Question

我正在为应用程序中的多个Panel设置新的Tab键顺序。我想创建一个新类，它允许我以与不推荐使用的setNextFocusableComponent方法相同的方式处理排序。我正在创建一个扩展DefaultTreversalPolicyClass的类，并重载getComponentBefore和getComponentAfter方法。在面板本身我希望实现就像创建一个新的自定义类（我称之为CustomizedTabOrderPolicy），然后添加我想要指定Tab键顺序的组件一样简单。我通过CustomizedTabOrderPolicy类上的便捷方法执行此操作，该类允许我将要为其指定Tab键顺序“链接”的组件添加到Hashtable，然后创建hastable的副本，其中键和值被切换。然后，我使用这些哈希表在两个组件之间建立向前和向后的Tab键顺序“链接”。

以下是我的自定义类：

import java.awt.Component;
import java.awt.Container;
import java.awt.DefaultFocusTraversalPolicy;
import java.util.Hashtable;

public class CustomizedTabOrderPolicy extends DefaultFocusTraversalPolicy {

    private Hashtable<Component, Component> exceptionsMap = new Hashtable<Component, Component>();
    private Hashtable<Component, Component> excpetionsMapReflection = new Hashtable<Component, Component>();
    private Component defaultComponent;
    private Component firstComponent;
    private Component lastComponent;

    public CustomizedTabOrderPolicy() {
    }

    @Override
    public Component getComponentAfter(Container container, Component component) {
        java.awt.Toolkit.getDefaultToolkit().beep();
        if (exceptionsMap.containsKey(component)) {
            return exceptionsMap.get(component);
        } else {
            return super.getComponentAfter(container, component);
        }
    }

    @Override
    public Component getComponentBefore(Container container, Component component) {
        if (exceptionsMap.containsValue(component)) {
            return excpetionsMapReflection.get(component);
        } else {
            return super.getComponentBefore(container, component);
        }
    }

    @Override
    public Component getDefaultComponent(Container container) {
        if (this.defaultComponent != null) {
            return this.defaultComponent;
        }
        return super.getDefaultComponent(container);
    }

    @Override
    public Component getFirstComponent(Container container) {
        if (this.firstComponent != null) {
            return this.firstComponent;
        }
        return super.getFirstComponent(container);
    }

    @Override
    public Component getLastComponent(Container container) {
        if (this.lastComponent != null) {
            return this.lastComponent;
        }
        return super.getLastComponent(container);
    }

    public void addNewException(Component origin, Component destination) {
        exceptionsMap.put(origin, destination);
        excpetionsMapReflection.put(destination, origin);
    }
    public void setDefaultComponent(Component defaultComponent) {
        this.defaultComponent = defaultComponent;
    }

    public void setLastComponent(Component lastComponent) {
        this.lastComponent = lastComponent;
    }

    public void setFirstComponent(Component firstComponent) {
        this.firstComponent = firstComponent;
    }
}

为了实现这一点，我在我的JPanel上使用了以下内容：

CustomizedTabOrderPolicy customPolicy = new CustomizedTabOrderPolicy();

customPolicy.addNewException(<component1>, <component2>);
customPolicy.addNewException(<component3>, <component4>);
customPolicy.addNewException(<component5>, <component6>);

this.setFocusTraversalPolicy(customPolicy);

我没有得到任何编译器或运行时错误，但似乎JPanel根本没有使用我的CustomTabOrderPolicy。当我在getComponentBefore和getComponentAfter方法中插入断点时，它们永远不会被触发。我对使用Focus Traversal政策非常陌生，所以我想知道我在这里缺少什么......

