Profiles

mastodon/src/main/java/org/joinmastodon/android/ui/displayitems/HeaderStatusDisplayItem.java

@@ -5,7 +5,6 @@ import android.app.Fragment;
 import android.graphics.Outline;
 import android.graphics.drawable.Animatable;
 import android.graphics.drawable.Drawable;
-import android.os.Build;
 import android.os.Bundle;
 import android.view.View;
 import android.view.ViewGroup;

mastodon/src/main/java/org/joinmastodon/android/ui/drawables/CoverOverlayGradientDrawable.java

@@ -0,0 +1,58 @@
+package org.joinmastodon.android.ui.drawables;
+
+import android.graphics.Canvas;
+import android.graphics.ColorFilter;
+import android.graphics.LinearGradient;
+import android.graphics.Matrix;
+import android.graphics.Paint;
+import android.graphics.PixelFormat;
+import android.graphics.Rect;
+import android.graphics.Shader;
+import android.graphics.drawable.Drawable;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import me.grishka.appkit.utils.V;
+
+public class CoverOverlayGradientDrawable extends Drawable{
+	private LinearGradient gradient=new LinearGradient(0f, 0f, 0f, 100f, 0xB0000000, 0, Shader.TileMode.CLAMP);
+	private Matrix gradientMatrix=new Matrix();
+	private int topPadding, topOffset;
+	private Paint paint=new Paint();
+
+	public CoverOverlayGradientDrawable(){
+		paint.setShader(gradient);
+	}
+
+	@Override
+	public void draw(@NonNull Canvas canvas){
+		Rect bounds=getBounds();
+		gradientMatrix.setScale(1f, (bounds.height()-V.dp(40)-topPadding)/100f);
+		gradientMatrix.postTranslate(0, topPadding+topOffset);
+		gradient.setLocalMatrix(gradientMatrix);
+		canvas.drawRect(bounds, paint);
+	}
+
+	@Override
+	public void setAlpha(int alpha){
+
+	}
+
+	@Override
+	public void setColorFilter(@Nullable ColorFilter colorFilter){
+
+	}
+
+	@Override
+	public int getOpacity(){
+		return PixelFormat.TRANSLUCENT;
+	}
+
+	public void setTopPadding(int topPadding){
+		this.topPadding=topPadding;
+	}
+
+	public void setTopOffset(int topOffset){
+		this.topOffset=topOffset;
+	}
+}

mastodon/src/main/java/org/joinmastodon/android/ui/tabs/ElasticTabIndicatorInterpolator.java

@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.joinmastodon.android.ui.tabs;
+
+import android.graphics.RectF;
+import android.graphics.drawable.Drawable;
+import android.view.View;
+import androidx.annotation.FloatRange;
+import androidx.annotation.NonNull;
+import me.grishka.appkit.utils.V;
+
+import static org.joinmastodon.android.ui.utils.UiUtils.lerp;
+
+/**
+ * An implementation of {@link TabIndicatorInterpolator} that translates the left and right sides of
+ * a selected tab indicator independently to make the indicator grow and shrink between
+ * destinations.
+ */
+class ElasticTabIndicatorInterpolator extends TabIndicatorInterpolator {
+
+  /** Fit a linear 0F - 1F curve to an ease out sine (decelerating) curve. */
+  private static float decInterp(@FloatRange(from = 0.0, to = 1.0) float fraction) {
+    // Ease out sine
+    return (float) Math.sin((fraction * Math.PI) / 2.0);
+  }
+
+  /** Fit a linear 0F - 1F curve to an ease in sine (accelerating) curve. */
+  private static float accInterp(@FloatRange(from = 0.0, to = 1.0) float fraction) {
+    // Ease in sine
+    return (float) (1.0 - Math.cos((fraction * Math.PI) / 2.0));
+  }
+
+  @Override
+  void setIndicatorBoundsForOffset(
+      TabLayout tabLayout,
+      View startTitle,
+      View endTitle,
+      float offset,
+      @NonNull Drawable indicator) {
+      // The indicator should be positioned somewhere between start and end title. Override the
+      // super implementation and adjust the indicator's left and right bounds independently.
+      RectF startIndicator = calculateIndicatorWidthForTab(tabLayout, startTitle);
+      RectF endIndicator = calculateIndicatorWidthForTab(tabLayout, endTitle);
+
+      float leftFraction;
+      float rightFraction;
+
+      final boolean isMovingRight = startIndicator.left < endIndicator.left;
+      // If the selection indicator should grow and shrink during the animation, interpolate
+      // the left and right bounds of the indicator using separate easing functions.
+      // The side in which the indicator is moving should always be the accelerating
+      // side.
+      if (isMovingRight) {
+        leftFraction = accInterp(offset);
+        rightFraction = decInterp(offset);
+      } else {
+        leftFraction = decInterp(offset);
+        rightFraction = accInterp(offset);
+      }
+      indicator.setBounds(
+          lerp((int) startIndicator.left, (int) endIndicator.left, leftFraction),
+          indicator.getBounds().top,
+          lerp((int) startIndicator.right, (int) endIndicator.right, rightFraction),
+          indicator.getBounds().bottom);
+  }
+}

