1 /* 2 * Copyright (C) 2022 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.window; 18 19 import android.annotation.NonNull; 20 import android.app.Activity; 21 import android.app.Dialog; 22 import android.view.View; 23 24 /** 25 * Interface for applications to register back animation callbacks along their custom back 26 * handling. 27 * <p> 28 * This allows the client to customize various back behaviors by overriding the corresponding 29 * callback methods. 30 * <p> 31 * Callback instances can be added to and removed from {@link OnBackInvokedDispatcher}, held 32 * by classes that implement {@link OnBackInvokedDispatcherOwner} (such as {@link Activity}, 33 * {@link Dialog} and {@link View}). 34 * <p> 35 * When back is triggered, callbacks on the in-focus window are invoked in reverse order in which 36 * they are added within the same priority. Between different priorities, callbacks with higher 37 * priority are invoked first. 38 * <p> 39 * @see OnBackInvokedCallback 40 * @hide 41 */ 42 public interface OnBackAnimationCallback extends OnBackInvokedCallback { 43 /** 44 * Called when a back gesture has been started, or back button has been pressed down. 45 * 46 * @param backEvent An {@link BackEvent} object describing the progress event. 47 */ onBackStarted(@onNull BackEvent backEvent)48 default void onBackStarted(@NonNull BackEvent backEvent) {} 49 50 /** 51 * Called on back gesture progress. 52 * 53 * @param backEvent An {@link BackEvent} object describing the progress event. 54 * 55 * @see BackEvent 56 */ onBackProgressed(@onNull BackEvent backEvent)57 default void onBackProgressed(@NonNull BackEvent backEvent) { } 58 59 /** 60 * Called when a back gesture or back button press has been cancelled. 61 */ onBackCancelled()62 default void onBackCancelled() { } 63 } 64