如何从房间数据库中返回单个 object？

Question

As this document tells:

So I've returned a object TaskStat from the database(all tables in database are created successfully). My Dao is:

Dao.class

    @Query("SELECT * FROM task_statistics WHERE owner_ID = :ownerId")
    TaskStat getTaskStatOf(long ownerId);

Then I've called the getTaskStaOf() method from Repository class and further from ViewModel class . Here is the code for Repository & ViewModel:

Repository

public TaskStat getTaskStatOf(Task task) {
        return taskDao.getTaskStatOf(task.getTaskId());
    }

ViewModel.class

if (task.getProgress() == task.getMaxProgress()) {
                TaskStat taskStat = taskRepository.getTaskStatOf(task);
                taskStat.setStatus(true);
                taskRepository.updateStat(taskStat);
            }

But when I reach the first line of if() condition in ViewModel the app crushes.. Log says:

at androidx.room.RoomDatabase.assertNotMainThread(RoomDatabase.java:267)
        at androidx.room.RoomDatabase.query(RoomDatabase.java:323)
        at androidx.room.util.DBUtil.query(DBUtil.java:83)
        at taskHelper.TaskDao_Impl.getTaskStatOf(TaskDao_Impl.java:276)
        at taskHelper.TaskRepository.getTaskStatOf(TaskRepository.java:86)
        at taskHelper.TaskViewModel.incrementProgress(TaskViewModel.java:46)
        at com.example.mohasaba.MainActivity$2.onItemLongClick(MainActivity.java:71)
        at taskHelper.TaskAdapter$TaskHolder$2.onLongClick(TaskAdapter.java:113)
        at android.view.View.performLongClickInternal(View.java:7205)
        at android.view.View.performLongClick(View.java:7163)
        at android.view.View.performLongClick(View.java:7181)
        at android.view.View$CheckForLongPress.run(View.java:27294)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)

I'm confused where I'm doing wrong? Can you help me?

Answer 1

You can do this. In the ViewModel class change this lines:

if (task.getProgress() == task.getMaxProgress()) {
                TaskStat taskStat = taskRepository.getTaskStatOf(task);
                taskStat.setStatus(true);
                taskRepository.updateStat(taskStat);
            }

to:

if (task.getProgress() == task.getMaxProgress()) {
                    Thread thread = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            TaskStat taskStat = taskRepository.getTaskStatOf(task);
                            taskStat.setStatus(true);
                            taskRepository.updateStat(taskStat);
                        }
                    });
                    thread.start();
                }

Hope this will work.