需求描述
对于一个已经存在的集合/映射对象(普通的List,Set,Map,非observable),我们希望把将它转换成一个observable对象，这个observable对象就像是原对象的代理一样，当对observable对象操作(增加删除元素)时，实际是对原对象的操作。
jface为List,Set,Map三种类型提供了对应的三种可写对象WritableList,WritableSet,WritableMap，研究了这三个类的代码，发现它们99%是满足这个需求，然并卵，因为构造函数上设计区别，造成这三个类的构造函数生成的observable对象与原对象是隔离的。
以WritableSet的构造函数为例,WritableSet的构造函数重新用外部传入的Collection的内容构造了一个新的HashSet对象，所以WritableSet中的Set对象与传入的原对象(Collection)没有半毛钱关系：
public WritableSet(Realm realm, Collection<? extends E> c, Object elementType) {
// 创建了一个新的Set对象传给父类的构造函数
super(realm, new HashSet<E>(c), elementType);
this.elementType = elementType;
}只有WritableList类可以实现的上述的需求,而且貌似还是为了兼容之前版本的设计失误，而留的。
参见下面WritableList的构造函数的说明org.eclipse.core.databinding.observable.list.WritableList.WritableList(Realm realm, List<E> toWrap, Object elementType)
/** * Creates a writable list containing elements of the given type, wrapping * an existing client-supplied list. Note that for backwards compatibility * reasons, the contents of the created WritableList will change with the * contents of the given list. If this is not desired, * {@link #WritableList(Realm, Collection, Object)} should be used by * casting the second argument to {@link Collection}. * * @param realm * the observable's realm * @param toWrap * The java.util.List to wrap * @param elementType * can be <code>null</code> */
public WritableList(Realm realm, List<E> toWrap, Object elementType) {
// 没有对toWrap做任何处理就传给了父类的构造函数，这才是我想要的
super(realm, toWrap, elementType);
}所以这虽然是一个很普遍的需求，但jface并没有提供完整的支持，需要自己写代码支持。好在jface的基础框架比较扎实，所以如果搞清楚jface的类继承结构，自己写代码也不复杂，所以我为List,Set,Map三种类型的分别写了三个类用于实现Observable封装(WrappedObservableList,WrappedObservableSet,WrappedObservableMap),这三个类的代码都参考自对应的WritableList,WritableSet,WritableMap三个类，大部分代码都是直接抄来的。以下是三个类对应的实现代码
WrappedObservableList
WrappedObservableList类实现最简单，因为WritableList本身就因为历史原因支持这种代理封装，所以WrappedObservableList类只是在构造函数中加了参数检查
WrappedObservableList.java
package net.gdface.ui.binding;
import java.util.List;
import java.util.Objects;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.list.WritableList;
/** * 将指定的{@link List}对象(wrappedList)封装为 {@link ObservableList},<br> * 对observable对象的操作同步到原对象<br> * @author guyadong * * @param <E> */
public class WrappedObservableList<E> extends WritableList<E> {
public WrappedObservableList(List<E> wrappedList, Object elementType) {
this(Realm.getDefault(),wrappedList, elementType);
}
public WrappedObservableList(Realm realm, List<E> wrappedList, Object elementType) {
super(realm, Objects.requireNonNull(wrappedList,"the argument wrappedList must not be null"), elementType);
}
}
WrappedObservableSet
WrappedObservableSet类的大部分代码都抄自WritableSet
WrappedObservableSet.java
package net.gdface.ui.binding;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Objects;
import java.util.Set;
import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.set.ObservableSet;
/** * 将指定的{@link Set}对象(wrappedSet)封装为 {@link ObservableSet},<br> * 对observable对象的操作同步到原对象<br> * override方法实现代码抄自{@link org.eclipse.core.databinding.observable.set.WritableSet} * @author guyadong * * @param <E> */
public class WrappedObservableSet<E> extends ObservableSet<E>{
/** * @param realm * @param wrappedSet 为null抛出异常 * @param elementType */
protected WrappedObservableSet(Realm realm, Set<E> wrappedSet, Object elementType) {
super(realm, Objects.requireNonNull(wrappedSet,"the argument wrappedSet must not be null"), elementType);
}
public WrappedObservableSet(Set<E> wrappedSet, Object elementType) {
this(Realm.getDefault(),wrappedSet, elementType);
}
public WrappedObservableSet(Set<E> wrappedSet) {
this(Realm.getDefault(),wrappedSet, null);
}
@Override
public boolean add(E o) {
getterCalled();
boolean added = wrappedSet.add(o);
if (added) {
Set<E> removals = Collections.emptySet();
fireSetChange(Diffs.createSetDiff(Collections.singleton(o), removals));
}
return added;
}
@Override
public boolean addAll(Collection<? extends E> c) {
getterCalled();
Set<E> additions = new HashSet<E>();
Iterator<? extends E> it = c.iterator();
while (it.hasNext()) {
E element = it.next();
if (wrappedSet.add(element)) {
additions.add(element);
}
}
if (additions.size() > 0) {
Set<E> removals = Collections.emptySet();
fireSetChange(Diffs.createSetDiff(additions, removals));
return true;
}
return false;
}
@SuppressWarnings("unchecked")
@Override
public boolean remove(Object o) {
getterCalled();
boolean removed = wrappedSet.remove(o);
if (removed) {
