EditText 中的双向数据绑定

Question

我有这个对象

ObservableInt someNumber;

public ObservableInt getSomeNumber()
{
    return someNumber;
}

public void setSomeNumber(ObservableInt number)
{
    this.someNumber = number;
}

而我的 AppCompatEditText 在 xml 代码中是这样的：

<android.support.v7.widget.AppCompatEditText
        android:layout_width="0dp"
        android:layout_height="@dimen/agro_item_height"
        android:layout_weight="1"
        android:inputType="numberDecimal"
        android:text="@={String.valueOf(myObject.someNumber)}"
        android:gravity="center_horizontal"/>

我遇到了这个错误：

Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
java.lang.RuntimeException: failure, see logs for details.
cannot generate view binders java.lang.NullPointerException
at android.databinding.tool.expr.MethodCallExpr.generateCode(MethodCallExpr.java:69)
at android.databinding.tool.expr.Expr.toFullCode(Expr.java:745)
at android.databinding.tool.expr.Expr.assertIsInvertible(Expr.java:767)
at android.databinding.tool.BindingTarget.addInverseBinding(BindingTarget.java:68)
at android.databinding.tool.LayoutBinder.<init>(LayoutBinder.java:228)
at android.databinding.tool.DataBinder.<init>(DataBinder.java:52)
at android.databinding.tool.CompilerChef.ensureDataBinder(CompilerChef.java:83)
at android.databinding.tool.CompilerChef.sealModels(CompilerChef.java:168)
at android.databinding.annotationprocessor.ProcessExpressions.writeResourceBundle(ProcessExpressions.java:149)
at android.databinding.annotationprocessor.ProcessExpressions.onHandleStep(ProcessExpressions.java:82)
at android.databinding.annotationprocessor.ProcessDataBinding$ProcessingStep.runStep(ProcessDataBinding.java:154)
at android.databinding.annotationprocessor.ProcessDataBinding$ProcessingStep.access$000(ProcessDataBinding.java:139)
at android.databinding.annotationprocessor.ProcessDataBinding.process(ProcessDataBinding.java:66)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.callProcessor(JavacProcessingEnvironment.java:794)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.discoverAndRunProcs(JavacProcessingEnvironment.java:705)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.access$1800(JavacProcessingEnvironment.java:91)
at com.sun.tools.javac.processing.JavacProcessingEnvironment$Round.run(JavacProcessingEnvironment.java:1035)
at com.sun.tools.javac.processing.JavacProcessingEnvironment.doProcessing(JavacProcessingEnvironment.java:1176)
at com.sun.tools.javac.main.JavaCompiler.processAnnotations(JavaCompiler.java:1170)
at com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:856)
at com.sun.tools.javac.main.Main.compile(Main.java:523)
at com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:129)
at com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:138)
at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:46)
at org.gradle.api.internal.tasks.compile.JdkJavaCompiler.execute(JdkJavaCompiler.java:33)
at org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.delegateAndHandleErrors(NormalizingJavaCompiler.java:104)
at org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.execute(NormalizingJavaCompiler.java:53)
at org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler.execute(NormalizingJavaCompiler.java:38)
at org.gradle.api.internal.tasks.compile.CleaningJavaCompilerSupport.execute(CleaningJavaCompilerSupport.java:35)
at org.gradle.api.internal.tasks.compile.CleaningJavaCompilerSupport.execute(CleaningJavaCompilerSupport.java:25)
at org.gradle.api.tasks.compile.JavaCompile.performCompilation(JavaCompile.java:163)
at org.gradle.api.tasks.compile.JavaCompile.compile(JavaCompile.java:145)
at org.gradle.api.tasks.compile.JavaCompile.compile(JavaCompile.java:93)
at com.android.build.gradle.tasks.factory.AndroidJavaCompile.compile(AndroidJavaCompile.java:49)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:75)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$IncrementalTaskAction.doExecute(AnnotationProcessingTaskFactory.java:245)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:221)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$IncrementalTaskAction.execute(AnnotationProcessingTaskFactory.java:232)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:210)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61)
at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46)
at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:35)
at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:66)
at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:52)
at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:53)
at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:203)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:185)
at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:66)
at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:50)
at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:25)
at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:110)
at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:37)
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
at org.gradle.execution.DefaultBuildExecuter.access$000(DefaultBuildExecuter.java:23)
at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:43)
at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:30)
at org.gradle.initialization.DefaultGradleLauncher$4.run(DefaultGradleLauncher.java:153)
at org.gradle.internal.Factories$1.create(Factories.java:22)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:91)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:53)
at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:150)
at org.gradle.initialization.DefaultGradleLauncher.access$200(DefaultGradleLauncher.java:32)
at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:98)
at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:92)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:91)
at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:63)
at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:92)
at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:83)
at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:99)
at org.gradle.tooling.internal.provider.runner.BuildModelActionRunner.run(BuildModelActionRunner.java:46)
at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
at org.gradle.tooling.internal.provider.runner.SubscribableBuildActionRunner.run(SubscribableBuildActionRunner.java:58)
at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:48)
at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:30)
at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:81)
at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:46)
at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:52)
at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:37)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:26)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfSingleUsedDaemon.java:34)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:74)
at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:72)
at org.gradle.util.Swapper.swap(Swapper.java:38)
at org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute(ForwardClientInput.java:72)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.health.DaemonHealthTracker.execute(DaemonHealthTracker.java:47)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:60)
at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:72)
at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.health.HintGCAfterBuild.execute(HintGCAfterBuild.java:41)
at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:50)
at org.gradle.launcher.daemon.server.DaemonStateCoordinator$1.run(DaemonStateCoordinator.java:237)
at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)

