CustomFragmentContainerView

CustomFragmentContainerView.java

import android.animation.LayoutTransition;
import android.content.Context;
import android.graphics.Canvas;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowInsets;
import android.widget.FrameLayout;

import java.util.ArrayList;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentManager;

public class CustomFragmentContainerView extends FrameLayout {
    private ArrayList<View> mAppearingFragmentChildren = new ArrayList<>();
    private ArrayList<View> mDisappearingFragmentChildren = new ArrayList<>();
    private ArrayList<View> mTransitioningFragmentViews = new ArrayList<>();

    private boolean mDrawAppearingViewsFirst = false;
    private boolean mDrawDisappearingViewsFirst = false;

    public CustomFragmentContainerView(@NonNull Context context) {
        super(context);
    }

    public CustomFragmentContainerView(@NonNull Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public CustomFragmentContainerView(
        @NonNull Context context,
        @Nullable AttributeSet attrs,
        int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    /**
     * When called, this method throws a {@link UnsupportedOperationException} on APIs above 17.
     * On APIs 17 and below, it calls {@link FrameLayout#setLayoutTransition(LayoutTransition)}
     * This can be called either explicitly, or implicitly by setting animateLayoutChanges to
     * <code>true</code>.
     *
     * <p>View animations and transitions are disabled for CustomFragmentContainerView for APIs above 17.
     * Use {@link FragmentTransaction#setCustomAnimations(int, int, int, int)} and
     * {@link FragmentTransaction#setTransition(int)}.
     *
     * @param transition The LayoutTransition object that will animated changes in layout. A value
     *                   of <code>null</code> means no transition will run on layout changes.
     * @attr ref android.R.styleable#ViewGroup_animateLayoutChanges
     */
    @Override
    public void setLayoutTransition(@Nullable LayoutTransition transition) {
        if (Build.VERSION.SDK_INT < 18) {
            // Transitions on APIs below 18 are using an empty LayoutTransition as a replacement
            // for suppressLayout(true) and null LayoutTransition to then unsuppress it. If the
            // API is below 18, we should allow FrameLayout to handle this call.
            super.setLayoutTransition(transition);
            return;
        }

        throw new UnsupportedOperationException(
            "CustomFragmentContainerView does not support Layout Transitions or "
                + "animateLayoutChanges=\"true\".");
    }

    /**
     * {@inheritDoc}
     *
     * <p>The sys ui flags must be set to enable extending the layout into the window insets.
     */
    @NonNull
    @RequiresApi(20)
    @Override
    public WindowInsets onApplyWindowInsets(@NonNull WindowInsets insets) {
        for (int i = 0; i < getChildCount(); i++) {
            View child = getChildAt(i);
            // Give child views fresh insets.
            child.dispatchApplyWindowInsets(new WindowInsets(insets));
        }
        return insets;
    }

    @Override
    protected void dispatchDraw(@NonNull Canvas canvas) {
        if (mDrawDisappearingViewsFirst) {
            for (int i = 0; i < mDisappearingFragmentChildren.size(); i++) {
                super.drawChild(canvas, mDisappearingFragmentChildren.get(i), getDrawingTime());
            }
        }
        if (mDrawAppearingViewsFirst) {
            for (int i = 0; i < mAppearingFragmentChildren.size(); i++) {
                super.drawChild(canvas, mAppearingFragmentChildren.get(i), getDrawingTime());
            }
        }
        super.dispatchDraw(canvas);
    }

    @Override
    protected boolean drawChild(@NonNull Canvas canvas, @NonNull View child, long drawingTime) {
        if (mDrawDisappearingViewsFirst && mDisappearingFragmentChildren.size() > 0) {
            // If the child is disappearing, we have already drawn it so skip.
            if (mDisappearingFragmentChildren.contains(child)) {
                return false;
            }
        }

        if (mDrawAppearingViewsFirst && mAppearingFragmentChildren.size() > 0) {
            // If the child is appearing, we have already drawn it so skip.
            if (mAppearingFragmentChildren.contains(child)) {
                return false;
            }
        }
        return super.drawChild(canvas, child, drawingTime);
    }

