blocks|key|2692672|text|将OnOffsetChangedListener挂接到您的AppBarLayout上。当verticalOffset达到0或小于Toolbar高度时，表示CollapsingToolbarLayout已折叠，否则将展开或展开。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2692673|mAppBarLayout.addOnOffsetChangedListener(new+AppBarLayout.OnOffsetChangedListener()+{
++++++++++++@Override
++++++++++++public+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+verticalOffset)+{
++++++++++++++++if(verticalOffset+==+0+%7C%7C+verticalOffset+<=+mToolbar.getHeight()+&&+!mToolbar.getTitle().equals(mCollapsedTitle)){
++++++++++++++++++++mCollapsingToolbar.setTitle(mCollapsedTitle);
++++++++++++++++}else+if(!mToolbar.getTitle().equals(mExpandedTitle)){
++++++++++++++++++++mCollapsingToolbar.setTitle(mExpandedTitle);
++++++++++++++++}

++++++++++++}
++++++++});|code-block|syntax|javascript|2692674|entityMap^0|1|N|T|C|18|E|1S|7|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|L|$]]

Hook a <code>OnOffsetChangedListener</code> to your <code>AppBarLayout</code>. When the <code>verticalOffset</code> reaches 0 or less than the <code>Toolbar</code> height, it means that CollapsingToolbarLayout has collapsed, otherwise it is expanding or expanded. 

<pre><code>mAppBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
 @Override
 public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
 if(verticalOffset == 0 || verticalOffset &lt;= mToolbar.getHeight() &amp;&amp; !mToolbar.getTitle().equals(mCollapsedTitle)){
 mCollapsingToolbar.setTitle(mCollapsedTitle);
 }else if(!mToolbar.getTitle().equals(mExpandedTitle)){
 mCollapsingToolbar.setTitle(mExpandedTitle);
 }

 }
 });
</code></pre>

blocks|key|128741|text|这个解决方案对我很有效：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|128742|@Override
public+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+i)+{
++if+(i+==+0)+{
++++if+(onStateChangeListener+!=+null+&&+state+!=+State.EXPANDED)+{
++++++onStateChangeListener.onStateChange(State.EXPANDED);
++++}
++++state+=+State.EXPANDED;
++}+else+if+(Math.abs(i)+>=+appBarLayout.getTotalScrollRange())+{
++++if+(onStateChangeListener+!=+null+&&+state+!=+State.COLLAPSED)+{
++++++onStateChangeListener.onStateChange(State.COLLAPSED);
++++}
++++state+=+State.COLLAPSED;
++}+else+{
++++if+(onStateChangeListener+!=+null+&&+state+!=+State.IDLE)+{
++++++onStateChangeListener.onStateChange(State.IDLE);
++++}
++++state+=+State.IDLE;
++}
}|code-block|syntax|javascript|128743|在AppBarLayout上使用addOnOffsetChangedListener。|128744|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

This solution is working for me: 

<pre><code>@Override
public void onOffsetChanged(AppBarLayout appBarLayout, int i) {
 if (i == 0) {
 if (onStateChangeListener != null &amp;&amp; state != State.EXPANDED) {
 onStateChangeListener.onStateChange(State.EXPANDED);
 }
 state = State.EXPANDED;
 } else if (Math.abs(i) &gt;= appBarLayout.getTotalScrollRange()) {
 if (onStateChangeListener != null &amp;&amp; state != State.COLLAPSED) {
 onStateChangeListener.onStateChange(State.COLLAPSED);
 }
 state = State.COLLAPSED;
 } else {
 if (onStateChangeListener != null &amp;&amp; state != State.IDLE) {
 onStateChangeListener.onStateChange(State.IDLE);
 }
 state = State.IDLE;
 }
}
</code></pre>

Use addOnOffsetChangedListener on the AppBarLayout.

blocks|key|2904676|text|private+enum+State+{
++++EXPANDED,
++++COLLAPSED,
++++IDLE
}

private+void+initViews()+{
++++final+String+TAG+=+"AppBarTest";
++++final+AppBarLayout+mAppBarLayout+=+findViewById(R.id.appbar);
++++mAppBarLayout.addOnOffsetChangedListener(new+AppBarLayout.OnOffsetChangedListener()+{
++++++++private+State+state;