我已经试过了

android:text="@={myObject.someNumber}"

但我遇到了这个错误：

Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
java.lang.RuntimeException: Found data binding errors.
****/ data binding error ****msg:Cannot find the getter for attribute     'android:text' with value type int on android.support.v7.widget.AppCompatEditText.
file:C:\Users\Moviit\AndroidStudioProjects\pbbchile-android\app\src\main\res\layout\row_agro_tab.xml
loc:51:8 - 60:48
****\ data binding error ****

任何人都有如何做到这一点的例子？

Answer 1

您可以在 EditText 上进行双向绑定。

使用单向数据绑定，您可以在属性上设置值并 设置一个对该属性的变化做出反应的监听器

变量为字符串类型

<android.support.v7.widget.AppCompatEditText
    ...
    android:text="@={model.someString}"
    />

变量是数字

<android.support.v7.widget.AppCompatEditText
    ...
    android:text="@={`` + model.someNumber}"
    />

``两个后撇号自动绑定

• 在 EditText 上设置时将数字转换为字符串
• 在模型中设置时将字符串文本转换为数字

提示

从documentation 可以看到，双向绑定可以用于多种用途。

1. 复选框、单选按钮、开关、切换按钮

android:checked="@={model.checked}"

1. 无线电组 - android:checkedButton

android:checkedButton="@={model.selectedId}"

1. 评分栏 - android:rating

android:rating="@={model.rating}"

等等

Answer 2

有一个未发表的简单原始转换技巧：

<android.support.v7.widget.AppCompatEditText
    android:layout_width="0dp"
    android:layout_height="@dimen/agro_item_height"
    android:layout_weight="1"
    android:inputType="numberDecimal"
    android:text="@={`` + myObject.someNumber}"
    android:gravity="center_horizontal"/>

我相信它只是在 Android Studio 2.2 中添加的。

Answer 3

我尝试使用@George Mount 提到的自定义设置器（https://medium.com/google-developers/android-data-binding-custom-setters-55a25a7aea47#.vsry4d95w），并受到这个答案的启发（Android two way binding with Integer type causes databinding does not exist）

您仍然可以使用原始代码进行双向绑定。

模型类

public class Age {
    private ObservableInt someNumber;
    private ObservableField<String> someStr;
    public Age() {
        someNumber = new ObservableInt();
        someStr = new ObservableField<>();
    }
    public ObservableInt getSomeNumber() {
        return someNumber;
    }
    public void setSomeNumber(ObservableInt pSomeNumber) {
        someNumber.set(pSomeNumber.get());
    }
    public ObservableField<String> getSomeStr() {
        return someStr;
    }
    public void setSomeStr(ObservableField<String> pSomeStr) {
        someStr.set(pSomeStr.get());
    }
}

