Cómo ampliar una vista con una animación de zoom

En esta guía, se muestra cómo implementar una animación de presionar para acercar. La función de presionar para acercar permite que las apps, como las galerías de fotos, animen una vista desde una miniatura para llenar la pantalla.

A continuación, se muestra una animación de presionar para acercar cuando se expande una miniatura para llenar la pantalla:

Para ver un ejemplo completo, consulta la clase UIAnimation del proyecto WearSpeakerSample en GitHub.

Cómo crear las vistas

Crea un archivo de diseño que contenga la versión pequeña y grande del contenido al que deseas acercar. En el siguiente ejemplo, se crea un ImageButton para una miniatura de imagen que se puede presionar y un ImageView que muestra la vista agrandada de la imagen:

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="16dp">

        <ImageButton
            android:id="@+id/thumb_button_1"
            android:layout_width="100dp"
            android:layout_height="75dp"
            android:layout_marginRight="1dp"
            android:src="@drawable/thumb1"
            android:scaleType="centerCrop"
            android:contentDescription="@string/description_image_1" />

    </LinearLayout>

    <!-- This initially hidden ImageView holds the zoomed version of
         the preceding images. Without transformations applied, it fills the entire
         screen. To achieve the zoom animation, this view's bounds are animated
         from the bounds of the preceding thumbnail button to its final laid-out
         bounds.
         -->

    <ImageView
        android:id="@+id/expanded_image"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="invisible"
        android:contentDescription="@string/description_zoom_touch_close" />

</FrameLayout>

Cómo configurar la animación de zoom

Una vez que apliques tu diseño, configura los controladores de eventos que activan la animación de zoom. En el siguiente ejemplo, se agrega un View.OnClickListener a ImageButton para ejecutar la animación de zoom cuando el usuario presiona el botón de la imagen:

Kotlin

class ZoomActivity : FragmentActivity() {

    // Hold a reference to the current animator so that it can be canceled
    // midway.
    private var currentAnimator: Animator? = null

    // The system "short" animation time duration in milliseconds. This duration
    // is ideal for subtle animations or animations that occur frequently.
    private var shortAnimationDuration: Int = 0

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_zoom)

        // Hook up taps on the thumbnail views.

        binding.thumbButton1.setOnClickListener {
            zoomImageFromThumb(thumb1View, R.drawable.image1)
        }

        // Retrieve and cache the system's default "short" animation time.
        shortAnimationDuration = resources.getInteger(android.R.integer.config_shortAnimTime)
    }
    ...
}

Java

public class ZoomActivity extends FragmentActivity {
    // Hold a reference to the current animator so that it can be canceled
    // mid-way.
    private Animator currentAnimator;

    // The system "short" animation time duration in milliseconds. This duration
    // is ideal for subtle animations or animations that occur frequently.
    private int shortAnimationDuration;

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

        // Hook up taps on the thumbnail views.

        binding.thumbButton1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                zoomImageFromThumb(thumb1View, R.drawable.image1);
            }
        });

        // Retrieve and cache the system's default "short" animation time.
        shortAnimationDuration = getResources().getInteger(
                android.R.integer.config_shortAnimTime);
    }
    ...
}

Cómo acercar la vista

Realiza animaciones de la vista de tamaño normal a la vista con zoom cuando corresponda. En general, debes animar desde los límites de la vista de tamaño normal hasta los límites de la vista de tamaño más grande. En los siguientes métodos, se muestra cómo implementar una animación de zoom que pase de ser una miniatura a una vista ampliada. Para ello, asigna la imagen de alta resolución al ImageView oculto "acercado" (agrandado).

En el siguiente ejemplo, se carga un recurso de imagen grande en el subproceso de IU para hacerlo más simple. Cárgalo en un subproceso separado para evitar bloqueos en el subproceso de IU y, luego, establece el mapa de bits en el subproceso de IU. Por lo general, el mapa de bits no debe ser mayor que el tamaño de la pantalla. A continuación, calcula los límites de inicio y finalización del ImageView.

Kotlin

    private fun zoomImageFromThumb(thumbView: View, imageResId: Int) {
        // If there's an animation in progress, cancel it immediately and
        // proceed with this one.
        currentAnimator?.cancel()

        // Load the high-resolution "zoomed-in" image.
        binding.expandedImage.setImageResource(imageResId)

        // Calculate the starting and ending bounds for the zoomed-in image.
        val startBoundsInt = Rect()
        val finalBoundsInt = Rect()
        val globalOffset = Point()

        // The start bounds are the global visible rectangle of the thumbnail,
        // and the final bounds are the global visible rectangle of the
        // container view. Set the container view's offset as the origin for the
        // bounds, since that's the origin for the positioning animation
        // properties (X, Y).
        thumbView.getGlobalVisibleRect(startBoundsInt)
        binding.container.getGlobalVisibleRect(finalBoundsInt, globalOffset)
        startBoundsInt.offset(-globalOffset.x, -globalOffset.y)
        finalBoundsInt.offset(-globalOffset.x, -globalOffset.y)

        val startBounds = RectF(startBoundsInt)
        val finalBounds = RectF(finalBoundsInt)

