1 /* 2 * Copyright (C) 2014 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 com.android.camera.async; 18 19 import com.android.camera.util.Callback; 20 21 /** 22 * Wraps {@link ConcurrentState} with {@link #setCallback} semantics which 23 * overwrite any existing callback. 24 */ 25 public class Listenable<T> implements SafeCloseable { 26 private final ConcurrentState<T> mState; 27 private final MainThread mMainThread; 28 private final Object mLock; 29 private boolean mClosed; 30 private SafeCloseable mExistingCallbackHandle; 31 32 public Listenable(ConcurrentState<T> state, MainThread mainThread) { 33 mState = state; 34 mMainThread = mainThread; 35 mLock = new Object(); 36 mClosed = false; 37 mExistingCallbackHandle = null; 38 } 39 40 /** 41 * Sets the callback, removing any existing callback first. 42 */ 43 public void setCallback(final Callback<T> callback) { 44 synchronized (mLock) { 45 if (mClosed) { 46 return; 47 } 48 if (mExistingCallbackHandle != null) { 49 // Unregister any existing callback 50 mExistingCallbackHandle.close(); 51 } 52 mExistingCallbackHandle = mState.addCallback(new Runnable() { 53 @Override 54 public void run() { 55 callback.onCallback(mState.get()); 56 } 57 }, mMainThread); 58 } 59 } 60 61 /** 62 * Removes any existing callbacks. 63 */ 64 public void clear() { 65 synchronized (mLock) { 66 mClosed = true; 67 if (mExistingCallbackHandle != null) { 68 // Unregister any existing callback 69 mExistingCallbackHandle.close(); 70 } 71 } 72 } 73 74 /** 75 * Removes any existing callbacks. Once closed, no more callbacks will be registered. 76 */ 77 @Override 78 public void close() { 79 synchronized (mLock) { 80 mClosed = true; 81 clear(); 82 } 83 } 84 } 85
