param child View whose attributes have changed. 109 */ 110 public void recomputeViewAttributes(View child); 111 112 /** 113 * Called when a child of this parent is giving up focus 114 * 115 * @param child The view that is giving up focus 116 */ 117 public void clearChildFocus(View child); 118 119 /** 120 * Compute the visible part of a rectangular region defined in terms of a child view's 121 * coordinates. 122 * 123 * <p>Returns the clipped visible part of the rectangle <code>r</code>, defined in the 124 * <code>child</code>'s local coordinate system. <code>r</code> is modified by this method to 125 * contain the result, expressed in the global (root) coordinate system.</p> 126 * 127 * <p>The resulting rectangle is always axis aligned. If a rotation is applied to a node in the 128 * View hierarchy, the result is the axis-aligned bounding box of the visible rectangle.</p> 129 * 130 * @param child A child View, whose rectangular visible region we want to compute 131 * @param r The input rectangle, defined in the child coordinate system. Will be overwritten to 132 * contain the resulting visible rectangle, expressed in global (root) coordinates 133 * @param offset The input coordinates of a point, defined in the child coordinate system. 134 * As with the <code>r</code> parameter, this will be overwritten to contain the global (root) 135 * coordinates of that point. 136 * A <code>null</code> value is valid (in case you are not interested in this result) 137 * @return true if the resulting rectangle is not empty, false otherwise 138 */ 139 public boolean getChildVisibleRect(View child, Rect r, android.graphics.Point offset); 140 141 /** 142 * Find the nearest view in the specified direction that wants to take focus 143 * 144 * @param v The view that currently has focus 145 * @param direction One of FOCUS_UP, FOCUS_DOWN, FOCUS_LEFT, and FOCUS_RIGHT 146 */ 147 public View focusSearch(View v, int direction); 148 149 /** 150 * Change the z order of the child so it's on top of all other children. 151 * This ordering change may affect layout, if this container 152 * uses an order-dependent layout scheme (e.g., LinearLayout). Prior 153 * to {@link android.os.Build.VERSION_CODES#KITKAT} this 154 * method should be followed by calls to {@link #requestLayout()} and 155 * {@link View#invalidate()} on this parent to force the parent to redraw 156 * with the new child ordering. 157 * 158 * @param child The child to bring to the top of the z order 159 */ 160 public void bringChildToFront(View child); 161 162 /** 163 * Tells the parent that a new focusable view has become available. This is 164 * to handle transitions from the case where there are no focusable views to 165 * the case where the first focusable view appears. 166 * 167 * @param v The view that has become newly focusable 168 */ 169 public void focusableViewAvailable(View v); 170 171 /** 172 * Bring up a context menu for the specified view or its ancestors. 173 * 174 * <p>In most cases, a subclass does not need to override this. However, if 175 * the subclass is added directly to the window manager (for example, 176 * {@link ViewManager#addView(View, android.view.ViewGroup.LayoutParams)}) 177 * then it should override this and show the context menu.</p> 178 * 179 * @param originalView The source view where the context menu was first invoked 180 * @return true if a context menu was displayed 181 */ 182 public boolean showContextMenuForChild(View originalView); 183 184 /** 185 * Have the parent populate the specified context menu if it has anything to 186 * add (and then recurse on its parent). 187 * 188 * @param menu The menu to populate 189 */ 190 public void createContextMenu(ContextMenu menu); 191 192 /** 193 * Start an action mode for the specified view. 194 * 195 * <p>In most cases, a subclass does not need to override this. However, if the 196 * subclass is added directly to the window manager (for example, 197 * {@link ViewManager#addView(View, android.view.ViewGroup.LayoutParams)}) 198 * then it should override this and start the action mode.</p> 199 * 200 * @param originalView The source view where the action mode was first invoked 201 * @param callback The callback that will handle lifecycle events for the action mode 202 * @return The new action mode if it was started, null otherwise 203 */ 204 public ActionMode startActionModeForChild(View originalView, ActionMode.Callback callback); 205 206 /** 207 * This method is called on the parent when a child's drawable state 208 * has changed. 