++++++++@Override
++++++++public+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+verticalOffset)+{
++++++++++++if+(verticalOffset+==+0)+{
++++++++++++++++if+(state+!=+State.EXPANDED)+{
++++++++++++++++++++Log.d(TAG,"Expanded");
++++++++++++++++}
++++++++++++++++state+=+State.EXPANDED;
++++++++++++}+else+if+(Math.abs(verticalOffset)+>=+appBarLayout.getTotalScrollRange())+{
++++++++++++++++if+(state+!=+State.COLLAPSED)+{
++++++++++++++++++++Log.d(TAG,"Collapsed");
++++++++++++++++}
++++++++++++++++state+=+State.COLLAPSED;
++++++++++++}+else+{
++++++++++++++++if+(state+!=+State.IDLE)+{
++++++++++++++++++++Log.d(TAG,"Idle");
++++++++++++++++}
++++++++++++++++state+=+State.IDLE;
++++++++++++}
++++++++}
++++});
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2904677|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>private enum State {
 EXPANDED,
 COLLAPSED,
 IDLE
}

private void initViews() {
 final String TAG = "AppBarTest";
 final AppBarLayout mAppBarLayout = findViewById(R.id.appbar);
 mAppBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
 private State state;

 @Override
 public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
 if (verticalOffset == 0) {
 if (state != State.EXPANDED) {
 Log.d(TAG,"Expanded");
 }
 state = State.EXPANDED;
 } else if (Math.abs(verticalOffset) &gt;= appBarLayout.getTotalScrollRange()) {
 if (state != State.COLLAPSED) {
 Log.d(TAG,"Collapsed");
 }
 state = State.COLLAPSED;
 } else {
 if (state != State.IDLE) {
 Log.d(TAG,"Idle");
 }
 state = State.IDLE;
 }
 }
 });
}
</code></pre>

blocks|key|131471|text|我分享了基于@Frodio+Beggins和@Nifhel代码的完整实现：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|131472|public+abstract+class+AppBarStateChangeListener+implements+AppBarLayout.OnOffsetChangedListener+{

++++public+enum+State+{
++++++++EXPANDED,
++++++++COLLAPSED,
++++++++IDLE
++++}

++++private+State+mCurrentState+=+State.IDLE;

++++@Override
++++public+final+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+i)+{
++++++++if+(i+==+0)+{
++++++++++++if+(mCurrentState+!=+State.EXPANDED)+{
++++++++++++++++onStateChanged(appBarLayout,+State.EXPANDED);
++++++++++++}
++++++++++++mCurrentState+=+State.EXPANDED;
++++++++}+else+if+(Math.abs(i)+>=+appBarLayout.getTotalScrollRange())+{
++++++++++++if+(mCurrentState+!=+State.COLLAPSED)+{
++++++++++++++++onStateChanged(appBarLayout,+State.COLLAPSED);
++++++++++++}
++++++++++++mCurrentState+=+State.COLLAPSED;
++++++++}+else+{
++++++++++++if+(mCurrentState+!=+State.IDLE)+{
++++++++++++++++onStateChanged(appBarLayout,+State.IDLE);
++++++++++++}
++++++++++++mCurrentState+=+State.IDLE;
++++++++}
++++}

++++public+abstract+void+onStateChanged(AppBarLayout+appBarLayout,+State+state);
}|code-block|syntax|javascript|131473|然后你就可以使用它了：|131474|appBarLayout.addOnOffsetChangedListener(new+AppBarStateChangeListener()+{
++++@Override
++++public+void+onStateChanged(AppBarLayout+appBarLayout,+State+state)+{
++++++++Log.d("STATE",+state.name());
++++}
});|131475|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I share the full implementation, based on @Frodio Beggins and @Nifhel code:

<pre><code>public abstract class AppBarStateChangeListener implements AppBarLayout.OnOffsetChangedListener {

 public enum State {
 EXPANDED,
 COLLAPSED,
 IDLE
 }

 private State mCurrentState = State.IDLE;

 @Override
 public final void onOffsetChanged(AppBarLayout appBarLayout, int i) {
 if (i == 0) {
 if (mCurrentState != State.EXPANDED) {
 onStateChanged(appBarLayout, State.EXPANDED);
 }
 mCurrentState = State.EXPANDED;
 } else if (Math.abs(i) &gt;= appBarLayout.getTotalScrollRange()) {
 if (mCurrentState != State.COLLAPSED) {
 onStateChanged(appBarLayout, State.COLLAPSED);
 }
 mCurrentState = State.COLLAPSED;
 } else {
 if (mCurrentState != State.IDLE) {
 onStateChanged(appBarLayout, State.IDLE);
 }
 mCurrentState = State.IDLE;
 }
 }

 public abstract void onStateChanged(AppBarLayout appBarLayout, State state);
}
</code></pre>

