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我正在创建一个应用程序，用户可以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：无法在未调用 Looper.prepare() 的线程内创建处理程序

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) 

错误在这里抛出：

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'
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1 回答 1

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

在 Worker Class 中，您可以尝试声明一个附加到 Main Thread 的 Handler ：

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

然后使用 Handler 的 post() 方法运行你的剪贴板代码

于 2019-04-07T09:31:38.770 回答