android - 无法在后台线程上调用观察

Question

我刚升级到AndroidX在完成我的所有要求之后。我让后台线程不运行但出现此错误。

private void getContactsList() {
    Task.callInBackground((Callable<Void>) () -> { 
     mainActivityViewModel.geContacts(contactListRequest).observe(MainActivity.this, new Observer<ContactListResponse>() {
            @Override
            public void onChanged(@Nullable ContactListResponse contactListResponse) {
                if(contactListRequest != null){
                    System.out.println("Successful");
                }
            }
        });
        return null;
    }).continueWith((Continuation<Void, Void>) task -> {
        if (task.isFaulted()) {
            Log.e(TAG, "find failed", task.getError());
        }
        return null;
    });
}



java.lang.IllegalStateException: Cannot invoke observe on a background thread
    at androidx.lifecycle.LiveData.assertMainThread(LiveData.java:443)
    at androidx.lifecycle.LiveData.observe(LiveData.java:171)
    at com.qucoon.rubies.MainActivity.lambda$getContactsList$12(MainActivity.java:887)
    at com.qucoon.rubies.-$$Lambda$MainActivity$qPAxeGqyWT-wT3M7e8stM1rX2gQ.call(lambda)
    at bolts.Task$4.run(Task.java:357)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
    at java.lang.Thread.run(Thread.java:818)

Answer 1

您需要在主线程中执行您的代码尝试调用 getContactsList()通过处理程序:

Handler handler = new Handler(Looper.getMainLooper());
    handler.post(new Runnable() {
        public void run() {
            getContactsList()
        }
    });