And then you can use it:

<pre><code>appBarLayout.addOnOffsetChangedListener(new AppBarStateChangeListener() {
 @Override
 public void onStateChanged(AppBarLayout appBarLayout, State state) {
 Log.d("STATE", state.name());
 }
});
</code></pre>

blocks|key|2904693|text|这段代码对我很有效|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2904694|mAppBarLayout.addOnOffsetChangedListener(new+++AppBarLayout.OnOffsetChangedListener()+{
++++++++@Override
++++++++public+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+verticalOffset)+{
++++++++++++if+(verticalOffset+==+-mCollapsingToolbarLayout.getHeight()+%2B+mToolbar.getHeight())+{
++++++++++++++++//toolbar+is+collapsed+here
++++++++++++++++//write+your+code+here
++++++++++++}
++++++++}
++++});|code-block|syntax|javascript|2904695|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This code worked for me

<pre><code>mAppBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
 @Override
 public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
 if (verticalOffset == -mCollapsingToolbarLayout.getHeight() + mToolbar.getHeight()) {
 //toolbar is collapsed here
 //write your code here
 }
 }
 });
</code></pre>

blocks|key|2692758|text|这个解决方案非常适合我来检测AppBarLayout的折叠或展开。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|2692759|appBarLayout.addOnOffsetChangedListener(new+AppBarLayout.OnOffsetChangedListener()+{
++++++++@Override
++++++++public+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+verticalOffset)+{

++++++++++++if+(Math.abs(verticalOffset)-appBarLayout.getTotalScrollRange()+==+0)
++++++++++++{
++++++++++++++++//++Collapsed


++++++++++++}
++++++++++++else
++++++++++++{
++++++++++++++++//Expanded


++++++++++++}
++++++++}
++++});|code-block|syntax|javascript|2692760|已在AppBarLayout上使用addOnOffsetChangedListener。|2692761|entityMap^0|E|C|0|0|2|C|H|Q|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|X|8|@]|D|@]|E|$]]]|N|$]]

This solution works perfectly for me to detect <code>AppBarLayout</code> collapsed or expanded.

<pre><code>appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
 @Override
 public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {

 if (Math.abs(verticalOffset)-appBarLayout.getTotalScrollRange() == 0)
 {
 // Collapsed


 }
 else
 {
 //Expanded


 }
 }
 });
</code></pre>

Used <code>addOnOffsetChangedListener</code> on the <code>AppBarLayout</code>.

blocks|key|131999|text|如果您使用的是CollapsingToolBarLayout，您可以将以下内容|type|unstyled|depth|inlineStyleRanges|entityRanges|data|132000|collapsingToolbar.setExpandedTitleColor(ContextCompat.getColor(activity,+android.R.color.transparent));
collapsingToolbar.setTitle(title);|code-block|syntax|javascript|132001|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you are using CollapsingToolBarLayout you can put this

<pre><code>collapsingToolbar.setExpandedTitleColor(ContextCompat.getColor(activity, android.R.color.transparent));
collapsingToolbar.setTitle(title);
</code></pre>

blocks|key|131511|text|您可以通过以下方式获取collapsingToolBar+alpha百分比：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|131512|appbarLayout.addOnOffsetChangedListener(+new+AppBarLayout.OnOffsetChangedListener()+{
++++++++@Override
++++++++public+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+verticalOffset)+{
++++++++++++float+percentage+=+((float)Math.abs(verticalOffset)/appBarLayout.getTotalScrollRange());
++++++++++++fadedView.setAlpha(percentage);
++++});|code-block|syntax|javascript|131513|参考：link|offset|length|131514|entityMap|0|LINK|mutability|MUTABLE|url|https://androidcot.wordpress.com/2015/12/07/android-collapsingtoolbarlayout-animation-header-fade-inout/^0|0|0|3|4|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

You can get collapsingToolBar alpha percentage using below :

<pre><code>appbarLayout.addOnOffsetChangedListener( new AppBarLayout.OnOffsetChangedListener() {
 @Override
 public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
 float percentage = ((float)Math.abs(verticalOffset)/appBarLayout.getTotalScrollRange());
 fadedView.setAlpha(percentage);
 });
</code></pre>