属性的自定义setter和getter

@BindingAdapter("android:text")
public static void bindIntegerInText(AppCompatEditText tv, int value) {
    tv.setText(String.valueOf(value));
}
@InverseBindingAdapter(attribute = "android:text")
public static int getIntegerFromBinding(TextView view) {
    return Integer.parseInt(view.getText().toString());
}

活动中的代码

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ActivityMain2Binding binding = DataBindingUtil.setContentView(this, R.layout.activity_main2);
    mAge = new Age();
    mAge.setSomeNumber(new ObservableInt(3));
    mAge.setSomeStr(new ObservableField<>("Test"));
    binding.setAge(mAge);
    binding.btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            mAge.setSomeNumber(new ObservableInt(4));
            mAge.setSomeStr(new ObservableField<>("Hello World"));
        }
    });
}

我用 xml 中的 ObservableInt、Observable、普通字符串资源和绑定字符串资源做了 4 个演示。

<string name="helloworld">Hello World</string>

activity_main3.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"

    >

    <data>

        <variable
            name="age"
            type="example.com.testerapplication.Age"/>
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <android.support.v7.widget.AppCompatEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@={age.someNumber}"/>

        <android.support.v7.widget.AppCompatEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@={age.someStr}"/>

        <android.support.v7.widget.AppCompatEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/helloworld"/>

        <android.support.v7.widget.AppCompatEditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@{@string/helloworld}"/>

        <Button
            android:id="@+id/btn"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Test"
            />
    </LinearLayout>

</layout>

Answer 4

感谢@LongRanger 的绑定适配器，我能够在我的解决方案中取得更多进步，但我不得不对适配器和我的代码进行一些更改。首先，我必须像这样初始化 ObservableInt 成员：

ObservableInt someNumber;

public ObservableInt getSomeNumber()
{
    return someNumber;
}

public void setSomeNumber(ObservableInt number)
{
    this.someNumber = number;
}

其次，我必须将@LongRanger 提供的适配器更改为：

@BindingAdapter("android:text")
public static void bindIntegerInText(AppCompatEditText tv, int value)
{
    tv.setText(String.valueOf(value));    

    // Set the cursor to the end of the text
    tv.setSelection(tv.getText().length());
}

@InverseBindingAdapter(attribute = "android:text")
public static int getIntegerFromBinding(TextView view)
{
    String string = view.getText().toString();

    return string.isEmpty() ? 0 : Integer.parseInt(string);
}

这样我可以避免错误：Invalid int ""，当尝试在 @InverseBindingAdapter 上执行 Integer.parse(...) 时。在此之后，我必须将光标放在带有@BindingAdapter 的 EditText 的末尾，否则光标会一直移动到开头。

Answer 5

@CommonsWare 是对的，你应该使用ObservableField<Str‌​ing> 而不是ObservableInt。如果你真的需要它作为数字，只需解析它Integer.valueOf(stringNumber)。

public ObservableField<Str‌​ing> someNumber;

//and in xml code:

<EditText
        android:layout_width="0dp"
        android:layout_height="@dimen/agro_item_height"
        android:layout_weight="1"
        android:inputType="numberDecimal"
        android:text="@={myObject.someNumber}"
        android:gravity="center_horizontal"/>

EDITED：或者，如上所述，编写自定义 @InverseBindingAdapter

public class MyEditTextBindingAdapters {

    @BindingConversion
    public static String intToStr(Integer value) {
        return value != null ? String.valueOf(value) : "";
    }

    @InverseBindingAdapter(attribute = "android:text")
    public static Integer captureIntValue(EditText view) {
        long value = 0;
        try {
            value = Integer.parseInt(view.getText().toString());
        } catch (NumberFormatException e) {
            e.printStackTrace();
        }
        return value;
    }
}

Answer 6

只需这样做：

android:text="@={user.username}"

完整代码：

 <EditText
            android:id="@+id/username"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="user name"
            android:text="@={user.username}"/>

和用户类

public class User {
public ObservableField<String> username = new ObservableField<>();
public ObservableField<String> password = new ObservableField<>();

public User() {
    this("", "");
}

public User(String username, String password) {
    this.username.set(username);
    this.password.set(password);
}