Title of Collapsing toolbar is not changing when setting dynamically?

Question

I have used viewpager for showing the data of per month. and I want to change the title of collapsing toolbar accroding to change in viewpager's page. Collapsing toolbar title only changes when scrolling up the toolbar.

my layout

<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical">

            <android.support.v4.view.ViewPager
                android:id="@+id/view_pager"
                android:layout_width="match_parent"
                android:layout_height="@dimen/activity_history_view_pager_height" />
        </LinearLayout>
    </android.support.v4.widget.NestedScrollView>

    <android.support.design.widget.AppBarLayout
        android:id="@+id/my_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="@dimen/activity_history_collapsing_toolbar_height"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar_flexible_space"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:background="?attr/colorPrimary"
                android:fitsSystemWindows="true"
                android:minHeight="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
                app:theme="@style/ThemeOverlay.AppCompat.Light" />
        </android.support.design.widget.CollapsingToolbarLayout>

        <TextView
            android:id="@+id/txt_year"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="@dimen/activity_history_margin_left"
            android:layout_marginStart="@dimen/activity_history_margin_left"
            android:text="@string/activity_history_year"
            android:textColor="@color/white"
            android:textSize="@dimen/activity_history_text_size" />

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_marginBottom="@dimen/activity_history_margin_bottom"
            android:orientation="vertical"
            app:layout_scrollFlags="scroll">

            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_alignParentEnd="true"
                android:layout_alignParentRight="true"
                android:layout_marginEnd="@dimen/activity_history_margin_right"
                android:layout_marginRight="@dimen/activity_history_margin_right"
                android:orientation="horizontal">

                <ImageView
                    android:id="@+id/img_leftBackArrow"
                    android:layout_width="@dimen/activity_history_arrow_size"
                    android:layout_height="@dimen/activity_history_arrow_size"
                    android:contentDescription="@string/content_description"
                    android:src="@drawable/previous_arrow" />

                <ImageView
                    android:id="@+id/img_rightBackArrow"
                    android:layout_width="@dimen/activity_history_arrow_size"
                    android:layout_height="@dimen/activity_history_arrow_size"
                    android:layout_marginLeft="@dimen/activity_history_arrow_size"
                    android:layout_marginStart="@dimen/activity_history_arrow_size"
                    android:contentDescription="@string/content_description"
                    android:src="@drawable/next_arrow" />

            </LinearLayout>


        </RelativeLayout>

    </android.support.design.widget.AppBarLayout>

</android.support.design.widget.CoordinatorLayout>

In Activity

    /**
     * Lists History of the Tasks and it's status on the basis of Date
     */
    public class HistoryActivity extends BaseActivity implements ViewPager.OnPageChangeListener {

        @InjectView(R.id.toolbar_flexible_space)
        Toolbar toolbar;

        @InjectView(R.id.collapsing_toolbar)
        CollapsingToolbarLayout mCollapsingToolbar;

        @InjectView(R.id.view_pager)
        ViewPager viewPager;

        @InjectView(R.id.txt_year)
        TextView txtYear;
        int viewPagerSize = 0;

        ArrayList<String> taskAddedMonths;

        @OnClick({R.id.img_leftBackArrow, R.id.img_rightBackArrow})
        public void onClick(View v) {
            switch (v.getId()) {
                case R.id.img_rightBackArrow:
                    moveForward();
                    break;
                case R.id.img_leftBackArrow:
                    moveBackWard();
                    break;

            }

        }

        /**
         * move view pager page as accroding to clicking on backword arrow.
         */
        private void moveBackWard() {
            int currentPosition = viewPager.getCurrentItem();
            if (currentPosition > 0) {
                int nextPosition = currentPosition - 1;
                viewPager.setCurrentItem(nextPosition);
                mCollapsingToolbar.setTitle(getCollapsingToolbarTitle(taskAddedMonths.get(nextPosition)));
            }
        }

        /**
         * move view pager page as according to clicking on forward arrow.
         */
        private void moveForward() {
            int currentPosition = viewPager.getCurrentItem();

            if (currentPosition < viewPagerSize-1) {
                int nextPosition = currentPosition + 1;
                if (viewPagerSize == 1) {
                    //do nothing
                } else {
                    viewPager.setCurrentItem(currentPosition + 1);
                    mCollapsingToolbar.setTitle(getCollapsingToolbarTitle(taskAddedMonths.get(nextPosition)));
                }
            }
        }


        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            taskAddedMonths = DatabaseManager.getInstance(HistoryActivity.this).getAllMonths();
            viewPagerSize = taskAddedMonths.size();

            mCollapsingToolbar.setTitle(getCollapsingToolbarTitle(taskAddedMonths.get(0)));
            mCollapsingToolbar.setExpandedTitleColor(Color.WHITE);
            toolbar.setNavigationIcon(ContextCompat.getDrawable(this, R.drawable.ic_backarrow));

            viewPager.setAdapter(new ViewPagerAdapter(HistoryActivity.this, DatabaseManager.getInstance(HistoryActivity.this).getAllMonths()));
            viewPager.addOnPageChangeListener(this);

        }

        @Override
        public int getLayoutId() {
            return R.layout.activity_history;
        }

        @Override
        public Toolbar getToolbar() {
            return toolbar;
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.menu_history, menu);
            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            int id = item.getItemId();
            //noinspection SimplifiableIfStatement
            if (id == android.R.id.home) {
                onBackPressed();
            }
            return super.onOptionsItemSelected(item);
        }

        /**
         * get the name of month with concatenating History as like this{May History};
         *
         * @param month
         * @return
         */
        private String getCollapsingToolbarTitle(String month) {
            return month + " " + "History";
        }

        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {
/******************* what i have done*******************/
            //change the title of collapsing toolbar accroding to change in page of viewpager
            mCollapsingToolbar.setTitle(getCollapsingToolbarTitle(taskAddedMonths.get(position)));
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    }

Answer 1

This was a known bug that should be fixed in the v22.2.1 release of the design library.