使用JavaFX 8创建一个空安全BooleanBinding [英] Create a null-safe BooleanBinding with JavaFX 8
问题描述
我需要帮助创建一个空 -safe BooleanBinding 。它必须是空 -safe因为我不能对模型中的所有属性提供缺省值（一个原因：模型包含枚举）。我的第一个方法是如下：
I need help creating a null-safe BooleanBinding. It has to be null-safe since I can not provide default values for all attributes in the model (one reason: the model contains enumerations). My first approach has been as follows:
executeButtonDisabled.bind(missionProperty().isNotNull().and(missionProperty().get().statusProperty().isNotEqualTo(MissionStatus.CREATED)));
final BooleanBinding isNotExecutingBinding = missionProperty().isNotNull().and(missionProperty().get().statusProperty().isNotEqualTo(MissionStatus.EXECUTING));
completeButtonDisabled.bind(isNotExecutingBinding);
cancelButtonDisabled.bind(isNotExecutingBinding)
但由于完整的前pression评估这导致方法不起作用一个 NullPointerException异常（但它正确更新按钮，提供物业时）。现在我试图使用绑定类中的 JavaFX绑定和空值，但我不能使它工作。这是我目前的做法：
But that approach does not work because the complete expression is evaluated which results in a NullPointerException (but it correctly updates the buttons, when a property is provided). Now I am trying to use the Bindings class as suggested in JavaFX binding and null values, but I can't make it work. Here's my current approach:
final BooleanBinding isNotCreatedBinding = Bindings.createBooleanBinding(
() -> mission.isNull().getValue()
? true
: missionProperty().get().statusProperty().isNotEqualTo(MissionStatus.CREATED).getValue());
final BooleanBinding isNotExecutingBinding = Bindings.createBooleanBinding(
() -> mission.isNull().getValue()
? true
: missionProperty().get().statusProperty().isNotEqualTo(MissionStatus.EXECUTING).getValue());
executeButtonDisabled.bind(isNotCreatedBinding);
completeButtonDisabled.bind(isNotExecutingBinding);
cancelButtonDisabled.bind(isNotExecutingBinding);
但是，这并不工作，我不明白为什么。看来，财产 modelProperty（）结合不在这里工作了！你能向我解释如何对第一个工作的解决方案转换（至少在没有空）以适当的空 - 安全的解决方案？
But this does not work and I do not understand why. It seems that the property binding for modelProperty() does not work here! Can you explain to me how-to convert the first working solution (at least without null) to a proper null-safe solution?
修改2016年4月26日：建议的解决方案不起作用，所以我创建了一个简单的完全正常的工作例如：
Edit 2016-04-26: The suggested solution does not work, therefore I created a simple fully-working example:
Mission.java ：
package de.florianwolters.example.javafx.bindings;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
public class Mission {
enum Status {
CREATED,
EXECUTING,
COMPLETED,
CANCELED;
}
private final StringProperty shortName = new SimpleStringProperty();
private final ObjectProperty<Status> status = new SimpleObjectProperty<>();
public Mission(final String shortName) {
this.setShortName(shortName);
this.setStatus(Status.CREATED);
}
public String getShortName() {
return shortNameProperty().get();
}
public void setShortName(final String shortName) {
shortNameProperty().set(shortName);
}
public StringProperty shortNameProperty() {
return shortName;
}
public Status getStatus() {
return statusProperty().get();
}
public void setStatus(final Status status) {
statusProperty().set(status);
}
public ObjectProperty<Status> statusProperty() {
return status;
}
}
MissionDetailsViewModel.java ：
package de.florianwolters.example.javafx.bindings;
import javafx.beans.binding.Bindings;
import javafx.beans.binding.BooleanBinding;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.ReadOnlyBooleanProperty;
import javafx.beans.property.ReadOnlyBooleanWrapper;
import javafx.beans.property.SimpleObjectProperty;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public final class MissionDetailsViewModel {
/**
* The logger used for logging in the `MissionDetailsViewModel` class.
*/
private static final Logger LOGGER = LoggerFactory.getLogger(
MissionDetailsViewModel.class);
private ObjectProperty<Mission> mission = new SimpleObjectProperty<>();
private final ReadOnlyBooleanWrapper executeButtonDisabled = new ReadOnlyBooleanWrapper(true);
private final ReadOnlyBooleanWrapper completeButtonDisabled = new ReadOnlyBooleanWrapper(true);
private final ReadOnlyBooleanWrapper cancelButtonDisabled = new ReadOnlyBooleanWrapper(true);
/**
* Constructs a `MissionDetailsViewModel`.