Set<E> additions = Collections.emptySet();
fireSetChange(Diffs.createSetDiff(additions,
Collections.singleton((E) o)));
}
return removed;
}
@SuppressWarnings("unchecked")
@Override
public boolean removeAll(Collection<?> c) {
getterCalled();
Set<E> removes = new HashSet<E>();
Iterator<?> it = c.iterator();
while (it.hasNext()) {
Object element = it.next();
if (wrappedSet.remove(element)) {
removes.add((E) element);
}
}
if (removes.size() > 0) {
Set<E> additions = Collections.emptySet();
fireSetChange(Diffs.createSetDiff(additions, removes));
return true;
}
return false;
}
@Override
public boolean retainAll(Collection<?> c) {
getterCalled();
Set<E> removes = new HashSet<E>();
Iterator<E> it = wrappedSet.iterator();
while (it.hasNext()) {
E element = it.next();
if (!c.contains(element)) {
it.remove();
removes.add(element);
}
}
if (removes.size() > 0) {
Set<E> additions = Collections.emptySet();
fireSetChange(Diffs.createSetDiff(additions, removes));
return true;
}
return false;
}
@Override
public void clear() {
getterCalled();
Set<E> removes = new HashSet<E>(wrappedSet);
Set<E> additions = Collections.emptySet();
wrappedSet.clear();
fireSetChange(Diffs.createSetDiff(additions, removes));
}
}
WrappedObservableMap
WrappedObservableMap的大部分代码也都是抄自WritableMap
WrappedObservableMap.java
package net.gdface.ui.binding;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import org.eclipse.core.databinding.observable.Diffs;
import org.eclipse.core.databinding.observable.Realm;
import org.eclipse.core.databinding.observable.map.MapDiff;
import org.eclipse.core.databinding.observable.map.ObservableMap;
import org.eclipse.core.internal.databinding.observable.Util;
/** * 将指定的{@link Map}对象(wrappedMap)封装为 {@link ObservableMap},<br> * 对observable对象的操作同步到原对象<br> * override方法实现代码抄自 {@link org.eclipse.core.databinding.observable.map.WritableMap} * @author guyadong * * @param <K> * @param <V> */
public class WrappedObservableMap<K, V> extends ObservableMap<K, V> {
private final Object keyType;
private final Object valueType;
public WrappedObservableMap(Map<K, V> wrappedMap) {
this(Realm.getDefault(),wrappedMap, null, null);
}
public WrappedObservableMap(Map<K, V> wrappedMap, Object keyType, Object valueType) {
this(Realm.getDefault(),wrappedMap, keyType, valueType);
}
/** * @param realm * @param wrappedMap 为null抛出异常 * @param keyType * @param valueType */
public WrappedObservableMap(Realm realm, Map<K, V> wrappedMap, Object keyType, Object valueType) {
super(realm, Objects.requireNonNull(wrappedMap,"the argument wrappedMap must not be null"));
this.keyType=keyType;
this.valueType=valueType;
}
@Override
public Object getKeyType() {
return keyType;
}
@Override
public Object getValueType() {
return valueType;
}
@Override
public V put(K key, V value) {
checkRealm();
boolean containedKeyBefore = wrappedMap.containsKey(key);
V result = wrappedMap.put(key, value);
boolean containedKeyAfter = wrappedMap.containsKey(key);
if (containedKeyBefore != containedKeyAfter
|| !Util.equals(result, value)) {
MapDiff<K, V> diff;
if (containedKeyBefore) {
if (containedKeyAfter) {
diff = Diffs.createMapDiffSingleChange(key, result, value);
} else {
diff = Diffs.createMapDiffSingleRemove(key, result);
}
} else {
diff = Diffs.createMapDiffSingleAdd(key, value);
}
fireMapChange(diff);
}
return result;
}
@SuppressWarnings("unchecked")
@Override
public V remove(Object key) {
checkRealm();
if (wrappedMap.containsKey(key)) {
V result = wrappedMap.remove(key);
fireMapChange(Diffs.createMapDiffSingleRemove((K) key, result));
return result;
}
return null;
}
@Override
public void clear() {
checkRealm();
if (!isEmpty()) {
Map<K, V> copy = new HashMap<>(wrappedMap);
wrappedMap.clear();
fireMapChange(Diffs.createMapDiffRemoveAll(copy));
}
}
@Override
public void putAll(Map<? extends K, ? extends V> map) {
checkRealm();
Set<K> addedKeys = new HashSet<>(map.size());
Map<K, V> changes = new HashMap<>(map.size());
for (Map.Entry<? extends K, ? extends V> entry : map.entrySet()) {
boolean add = !wrappedMap.containsKey(entry.getKey());
V previousValue = wrappedMap.put(entry.getKey(), entry.getValue());
if (add) {
addedKeys.add(entry.getKey());
} else {
changes.put(entry.getKey(), previousValue);
}
}
if (!addedKeys.isEmpty() || !changes.isEmpty()) {
Set<K> removedKeys = Collections.emptySet();
fireMapChange(Diffs.createMapDiff(addedKeys, removedKeys,
changes.keySet(), changes, wrappedMap));
}
}
}
注意
上面代码中使用了java8才有方法，所以要在java8下编译