mastodon/src/main/java/org/joinmastodon/android/ui/tabs/MaterialResources.java

@@ -0,0 +1,16 @@
+package org.joinmastodon.android.ui.tabs;
+
+import android.content.Context;
+import android.content.res.ColorStateList;
+import android.content.res.TypedArray;
+import android.graphics.drawable.Drawable;
+
+class MaterialResources{
+	public static Drawable getDrawable(Context context, TypedArray a, int attr){
+		return a.getDrawable(attr);
+	}
+
+	public static ColorStateList getColorStateList(Context context, TypedArray a, int attr){
+		return a.getColorStateList(attr);
+	}
+}

mastodon/src/main/java/org/joinmastodon/android/ui/tabs/TabIndicatorInterpolator.java

@@ -0,0 +1,169 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.joinmastodon.android.ui.tabs;
+
+import static org.joinmastodon.android.ui.utils.UiUtils.lerp;
+
+import android.graphics.RectF;
+import android.graphics.drawable.Drawable;
+import android.view.View;
+import androidx.annotation.Dimension;
+import androidx.annotation.FloatRange;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import me.grishka.appkit.utils.V;
+
+/**
+ * A class used to manipulate the {@link SlidingTabIndicator}'s indicator {@link Drawable} at any
+ * point at or between tabs.
+ *
+ * <p>By default, this class will size the indicator according to {@link
+ * TabLayout#isTabIndicatorFullWidth()} and linearly move the indicator between tabs.
+ *
+ * <p>Subclasses can override {@link #setIndicatorBoundsForTab(TabLayout, View, Drawable)} and
+ * {@link #setIndicatorBoundsForOffset(TabLayout, View, View, float, Drawable)} (TabLayout, View,
+ * View, float, Drawable)} to define how the indicator should be drawn for a single tab or at any
+ * point between two tabs.
+ *
+ * <p>Additionally, subclasses can use the provided helpers {@link
+ * #calculateIndicatorWidthForTab(TabLayout, View)} and {@link
+ * #calculateTabViewContentBounds(TabView, int)} to capture the bounds of the tab or tab's content.
+ */
+class TabIndicatorInterpolator {
+
+  @Dimension(unit = Dimension.DP)
+  private static final int MIN_INDICATOR_WIDTH = 24;
+
+  /**
+   * A helper method that calculates the bounds of a {@link TabView}'s content.
+   *
+   * <p>For width, if only text label is present, calculates the width of the text label. If only
+   * icon is present, calculates the width of the icon. If both are present, the text label bounds
+   * take precedence. If both are present and inline mode is enabled, the sum of the bounds of the
+   * both the text label and icon are calculated. If neither are present or if the calculated
+   * difference between the left and right bounds is less than 24dp, then left and right bounds are
+   * adjusted such that the difference between them is equal to 24dp.
+   *
+   * <p>For height, this method calculates the combined height of the icon (if present) and label
+   * (if present).
+   *
+   * @param tabView {@link TabView} for which to calculate left and right content bounds.
+   * @param minWidth the min width between the returned RectF's left and right bounds. Useful if
+   *     enforcing a min width of the indicator.
+   */
+  static RectF calculateTabViewContentBounds(
+          @NonNull TabLayout.TabView tabView, @Dimension(unit = Dimension.DP) int minWidth) {
+    int tabViewContentWidth = tabView.getContentWidth();
+    int tabViewContentHeight = tabView.getContentHeight();
+    int minWidthPx = (int) V.dp(minWidth);
+
+    if (tabViewContentWidth < minWidthPx) {
+      tabViewContentWidth = minWidthPx;
+    }
+
+    int tabViewCenterX = (tabView.getLeft() + tabView.getRight()) / 2;
+    int tabViewCenterY = (tabView.getTop() + tabView.getBottom()) / 2;
+    int contentLeftBounds = tabViewCenterX - (tabViewContentWidth / 2);
+    int contentTopBounds = tabViewCenterY - (tabViewContentHeight / 2);
+    int contentRightBounds = tabViewCenterX + (tabViewContentWidth / 2);
+    int contentBottomBounds = tabViewCenterY + (tabViewCenterX / 2);
+
+    return new RectF(contentLeftBounds, contentTopBounds, contentRightBounds, contentBottomBounds);
+  }
+
+  /**
