Aumentar visualização com uma animação de zoom

Esta lição demonstra como fazer uma animação de tocar para aplicar zoom, que é útil para apps como galerias de fotos, animando a visualização de uma miniatura para uma imagem em tamanho original que preenche a tela.

Veja uma animação de tocar para aplicar zoom expandindo uma miniatura de imagem para preencher a tela:

Animação de zoom
 

Se você quiser pular para um exemplo funcional, veja a classe UIAnimation do projeto de amostra Wear Speaker no GitHub (link em inglês).

Criar as visualizações

Crie um arquivo de layout que contenha a versão pequena e grande do conteúdo em que você quer aplicar zoom. O exemplo a seguir cria um ImageButton para miniaturas de imagem clicáveis e um ImageView que exibe a versão ampliada da imagem:

    <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 will hold the expanded/zoomed version of
             the images above. Without transformations applied, it takes up the entire
             screen. To achieve the "zoom" animation, this view's bounds are animated
             from the bounds of the thumbnail button above, 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>
    

Configurar a animação de zoom

Depois de aplicar o layout, configure os manipuladores de eventos que acionam a animação de zoom. O exemplo a seguir adiciona um View.OnClickListener ao ImageButton para executar a animação de zoom quando o usuário clicar no botão de imagem:

Kotlin

    class ZoomActivity : FragmentActivity() {

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

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

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

            // Hook up clicks on the thumbnail views.

            val thumb1View: View = findViewById(R.id.thumb_button_1)
            thumb1View.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
        // very frequently.
        private int shortAnimationDuration;

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

            // Hook up clicks on the thumbnail views.

            final View thumb1View = findViewById(R.id.thumb_button_1);
            thumb1View.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);
        }
        ...
    }
    

Ampliar a visualização

Agora você precisará animar a partir da visualização de tamanho normal para a visualização ampliada, conforme for apropriado. Em geral, você precisa animar dos limites da visualização de tamanho normal para os limites da visualização de tamanho maior. O método a seguir mostra como implementar uma animação de zoom que amplia uma miniatura de imagem para uma visualização ampliada fazendo o seguinte:

  1. Atribua a imagem de alta resolução a ImageView "com zoom" (ampliado) oculto. O exemplo a seguir carrega um recurso de imagem grande na linha de execução da IU para simplificar. Faça isso carregando em uma linha de execução diferente para evitar o bloqueio na linha de execução da IU e, em seguida, defina o bitmap na linha de execução da IU. O ideal é que o bitmap não seja maior do que o tamanho da tela.
  2. Calcule os limites inicial e final de ImageView.
  3. Anime cada uma das quatro propriedades de posicionamento e dimensionamento X, Y, (SCALE_X e SCALE_Y) simultaneamente, desde os limites iniciais até os limites finais. Essas quatro animações são adicionadas a um AnimatorSet para que possam ser iniciadas ao mesmo tempo.
  4. Reduza o zoom executando uma animação semelhante, mas em ordem reversa, quando o usuário tocar na tela depois que a imagem for ampliada. Você pode fazer isso adicionando um View.OnClickListener ao ImageView. Quando clicado, o ImageView volta para o tamanho de miniatura da imagem e define a visibilidade como GONE para ocultá-la.

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.
        val expandedImageView: ImageView = findViewById(R.id.expanded_image)
        expandedImageView.setImageResource(imageResId)

        // Calculate the starting and ending bounds for the zoomed-in image.
        // This step involves lots of math. Yay, math.
        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. Also 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)
        findViewById<View>(R.id.container)
                .getGlobalVisibleRect(finalBoundsInt, globalOffset)
        startBoundsInt.offset(-globalOffset.x, -globalOffset.y)
        finalBoundsInt.offset(-globalOffset.x, -globalOffset.y)

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

        // Adjust the start bounds to be the same aspect ratio as the final
        // bounds using the "center crop" technique. This prevents undesirable
        // stretching during the animation. Also 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 will position the zoomed-in view in the place of the
        // thumbnail.
        thumbView.alpha = 0f
        expandedImageView.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).
        expandedImageView.pivotX = 0f
        expandedImageView.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(
                    expandedImageView,
                    View.X,
                    startBounds.left,
                    finalBounds.left)
            ).apply {
                with(ObjectAnimator.ofFloat(expandedImageView, View.Y, startBounds.top, finalBounds.top))
                with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_X, startScale, 1f))
                with(ObjectAnimator.ofFloat(expandedImageView, 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()
        }

        // Upon clicking the zoomed-in image, it should zoom back down
        // to the original bounds and show the thumbnail instead of
        // the expanded image.
        expandedImageView.setOnClickListener {
            currentAnimator?.cancel()

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

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

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

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.
        final ImageView expandedImageView = (ImageView) findViewById(
                R.id.expanded_image);
        expandedImageView.setImageResource(imageResId);

        // Calculate the starting and ending bounds for the zoomed-in image.
        // This step involves lots of math. Yay, math.
        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. Also 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);

        // Adjust the start bounds to be the same aspect ratio as the final
        // bounds using the "center crop" technique. This prevents undesirable
        // stretching during the animation. Also 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 will position the zoomed-in view in the place of the
        // thumbnail.
        thumbView.setAlpha(0f);
        expandedImageView.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).
        expandedImageView.setPivotX(0f);
        expandedImageView.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(expandedImageView, View.X,
                        startBounds.left, finalBounds.left))
                .with(ObjectAnimator.ofFloat(expandedImageView, View.Y,
                        startBounds.top, finalBounds.top))
                .with(ObjectAnimator.ofFloat(expandedImageView, View.SCALE_X,
                        startScale, 1f))
                .with(ObjectAnimator.ofFloat(expandedImageView,
                        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;

        // Upon clicking the zoomed-in image, it should zoom back down
        // to the original bounds and show the thumbnail instead of
        // the expanded image.
        final float startScaleFinal = startScale;
        expandedImageView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (currentAnimator != null) {
                    currentAnimator.cancel();
                }

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

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