每天在特定时间将项目添加到房间数据库

Question

我需要代码才能在每天上午 12 点将项目添加到 Room Database。我尝试了很多方法，例如WorkManager和AlarmManager，但都没有达到这个目标

Answer 1

这是我在评论中提到的实现：

public class MainActivity extends AppCompatActivity {
    private static final String PREF_PAUSE_TIME_KEY = "exit_time";

    private static final Long MILLIS_IN_DAY = 86400000L;

    private static final int TRIGGER_HOUR = 12;
    private static final int TRIGGER_MIN = 0;
    private static final int TRIGGER_SEC = 0;

    private final Handler handler = new Handler();
    private SharedPreferences prefs;

    private final Calendar calendar = Calendar.getInstance();

    private final Runnable addItemRunnable = new Runnable() {
        @Override
        public void run() {
            handler.postDelayed(addItemRunnable, MILLIS_IN_DAY);
            addItem();
        }
    };

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //...

        prefs = PreferenceManager.getDefaultSharedPreferences(this);
    }

    @Override
    protected void onResume() {
        super.onResume();

        // Add missing events since onPause.
        long resumeTime = System.currentTimeMillis();
        long pauseTime = prefs.getLong(PREF_PAUSE_TIME_KEY, resumeTime);

        // Set calendar to trigger time on the day the app was paused.
        calendar.setTimeInMillis(pauseTime);
        calendar.set(Calendar.HOUR_OF_DAY, TRIGGER_HOUR);
        calendar.set(Calendar.MINUTE, TRIGGER_MIN);
        calendar.set(Calendar.SECOND, TRIGGER_SEC);

        long time;
        while (true) {
            // If calendar time is during the time that app was on pause, add item.
            time = calendar.getTimeInMillis();
            if (time > resumeTime) {
                // Past current time, all items were added.
                break;
            } else if (time >= pauseTime) {
                // This time happened when app was on pause, add item.
                addItem();
            }

            // Set calendar time to same hour on next day.
            calendar.add(Calendar.DATE, 1);
        }

        // Set handler to add item on trigger time.
        handler.postDelayed(addItemRunnable, time - resumeTime);
    }

    @Override
    protected void onPause() {
        super.onPause();

        // Save pause time so items can be added on resume.
        prefs.edit().putLong(PREF_PAUSE_TIME_KEY, System.currentTimeMillis()).apply();

        // Cancel handler callback to add item.
        handler.removeCallbacks(addItemRunnable);
    }

    private void addItem() {
        // Add item to database and RecyclerView.
    }
}

• 调用onPause 时，当前时间保存在首选项中。
• 当调用onResume 时，程序会添加在未打开应用时应添加的所有项目。
• 打开应用后，程序会使用Handler 在特定时间发布任务。

您可以将代码移动到您想要的任何地方，最有可能在您的存储库或视图模型中（如果有的话）。对于计时器，您可以将 RxJava 用于应用内计时器或其他任何东西。

如果用户将时间更改为提前几天，添加的项目将不会被删除。如果用户随后将其设置为正常，则某些天的项目将被复制。您可以通过仅保存onPause 中的时间（如果它大于上次保存的时间）来防止这种情况发生。