+   * A helper method to calculate the left and right bounds of an indicator when {@code tab} is
+   * selected.
+   *
+   * <p>This method accounts for {@link TabLayout#isTabIndicatorFullWidth()}'s value. If true, the
+   * returned left and right bounds will span the full width of {@code tab}. If false, the returned
+   * bounds will span the width of the {@code tab}'s content.
+   *
+   * @param tabLayout The tab's parent {@link TabLayout}
+   * @param tab The view of the tab under which the indicator will be positioned
+   * @return A {@link RectF} containing the left and right bounds that the indicator should span
+   *     when {@code tab} is selected.
+   */
+  static RectF calculateIndicatorWidthForTab(TabLayout tabLayout, @Nullable View tab) {
+    if (tab == null) {
+      return new RectF();
+    }
+
+    // If the indicator should fit to the tab's content, calculate the content's widtd
+    if (!tabLayout.isTabIndicatorFullWidth() && tab instanceof TabLayout.TabView) {
+      return calculateTabViewContentBounds((TabLayout.TabView) tab, MIN_INDICATOR_WIDTH);
+    }
+
+    // Return the entire width of the tab
+    return new RectF(tab.getLeft(), tab.getTop(), tab.getRight(), tab.getBottom());
+  }
+
+  /**
+   * Called whenever {@code indicator} should be drawn to show the given {@code tab} as selected.
+   *
+   * <p>This method should update the bounds of indicator to be correctly positioned to indicate
+   * {@code tab} as selected.
+   *
+   * @param tabLayout The {@link TabLayout} parent of the tab and indicator being drawn.
+   * @param tab The tab that should be marked as selected
+   * @param indicator The drawable to be drawn to indicate the selected tab. Update the drawable's
+   *     bounds, color, etc to mark the given tab as selected.
+   */
+  void setIndicatorBoundsForTab(TabLayout tabLayout, View tab, @NonNull Drawable indicator) {
+    RectF startIndicator = calculateIndicatorWidthForTab(tabLayout, tab);
+    indicator.setBounds(
+        (int) startIndicator.left,
+        indicator.getBounds().top,
+        (int) startIndicator.right,
+        indicator.getBounds().bottom);
+  }
+
+  /**
+   * Called whenever the {@code indicator} should be drawn between two destinations and the {@link
+   * Drawable}'s bounds should be changed. When {@code offset} is 0.0, the tab {@code indicator}
+   * should indicate that the {@code startTitle} tab is selected. When {@code offset} is 1.0, the
+   * tab {@code indicator} should indicate that the {@code endTitle} tab is selected. When offset is
+   * between 0.0 and 1.0, the {@code indicator} is moving between the startTitle and endTitle and
+   * the indicator should reflect this movement.
+   *
+   * <p>By default, this class will move the indicator linearly between tab destinations.
+   *
+   * @param tabLayout The TabLayout parent of the indicator being drawn.
+   * @param startTitle The title that should be indicated as selected when offset is 0.0.
+   * @param endTitle The title that should be indicated as selected when offset is 1.0.
+   * @param offset The fraction between startTitle and endTitle where the indicator is for a given
+   *     frame
+   * @param indicator The drawable to be drawn to indicate the selected tab. Update the drawable's
+   *     bounds, color, etc as {@code offset} changes to show the indicator in the correct position.
+   */
+  void setIndicatorBoundsForOffset(
+      TabLayout tabLayout,
+      View startTitle,
+      View endTitle,
+      @FloatRange(from = 0.0, to = 1.0) float offset,
+      @NonNull Drawable indicator) {
+    RectF startIndicator = calculateIndicatorWidthForTab(tabLayout, startTitle);
+    // Linearly interpolate the indicator's position, using it's left and right bounds, between the
+    // two destinations.
+    RectF endIndicator = calculateIndicatorWidthForTab(tabLayout, endTitle);
+    indicator.setBounds(
+        lerp((int) startIndicator.left, (int) endIndicator.left, offset),
+        indicator.getBounds().top,
+        lerp((int) startIndicator.right, (int) endIndicator.right, offset),
+        indicator.getBounds().bottom);
+  }
+}