Answer 1

好的，我应该做的是继承FocusTraversalPolicy而不是DefaultFocusTraversalPolicy，并传入原始策略的副本，以便在没有“例外”时恢复。我还需要在面板上将FocusCycleRoot设置为true，以便它使用我的FocusTraversalPolicy。我现在已经设置好了，因此我在AbstractJPanel基类上有一个CustomizedTabOrderPolicy实例，所以我需要在面板初始化中调用所有这些：

    this.setTabOrderEnabled(true);
    this.getCustomTabOrder().addNewException(component1, component2);
    this.getCustomTabOrder().addNewException(component2, component3);
    this.getCustomTabOrder().addNewException(component3, component4);

我也改变了课程本身，使其更有效。

public class CustomizedTabOrderPolicy extends FocusTraversalPolicy {

    private FocusTraversalPolicy oldPolicy;
    private Hashtable<Component, Component> exceptionsMap = new Hashtable<Component, Component>();
    private Hashtable<Component, Component> exceptionsMapReflection = new Hashtable<Component, Component>();
    private Component defaultComponent;
    private Component firstComponent;
    private Component lastComponent;

    public CustomizedTabOrderPolicy(FocusTraversalPolicy oldPolicy) {
        this.oldPolicy = oldPolicy;
    }

    public Component getComponentAfter(Container container, Component component) {
        if (component == this.getLastComponent(container)) {
            if (isValid(this.getFirstComponent(container))) {
                return this.getFirstComponent(container);
            } else {
                return this.getComponentAfter(container, this.getFirstComponent(container));
            }
        }
        if (exceptionsMap.containsKey(component) && isValid(exceptionsMap.get(component))) {
            return exceptionsMap.get(component);
        } else {
            return oldPolicy.getComponentAfter(container, component);
        }
    }

    public Component getComponentBefore(Container container, Component component) {
        if (component == this.getFirstComponent(container)) {
            if (isValid(this.getLastComponent(container))) {
                return this.getLastComponent(container);
            } else {
                return this.getComponentBefore(container, this.getLastComponent(container));
            }
        }
        if (exceptionsMapReflection.containsKey(component) && isValid(exceptionsMapReflection.get(component))) {
            return exceptionsMapReflection.get(component);
        } else {
            return oldPolicy.getComponentBefore(container, component);
        }
    }

    public boolean isValid(Component component) {
        if (component.isEnabled() && component.isVisible() && component.isFocusable()) {
            return true;
        } else {
            return false;
        }
    }
    public Component getDefaultComponent(Container container) {
        if (this.defaultComponent != null) {
            return this.defaultComponent;
        }
        return oldPolicy.getDefaultComponent(container);
    }

    public Component getFirstComponent(Container container) {
        if (this.firstComponent != null) {
            return this.firstComponent;
        }
        return oldPolicy.getFirstComponent(container);
    }

    public Component getLastComponent(Container container) {
        if (this.lastComponent != null) {
            return this.lastComponent;
        } else {
            return oldPolicy.getLastComponent(container);
        }
    }

    public void addNewException(Component origin, Component destination) {
        exceptionsMap.put(origin, destination);
        exceptionsMapReflection.put(destination, origin);
    }
    public void setDefaultComponent(Component defaultComponent) {
        this.defaultComponent = defaultComponent;
    }

    public void setLastComponent(Component lastComponent) {
        this.lastComponent = lastComponent;
    }

    public void setFirstComponent(Component firstComponent) {
        this.firstComponent = firstComponent;
    }
 }

Answer 2

高效！我使用它进行了一些修改，让它在不是isValid（）时继续遍历（当然它应该在你的面板中至少有一个isValid（）组件）：

public Component getComponentAfter(Container container, Component component) {
    if (component == this.getLastComponent(container)) {
        if (isValid(this.getFirstComponent(container))) return this.getFirstComponent(container);
        else                                            return this.getComponentAfter(container, this.getFirstComponent(container));
    }
    if( exceptionsMap.containsKey(component) ) {
        component = exceptionsMap.get(component);
        if( isValid(component) ) return component;
        return this.getComponentAfter(container, component);
    }
    return oldPolicy.getComponentAfter(container, component);
}
public Component getComponentBefore(Container container, Component component) {
    if (component == this.getFirstComponent(container)) {
        if (isValid(this.getLastComponent(container))) return this.getLastComponent(container);
        else                                           return this.getComponentBefore(container, this.getLastComponent(container));
    }
    if( exceptionsMapReflection.containsKey(component) ) {
        component = exceptionsMapReflection.get(component);
        if( isValid(component) ) return component;
        return this.getComponentBefore(container, component);
    }
    return oldPolicy.getComponentBefore(container, component);
}

自定义FocusTraversalPolicy类Java Swing

2 个答案: