| /* |
| * Copyright (C) 2010 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 android.view; |
| |
| /** |
| * A display lists records a series of graphics related operation and can replay |
| * them later. Display lists are usually built by recording operations on a |
| * {@link android.graphics.Canvas}. Replaying the operations from a display list |
| * avoids executing views drawing code on every frame, and is thus much more |
| * efficient. |
| * |
| * @hide |
| */ |
| public abstract class DisplayList { |
| /** |
| * Starts recording the display list. All operations performed on the |
| * returned canvas are recorded and stored in this display list. |
| * |
| * @return A canvas to record drawing operations. |
| */ |
| abstract HardwareCanvas start(); |
| |
| /** |
| * Ends the recording for this display list. A display list cannot be |
| * replayed if recording is not finished. |
| */ |
| abstract void end(); |
| |
| /** |
| * Indicates whether this display list can be replayed or not. |
| * |
| * @return True if the display list can be replayed, false otherwise. |
| * |
| * @see android.view.HardwareCanvas#drawDisplayList(DisplayList) |
| */ |
| abstract boolean isReady(); |
| |
| /** |
| * Invalidates the display list, indicating that it should be repopulated |
| * with new drawing commands prior to being used again. Calling this method |
| * causes calls to {@link #isValid()} to return <code>false</code>. |
| */ |
| abstract void invalidate(); |
| |
| /** |
| * Returns whether the display list is currently usable. If this returns false, |
| * the display list should be re-recorded prior to replaying it. |
| * |
| * @return boolean true if the display list is able to be replayed, false otherwise. |
| */ |
| abstract boolean isValid(); |
| } |