1 /* 2 * Copyright (C) 2016 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.documentsui; 18 19 import static com.android.documentsui.base.Shared.VERBOSE; 20 21 import android.annotation.MainThread; 22 import android.annotation.Nullable; 23 import android.util.Log; 24 25 import com.android.documentsui.base.Shared; 26 import com.android.documentsui.selection.BandController; 27 28 /** 29 * A lock used by {@link DirectoryLoader} and {@link BandController} to ensure refresh is blocked 30 * while Band Selection is active. 31 */ 32 public final class DirectoryReloadLock { 33 private static final String TAG = "DirectoryReloadLock"; 34 35 private int mPauseCount = 0; 36 private @Nullable Runnable mCallback; 37 38 /** 39 * Increment the block count by 1 40 */ 41 @MainThread block()42 public void block() { 43 Shared.checkMainLoop(); 44 mPauseCount++; 45 if (VERBOSE) Log.v(TAG, "Block count increments to " + mPauseCount + "."); 46 } 47 48 /** 49 * Decrement the block count by 1; If no other object is trying to block and there exists some 50 * callback, that callback will be run 51 */ 52 @MainThread unblock()53 public void unblock() { 54 Shared.checkMainLoop(); 55 assert(mPauseCount > 0); 56 mPauseCount--; 57 if (VERBOSE) Log.v(TAG, "Block count decrements to " + mPauseCount + "."); 58 if (mPauseCount == 0 && mCallback != null) { 59 mCallback.run(); 60 mCallback = null; 61 } 62 } 63 64 /** 65 * Attempts to run the given Runnable if not-blocked, or else the Runnable is set to be ran next 66 * (replacing any previous set Runnables). 67 */ tryUpdate(Runnable update)68 public void tryUpdate(Runnable update) { 69 if (mPauseCount == 0) { 70 update.run(); 71 } else { 72 mCallback = update; 73 } 74 } 75 } 76