1 /*
2  * Copyright (C) 2023 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.car.carlauncher.pagination;
18 
19 import android.view.View;
20 import android.view.ViewTreeObserver.OnGlobalLayoutListener;
21 
22 import com.android.car.carlauncher.pagination.PageMeasurementHelper.GridDimensions;
23 import com.android.car.carlauncher.pagination.PageMeasurementHelper.PageDimensions;
24 
25 import java.util.HashSet;
26 import java.util.Set;
27 
28 /**
29  * Controller class that handling all pagination related logic.
30  */
31 public class PaginationController {
32     private final PageMeasurementHelper mPageMeasurementHelper;
33     private final DimensionUpdateCallback mCallback;
34 
PaginationController(View windowBackground, DimensionUpdateCallback callback)35     public PaginationController(View windowBackground, DimensionUpdateCallback callback) {
36         mCallback = callback;
37         mPageMeasurementHelper = new PageMeasurementHelper(windowBackground);
38         windowBackground.getViewTreeObserver().addOnGlobalLayoutListener(
39                 new OnGlobalLayoutListener() {
40                     @Override
41                     public void onGlobalLayout() {
42                         int windowHeight = windowBackground.getMeasuredHeight();
43                         int windowWidth = windowBackground.getMeasuredWidth();
44                         maybeHandleWindowResize(windowWidth, windowHeight);
45                     }
46                 });
47     }
48 
maybeHandleWindowResize(int windowWidth, int windowHeight)49     private void maybeHandleWindowResize(int windowWidth, int windowHeight) {
50         boolean consumed = mPageMeasurementHelper.handleWindowSizeChange(windowWidth, windowHeight);
51         if (consumed) {
52             mCallback.notifyDimensionsUpdated(mPageMeasurementHelper.getPageDimensions(),
53                     mPageMeasurementHelper.getGridDimensions());
54         }
55     }
56 
57     /**
58      * Callback contract between this controller and its {@link DimensionUpdateListener} classes.
59      *
60      * When {@link PageMeasurementHelper#handleWindowSizeChange} returns {@code true}, the callback
61      * will notify its listeners that the window size has changed.
62      */
63     public static class DimensionUpdateCallback {
64         Set<DimensionUpdateListener> mListeners = new HashSet<>();
65 
66         /**
67          * Adds an {@link DimensionUpdateListener} to
68          */
addListener(DimensionUpdateListener listener)69         public void addListener(DimensionUpdateListener listener) {
70             mListeners.add(listener);
71         }
72 
73         /**
74          * Updates all listeners with the new measured dimensions.
75          */
notifyDimensionsUpdated(PageDimensions pageDimens, GridDimensions gridDimens)76         public void notifyDimensionsUpdated(PageDimensions pageDimens, GridDimensions gridDimens) {
77             for (DimensionUpdateListener listener : mListeners) {
78                 listener.onDimensionsUpdated(pageDimens, gridDimens);
79             }
80         }
81     }
82 
83     /**
84      * Listener interface for {@link DimensionUpdateCallback}.
85      *
86      * Classes that implement the listener should use the measured dimensions from
87      * {@link DimensionUpdateListener#onDimensionsUpdated} to update relevant layout params.
88      */
89     public interface DimensionUpdateListener {
90         /**
91          * Updates layout params from the updated dimensions measurements in {@link PageDimensions}
92          * and {@link GridDimensions}*/
onDimensionsUpdated(PageDimensions pageDimens, GridDimensions gridDimens)93         void onDimensionsUpdated(PageDimensions pageDimens, GridDimensions gridDimens);
94     }
95 }
96