Android CollapsingToolbarLayout collapse Listener

Question

I am using CollapsingToolBarLayout alongside with AppBarLayout and CoordinatorLayout, and they are working Fine altogether. I set my <

Answer 1

This solution works perfectly for me to detect AppBarLayout collapsed or expanded.

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

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


            }
            else
            {
                //Expanded


            }
        }
    });

Used addOnOffsetChangedListener on the AppBarLayout.

Answer 2

This solution is working for me:

@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;
  }
}

Use addOnOffsetChangedListener on the AppBarLayout.

Answer 3

Here's a Kotlin solution. Add an OnOffsetChangedListener to the AppBarLayout.

Method A:

Add AppBarStateChangeListener.kt to your project:

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?
    )

}

Add the listener to your appBarLayout:

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 */ }
            }
        }
    }
)

Method B:

appBarLayout.addOnOffsetChangedListener(AppBarLayout.OnOffsetChangedListener { appBarLayout, verticalOffset ->
        if (abs(verticalOffset) - appBarLayout.totalScrollRange == 0) { 
            // Collapsed
        } else if (verticalOffset == 0) {
            // Expanded
        } else {
            // Idle
        }
    }
)

Answer 4

I share the full implementation, based on @Frodio Beggins and @Nifhel 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) >= 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);
}

And then you can use it:

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

Answer 5

Here is the solution in Kotlin:

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?
    )
}

Here is the listener:

  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
            }
        }
    })

Answer 6

This code worked for me

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
            }
        }
    });