com.google.devtools.depan.platform.eclipse.ui.widgets.Selections.java Source code

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Here is the source code for com.google.devtools.depan.platform.eclipse.ui.widgets.Selections.java

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/*
 * Copyright 2017 The Depan Project Authors
 *
 * 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.devtools.depan.platform.eclipse.ui.widgets;

import com.google.common.collect.Lists;

import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.IStructuredSelection;

import java.util.Collection;
import java.util.Collections;
import java.util.List;

/**
 * Utility methods for dealing with Eclipse selection entities.
 * 
 * These methods allow the type {@link IStructuredSelection} to be hidden
 * in many UX support methods.
 * 
 * @author Lee Carver
 */
public class Selections {

    /**
     * Provide a type correct collection based on the supplied selection
     * and type. Selection objects of a non-assignable type are silently
     * ignored.
     */
    public static <T> Collection<T> getSelection(ISelection selection, Class<T> type) {
        // TODO: Randomize the order ..
        return getSelectionList(selection, type);
    }

    /**
     * Use only when it is essential to have the elements in order.
     */
    public static <T> List<T> getSelectionList(ISelection selection, Class<T> type) {
        List<?> choices = getObjects(selection);
        if (choices.isEmpty()) {
            return Collections.emptyList();
        }
        List<T> result = Lists.newArrayListWithExpectedSize(choices.size());
        for (Object item : choices) {
            if (type.isAssignableFrom(item.getClass())) {
                result.add(type.cast(item));
            }
        }
        return result;
    }

    /**
     * Use when type-coercion occurs late in the process flow.
     */
    public static List<?> getObjects(ISelection selection) {
        if (!(selection instanceof IStructuredSelection)) {
            return Collections.emptyList();
        }
        return ((IStructuredSelection) selection).toList();
    }

    /**
     * Provide a type correct instance based on the supplied selection
     * and type. Selection objects of a non-assignable type are silently
     * ignored.
     */
    public static <T> T getFirstElement(ISelection selection, Class<T> type) {
        Object result = getFirstObject(selection);
        if ((result != null) && type.isAssignableFrom(result.getClass())) {
            return type.cast(result);
        }
        return null;
    }

    /**
     * Use when type-coercion occurs late in the process flow.
     */
    public static Object getFirstObject(ISelection selection) {
        if (!(selection instanceof IStructuredSelection)) {
            return null;
        }
        IStructuredSelection choices = ((IStructuredSelection) selection);
        if (choices.isEmpty()) {
            return null;
        }
        return choices.getFirstElement();
    }
}