mastodon/src/main/java/org/joinmastodon/android/ui/tabs/TabItem.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.joinmastodon.android.ui.tabs;
+
+
+import android.content.Context;
+import android.content.res.TypedArray;
+import android.graphics.drawable.Drawable;
+import android.util.AttributeSet;
+import android.view.View;
+
+import org.joinmastodon.android.R;
+
+/**
+ * TabItem is a special 'view' which allows you to declare tab items for a {@link TabLayout} within
+ * a layout. This view is not actually added to TabLayout, it is just a dummy which allows setting
+ * of a tab items's text, icon and custom layout. See TabLayout for more information on how to use
+ * it.
+ *
+ * @attr ref com.google.android.material.R.styleable#TabItem_android_icon
+ * @attr ref com.google.android.material.R.styleable#TabItem_android_text
+ * @attr ref com.google.android.material.R.styleable#TabItem_android_layout
+ * @see TabLayout
+ */
+//TODO(b/76413401): make class final after the widget migration
+public class TabItem extends View {
+  //TODO(b/76413401): make package private after the widget migration
+  public final CharSequence text;
+  //TODO(b/76413401): make package private after the widget migration
+  public final Drawable icon;
+  //TODO(b/76413401): make package private after the widget migration
+  public final int customLayout;
+
+  public TabItem(Context context) {
+    this(context, null);
+  }
+
+  public TabItem(Context context, AttributeSet attrs) {
+    super(context, attrs);
+
+    final TypedArray a =
+        context.obtainStyledAttributes(attrs, R.styleable.TabItem);
+    text = a.getText(R.styleable.TabItem_android_text);
+    icon = a.getDrawable(R.styleable.TabItem_android_icon);
+    customLayout = a.getResourceId(R.styleable.TabItem_android_layout, 0);
+    a.recycle();
+  }
+}