209 * 210 * @param child The child whose drawable state has changed. 211 */ 212 public void childDrawableStateChanged(View child); 213 214 /** 215 * Called when a child does not want this parent and its ancestors to 216 * intercept touch events with 217 * {@link ViewGroup#onInterceptTouchEvent(MotionEvent)}. 218 * 219 * <p>This parent should pass this call onto its parents. This parent must obey 220 * this request for the duration of the touch (that is, only clear the flag 221 * after this parent has received an up or a cancel.</p> 222 * 223 * @param disallowIntercept True if the child does not want the parent to 224 * intercept touch events. 225 */ 226 public void requestDisallowInterceptTouchEvent(boolean disallowIntercept); 227 228 /** 229 * Called when a child of this group wants a particular rectangle to be 230 * positioned onto the screen. {@link ViewGroup}s overriding this can trust 231 * that: 232 * <ul> 233 * <li>child will be a direct child of this group</li> 234 * <li>rectangle will be in the child's coordinates</li> 235 * </ul> 236 * 237 * <p>{@link ViewGroup}s overriding this should uphold the contract:</p> 238 * <ul> 239 * <li>nothing will change if the rectangle is already visible</li> 240 * <li>the view port will be scrolled only just enough to make the 241 * rectangle visible</li> 242 * <ul> 243 * 244 * @param child The direct child making the request. 245 * @param rectangle The rectangle in the child's coordinates the child 246 * wishes to be on the screen. 247 * @param immediate True to forbid animated or delayed scrolling, 248 * false otherwise 249 * @return Whether the group scrolled to handle the operation 250 */ 251 public boolean requestChildRectangleOnScreen(View child, Rect rectangle, 252 boolean immediate); 253 254 /** 255 * Called by a child to request from its parent to send an {@link AccessibilityEvent}. 256 * The child has already populated a record for itself in the event and is delegating 257 * to its parent to send the event. The parent can optionally add a record for itself. 258 * <p> 259 * Note: An accessibility event is fired by an individual view which populates the 260 * event with a record for its state and requests from its parent to perform 261 * the sending. The parent can optionally add a record for itself before 262 * dispatching the request to its parent. A parent can also choose not to 263 * respect the request for sending the event. The accessibility event is sent 264 * by the topmost view in the view tree.</p> 265 * 266 * @param child The child which requests sending the event. 267 * @param event The event to be sent. 268 * @return True if the event was sent. 269 */ 270 public boolean requestSendAccessibilityEvent(View child, AccessibilityEvent event); 271 272 /** 273 * Called when a child view now has or no longer is tracking transient state. 274 * 275 * <p>"Transient state" is any state that a View might hold that is not expected to 276 * be reflected in the data model that the View currently presents. This state only 277 * affects the presentation to the user within the View itself, such as the current 278 * state of animations in progress or the state of a text selection operation.</p> 279 * 280 * <p>Transient state is useful for hinting to other components of the View system 281 * that a particular view is tracking something complex but encapsulated. 282 * A <code>ListView</code> for example may acknowledge that list item Views 283 * with transient state should be preserved within their position or stable item ID 284 * instead of treating that view as trivially replaceable by the backing adapter. 285 * This allows adapter implementations to be simpler instead of needing to track 286 * the state of item view animations in progress such that they could be restored 287 * in the event of an unexpected recycling and rebinding of attached item views.</p> 288 * 289 * <p>This method is called on a parent view when a child view or a view within 290 * its subtree begins or ends tracking of internal transient state.