1 /*
2  * Copyright (C) 2019 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.wallpaper.livepicker.widget;
18 
19 import android.content.Context;
20 import android.util.AttributeSet;
21 import android.view.View;
22 
23 import androidx.annotation.NonNull;
24 import androidx.annotation.Nullable;
25 import androidx.viewpager.widget.ViewPager;
26 
27 import com.android.wallpaper.livepicker.R;
28 
29 /**
30  * When ConstraintViewPager is being measured, it will get all height of pages and makes itself
31  * height as the same as the maximum height.
32  */
33 public class ConstraintViewPager extends ViewPager {
34 
35     private final int mExtraSpacerHeight;
36 
ConstraintViewPager(@onNull Context context)37     public ConstraintViewPager(@NonNull Context context) {
38         this(context, null /* attrs */);
39     }
40 
ConstraintViewPager(@onNull Context context, @Nullable AttributeSet attrs)41     public ConstraintViewPager(@NonNull Context context, @Nullable AttributeSet attrs) {
42         super(context, attrs);
43         mExtraSpacerHeight = context.getResources().getDimensionPixelSize(
44                 R.dimen.preview_attribution_pane_extra_spacer_height);
45     }
46 
47     /**
48      * Visit all child views first and then determine the maximum height for ViewPager.
49      * Info page will add extra height in top area determined by empty space.
50      */
51     @Override
onMeasure(int widthMeasureSpec, int heightMeasureSpec)52     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
53         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
54 
55         int maxChildHeight = 0;
56         int infoChildHeight = 0;
57         int infoTopPadding = 0;
58         View infoPage = null;
59         for (int i = 0; i < getChildCount(); i++) {
60             View view = getChildAt(i);
61             view.measure(widthMeasureSpec,
62                     MeasureSpec.makeMeasureSpec(0 /* size */, MeasureSpec.UNSPECIFIED));
63             int childHeight = view.getMeasuredHeight();
64             // Get info page height and top padding.
65             if (view.getId() == R.id.page_info) {
66                 infoPage = view;
67                 infoChildHeight = childHeight;
68                 infoTopPadding = view.getPaddingTop();
69             }
70             if (childHeight > maxChildHeight) {
71                 maxChildHeight = childHeight;
72             }
73         }
74 
75         // Add extra padding in info page top area if info page has enough empty space to
76         // accommodate above and below extra height.
77         // 1. "infoChildHeight - infoTopPadding" means info page height without extra padding.
78         // 2. "mExtraSpacerHeight * 2" means above and below extra height.
79         if (maxChildHeight > (infoChildHeight - infoTopPadding + mExtraSpacerHeight * 2)) {
80             if (infoPage != null && infoTopPadding != mExtraSpacerHeight) {
81                 infoPage.setPadding(infoPage.getPaddingLeft(), mExtraSpacerHeight,
82                         infoPage.getPaddingRight(), infoPage.getPaddingBottom());
83             }
84         }
85 
86         setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec), maxChildHeight);
87     }
88 }
89