mastodon/src/main/java/org/joinmastodon/android/ui/tabs/TabLayoutMediator.java

@@ -0,0 +1,315 @@
+/*
+ * Copyright 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.joinmastodon.android.ui.tabs;
+
+import static androidx.viewpager2.widget.ViewPager2.SCROLL_STATE_DRAGGING;
+import static androidx.viewpager2.widget.ViewPager2.SCROLL_STATE_IDLE;
+import static androidx.viewpager2.widget.ViewPager2.SCROLL_STATE_SETTLING;
+
+import androidx.recyclerview.widget.RecyclerView;
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.viewpager2.widget.ViewPager2;
+import java.lang.ref.WeakReference;
+
+/**
+ * A mediator to link a TabLayout with a ViewPager2. The mediator will synchronize the ViewPager2's
+ * position with the selected tab when a tab is selected, and the TabLayout's scroll position when
+ * the user drags the ViewPager2. TabLayoutMediator will listen to ViewPager2's OnPageChangeCallback
+ * to adjust tab when ViewPager2 moves. TabLayoutMediator listens to TabLayout's
+ * OnTabSelectedListener to adjust VP2 when tab moves. TabLayoutMediator listens to RecyclerView's
+ * AdapterDataObserver to recreate tab content when dataset changes.
+ *
+ * <p>Establish the link by creating an instance of this class, make sure the ViewPager2 has an
+ * adapter and then call {@link #attach()} on it. Instantiating a TabLayoutMediator will only create
+ * the mediator object, {@link #attach()} will link the TabLayout and the ViewPager2 together. When
+ * creating an instance of this class, you must supply an implementation of {@link
+ * TabConfigurationStrategy} in which you set the text of the tab, and/or perform any styling of the
+ * tabs that you require. Changing ViewPager2's adapter will require a {@link #detach()} followed by
+ * {@link #attach()} call. Changing the ViewPager2 or TabLayout will require a new instantiation of
+ * TabLayoutMediator.
+ */
+public final class TabLayoutMediator {
+  @NonNull private final TabLayout tabLayout;
+  @NonNull private final ViewPager2 viewPager;
+  private final boolean autoRefresh;
+  private final boolean smoothScroll;
+  private final TabConfigurationStrategy tabConfigurationStrategy;
+  @Nullable private RecyclerView.Adapter<?> adapter;
+  private boolean attached;
+
+  @Nullable private TabLayoutOnPageChangeCallback onPageChangeCallback;
+  @Nullable private TabLayout.OnTabSelectedListener onTabSelectedListener;
+  @Nullable private RecyclerView.AdapterDataObserver pagerAdapterObserver;
+
+  /**
+   * A callback interface that must be implemented to set the text and styling of newly created
+   * tabs.
+   */
+  public interface TabConfigurationStrategy {
+    /**
+     * Called to configure the tab for the page at the specified position. Typically calls {@link
+     * TabLayout.Tab#setText(CharSequence)}, but any form of styling can be applied.
+     *
+     * @param tab The Tab which should be configured to represent the title of the item at the given
+     *     position in the data set.
+     * @param position The position of the item within the adapter's data set.
+     */
+    void onConfigureTab(@NonNull TabLayout.Tab tab, int position);
+  }
+
+  public TabLayoutMediator(
+      @NonNull TabLayout tabLayout,
+      @NonNull ViewPager2 viewPager,
+      @NonNull TabConfigurationStrategy tabConfigurationStrategy) {
+    this(tabLayout, viewPager, /* autoRefresh= */ true, tabConfigurationStrategy);
+  }
+
+  public TabLayoutMediator(
+      @NonNull TabLayout tabLayout,
+      @NonNull ViewPager2 viewPager,
+      boolean autoRefresh,
+      @NonNull TabConfigurationStrategy tabConfigurationStrategy) {
+    this(tabLayout, viewPager, autoRefresh, /* smoothScroll= */ true, tabConfigurationStrategy);
+  }
+
+  public TabLayoutMediator(
+      @NonNull TabLayout tabLayout,
+      @NonNull ViewPager2 viewPager,
+      boolean autoRefresh,
+      boolean smoothScroll,
+      @NonNull TabConfigurationStrategy tabConfigurationStrategy) {