For Reference : <a href="https://androidcot.wordpress.com/2015/12/07/android-collapsingtoolbarlayout-animation-header-fade-inout/" rel="noreferrer">link</a>

blocks|key|2692856|text|这段代码非常适合我。您可以根据自己的喜好使用百分比比例|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2692857|@Override
public+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+verticalOffset)+{
++++double+percentage+=+(double)+Math.abs(verticalOffset)+/+collapsingToolbar.getHeight();
++++if+(percentage+>+0.8)+{
++++++++collapsingToolbar.setTitle("Collapsed");
++++}+else+{
++++++++collapsingToolbar.setTitle("Expanded");
++++}
}|code-block|syntax|javascript|2692858|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This code is working perfect for me. You can use percentage scale How you like

<pre><code>@Override
public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
 double percentage = (double) Math.abs(verticalOffset) / collapsingToolbar.getHeight();
 if (percentage &gt; 0.8) {
 collapsingToolbar.setTitle("Collapsed");
 } else {
 collapsingToolbar.setTitle("Expanded");
 }
}
</code></pre>

blocks|key|2904941|text|我的工具栏偏移值在折叠时得到-582时，在expand=0上，所以我通过在Toast中设置offsetvalue来找到值，并相应地更改代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2904942|+mAppBarLayout.addOnOffsetChangedListener(new+AppBarLayout.OnOffsetChangedListener()+{
++++++++@Override
++++++++public+void+onOffsetChanged(AppBarLayout+appBarLayout,+int+verticalOffset)+{
++++++++++++if(verticalOffset+==+-582)+{
++++++++++++Toast.makeText(MainActivity.this,+"collaped"+%2B+verticalOffset,+Toast.LENGTH_SHORT).show();
++++++++++++mCollapsingToolbarLayout.setTitle("Collapsed");
++++++++++++}else+if(verticalOffset+==+0){
++++++++++++++++Toast.makeText(MainActivity.this,+"expanded"+%2B+verticalOffset,+Toast.LENGTH_SHORT).show();
++++++++++++mCollapsingToolbarLayout.setTitle("expanded");
++++++++++++}
++++++++}
++++});|code-block|syntax|javascript|2904943|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

My Toolbar offset value get -582 when collapse, on expand=0
So I find value by setting offsetvalue in Toast &amp; change code accordingly.

<pre><code> mAppBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
 @Override
 public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
 if(verticalOffset == -582) {
 Toast.makeText(MainActivity.this, "collaped" + verticalOffset, Toast.LENGTH_SHORT).show();
 mCollapsingToolbarLayout.setTitle("Collapsed");
 }else if(verticalOffset == 0){
 Toast.makeText(MainActivity.this, "expanded" + verticalOffset, Toast.LENGTH_SHORT).show();
 mCollapsingToolbarLayout.setTitle("expanded");
 }
 }
 });
</code></pre>

blocks|key|132131|text|这是一个Kotlin解决方案。向AppBarLayout添加OnOffsetChangedListener。|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|CODE|entityRanges|data|132132|方法A:|132133|将AppBarStateChangeListener.kt添加到项目中：|132134|import+com.google.android.material.appbar.AppBarLayout
import+kotlin.math.abs

abstract+class+AppBarStateChangeListener+:+AppBarLayout.OnOffsetChangedListener+{

++++enum+class+State+{
++++++++EXPANDED,+COLLAPSED,+IDLE
++++}

++++private+var+mCurrentState+=+State.IDLE

++++override+fun+onOffsetChanged(appBarLayout:+AppBarLayout,+i:+Int)+{
++++++++if+(i+==+0+&&+mCurrentState+!=+State.EXPANDED)+{
++++++++++++onStateChanged(appBarLayout,+State.EXPANDED)
++++++++++++mCurrentState+=+State.EXPANDED
++++++++}
++++++++else+if+(abs(i)+>=+appBarLayout.totalScrollRange+&&+mCurrentState+!=+State.COLLAPSED)+{
++++++++++++onStateChanged(appBarLayout,+State.COLLAPSED)
++++++++++++mCurrentState+=+State.COLLAPSED
++++++++}
++++++++else+if+(mCurrentState+!=+State.IDLE)+{
++++++++++++onStateChanged(appBarLayout,+State.IDLE)
++++++++++++mCurrentState+=+State.IDLE
++++++++}
++++}

++++abstract+fun+onStateChanged(
++++++++appBarLayout:+AppBarLayout?,
++++++++state:+State?
++++)