*/
public MissionDetailsViewModel(final ObjectProperty<Mission> mission) {
this.mission.bind(mission);
// partialWorkingBinding();
notWorkingBinding();
}
private void notWorkingBinding() {
final BooleanBinding isNotCreatedBinding = Bindings.createBooleanBinding(
() -> missionProperty().isNull().get()
? true
: missionProperty().get().statusProperty().isNotEqualTo(Mission.Status.CREATED).get(),
missionProperty());
final BooleanBinding isNotExecutingBinding = Bindings.createBooleanBinding(
() -> mission.isNull().get()
? true
: missionProperty().get().statusProperty().isNotEqualTo(Mission.Status.EXECUTING).get(),
missionProperty());
executeButtonDisabled.bind(isNotCreatedBinding);
completeButtonDisabled.bind(isNotExecutingBinding);
cancelButtonDisabled.bind(isNotExecutingBinding);
}
private void partialWorkingBinding() {
executeButtonDisabled.bind(missionProperty().isNotNull().and(missionProperty().get().statusProperty().isNotEqualTo(Mission.Status.CREATED)));
final BooleanBinding isNotExecutingBinding = missionProperty().isNotNull().and(missionProperty().get().statusProperty().isNotEqualTo(Mission.Status.EXECUTING));
completeButtonDisabled.bind(isNotExecutingBinding);
cancelButtonDisabled.bind(isNotExecutingBinding);
}
public boolean isExecuteButtonDisabled() {
return executeButtonDisabledProperty().get();
}
public ReadOnlyBooleanProperty executeButtonDisabledProperty() {
return executeButtonDisabled;
}
public boolean isCompleteButtonDisabled() {
return completeButtonDisabledProperty().get();
}
public ReadOnlyBooleanProperty completeButtonDisabledProperty() {
return completeButtonDisabled;
}
public boolean isCancelButtonDisabled() {
return cancelButtonDisabledProperty().get();
}
public ReadOnlyBooleanProperty cancelButtonDisabledProperty() {
return cancelButtonDisabled;
}
public Mission getMission() {
return missionProperty().get();
}
public void setMission(final Mission mission) {
missionProperty().set(mission);
}
public ObjectProperty<Mission> missionProperty() {
return mission;
}
}
MissionDetailsViewModelTest.java ：
package de.florianwolters.example.javafx.bindings;
import static eu.lestard.assertj.javafx.api.Assertions.assertThat;
import javafx.beans.property.SimpleObjectProperty;
import org.junit.Before;
import org.junit.Test;
public final class MissionDetailsViewModelTest {
private Mission mission;
private MissionDetailsViewModel viewModel;
@Before
public void setUp() {
mission = new Mission("My Short Name");
viewModel = new MissionDetailsViewModel(new SimpleObjectProperty<Mission>(mission));
}
@Test
public void testInitialValues() {
assertThat(viewModel.executeButtonDisabledProperty()).isFalse();
assertThat(viewModel.completeButtonDisabledProperty()).isTrue();
assertThat(viewModel.cancelButtonDisabledProperty()).isTrue();
}
@Test
public void testMissionStatusSetToExecuting() {
mission.setStatus(Mission.Status.EXECUTING);
assertThat(viewModel.executeButtonDisabledProperty()).isTrue();
assertThat(viewModel.completeButtonDisabledProperty()).isFalse();
assertThat(viewModel.cancelButtonDisabledProperty()).isFalse();
}
@Test
public void testMissionStatusSetToCompleted() {
mission.setStatus(Mission.Status.COMPLETED);
assertThat(viewModel.executeButtonDisabledProperty()).isTrue();
assertThat(viewModel.completeButtonDisabledProperty()).isTrue();
assertThat(viewModel.cancelButtonDisabledProperty()).isTrue();
}
@Test
public void testMissionStatusSetToCanceled() {
mission.setStatus(Mission.Status.CANCELED);
assertThat(viewModel.executeButtonDisabledProperty()).isTrue();
assertThat(viewModel.completeButtonDisabledProperty()).isTrue();
assertThat(viewModel.cancelButtonDisabledProperty()).isTrue();
}
}
单元测试失败与code以上（方法 notWorkingBinding（）使用），但该方法适用 partialWorkingBinding（） 。我在做什么错了？
The unit test fails with the code above (the method notWorkingBinding() is used) but works with the method partialWorkingBinding(). What am I doing wrong?
推荐答案
您设置了 isNotCreatedBinding 计算功能，但你没有设置的依赖关系为绑定。您需要添加米西的依赖性：
You set up the calculation function for isNotCreatedBinding, but you didn't set the dependencies for the binding. You need to add mision as dependency:
Bindings.createBooleanBinding(
() -> mission.isNull().getValue()
? true
: missionProperty().get().statusProperty().isNotEqualTo(MissionStatus.CREATED).getValue(), mission);
修改
您需要听statusProperty而不是missionProperty，不会与 createBooleanBinding 时missionProperty（）。获得（）== NULL工作。
You need to listen to the statusProperty instead of missionProperty, which will not work with createBooleanBinding when missionProperty().get() == null.
<击>但是，你可以使用在绑定：
（是造成 NullPointerException异常中的问题已经提到）
(is causing a NullPointerException as already mentioned in the question)
BooleanBinding isNotCreatedBinding = new When(mission.isNotNull()).then(mission.get().statusProperty().isNotEqualTo(Mission.Status.CREATED)).otherwise(false);
还是比较低层次的解决方案：
Or a more low-level solution:
missionProperty().addListener((ov, m, m1) -> {
if (m1 != null) {
executeButtonDisabled.bind(m1.statusProperty().isNotEqualTo(Mission.Status.CREATED));
}else {
executeButtonDisabled.unbind();
executeButtonDisabled.set(false);
}
});
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