+    this.tabLayout = tabLayout;
+    this.viewPager = viewPager;
+    this.autoRefresh = autoRefresh;
+    this.smoothScroll = smoothScroll;
+    this.tabConfigurationStrategy = tabConfigurationStrategy;
+  }
+
+  /**
+   * Link the TabLayout and the ViewPager2 together. Must be called after ViewPager2 has an adapter
+   * set. To be called on a new instance of TabLayoutMediator or if the ViewPager2's adapter
+   * changes.
+   *
+   * @throws IllegalStateException If the mediator is already attached, or the ViewPager2 has no
+   *     adapter.
+   */
+  public void attach() {
+    if (attached) {
+      throw new IllegalStateException("TabLayoutMediator is already attached");
+    }
+    adapter = viewPager.getAdapter();
+    if (adapter == null) {
+      throw new IllegalStateException(
+          "TabLayoutMediator attached before ViewPager2 has an " + "adapter");
+    }
+    attached = true;
+
+    // Add our custom OnPageChangeCallback to the ViewPager
+    onPageChangeCallback = new TabLayoutOnPageChangeCallback(tabLayout);
+    viewPager.registerOnPageChangeCallback(onPageChangeCallback);
+
+    // Now we'll add a tab selected listener to set ViewPager's current item
+    onTabSelectedListener = new ViewPagerOnTabSelectedListener(viewPager, smoothScroll);
+    tabLayout.addOnTabSelectedListener(onTabSelectedListener);
+
+    // Now we'll populate ourselves from the pager adapter, adding an observer if
+    // autoRefresh is enabled
+    if (autoRefresh) {
+      // Register our observer on the new adapter
+      pagerAdapterObserver = new PagerAdapterObserver();
+      adapter.registerAdapterDataObserver(pagerAdapterObserver);
+    }
+
+    populateTabsFromPagerAdapter();
+
+    // Now update the scroll position to match the ViewPager's current item
+    tabLayout.setScrollPosition(viewPager.getCurrentItem(), 0f, true);
+  }
+
+  /**
+   * Unlink the TabLayout and the ViewPager. To be called on a stale TabLayoutMediator if a new one
+   * is instantiated, to prevent holding on to a view that should be garbage collected. Also to be
+   * called before {@link #attach()} when a ViewPager2's adapter is changed.
+   */
+  public void detach() {
+    if (autoRefresh && adapter != null) {
+      adapter.unregisterAdapterDataObserver(pagerAdapterObserver);
+      pagerAdapterObserver = null;
+    }
+    tabLayout.removeOnTabSelectedListener(onTabSelectedListener);
+    viewPager.unregisterOnPageChangeCallback(onPageChangeCallback);
+    onTabSelectedListener = null;
+    onPageChangeCallback = null;
+    adapter = null;
+    attached = false;
+  }
+
+  /**
+   * Returns whether the {@link TabLayout} and the {@link ViewPager2} are linked together.
+   */
+  public boolean isAttached() {
+    return attached;
+  }
+
+  @SuppressWarnings("WeakerAccess")
+  void populateTabsFromPagerAdapter() {
+    tabLayout.removeAllTabs();
+
+    if (adapter != null) {
+      int adapterCount = adapter.getItemCount();
+      for (int i = 0; i < adapterCount; i++) {
+        TabLayout.Tab tab = tabLayout.newTab();
+        tabConfigurationStrategy.onConfigureTab(tab, i);
+        tabLayout.addTab(tab, false);
+      }
+      // Make sure we reflect the currently set ViewPager item
+      if (adapterCount > 0) {
+        int lastItem = tabLayout.getTabCount() - 1;
+        int currItem = Math.min(viewPager.getCurrentItem(), lastItem);
+        if (currItem != tabLayout.getSelectedTabPosition()) {
+          tabLayout.selectTab(tabLayout.getTabAt(currItem));
+        }
+      }
+    }
+  }
+
+  /**
+   * A {@link ViewPager2.OnPageChangeCallback} class which contains the necessary calls back to the
+   * provided {@link TabLayout} so that the tab position is kept in sync.
+   *
+   * <p>This class stores the provided TabLayout weakly, meaning that you can use {@link
+   * ViewPager2#registerOnPageChangeCallback(ViewPager2.OnPageChangeCallback)} without removing the
+   * callback and not cause a leak.
+   */