}|code-block|syntax|javascript|132135|将监听程序添加到appBarLayout|132136|appBarLayout.addOnOffsetChangedListener(object:+AppBarStateChangeListener()+{
++++++++override+fun+onStateChanged(appBarLayout:+AppBarLayout?,+state:+State?)+{
++++++++++++Log.d("State",+state.name)
++++++++++++when(state)+{
++++++++++++++++State.COLLAPSED+->+{+/*+Do+something+*/+}
++++++++++++++++State.EXPANDED+->+{+/*+Do+something+*/+}
++++++++++++++++State.IDLE+->+{+/*+Do+something+*/+}
++++++++++++}
++++++++}
++++}
)|132137|方法B:|132138|appBarLayout.addOnOffsetChangedListener(AppBarLayout.OnOffsetChangedListener+{+appBarLayout,+verticalOffset+->
++++++++if+(abs(verticalOffset)+-+appBarLayout.totalScrollRange+==+0)+{+
++++++++++++//+Collapsed
++++++++}+else+if+(verticalOffset+==+0)+{
++++++++++++//+Expanded
++++++++}+else+{
++++++++++++//+Idle
++++++++}
++++}
)|132139|entityMap^0|4|6|G|C|U|N|0|0|4|0|1|S|0|0|8|C|0|0|0|4|0|0^^$0|@$1|2|3|4|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|D]|$9|14|A|15|B|D]]|E|@]|F|$]]|$1|G|3|H|5|6|7|16|8|@$9|17|A|18|B|C]]|E|@]|F|$]]|$1|I|3|J|5|6|7|19|8|@$9|1A|A|1B|B|D]]|E|@]|F|$]]|$1|K|3|L|5|M|7|1C|8|@]|E|@]|F|$N|O]]|$1|P|3|Q|5|6|7|1D|8|@$9|1E|A|1F|B|D]]|E|@]|F|$]]|$1|R|3|S|5|M|7|1G|8|@]|E|@]|F|$N|O]]|$1|T|3|U|5|6|7|1H|8|@$9|1I|A|1J|B|C]]|E|@]|F|$]]|$1|V|3|W|5|M|7|1K|8|@]|E|@]|F|$N|O]]|$1|X|3|-4|5|6|7|1L|8|@]|E|@]|F|$]]]|Y|$]]

Here's a Kotlin solution. Add an <code>OnOffsetChangedListener</code> to the <code>AppBarLayout</code>.

Method A: 

Add <code>AppBarStateChangeListener.kt</code> to your project:

<pre><code>import com.google.android.material.appbar.AppBarLayout
import kotlin.math.abs

abstract class AppBarStateChangeListener : AppBarLayout.OnOffsetChangedListener {

 enum class State {
 EXPANDED, COLLAPSED, IDLE
 }

 private var mCurrentState = State.IDLE

 override fun onOffsetChanged(appBarLayout: AppBarLayout, i: Int) {
 if (i == 0 &amp;&amp; mCurrentState != State.EXPANDED) {
 onStateChanged(appBarLayout, State.EXPANDED)
 mCurrentState = State.EXPANDED
 }
 else if (abs(i) &gt;= appBarLayout.totalScrollRange &amp;&amp; mCurrentState != State.COLLAPSED) {
 onStateChanged(appBarLayout, State.COLLAPSED)
 mCurrentState = State.COLLAPSED
 }
 else if (mCurrentState != State.IDLE) {
 onStateChanged(appBarLayout, State.IDLE)
 mCurrentState = State.IDLE
 }
 }

 abstract fun onStateChanged(
 appBarLayout: AppBarLayout?,
 state: State?
 )

}
</code></pre>

Add the listener to your <code>appBarLayout</code>:

<pre><code>appBarLayout.addOnOffsetChangedListener(object: AppBarStateChangeListener() {
 override fun onStateChanged(appBarLayout: AppBarLayout?, state: State?) {
 Log.d("State", state.name)
 when(state) {
 State.COLLAPSED -&gt; { /* Do something */ }
 State.EXPANDED -&gt; { /* Do something */ }
 State.IDLE -&gt; { /* Do something */ }
 }
 }
 }
)
</code></pre>

Method B: 

<pre><code>appBarLayout.addOnOffsetChangedListener(AppBarLayout.OnOffsetChangedListener { appBarLayout, verticalOffset -&gt;
 if (abs(verticalOffset) - appBarLayout.totalScrollRange == 0) { 
 // Collapsed
 } else if (verticalOffset == 0) {
 // Expanded
 } else {
 // Idle
 }
 }
)
</code></pre>

blocks|key|2692966|text|以下是Kotlin中的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2692967|abstract+class+AppBarStateChangeListener+:+OnOffsetChangedListener+{
++++enum+class+State+{
++++++++EXPANDED,+COLLAPSED,+IDLE
++++}

