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A modified version of ControllableAppBarLayout that allows to add/remove multiple listeners for layout state change (collapsed, expanded or idle). The original ControllableAppBarLayout is here https://gist.github.com/blipinsk/3f8fb37209de6d3eea99
/**
* Copyright 2015 Bartosz Lipinski
* <p/>
* 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
* <p/>
* http://www.apache.org/licenses/LICENSE-2.0
* <p/>
* 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.
*/
import android.content.Context;
import android.graphics.Canvas;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CoordinatorLayout;
import android.util.AttributeSet;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
public class ControllableAppBarLayout extends AppBarLayout implements AppBarLayout.OnOffsetChangedListener {
private Behavior mBehavior;
private WeakReference<CoordinatorLayout> mParent;
private ToolbarChange mQueuedChange = ToolbarChange.NONE;
private boolean mAfterFirstDraw = false;
private State state;
private List<WeakReference<OnStateChangeListener>> mListeners;
public ControllableAppBarLayout(Context context) {
super(context);
}
public ControllableAppBarLayout(Context context, AttributeSet attrs) {
super(context, attrs);
this.mListeners = new ArrayList<>();
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
if (!(getLayoutParams() instanceof CoordinatorLayout.LayoutParams) || !(getParent() instanceof CoordinatorLayout)) {
throw new IllegalStateException("ControllableAppBarLayout must be a direct child of CoordinatorLayout.");
} else {
mParent = new WeakReference<>((CoordinatorLayout) getParent());
}
addOnOffsetChangedListener(this);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
if (mBehavior == null) {
mBehavior = (Behavior) ((CoordinatorLayout.LayoutParams) getLayoutParams()).getBehavior();
}
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
super.onLayout(changed, l, t, r, b);
if (r - l > 0 && b - t > 0 && mAfterFirstDraw && mQueuedChange != ToolbarChange.NONE) {
analyzeQueuedChange();
}
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (!mAfterFirstDraw) {
mAfterFirstDraw = true;
if (mQueuedChange != ToolbarChange.NONE) {
analyzeQueuedChange();
}
}
}
private synchronized void analyzeQueuedChange() {
switch (mQueuedChange) {
case COLLAPSE:
performCollapsingWithoutAnimation();
break;
case COLLAPSE_WITH_ANIMATION:
performCollapsingWithAnimation();
break;
case EXPAND:
performExpandingWithoutAnimation();
break;
case EXPAND_WITH_ANIMATION:
performExpandingWithAnimation();
break;
}
mQueuedChange = ToolbarChange.NONE;
}
public void collapseToolbar() {
collapseToolbar(false);
}
public void collapseToolbar(boolean withAnimation) {
mQueuedChange = withAnimation ? ToolbarChange.COLLAPSE_WITH_ANIMATION : ToolbarChange.COLLAPSE;
requestLayout();
}
public void expandToolbar() {
expandToolbar(false);
}
public void expandToolbar(boolean withAnimation) {
mQueuedChange = withAnimation ? ToolbarChange.EXPAND_WITH_ANIMATION : ToolbarChange.EXPAND;
requestLayout();
}
private void performCollapsingWithoutAnimation() {
if (mParent.get() != null) {
mBehavior.onNestedPreScroll(mParent.get(), this, null, 0, getHeight(), new int[]{0, 0});
}
}
private void performCollapsingWithAnimation() {
if (mParent.get() != null) {
mBehavior.onNestedFling(mParent.get(), this, null, 0, getHeight(), true);
}
}
private void performExpandingWithoutAnimation() {
if (mParent.get() != null) {
mBehavior.setTopAndBottomOffset(0);
}
}
private void performExpandingWithAnimation() {
if (mParent.get() != null) {
mBehavior.onNestedFling(mParent.get(), this, null, 0, -getHeight() * 5, false);
}
}
private void dispatchStateChange(ControllableAppBarLayout layout) {
List listeners = layout.mListeners;
int i = 0;
for (int z = listeners.size(); i < z; ++i) {
WeakReference ref = (WeakReference) listeners.get(i);
OnStateChangeListener listener = ref != null ? (OnStateChangeListener) ref.get() : null;
if (listener != null) {
listener.onAppBarStateChange(layout, state);
}
}
}
@Override
public void onOffsetChanged(AppBarLayout appBarLayout, int i) {
if (i == 0) {
if (state != State.EXPANDED) {
state = State.EXPANDED;
dispatchStateChange(this);
}
} else if (Math.abs(i) >= appBarLayout.getTotalScrollRange()) {
if (state != State.COLLAPSED) {
state = State.COLLAPSED;
dispatchStateChange(this);
}
} else {
if (state != State.IDLE) {
state = State.IDLE;
dispatchStateChange(this);
}
}
}
public void addOnStateChangeListener(OnStateChangeListener listener) {
int i = 0;
for (int z = this.mListeners.size(); i < z; ++i) {
WeakReference ref = (WeakReference) this.mListeners.get(i);
if (ref != null && ref.get() == listener) {
return;
}
}
this.mListeners.add(new WeakReference<>(listener));
}
public void removeOnStateChangeListener(OnStateChangeListener listener) {
Iterator i = this.mListeners.iterator();
while (true) {
OnStateChangeListener item;
do {
if (!i.hasNext()) {
return;
}
WeakReference ref = (WeakReference) i.next();
item = (OnStateChangeListener) ref.get();
} while (item != listener && item != null);
i.remove();
}
}
public State getState() {
return state;
}
private enum ToolbarChange {
COLLAPSE,
COLLAPSE_WITH_ANIMATION,
EXPAND,
EXPAND_WITH_ANIMATION,
NONE
}
public interface OnStateChangeListener {
void onAppBarStateChange(ControllableAppBarLayout layout, State state);
}
public enum State {
COLLAPSED,
EXPANDED,
IDLE
}
}
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