+  private static class TabLayoutOnPageChangeCallback extends ViewPager2.OnPageChangeCallback {
+    @NonNull private final WeakReference<TabLayout> tabLayoutRef;
+    private int previousScrollState;
+    private int scrollState;
+
+    TabLayoutOnPageChangeCallback(TabLayout tabLayout) {
+      tabLayoutRef = new WeakReference<>(tabLayout);
+      reset();
+    }
+
+    @Override
+    public void onPageScrollStateChanged(final int state) {
+      previousScrollState = scrollState;
+      scrollState = state;
+    }
+
+    @Override
+    public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
+      TabLayout tabLayout = tabLayoutRef.get();
+      if (tabLayout != null) {
+        // Only update the text selection if we're not settling, or we are settling after
+        // being dragged
+        boolean updateText =
+            scrollState != SCROLL_STATE_SETTLING || previousScrollState == SCROLL_STATE_DRAGGING;
+        // Update the indicator if we're not settling after being idle. This is caused
+        // from a setCurrentItem() call and will be handled by an animation from
+        // onPageSelected() instead.
+        boolean updateIndicator =
+            !(scrollState == SCROLL_STATE_SETTLING && previousScrollState == SCROLL_STATE_IDLE);
+        tabLayout.setScrollPosition(position, positionOffset, updateText, updateIndicator);
+      }
+    }
+
+    @Override
+    public void onPageSelected(final int position) {
+      TabLayout tabLayout = tabLayoutRef.get();
+      if (tabLayout != null
+          && tabLayout.getSelectedTabPosition() != position
+          && position < tabLayout.getTabCount()) {
+        // Select the tab, only updating the indicator if we're not being dragged/settled
+        // (since onPageScrolled will handle that).
+        boolean updateIndicator =
+            scrollState == SCROLL_STATE_IDLE
+                || (scrollState == SCROLL_STATE_SETTLING
+                    && previousScrollState == SCROLL_STATE_IDLE);
+        tabLayout.selectTab(tabLayout.getTabAt(position), updateIndicator);
+      }
+    }
+
+    void reset() {
+      previousScrollState = scrollState = SCROLL_STATE_IDLE;
+    }
+  }
+
+  /**
+   * A {@link TabLayout.OnTabSelectedListener} class which contains the necessary calls back to the
+   * provided {@link ViewPager2} so that the tab position is kept in sync.
+   */
+  private static class ViewPagerOnTabSelectedListener implements TabLayout.OnTabSelectedListener {
+    private final ViewPager2 viewPager;
+    private final boolean smoothScroll;
+
+    ViewPagerOnTabSelectedListener(ViewPager2 viewPager, boolean smoothScroll) {
+      this.viewPager = viewPager;
+      this.smoothScroll = smoothScroll;
+    }
+
+    @Override
+    public void onTabSelected(@NonNull TabLayout.Tab tab) {
+      viewPager.setCurrentItem(tab.getPosition(), smoothScroll);
+    }
+
+    @Override
+    public void onTabUnselected(TabLayout.Tab tab) {
+      // No-op
+    }
+
+    @Override
+    public void onTabReselected(TabLayout.Tab tab) {
+      // No-op
+    }
+  }
+
+  private class PagerAdapterObserver extends RecyclerView.AdapterDataObserver {
+    PagerAdapterObserver() {}
+
+    @Override
+    public void onChanged() {
+      populateTabsFromPagerAdapter();
+    }
+
+    @Override
+    public void onItemRangeChanged(int positionStart, int itemCount) {
+      populateTabsFromPagerAdapter();
+    }
+
+    @Override
+    public void onItemRangeChanged(int positionStart, int itemCount, @Nullable Object payload) {
+      populateTabsFromPagerAdapter();
+    }
+
+    @Override
+    public void onItemRangeInserted(int positionStart, int itemCount) {
+      populateTabsFromPagerAdapter();
+    }
+
+    @Override
+    public void onItemRangeRemoved(int positionStart, int itemCount) {
+      populateTabsFromPagerAdapter();
+    }
+
+    @Override
+    public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
+      populateTabsFromPagerAdapter();
+    }
+  }
+}