++++private+var+mCurrentState+=
++++++++State.IDLE

++++override+fun+onOffsetChanged(appBarLayout:+AppBarLayout,+i:+Int)+{
++++++++mCurrentState+=+if+(i+==+0)+{
++++++++++++if+(mCurrentState+!=+State.EXPANDED)+{
++++++++++++++++onStateChanged(appBarLayout,+State.EXPANDED)
++++++++++++}
++++++++++++State.EXPANDED
++++++++}+else+if+(Math.abs(i)+>=+appBarLayout.totalScrollRange)+{
++++++++++++if+(mCurrentState+!=+State.COLLAPSED)+{
++++++++++++++++onStateChanged(appBarLayout,+State.COLLAPSED)
++++++++++++}
++++++++++++State.COLLAPSED
++++++++}+else+{
++++++++++++if+(mCurrentState+!=+State.IDLE)+{
++++++++++++++++onStateChanged(appBarLayout,+State.IDLE)
++++++++++++}
++++++++++++State.IDLE
++++++++}
++++}

++++abstract+fun+onStateChanged(
++++++++appBarLayout:+AppBarLayout?,
++++++++state:+State?
++++)
}|code-block|syntax|javascript|2692968|下面是监听程序：|2692969|++appbar.addOnOffsetChangedListener(object+:+AppBarStateChangeListener()+{
++++++++override+fun+onStateChanged(
++++++++++++appBarLayout:+AppBarLayout?,
++++++++++++state:+State?
++++++++)+{
++++++++++++if(state+==+State.COLLAPSED){
++++++++++++++++LayoutBottom.visibility+=+View.GONE
++++++++++++}else+if(state+==+State.EXPANDED){
++++++++++++++++LayoutBottom.visibility+=+View.VISIBLE
++++++++++++}
++++++++}
++++})|2692970|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Here is the solution in Kotlin:
<pre><code>abstract class AppBarStateChangeListener : OnOffsetChangedListener {
 enum class State {
 EXPANDED, COLLAPSED, IDLE
 }

 private var mCurrentState =
 State.IDLE

 override fun onOffsetChanged(appBarLayout: AppBarLayout, i: Int) {
 mCurrentState = if (i == 0) {
 if (mCurrentState != State.EXPANDED) {
 onStateChanged(appBarLayout, State.EXPANDED)
 }
 State.EXPANDED
 } else if (Math.abs(i) &gt;= appBarLayout.totalScrollRange) {
 if (mCurrentState != State.COLLAPSED) {
 onStateChanged(appBarLayout, State.COLLAPSED)
 }
 State.COLLAPSED
 } else {
 if (mCurrentState != State.IDLE) {
 onStateChanged(appBarLayout, State.IDLE)
 }
 State.IDLE
 }
 }

 abstract fun onStateChanged(
 appBarLayout: AppBarLayout?,
 state: State?
 )
}
</code></pre>
Here is the listener:
<pre><code> appbar.addOnOffsetChangedListener(object : AppBarStateChangeListener() {
 override fun onStateChanged(
 appBarLayout: AppBarLayout?,
 state: State?
 ) {
 if(state == State.COLLAPSED){
 LayoutBottom.visibility = View.GONE
 }else if(state == State.EXPANDED){
 LayoutBottom.visibility = View.VISIBLE
 }
 }
 })
</code></pre>

I am using <code>CollapsingToolBarLayout</code> alongside with <code>AppBarLayout</code> and <code>CoordinatorLayout</code>, and they are working Fine altogether. I set my <code>Toolbar</code> to be fixed when I scroll up, I want to know if there is a way to change the title text of the Toolbar, when <code>CollapsingToolBarLayout</code> it is collapsed. 

Wrapping up, I want two different titles when scrolled and when expanded.

Thank you all in advance

Android CollapsingToolbarLayout collapse Listener

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我将CollapsingToolBarLayout与AppBarLayout和CoordinatorLayout一起使用，它们都工作得很好。我设置我的Toolbar是固定的当我向上滚动，我想知道是否有一种方法来改变标题文本的工具栏，当CollapsingToolBarLayout它是折叠的。总结一下，我想要两个不同的标...

问安卓CollapsingToolbarLayout折叠监听器
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