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/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.setupwizardlib.view;
import android.content.Context;
import androidx.annotation.VisibleForTesting;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ScrollView;
/**
* An extension of ScrollView that will invoke a listener callback when the ScrollView needs
* scrolling, and when the ScrollView is being scrolled to the bottom. This is often used in Setup
* Wizard as a way to ensure that users see all the content before proceeding.
*/
public class BottomScrollView extends ScrollView {
public interface BottomScrollListener {
void onScrolledToBottom();
void onRequiresScroll();
}
private BottomScrollListener listener;
private int scrollThreshold;
private boolean requiringScroll = false;
private final Runnable checkScrollRunnable =
new Runnable() {
@Override
public void run() {
checkScroll();
}
};
public BottomScrollView(Context context) {
super(context);
}
public BottomScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public BottomScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public void setBottomScrollListener(BottomScrollListener l) {
listener = l;
}
@VisibleForTesting
public BottomScrollListener getBottomScrollListener() {
return listener;
}
@VisibleForTesting
public int getScrollThreshold() {
return scrollThreshold;
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
final View child = getChildAt(0);
if (child != null) {
scrollThreshold = Math.max(0, child.getMeasuredHeight() - b + t - getPaddingBottom());
}
if (b - t > 0) {
// Post check scroll in the next run loop, so that the callback methods will be invoked
// after the layout pass. This way a new layout pass will be scheduled if view
// properties are changed in the callbacks.
post(checkScrollRunnable);
}
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
if (oldt != t) {
checkScroll();
}
}
private void checkScroll() {
if (listener != null) {
if (getScrollY() >= scrollThreshold) {
listener.onScrolledToBottom();
} else if (!requiringScroll) {
requiringScroll = true;
listener.onRequiresScroll();
}
}
}
}
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