material-components_material-components-android/lib/java/com/google/android/material/internal/TouchDelegateGroup.java

/*
 * 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
 *
 *     https://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.internal;

import static android.support.annotation.RestrictTo.Scope.LIBRARY_GROUP;

import android.graphics.Rect;
import android.support.annotation.Nullable;
import android.support.annotation.RestrictTo;
import android.support.annotation.VisibleForTesting;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.TouchDelegate;
import android.view.View;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * A group of TouchDelegates for a single ancestor view. Touches are delegated to the appropriate
 * TouchDelegate.
 *
 * @hide
 */
@RestrictTo(LIBRARY_GROUP)
public class TouchDelegateGroup extends TouchDelegate {
  private static final Rect IGNORED = new Rect();

  private List<TouchDelegate> touchDelegates;
  @Nullable private TouchDelegate currentTouchDelegate;

  public TouchDelegateGroup(View ancestor) {
    super(IGNORED, ancestor);

    touchDelegates = new ArrayList<>();
  }

  public void addTouchDelegate(TouchDelegate touchDelegate) {
    if (touchDelegate == null) {
      throw new NullPointerException("Cannot add null touchDelegate");
    }
    touchDelegates.add(touchDelegate);
  }

  public void removeTouchDelegate(TouchDelegate touchDelegate) {
    touchDelegates.remove(touchDelegate);
    if (touchDelegate == currentTouchDelegate) {
      currentTouchDelegate = null;
    }
  }

  public void clearTouchDelegates() {
    touchDelegates.clear();
  }

  @VisibleForTesting
  public List<TouchDelegate> getTouchDelegates() {
    return Collections.unmodifiableList(new ArrayList<>(touchDelegates));
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) {
    int action = event.getActionMasked();
    if (action == MotionEvent.ACTION_DOWN) {
      // Ignore all pointers except the first.
      if (event.getPointerCount() > 1) {
        return false;
      }
      for (int i = touchDelegates.size() - 1; i >= 0; i--) {
        TouchDelegate touchDelegate = touchDelegates.get(i);

        // Save event coordinates since TouchDelegate mutates the location.
        float savedX = event.getX();
        float savedY = event.getY();
        boolean handled = touchDelegate.onTouchEvent(event);
        // Restore event coordinates that we can bubble up to parent.
        event.setLocation(savedX, savedY);

        if (handled) {
          currentTouchDelegate = touchDelegate;
          return true;
        }
      }
      return false;
    }

    boolean handled = currentTouchDelegate != null && currentTouchDelegate.onTouchEvent(event);

    if (action == KeyEvent.ACTION_UP || action == KeyEvent.FLAG_CANCELED) {
      currentTouchDelegate = null;
    }

    return handled;
  }
}