        // Using the "center crop" technique, adjust the start bounds to be the
        // same aspect ratio as the final bounds. This prevents unwanted
        // stretching during the animation. Calculate the start scaling factor.
        // The end scaling factor is always 1.0.
        val startScale: Float
        if ((finalBounds.width() / finalBounds.height() > startBounds.width() / startBounds.height())) {
            // Extend start bounds horizontally.
            startScale = startBounds.height() / finalBounds.height()
            val startWidth: Float = startScale * finalBounds.width()
            val deltaWidth: Float = (startWidth - startBounds.width()) / 2
            startBounds.left -= deltaWidth.toInt()
            startBounds.right += deltaWidth.toInt()
        } else {
            // Extend start bounds vertically.
            startScale = startBounds.width() / finalBounds.width()
            val startHeight: Float = startScale * finalBounds.height()
            val deltaHeight: Float = (startHeight - startBounds.height()) / 2f
            startBounds.top -= deltaHeight.toInt()
            startBounds.bottom += deltaHeight.toInt()
        }

        // Hide the thumbnail and show the zoomed-in view. When the animation
        // begins, it positions the zoomed-in view in the place of the
        // thumbnail.
        thumbView.alpha = 0f

        animateZoomToLargeImage(startBounds, finalBounds, startScale)

        setDismissLargeImageAnimation(thumbView, startBounds, startScale)
    }

Java

    private void zoomImageFromThumb(final View thumbView, int imageResId) {
        // If there's an animation in progress, cancel it immediately and
        // proceed with this one.
        if (currentAnimator != null) {
            currentAnimator.cancel();
        }

        // Load the high-resolution "zoomed-in" image.
        binding.expandedImage.setImageResource(imageResId);

        // Calculate the starting and ending bounds for the zoomed-in image.
        final Rect startBounds = new Rect();
        final Rect finalBounds = new Rect();
        final Point globalOffset = new Point();

        // The start bounds are the global visible rectangle of the thumbnail,
        // and the final bounds are the global visible rectangle of the
        // container view. Set the container view's offset as the origin for the
        // bounds, since that's the origin for the positioning animation
        // properties (X, Y).
        thumbView.getGlobalVisibleRect(startBounds);
        findViewById(R.id.container)
                .getGlobalVisibleRect(finalBounds, globalOffset);
        startBounds.offset(-globalOffset.x, -globalOffset.y);
        finalBounds.offset(-globalOffset.x, -globalOffset.y);

        // Using the "center crop" technique, adjust the start bounds to be the
        // same aspect ratio as the final bounds. This prevents unwanted
        // stretching during the animation. Calculate the start scaling factor.
        // The end scaling factor is always 1.0.
        float startScale;
        if ((float) finalBounds.width() / finalBounds.height()
                > (float) startBounds.width() / startBounds.height()) {
            // Extend start bounds horizontally.
            startScale = (float) startBounds.height() / finalBounds.height();
            float startWidth = startScale * finalBounds.width();
            float deltaWidth = (startWidth - startBounds.width()) / 2;
            startBounds.left -= deltaWidth;
            startBounds.right += deltaWidth;
        } else {
            // Extend start bounds vertically.
            startScale = (float) startBounds.width() / finalBounds.width();
            float startHeight = startScale * finalBounds.height();
            float deltaHeight = (startHeight - startBounds.height()) / 2;
            startBounds.top -= deltaHeight;
            startBounds.bottom += deltaHeight;
        }

        // Hide the thumbnail and show the zoomed-in view. When the animation
        // begins, it positions the zoomed-in view in the place of the
        // thumbnail.
        thumbView.setAlpha(0f);

        animateZoomToLargeImage(startBounds, finalBounds, startScale);

        setDismissLargeImageAnimation(thumbView, startBounds, startScale);
    }

Anima las cuatro propiedades de posicionamiento y tamaño (X, Y, SCALE_X y SCALE_Y) de forma simultánea desde los límites de inicio hasta los límites de finalización. Agrega estas cuatro animaciones a un objeto AnimatorSet para que comiencen al mismo tiempo.

Kotlin

    private fun animateZoomToLargeImage(startBounds: RectF, finalBounds: RectF, startScale: Float) {
        binding.expandedImage.visibility = View.VISIBLE

        // Set the pivot point for SCALE_X and SCALE_Y transformations to the
        // top-left corner of the zoomed-in view. The default is the center of
        // the view.
        binding.expandedImage.pivotX = 0f
        binding.expandedImage.pivotY = 0f

        // Construct and run the parallel animation of the four translation and
        // scale properties: X, Y, SCALE_X, and SCALE_Y.
        currentAnimator = AnimatorSet().apply {
            play(
                ObjectAnimator.ofFloat(
                    binding.expandedImage,
                    View.X,
                    startBounds.left,
                    finalBounds.left)
            ).apply {
                with(ObjectAnimator.ofFloat(binding.expandedImage, View.Y, startBounds.top, finalBounds.top))
                with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_X, startScale, 1f))
                with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_Y, startScale, 1f))
            }
            duration = shortAnimationDuration.toLong()
            interpolator = DecelerateInterpolator()
            addListener(object : AnimatorListenerAdapter() {

                override fun onAnimationEnd(animation: Animator) {
                    currentAnimator = null
                }

                override fun onAnimationCancel(animation: Animator) {
                    currentAnimator = null
                }
            })
            start()
        }
    }