</p> 291 * 292 * @param child Child view whose state has changed 293 * @param hasTransientState true if this child has transient state 294 */ 295 public void childHasTransientStateChanged(View child, boolean hasTransientState); 296 297 /** 298 * Ask that a new dispatch of {@link View#fitSystemWindows(Rect) 299 * View.fitSystemWindows(Rect)} be performed. 300 */ 301 public void requestFitSystemWindows(); 302 303 /** 304 * Gets the parent of a given View for accessibility. Since some Views are not 305 * exposed to the accessibility layer the parent for accessibility is not 306 * necessarily the direct parent of the View, rather it is a predecessor. 307 * 308 * @return The parent or <code>null</code> if no such is found. 309 */ 310 public ViewParent getParentForAccessibility(); 311 312 /** 313 * Notifies a view parent that the accessibility state of one of its 314 * descendants has changed and that the structure of the subtree is 315 * different. 316 * @param child The direct child whose subtree has changed. 317 * @param source The descendant view that changed. 318 * @param changeType A bit mask of the types of changes that occurred. One 319 * or more of: 320 * <ul> 321 * <li>{@link AccessibilityEvent#CONTENT_CHANGE_TYPE_CONTENT_DESCRIPTION} 322 * <li>{@link AccessibilityEvent#CONTENT_CHANGE_TYPE_SUBTREE} 323 * <li>{@link AccessibilityEvent#CONTENT_CHANGE_TYPE_TEXT} 324 * <li>{@link AccessibilityEvent#CONTENT_CHANGE_TYPE_UNDEFINED} 325 * </ul> 326 */ 327 public void notifySubtreeAccessibilityStateChanged(View child, View source, int changeType); 328 329 /** 330 * Tells if this view parent can resolve the layout direction. 331 * See {@link View#setLayoutDirection(int)} 332 * 333 * @return True if this view parent can resolve the layout direction. 334 */ 335 public boolean canResolveLayoutDirection(); 336 337 /** 338 * Tells if this view parent layout direction is resolved. 339 * See {@link View#setLayoutDirection(int)} 340 * 341 * @return True if this view parent layout direction is resolved. 342 */ 343 public boolean isLayoutDirectionResolved(); 344 345 /** 346 * Return this view parent layout direction. See {@link View#getLayoutDirection()} 347 * 348 * @return {@link View#LAYOUT_DIRECTION_RTL} if the layout direction is RTL or returns 349 * {@link View#LAYOUT_DIRECTION_LTR} if the layout direction is not RTL. 350 */ 351 public int getLayoutDirection(); 352 353 /** 354 * Tells if this view parent can resolve the text direction. 355 * See {@link View#setTextDirection(int)} 356 * 357 * @return True if this view parent can resolve the text direction. 358 */ 359 public boolean canResolveTextDirection(); 360 361 /** 362 * Tells if this view parent text direction is resolved. 363 * See {@link View#setTextDirection(int)} 364 * 365 * @return True if this view parent text direction is resolved. 366 */ 367 public boolean isTextDirectionResolved(); 368 369 /** 370 * Return this view parent text direction. See {@link View#getTextDirection()} 371 * 372 * @return the resolved text direction. Returns one of: 373 * 374 * {@link View#TEXT_DIRECTION_FIRST_STRONG} 375 * {@link View#TEXT_DIRECTION_ANY_RTL}, 376 * {@link View#TEXT_DIRECTION_LTR}, 377 * {@link View#TEXT_DIRECTION_RTL}, 378 * {@link View#TEXT_DIRECTION_LOCALE} 379 */ 380 public int getTextDirection(); 381 382 /** 383 * Tells if this view parent can resolve the text alignment. 384 * See {@link View#setTextAlignment(int)} 385 * 386 * @return True if this view parent can resolve the text alignment. 387 */ 388 public boolean canResolveTextAlignment(); 389 390 /** 391 * Tells if this view parent text alignment is resolved. 392 * See {@link View#setTextAlignment(int)} 393 * 394 * @return True if this view parent text alignment is resolved. 395 */ 396 public boolean isTextAlignmentResolved(); 397 398 /** 399 * Return this view parent text alignment. See {@link android.view.View#getTextAlignment()} 400 * 401 * @return the resolved text alignment. Returns one of: 402 * 403 * {@link View#TEXT_ALIGNMENT_GRAVITY}, 404 * {@link View#TEXT_ALIGNMENT_CENTER}, 405 * {@link View#TEXT_ALIGNMENT_TEXT_START}, 406 * {@link View#TEXT_ALIGNMENT_TEXT_END}, 407 * {@link View#TEXT_ALIGNMENT_VIEW_START}, 408 * {@link View#TEXT_ALIGNMENT_VIEW_END} 409 */ 410 public int getTextAlignment(); 411 412 /** 413 * React to a descendant view initiating a nestable scroll operation, claiming the 414 * nested scroll operation if appropriate. 