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 int maxChildHeight = 0; 54 int infoChildHeight = 0; 55 int infoTopPadding = 0; 56 View infoPage = null; 57 for (int i = 0; i < getChildCount(); i++) { 58 View view = getChildAt(i); 59 view.measure(widthMeasureSpec, 60 MeasureSpec.makeMeasureSpec(0 /* size */, MeasureSpec.UNSPECIFIED)); 61 int childHeight = view.getMeasuredHeight(); 62 // Get info page height and top padding. 63 if (view.getId() == R.id.page_info) { 64 infoPage = view; 65 infoChildHeight = childHeight; 66 infoTopPadding = view.getPaddingTop(); 67 } 68 if (childHeight > maxChildHeight) { 69 maxChildHeight = childHeight; 70 } 71 } 72 73 // Add extra padding in info page top area if info page has enough empty space to 74 // accommodate above and below extra height. 75 // 1. "infoChildHeight - infoTopPadding" means info page height without extra padding. 76 // 2. "mExtraSpacerHeight * 2" means above and below extra height. 77 if (maxChildHeight > (infoChildHeight - infoTopPadding + mExtraSpacerHeight * 2)) { 78 if (infoPage != null && infoTopPadding != mExtraSpacerHeight) { 79 infoPage.setPadding(infoPage.getPaddingLeft(), mExtraSpacerHeight, 80 infoPage.getPaddingRight(), infoPage.getPaddingBottom()); 81 } 82 } 83 84 if (maxChildHeight != 0) { 85 heightMeasureSpec = MeasureSpec.makeMeasureSpec(maxChildHeight, MeasureSpec.EXACTLY); 86 } 87 super.onMeasure(widthMeasureSpec, heightMeasureSpec); 88 } 89 } 90