ClipboardManager 抛出以下错误：Can't create handler inside thread that has not called Looper.prepare() usin

Posted 2023-04-18

【中文标题】ClipboardManager 抛出以下错误：Can\'t create handler inside thread that has not called Looper.prepare() using WorkManager

【英文标题】：ClipboardManager throws the following error: Can't create handler inside thread that has not called Looper.prepare() using WorkManagerClipboardManager 抛出以下错误：Can't create handler inside thread that has not called Looper.prepare() using WorkManager

【发布时间】：2019-08-28 15:08:14

【问题描述】：

我正在创建一个应用程序，用户可以在其中将文本复制到剪贴板 30 秒。 30 秒后需要从剪贴板中删除文本，即使应用程序已关闭 在我的主要活动中，我有以下代码：

OneTimeWorkRequest worker = new OneTimeWorkRequest.Builder(clipboardWorker.class)
                .setInitialDelay(30, TimeUnit.SECONDS).build();
        WorkManager.getInstance().enqueue(worker);

clipboardWorker 如下所示：

public class clipboardWorker extends Worker 
    private static final String TAG = "clipboardWorker";

    public clipboardWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) 
        super(context, workerParams);
    

    @NonNull
    @Override
    public Result doWork() 

        ClipboardManager clipboardManager = (ClipboardManager) getApplicationContext().getSystemService(Context.CLIPBOARD_SERVICE);
        ClipData clip = ClipData.newPlainText("clp", "");
        clipboardManager.setPrimaryClip(clip);

        return Result.success();
    

这适用于 android 版本 28，但在 27 上会引发以下错误：

原因：java.lang.RuntimeException: Can't create handler inside the thread that has not called Looper.prepare()

这是堆栈跟踪：

2019-04-07 11:41:15.948 18924-18944/com.example.clipboard E/WM-WorkerWrapper: Work [ id=fa06342b-0130-4562-b323-5871ea0e67fb, tags= com.example.clipboard.clipboardWorker  ] failed because it threw an exception/error
    java.util.concurrent.ExecutionException: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
        at androidx.work.impl.utils.futures.AbstractFuture.getDoneValue(AbstractFuture.java:516)
        at androidx.work.impl.utils.futures.AbstractFuture.get(AbstractFuture.java:475)
        at androidx.work.impl.WorkerWrapper$2.run(WorkerWrapper.java:289)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
        at android.os.Handler.<init>(Handler.java:204)
        at android.os.Handler.<init>(Handler.java:118)
        at android.content.ClipboardManager$2.<init>(ClipboardManager.java:62)
        at android.content.ClipboardManager.<init>(ClipboardManager.java:62)
        at android.app.SystemServiceRegistry$11.createService(SystemServiceRegistry.java:254)
        at android.app.SystemServiceRegistry$11.createService(SystemServiceRegistry.java:252)
        at android.app.SystemServiceRegistry$CachedServiceFetcher.getService(SystemServiceRegistry.java:962)
        at android.app.SystemServiceRegistry.getSystemService(SystemServiceRegistry.java:914)
        at android.app.ContextImpl.getSystemService(ContextImpl.java:1667)
        at android.content.ContextWrapper.getSystemService(ContextWrapper.java:714)
        at com.example.clipboard.clipboardWorker.doWork(clipboardWorker.java:26)
        at androidx.work.Worker$1.run(Worker.java:85)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) 
        at java.lang.Thread.run(Thread.java:764) 

这里抛出错误：

ClipboardManager clipboardManager = (ClipboardManager) getApplicationContext().getSystemService(Context.CLIPBOARD_SERVICE);

以下是 gradle 插件：

    implementation 'androidx.appcompat:appcompat:1.0.2'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
    implementation 'com.google.android.material:material:1.0.0'
    implementation 'androidx.work:work-runtime:2.0.0'

【问题讨论】：

嗯，是的，你是对的。在 API 级别 28 之前，ClipboardManager 在字段初始化程序中实例化 Handler，这就是当您尝试在 doWork() 中获取该服务时抛出的原因。从 28 日起，它通过其构造函数传递了一个 Handler。尝试将clipboardManager 设为一个字段——例如private ClipboardManager clipboardManager;——并在super 调用之后进入clipboardWorker 的构造函数——clipboardManager = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE);。

我的意思是，像这样：drive.google.com/file/d/1Rh6nH4AzyEI_2f1rhmauwHBKWbrog2c2/…。抱歉，我试图在我的评论中缩写一些东西，结果让人困惑。

嗨，迈克，感谢您的回答。我已经像您一样更改了代码，但似乎错误仍然存​​在。

好的，我不确定Workers 是否在主线程上实例化。显然，他们不是。再次检查该链接，然后尝试。

它有效，谢谢。

【参考方案1】：

那是因为 WorkManager Api 的 Worker 类在后台线程上运行，

在 Worker 类中，您可以尝试声明一个附加到主线程的处理程序：

Handler mainThreadHandler = new Handler(Looper.getMainLooper());

然后使用 Handler 的 post() 方法运行你的剪贴板代码