415 * 416 * <p>This method will be called in response to a descendant view invoking 417 * {@link View#startNestedScroll(int)}. Each parent up the view hierarchy will be 418 * given an opportunity to respond and claim the nested scrolling operation by returning 419 * <code>true</code>.</p> 420 * 421 * <p>This method may be overridden by ViewParent implementations to indicate when the view 422 * is willing to support a nested scrolling operation that is about to begin. If it returns 423 * true, this ViewParent will become the target view's nested scrolling parent for the duration 424 * of the scroll operation in progress. When the nested scroll is finished this ViewParent 425 * will receive a call to {@link #onStopNestedScroll(View)}. 426 * </p> 427 * 428 * @param child Direct child of this ViewParent containing target 429 * @param target View that initiated the nested scroll 430 * @param nestedScrollAxes Flags consisting of {@link View#SCROLL_AXIS_HORIZONTAL}, 431 * {@link View#SCROLL_AXIS_VERTICAL} or both 432 * @return true if this ViewParent accepts the nested scroll operation 433 */ 434 public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes); 435 436 /** 437 * React to the successful claiming of a nested scroll operation. 438 * 439 * <p>This method will be called after 440 * {@link #onStartNestedScroll(View, View, int) onStartNestedScroll} returns true. It offers 441 * an opportunity for the view and its superclasses to perform initial configuration 442 * for the nested scroll. Implementations of this method should always call their superclass's 443 * implementation of this method if one is present.</p> 444 * 445 * @param child Direct child of this ViewParent containing target 446 * @param target View that initiated the nested scroll 447 * @param nestedScrollAxes Flags consisting of {@link View#SCROLL_AXIS_HORIZONTAL}, 448 * {@link View#SCROLL_AXIS_VERTICAL} or both 449 * @see #onStartNestedScroll(View, View, int) 450 * @see #onStopNestedScroll(View) 451 */ 452 public void onNestedScrollAccepted(View child, View target, int nestedScrollAxes); 453 454 /** 455 * React to a nested scroll operation ending. 456 * 457 * <p>Perform cleanup after a nested scrolling operation. 458 * This method will be called when a nested scroll stops, for example when a nested touch 459 * scroll ends with a {@link MotionEvent#ACTION_UP} or {@link MotionEvent#ACTION_CANCEL} event. 460 * Implementations of this method should always call their superclass's implementation of this 461 * method if one is present.</p> 462 * 463 * @param target View that initiated the nested scroll 464 */ 465 public void onStopNestedScroll(View target); 466 467 /** 468 * React to a nested scroll in progress. 469 * 470 * <p>This method will be called when the ViewParent's current nested scrolling child view 471 * dispatches a nested scroll event. To receive calls to this method the ViewParent must have 472 * previously returned <code>true</code> for a call to 473 * {@link #onStartNestedScroll(View, View, int)}.</p> 474 * 475 * <p>Both the consumed and unconsumed portions of the scroll distance are reported to the 476 * ViewParent. An implementation may choose to use the consumed portion to match or chase scroll 477 * position of multiple child elements, for example. The unconsumed portion may be used to 478 * allow continuous dragging of multiple scrolling or draggable elements, such as scrolling 479 * a list within a vertical drawer where the drawer begins dragging once the edge of inner 480 * scrolling content is reached.</p> 481 * 482 * @param target The descendent view controlling the nested scroll 483 * @param dxConsumed Horizontal scroll distance in pixels already consumed by target 484 * @param dyConsumed Vertical scroll distance in pixels already consumed by target 485 * @param dxUnconsumed Horizontal scroll distance in pixels not consumed by target 486 * @param dyUnconsumed Vertical scroll distance in pixels not consumed by target 487 */ 488 public void onNestedScroll(View target, int dxConsumed, int dyConsumed, 489 int dxUnconsumed, int dyUnconsumed); 490 491 /** 492 * React to a nested scroll in progress before the target view consumes a portion of the scroll. 493 * 494 * <p>When working with nested scrolling often the parent view may want an opportunity 495 * to consume the scroll before the nested scrolling child does. An example of this is a 496 * drawer that contains a scrollable list. The user will want to be able to scroll the list 497 * fully into view before the list itself begins scrolling.