mastodon/src/main/java/org/joinmastodon/android/ui/utils/UiUtils.java

@@ -1,5 +1,6 @@
 package org.joinmastodon.android.ui.utils;
 
+import android.annotation.SuppressLint;
 import android.content.Context;
 import android.content.res.ColorStateList;
 import android.graphics.drawable.Drawable;
@@ -43,6 +44,16 @@ public class UiUtils{
 		}
 	}
 
+	@SuppressLint("DefaultLocale")
+	public static String abbreviateNumber(int n){
+		if(n<1000)
+			return String.format("%,d", n);
+		else if(n<1_000_000)
+			return String.format("%,.1fK", n/1000f);
+		else
+			return String.format("%,.1fM", n/1_000_000f);
+	}
+
 	/**
 	 * Android 6.0 has a bug where start and end compound drawables don't get tinted.
 	 * This works around it by setting the tint colors directly to the drawables.
@@ -64,4 +75,9 @@ public class UiUtils{
 	public static void runOnUiThread(Runnable runnable){
 		mainHandler.post(runnable);
 	}
+
+	/** Linear interpolation between {@code startValue} and {@code endValue} by {@code fraction}. */
+	public static int lerp(int startValue, int endValue, float fraction) {
+		return startValue + Math.round(fraction * (endValue - startValue));
+	}
 }

mastodon/src/main/java/org/joinmastodon/android/ui/views/CoverImageView.java

@@ -0,0 +1,37 @@
+package org.joinmastodon.android.ui.views;
+
+import android.content.Context;
+import android.graphics.Canvas;
+import android.util.AttributeSet;
+import android.widget.ImageView;
+
+import androidx.annotation.Nullable;
+
+public class CoverImageView extends ImageView{
+	private float imageTranslationY, imageScale=1f;
+
+	public CoverImageView(Context context){
+		super(context);
+	}
+
+	public CoverImageView(Context context, @Nullable AttributeSet attrs){
+		super(context, attrs);
+	}
+
+	public CoverImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr){
+		super(context, attrs, defStyleAttr);
+	}
+
+	@Override
+	protected void onDraw(Canvas canvas){
+		canvas.save();
+		canvas.translate(0, imageTranslationY);
+		super.onDraw(canvas);
+		canvas.restore();
+	}
+
+	public void setTransform(float transY, float scale){
+		imageTranslationY=transY;
+		imageScale=scale;
+	}
+}

mastodon/src/main/java/org/joinmastodon/android/ui/views/NestedRecyclerScrollView.java

@@ -0,0 +1,72 @@
+package org.joinmastodon.android.ui.views;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.View;
+
+import java.util.function.Supplier;
+
+import androidx.recyclerview.widget.LinearLayoutManager;
+import androidx.recyclerview.widget.RecyclerView;
+
+public class NestedRecyclerScrollView extends CustomScrollView{
+	private Supplier<RecyclerView> scrollableChildSupplier;
+
+	public NestedRecyclerScrollView(Context context){
+		super(context);
+	}
+
+	public NestedRecyclerScrollView(Context context, AttributeSet attrs){
+		super(context, attrs);
+	}
+
+	public NestedRecyclerScrollView(Context context, AttributeSet attrs, int defStyleAttr){
+		super(context, attrs, defStyleAttr);
+	}
+
+	@Override
+	public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
+		final RecyclerView rv = (RecyclerView) target;
+		if ((dy < 0 && isScrolledToTop(rv)) || (dy > 0 && !isScrolledToBottom())) {
+			scrollBy(0, dy);
+			consumed[1] = dy;
+			return;
+		}
+		super.onNestedPreScroll(target, dx, dy, consumed);
+	}
+
+	@Override
+	public boolean onNestedPreFling(View target, float velX, float velY) {
+		final RecyclerView rv = (RecyclerView) target;
+		if ((velY < 0 && isScrolledToTop(rv)) || (velY > 0 && !isScrolledToBottom())) {
+			fling((int) velY);
+			return true;
+		}
+		return super.onNestedPreFling(target, velX, velY);
+	}
+
+	private boolean isScrolledToBottom() {
+		return !canScrollVertically(1);
+	}
+
+	private boolean isScrolledToTop(RecyclerView rv) {
+		final LinearLayoutManager lm = (LinearLayoutManager) rv.getLayoutManager();
+		return lm.findFirstVisibleItemPosition() == 0
+				&& lm.findViewByPosition(0).getTop() == 0;
+	}
+
+	public void setScrollableChildSupplier(Supplier<RecyclerView> scrollableChildSupplier){
+		this.scrollableChildSupplier=scrollableChildSupplier;
+	}
+
+	@Override
+	protected boolean onScrollingHitEdge(float velocity){
+		if(velocity>0){
+			RecyclerView view=scrollableChildSupplier.get();
+			if(view!=null){
+				return view.fling(0, (int)velocity);
+			}
+		}
+		return false;
+	}
+}