material-components_material-components-android/lib/java/com/google/android/material/bottomsheet/BottomSheetDialogFragment.java

/*
 * Copyright (C) 2015 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 com.google.android.material.bottomsheet;

import com.google.android.material.R;

import android.app.Dialog;
import android.os.Bundle;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.DialogFragment;
import androidx.appcompat.app.AppCompatDialogFragment;
import android.view.View;

/**
 * Modal bottom sheet. This is a version of {@link DialogFragment} that shows a bottom sheet using
 * {@link BottomSheetDialog} instead of a floating dialog.
 */
public class BottomSheetDialogFragment extends AppCompatDialogFragment {

  /**
   * Tracks if we are waiting for a dismissAllowingStateLoss or a regular dismiss once the
   * BottomSheet is hidden and onStateChanged() is called.
   */
  private boolean waitingForDismissAllowingStateLoss;

  @NonNull
  @Override
  public Dialog onCreateDialog(Bundle savedInstanceState) {
    return new BottomSheetDialog(getContext(), getTheme());
  }

  @Override
  public void dismiss() {
    if (!tryDismissWithAnimation(false)) {
      super.dismiss();
    }
  }

  @Override
  public void dismissAllowingStateLoss() {
    if (!tryDismissWithAnimation(true)) {
      super.dismissAllowingStateLoss();
    }
  }

  @NonNull
  @Override
  public BottomSheetDialog getDialog() {
    return (BottomSheetDialog) super.getDialog();
  }

  /**
   * Tries to dismiss the dialog fragment with the bottom sheet animation. Returns true if possible,
   * false otherwise.
   */
  private boolean tryDismissWithAnimation(boolean allowingStateLoss) {
    BottomSheetBehavior<View> behavior = getBottomSheetBehavior();
    if (behavior != null && behavior.isHideable() && getDialog().getDismissWithAnimation()) {
      dismissWithAnimation(behavior, allowingStateLoss);
      return true;
    }

    return false;
  }

  @Nullable
  private BottomSheetBehavior<View> getBottomSheetBehavior() {
    Dialog dialog = getDialog();
    if (dialog != null) {
      View bottomSheet = dialog.findViewById(R.id.design_bottom_sheet);
      if (bottomSheet != null) {
        return BottomSheetBehavior.from(bottomSheet);
      }
    }
    return null;
  }

  private void dismissWithAnimation(
      @NonNull BottomSheetBehavior<View> behavior, boolean allowingStateLoss) {
    waitingForDismissAllowingStateLoss = allowingStateLoss;

    if (behavior.getState() == BottomSheetBehavior.STATE_HIDDEN) {
      dismissAfterAnimation();
    } else {
      // Wrap the old callback in a BottomSheetDismissCallback to pass along the state change.
      if (!(behavior.getBottomSheetCallback() instanceof BottomSheetDismissCallback)) {
        BottomSheetDismissCallback dismissCallback =
            new BottomSheetDismissCallback(behavior.getBottomSheetCallback());
        behavior.setBottomSheetCallback(dismissCallback);
      }

      behavior.setState(BottomSheetBehavior.STATE_HIDDEN);
    }
  }

  private void dismissAfterAnimation() {
    if (waitingForDismissAllowingStateLoss) {
      super.dismissAllowingStateLoss();
    } else {
      super.dismiss();
    }
  }

  private class BottomSheetDismissCallback extends BottomSheetBehavior.BottomSheetCallback {

    private final BottomSheetBehavior.BottomSheetCallback originalCallback;

    public BottomSheetDismissCallback(BottomSheetBehavior.BottomSheetCallback originalCallback) {
      this.originalCallback = originalCallback;
    }

    @Override
    public void onStateChanged(@NonNull View bottomSheet, int newState) {
      if (newState == BottomSheetBehavior.STATE_HIDDEN) {
        dismissAfterAnimation();
      }

      originalCallback.onStateChanged(bottomSheet, newState);
    }

    @Override
    public void onSlide(@NonNull View bottomSheet, float slideOffset) {
      originalCallback.onSlide(bottomSheet, slideOffset);
    }
  }
}