</p> 498 * 499 * <p><code>onNestedPreScroll</code> is called when a nested scrolling child invokes 500 * {@link View#dispatchNestedPreScroll(int, int, int[], int[])}. The implementation should 501 * report how any pixels of the scroll reported by dx, dy were consumed in the 502 * <code>consumed</code> array. Index 0 corresponds to dx and index 1 corresponds to dy. 503 * This parameter will never be null. Initial values for consumed[0] and consumed[1] 504 * will always be 0.</p> 505 * 506 * @param target View that initiated the nested scroll 507 * @param dx Horizontal scroll distance in pixels 508 * @param dy Vertical scroll distance in pixels 509 * @param consumed Output. The horizontal and vertical scroll distance consumed by this parent 510 */ 511 public void onNestedPreScroll(View target, int dx, int dy, int[] consumed); 512 513 /** 514 * Request a fling from a nested scroll. 515 * 516 * <p>This method signifies that a nested scrolling child has detected suitable conditions 517 * for a fling. Generally this means that a touch scroll has ended with a 518 * {@link VelocityTracker velocity} in the direction of scrolling that meets or exceeds 519 * the {@link ViewConfiguration#getScaledMinimumFlingVelocity() minimum fling velocity} 520 * along a scrollable axis.</p> 521 * 522 * <p>If a nested scrolling child view would normally fling but it is at the edge of 523 * its own content, it can use this method to delegate the fling to its nested scrolling 524 * parent instead. The parent may optionally consume the fling or observe a child fling.</p> 525 * 526 * @param target View that initiated the nested scroll 527 * @param velocityX Horizontal velocity in pixels per second 528 * @param velocityY Vertical velocity in pixels per second 529 * @param consumed true if the child consumed the fling, false otherwise 530 * @return true if this parent consumed or otherwise reacted to the fling 531 */ 532 public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed); 533 534 /** 535 * React to a nested fling before the target view consumes it. 536 * 537 * <p>This method siginfies that a nested scrolling child has detected a fling with the given 538 * velocity along each axis. Generally this means that a touch scroll has ended with a 539 * {@link VelocityTracker velocity} in the direction of scrolling that meets or exceeds 540 * the {@link ViewConfiguration#getScaledMinimumFlingVelocity() minimum fling velocity} 541 * along a scrollable axis.</p> 542 * 543 * <p>If a nested scrolling parent is consuming motion as part of a 544 * {@link #onNestedPreScroll(View, int, int, int[]) pre-scroll}, it may be appropriate for 545 * it to also consume the pre-fling to complete that same motion. By returning 546 * <code>true</code> from this method, the parent indicates that the child should not 547 * fling its own internal content as well.</p> 548 * 549 * @param target View that initiated the nested scroll 550 * @param velocityX Horizontal velocity in pixels per second 551 * @param velocityY Vertical velocity in pixels per second 552 * @return true if this parent consumed the fling ahead of the target view 553 */ 554 public boolean onNestedPreFling(View target, float velocityX, float velocityY); 555 556 /** 557 * React to an accessibility action delegated by a target descendant view before the target 558 * processes it. 559 * 560 * <p>This method may be called by a target descendant view if the target wishes to give 561 * a view in its parent chain a chance to react to the event before normal processing occurs. 562 * Most commonly this will be a scroll event such as 563 * {@link android.view.accessibility.AccessibilityNodeInfo#ACTION_SCROLL_FORWARD}. 564 * A ViewParent that supports acting as a nested scrolling parent should override this 565 * method and act accordingly to implement scrolling via accesibility systems.</p> 566 * 567 * @param target The target view dispatching this action 568 * @param action Action being performed; see 569 * {@link android.view.accessibility.AccessibilityNodeInfo} 570 * @param arguments Optional action arguments 571 * @return true if the action was consumed by this ViewParent 572 */ 573 public boolean onNestedPrePerformAccessibilityAction(View target, int action, Bundle arguments); 574} 575