ListMultiSortHandler.java

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package com.eas.grid.processing;

import com.google.gwt.user.cellview.client.Column;
import com.google.gwt.user.cellview.client.ColumnSortEvent;
import com.google.gwt.user.cellview.client.ColumnSortList.ColumnSortInfo;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 *
 * @author mg
 * @param <T>
 */
public class ListMultiSortHandler<T> extends ColumnSortEvent.ListHandler<T> {

    protected List<T> unsorted = new ArrayList<>();
    protected Runnable onComplete;

    public ListMultiSortHandler(List<T> aList, Runnable aOnComplete) {
    	this(aList);
    	onComplete = aOnComplete;
    }
    
    public ListMultiSortHandler(List<T> aList) {
        super(aList);
        setList(aList);
    }

    @Override
    public void setList(List<T> aList) {
        super.setList(aList);
        unsorted.clear();
        unsorted.addAll(aList);
    }

    protected void unsort() {
        List<T> sorted = getList();
        sorted.clear();
        sorted.addAll(unsorted);
    }

    @Override
    public void onColumnSort(final ColumnSortEvent event) {
        if (unsorted.size() != getList().size()) {
            setList(getList());
        }
        if (event.getColumnSortList() == null || event.getColumnSortList().size() == 0) {
            unsort();
        } else {
            // Sort using the multi comparator.
            List<T> sorted = getList();
            Collections.sort(sorted, new Comparator<T>() {
                @Override
                public int compare(T o1, T o2) {
                    for (int i = 0; i < event.getColumnSortList().size(); i++) {
                        ColumnSortInfo sortInfo = event.getColumnSortList().get(i);
                        Comparator<T> c = getComparator((Column<T, ?>) sortInfo.getColumn());
                        int res = 0;
                        if (c != null) {
                            res = c.compare(o1, o2);
                        }
                        if (res != 0) {
                            return sortInfo.isAscending() ? res : -res;
                        }
                    }
                    return 0;
                }

            });
        }
        if(onComplete != null)
        	onComplete.run();
    }

}