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public interface Continuation
<TResult, TContinuationResult>
A function that is called to continue execution after completion of a Task
.
Summary
Public methods
abstract TContinuationResult then
(@ NonNull
Task
<TResult> task)
Returns the result of applying this Continuation to task
.
To propagate failure from the completed Task call getResult
and allow the RuntimeExecutionException
to propagate. The RuntimeExecutionException will be unwrapped such that the Task returned by continueWith
or continueWithTask
fails with the original exception.
To suppress specific failures call getResult
and catch the exception types of interest:
task
.
continueWith
(
new
Continuation<String
,
String
> ()
{
@Override
public
String
then
(
Task<String>
task
)
{
try
{
return
task
.
getResult
(
IOException
.
class
);
}
catch
(
FileNotFoundException
e
)
{
return
"Not found"
;
}
catch
(
IOException
e
)
{
return
"Read failed"
;
}
}
}
To suppress all failures guard any calls to getResult
with isSuccessful
:
task
.
continueWith
(
new
Continuation<String
,
String
> ()
{
@Override
public
String
then
(
Task<String>
task
)
{
if
(
task
.
isSuccessful
())
{
return
task
.
getResult
();
}
else
{
return
DEFAULT_VALUE
;
}
}
}
Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.0 License
, and code samples are licensed under the Apache 2.0 License
. For details, see the Google Developers Site Policies
. Java is a registered trademark of Oracle and/or its affiliates.
Last updated 2024-10-31 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2024-10-31 UTC."],[[["\u003cp\u003e\u003ccode\u003eContinuation\u003c/code\u003e is an interface used to define a function for continuing execution after a \u003ccode\u003eTask\u003c/code\u003e completes.\u003c/p\u003e\n"],["\u003cp\u003eIt provides a \u003ccode\u003ethen\u003c/code\u003e method that takes the completed \u003ccode\u003eTask\u003c/code\u003e as input and returns the result of the continuation.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003ethen\u003c/code\u003e method can handle success and failure states of the preceding \u003ccode\u003eTask\u003c/code\u003e and define the subsequent behavior.\u003c/p\u003e\n"],["\u003cp\u003eYou can propagate, suppress specific, or suppress all failures from the preceding \u003ccode\u003eTask\u003c/code\u003e using methods like \u003ccode\u003egetResult()\u003c/code\u003e and \u003ccode\u003eisSuccessful()\u003c/code\u003e.\u003c/p\u003e\n"]]],["The `Continuation` interface is a function for post-`Task` execution. It uses a `then` method to apply the continuation to a completed `Task`. The `then` method can return a result of `TContinuationResult` type. Failures from the completed Task can be propagated through `getResult`, or specific exceptions handled by using `getResult` with the exception class or suppress all errors with `isSuccessful`. The `then` method accepts a non-null completed Task as a parameter and may throw an exception.\n"],null,["# Continuation\n============\n\n[Kotlin](/android/reference/kotlin/com/google/android/gms/tasks/Continuation \"View this page in Kotlin\") \\|Java \n\n\n```\npublic interface Continuation\u003cTResult, TContinuationResult\u003e\n```\n\n\u003cbr /\u003e\n\n*** ** * ** ***\n\nA function that is called to continue execution after completion of a [Task](/android/reference/com/google/android/gms/tasks/Task). \n\n| Parameters |\n|-------------------------|--------------------------------|\n| `\u003cTResult\u003e` | the Task's result type |\n| `\u003cTContinuationResult\u003e` | the Continuation's result type |\n\n| See also |\n|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---|\n| [continueWith](/android/reference/com/google/android/gms/tasks/Task#continueWith(com.google.android.gms.tasks.Continuation\u003cTResult,TContinuationResult\u003e)) | |\n| [continueWithTask](/android/reference/com/google/android/gms/tasks/Task#continueWithTask(com.google.android.gms.tasks.Continuation\u003cTResult,com.google.android.gms.tasks.Task\u003cTContinuationResult\u003e\u003e)) | |\n\nSummary\n-------\n\n| ### Public methods |\n|--------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| `abstract TContinuationResult` | [then](/android/reference/com/google/android/gms/tasks/Continuation#then(com.google.android.gms.tasks.Task\u003cTResult\u003e))`(@`[NonNull](https://developer.android.com/reference/androidx/annotation/NonNull.html)` `[Task](/android/reference/com/google/android/gms/tasks/Task)`\u003cTResult\u003e task)` Returns the result of applying this Continuation to `task`. |\n\nPublic methods\n--------------\n\n### then\n\n```\nabstract TContinuationResult then(@NonNull Task\u003cTResult\u003e task)\n```\n\nReturns the result of applying this Continuation to `task`.\n\nTo propagate failure from the completed Task call [getResult](/android/reference/com/google/android/gms/tasks/Task#getResult()) and allow the [RuntimeExecutionException](/android/reference/com/google/android/gms/tasks/RuntimeExecutionException) to propagate. The RuntimeExecutionException will be unwrapped such that the Task returned by [continueWith](/android/reference/com/google/android/gms/tasks/Task#continueWith(com.google.android.gms.tasks.Continuation\u003cTResult,TContinuationResult\u003e)) or [continueWithTask](/android/reference/com/google/android/gms/tasks/Task#continueWithTask(com.google.android.gms.tasks.Continuation\u003cTResult,com.google.android.gms.tasks.Task\u003cTContinuationResult\u003e\u003e)) fails with the original exception.\n\nTo suppress specific failures call [getResult](/android/reference/com/google/android/gms/tasks/Task#getResult(java.lang.Class\u003cX\u003e)) and catch the exception types of interest: \n\n```transact-sql\ntask.continueWith(new Continuation\u003cString, String\u003e() {\n @Override\n public String then(Task\u003cString\u003e task) {\n try {\n return task.getResult(IOException.class);\n } catch (FileNotFoundException e) {\n return \"Not found\";\n } catch (IOException e) {\n return \"Read failed\";\n }\n }\n}\n```\n\nTo suppress all failures guard any calls to [getResult](/android/reference/com/google/android/gms/tasks/Task#getResult()) with [isSuccessful](/android/reference/com/google/android/gms/tasks/Task#isSuccessful()): \n\n```transact-sql\ntask.continueWith(new Continuation\u003cString, String\u003e() {\n @Override\n public String then(Task\u003cString\u003e task) {\n if (task.isSuccessful()) {\n return task.getResult();\n } else {\n return DEFAULT_VALUE;\n }\n }\n}\n``` \n\n| Parameters |\n|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------|\n| `@`[NonNull](https://developer.android.com/reference/androidx/annotation/NonNull.html)` `[Task](/android/reference/com/google/android/gms/tasks/Task)`\u003cTResult\u003e task` | the completed Task. Never null |\n\n| Throws |\n|-----------------------------------------------------------------------------------------|------------------------------------|\n| [java.lang.Exception](https://developer.android.com/reference/java/lang/Exception.html) | if the result couldn't be produced |"]]