    @Override
    public void startViewTransition(@NonNull View view) {
        if (view.getParent() == this) {
            mTransitioningFragmentViews.add(view);
        }
        super.startViewTransition(view);
    }

    @Override
    public void endViewTransition(@NonNull View view) {
        mTransitioningFragmentViews.remove(view);
        mDisappearingFragmentChildren.remove(view);
        mAppearingFragmentChildren.remove(view);

        super.endViewTransition(view);
    }

    // Used to indicate the container should change the default drawing order.
    public void setDrawAppearingViewsLast(boolean drawAppearingViewsFirst) {
        mDrawAppearingViewsFirst = drawAppearingViewsFirst;
    }

    // Used to indicate the container should change the default drawing order.
    public void setDrawDisappearingViewsLast(boolean drawDisappearingViewsFirst) {
        mDrawDisappearingViewsFirst = drawDisappearingViewsFirst;
    }

    /**
     * <p>CustomFragmentContainerView will only allow views returned by a Fragment's
     * {@link Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}. Attempting to add any
     * other view will result in an {@link IllegalStateException}.
     * <p>
     * {@inheritDoc}
     */
    @Override
    public void addView(@NonNull View child, int index, @Nullable ViewGroup.LayoutParams params) {
        //noinspection unused
        Fragment fragment = FragmentManager.findFragment(child);
        addAppearingFragmentView(child);
        super.addView(child, index, params);
    }

    /**
     * <p>CustomFragmentContainerView will only allow views returned by a Fragment's
     * {@link Fragment#onCreateView(LayoutInflater, ViewGroup, Bundle)}. Attempting to add any
     * other view will result in an {@link IllegalStateException}.
     * <p>
     * {@inheritDoc}
     */
    @Override
    protected boolean addViewInLayout(@NonNull View child, int index,
                                      @Nullable ViewGroup.LayoutParams params, boolean preventRequestLayout) {
        //noinspection unused
        Fragment fragment = FragmentManager.findFragment(child);
        addAppearingFragmentView(child);
        return super.addViewInLayout(child, index, params, preventRequestLayout);
    }

    @Override
    public void removeViewAt(int index) {
        View view = getChildAt(index);
        addDisappearingFragmentView(view);
        super.removeViewAt(index);
    }

    @Override
    public void removeViewInLayout(@NonNull View view) {
        addDisappearingFragmentView(view);
        super.removeViewInLayout(view);
    }

    @Override
    public void removeView(@NonNull View view) {
        addDisappearingFragmentView(view);
        super.removeView(view);
    }

    @Override
    public void removeViews(int start, int count) {
        for (int i = start; i < start + count; i++) {
            final View view = getChildAt(i);
            addDisappearingFragmentView(view);
        }
        super.removeViews(start, count);
    }

    @Override
    public void removeViewsInLayout(int start, int count) {
        for (int i = start; i < start + count; i++) {
            final View view = getChildAt(i);
            addDisappearingFragmentView(view);
        }
        super.removeViewsInLayout(start, count);
    }

    @Override
    public void removeAllViewsInLayout() {
        for (int i = getChildCount() - 1; i >= 0; i--) {
            final View view = getChildAt(i);
            addDisappearingFragmentView(view);
        }
        super.removeAllViewsInLayout();
    }

    @Override
    protected void removeDetachedView(@NonNull View child, boolean animate) {
        if (animate) {
            addDisappearingFragmentView(child);
        }
        super.removeDetachedView(child, animate);
    }

    /**
     * This method adds a {@link View} to the list of disappearing views only if it meets the
     * proper conditions to be considered a disappearing view.
     *
     * @param v {@link View} that might be added to list of disappearing views
     */
    private void addDisappearingFragmentView(@NonNull View v) {
        if (v.getAnimation() != null || mTransitioningFragmentViews.contains(v)) {
            mDisappearingFragmentChildren.add(v);
        }
    }

    /**
     * This method adds a {@link View} to the list of disappearing views only if it meets the
     * proper conditions to be considered a disappearing view.
     *
     * @param v {@link View} that might be added to list of disappearing views
     */
    private void addAppearingFragmentView(@NonNull View v) {
        if (v.getAnimation() != null || mTransitioningFragmentViews.contains(v)) {
            mAppearingFragmentChildren.add(v);
        }
    }
}