Two-Way databinding in EditText

Question

I have this object

ObservableInt someNumber;

public ObservableInt getSomeNumber()
{
    return someNumber;
}

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

and my AppCompatEditText is like this in xml code:

<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"/>

I'm having this error:

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)

I already have tried just with

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

but I'm having this error:

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 ****

Anybody has an example of how to do this?

Answer 1

You can do two-way binding on EditText.

Using one-way data binding, you can set a value on an attribute and set a listener that reacts to a change in that attribute

variable is string type

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

variable is number

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

`` two back apostrophe do binding automatically

• convert number to string when setting it on EditText
• convert string text to number when setting in Model

Tip

From documentation you can see, two-way binding can be used for many purpose.

1. CheckBox, RadioButton, Switch, ToggleButton

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

2. RadioGroup - android:checkedButton

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

3. RatingBar - android:rating

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

etc.

Answer 2

There is an unpublished trick for simple primitive conversions:

<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"/>

I believe it was only added in Android Studio 2.2.

Answer 3

Thanks to the binding adapters from @LongRanger I was able to advance a lot more in my solution but I had to make some changes on the adapters and in my code. First of all I had to init the ObservableInt member like this:

ObservableInt someNumber;

public ObservableInt getSomeNumber()
{
    return someNumber;
}

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

Second, I had to change the adapters given by @LongRanger to be like this:

@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);
}

That way I avoid the error: Invalid int "", when trying to do Integer.parse(...) on the @InverseBindingAdapter. After this I had to put the cursor on the end of the EditText with the @BindingAdapter, otherwise the cursor kept moving to the start.