Java

    private void animateZoomToLargeImage(Rect startBounds, Rect finalBounds, Float startScale) {

        binding.expandedImage.setVisibility(View.VISIBLE);

        // Set the pivot point for SCALE_X and SCALE_Y transformations to the
        // top-left corner of the zoomed-in view. The default is the center of
        // the view.
        binding.expandedImage.setPivotX(0f);
        binding.expandedImage.setPivotY(0f);

        // Construct and run the parallel animation of the four translation and
        // scale properties: X, Y, SCALE_X, and SCALE_Y.
        AnimatorSet set = new AnimatorSet();
        set
                .play(ObjectAnimator.ofFloat(binding.expandedImage, View.X,
                        startBounds.left, finalBounds.left))
                .with(ObjectAnimator.ofFloat(binding.expandedImage, View.Y,
                        startBounds.top, finalBounds.top))
                .with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_X,
                        startScale, 1f))
                .with(ObjectAnimator.ofFloat(binding.expandedImage,
                        View.SCALE_Y, startScale, 1f));
        set.setDuration(shortAnimationDuration);
        set.setInterpolator(new DecelerateInterpolator());
        set.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
                currentAnimator = null;
            }

            @Override
            public void onAnimationCancel(Animator animation) {
                currentAnimator = null;
            }
        });
        set.start();
        currentAnimator = set;
    }

Para alejar, ejecuta una animación similar al revés cuando el usuario presiona la pantalla mientras la imagen está acercada. Agrega un elemento View.OnClickListener a ImageView. Cuando se presiona, ImageView se minimiza al tamaño de la miniatura de la imagen y establece su visibilidad en GONE para ocultarla.

Kotlin

    private fun setDismissLargeImageAnimation(thumbView: View, startBounds: RectF, startScale: Float) {
        // When the zoomed-in image is tapped, it zooms down to the original
        // bounds and shows the thumbnail instead of the expanded image.
        binding.expandedImage.setOnClickListener {
            currentAnimator?.cancel()

            // Animate the four positioning and sizing properties in parallel,
            // back to their original values.
            currentAnimator = AnimatorSet().apply {
                play(ObjectAnimator.ofFloat(binding.expandedImage, View.X, startBounds.left)).apply {
                    with(ObjectAnimator.ofFloat(binding.expandedImage, View.Y, startBounds.top))
                    with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_X, startScale))
                    with(ObjectAnimator.ofFloat(binding.expandedImage, View.SCALE_Y, startScale))
                }
                duration = shortAnimationDuration.toLong()
                interpolator = DecelerateInterpolator()
                addListener(object : AnimatorListenerAdapter() {

                    override fun onAnimationEnd(animation: Animator) {
                        thumbView.alpha = 1f
                        binding.expandedImage.visibility = View.GONE
                        currentAnimator = null
                    }

                    override fun onAnimationCancel(animation: Animator) {
                        thumbView.alpha = 1f
                        binding.expandedImage.visibility = View.GONE
                        currentAnimator = null
                    }
                })
                start()
            }
        }
    }

Java

    private void setDismissLargeImageAnimation(View thumbView, Rect startBounds, Float startScale) {
        // When the zoomed-in image is tapped, it zooms down to the original
        // bounds and shows the thumbnail instead of the expanded image.
        final float startScaleFinal = startScale;
        binding.expandedImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (currentAnimator != null) {
                    currentAnimator.cancel();
                }

                // Animate the four positioning and sizing properties in
                // parallel, back to their original values.
                AnimatorSet set = new AnimatorSet();
                set.play(ObjectAnimator
                                .ofFloat(binding.expandedImage, View.X, startBounds.left))
                        .with(ObjectAnimator
                                .ofFloat(binding.expandedImage,
                                        View.Y,startBounds.top))
                        .with(ObjectAnimator
                                .ofFloat(binding.expandedImage,
                                        View.SCALE_X, startScaleFinal))
                        .with(ObjectAnimator
                                .ofFloat(binding.expandedImage,
                                        View.SCALE_Y, startScaleFinal));
                set.setDuration(shortAnimationDuration);
                set.setInterpolator(new DecelerateInterpolator());
                set.addListener(new AnimatorListenerAdapter() {
                    @Override
                    public void onAnimationEnd(Animator animation) {
                        thumbView.setAlpha(1f);
                        binding.expandedImage.setVisibility(View.GONE);
                        currentAnimator = null;
                    }

                    @Override
                    public void onAnimationCancel(Animator animation) {
                        thumbView.setAlpha(1f);
                        binding.expandedImage.setVisibility(View.GONE);
                        currentAnimator = null;
                    }
                });
                set.start();
                currentAnimator = set;
            }
        });
    }