android - Animate LayoutChanges does not work properly

Question

I want to animate text in my textswitcher. I went through all the stack questions and the documentation, but they didn't solve my problem.

Here is my XML:

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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">


    <TextView
        android:id="@+id/tv__inc_pre_sing__screen_title"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:background="#fff"
        android:gravity="center"
        android:text="PRACTICE"
        android:textAllCaps="true"
        android:textColor="@color/colorAccent"
        android:textSize="16dp"
        android:textStyle="bold"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <android.support.constraint.ConstraintLayout
        android:id="@+id/rl__inc_pre_sing__tm_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:animateLayoutChanges="true"
        android:background="#efff"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/tv__inc_pre_sing__screen_title">

        <ImageView
            android:id="@+id/tv__inc_pre_sing__quotation_mark"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="12dp"
            android:src="@drawable/ic_archive_black_24dp"
            app:layout_constraintTop_toTopOf="parent" />

        <TextSwitcher
            android:id="@+id/tv__inc_pre_sing__teacher_message"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginEnd="8dp"
            android:layout_marginStart="24dp"
            android:layout_marginTop="16dp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@id/tv__inc_pre_sing__quotation_mark"
            app:layout_constraintTop_toTopOf="parent" />

        <ImageView
            android:id="@+id/iv"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="8dp"
            android:layout_marginTop="8dp"
            android:src="@drawable/ic_archive_black_24dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@id/tv__inc_pre_sing__teacher_message" />

    </android.support.constraint.ConstraintLayout>

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="8dp"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:text="Click Me"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <View
        android:layout_width="0dp"
        android:layout_height="16dp"
        android:background="@drawable/ic_launcher_background"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/rl__inc_pre_sing__tm_container" />


</android.support.constraint.ConstraintLayout>

Here is my code

public class Main3Activity extends AppCompatActivity {

    private TextSwitcher mSwitcher;
    Button btnNext;
    int currentIndex=-1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);

        Resources resources = getApplicationContext().getResources();
        final String[] textString = resources.getStringArray(R.array.teacher_messages);

        btnNext = findViewById(R.id.button);
        mSwitcher = findViewById(R.id.tv__inc_pre_sing__teacher_message);


        mSwitcher.setFactory(new ViewSwitcher.ViewFactory() {

            public View makeView() {
                // TODO Auto-generated method stub
                // create new textView and set the properties like clolr, size etc
                TextView myText = new TextView(Main3Activity.this);
                myText.setGravity(Gravity.TOP | Gravity.CENTER_HORIZONTAL);
                myText.setTextColor(Color.BLUE);
                return myText;
            }
        });


        // Declare the in and out animations and initialize them
        Animation in = AnimationUtils.loadAnimation(this,android.R.anim.slide_in_left);
        Animation out = AnimationUtils.loadAnimation(this,android.R.anim.slide_out_right);

        // set the animation type of textSwitcher
        mSwitcher.setInAnimation(in);
        mSwitcher.setOutAnimation(out);

        // ClickListener for NEXT button
        // When clicked on Button TextSwitcher will switch between texts
        // The current Text will go OUT and next text will come in with specified animation
        btnNext.setOnClickListener(new View.OnClickListener() {
            //
            public void onClick(View v) {
                // TODO Auto-generated method stub
                currentIndex++;
                // If index reaches maximum reset it
                if(currentIndex==textString.length)
                    currentIndex=0;
                mSwitcher.setText(textString[currentIndex]);

                ((ViewGroup) findViewById(R.id.rl__inc_pre_sing__tm_container)).getLayoutTransition()
                        .enableTransitionType(LayoutTransition.CHANGING);

            }
        });

    }
}

The animation on ConstraintLayout whose id is rl__inc_pre_sing__tm_container does not work properly. Suppose my TextSwitcher has text whose length is greater than 3 and then TextSwitcher shows text whose length is 1 then the ConstraintLayout does not animate, if the next text is of length 1 then the constraintlayout animates.

I am not able to figure out this weird behaviour.

Answer 1

Here is the issue: When the TextSwitcher transitions from X lines of text to something less than X lines then the TextSwitcher's height does not change.

The TextSwitcher inherits some behavior from ViewAnimator which considers the height of all views when determining the height of the widget. The solution is to add the following XML to the TextSwitcher definition in the layout file that will inhibit this behavior:

    android:measureAllChildren="false"

Thanks to this Stack Overflow answer that states all this better than I have.