android - Realm 和 RecyclerView Item 排序和自动 ViewPager Fragment 通信

Question

一段时间以来，我一直面临一些无法解决的问题。所以我指的是社区中的 Realm 和 RecyclerView 天才。我正在处理一个 ToDo-List，它在 2 天后将已完成的任务设置回 ToDo-List。该应用程序使用带有两个选项卡的 ViewPager:“TODO”和“DONE”。

<强>1。 RecyclerView

1.1。我希望 fragment 1 中完成的任务在 2 天后自动发送回 fragment 0。问题:如果计数器为 0(或更低)，则项目将被发送到 fragment 0。如果我删除下一行中的项目，我会收到异常错误:"java.lang.IllegalStateException: Cannot call this method while RecyclerView is computing a layout or scrolling"所以我把删除函数放到一个处理程序中。然后，只有当 ONE 被发回时，它才能正常工作。如果许多项目同时被发回，应用程序就会崩溃。当我重新打开应用程序时，一切正常，因为它已成功保存在 Realm 中，但一个项目总是保存两次。问题出在哪里(在 DoneAdapter.java 中)？

<强>2。 Realm

2.1。当我将一个项目添加到 RecyclerView(并同时添加到 Realm)时，该项目被添加到底部。但我想在位置 0 添加每个新项目。(我知道如何使用 ArrayList 实现此目的，但我希望在重新打开应用程序时存储和显示这些项目，所以我使用的是 Realm DB。)您对实现这一目标有什么建议吗？

2.2。是否可以稍后在 onLongClickListener 上实现用于拖放项目并重新排列 Realm 的位置？(我想用这个 https://www.youtube.com/watch?v=tNgevYpyA9E )

2.3。我想在添加和检查项目时添加一些漂亮的动画。 Realm 不支持 mRecyclerView.setItemAnimator(...); 但我听说可以通过添加 mAdapter.setHasStableIds(true); 来实现。不幸的是，它抛出一个异常:java.lang.IllegalStateException: Cannot change whether this adapter has stable IDs while the adapter has registered observers.(你可以在我下面的代码中看到这一点)您对此有什么解决方案吗？

(可选 1.4。你能推荐我可以与 Realm 同步的任何在线数据库(例如 Firebase)吗？或者更一般地说:是否可以将在线数据库与 Realm 同步？你知道任何教程(Udemy，YouTube)吗？设置此同步过程？)

最后:我想在每个午夜用后台服务更新数据库，因此已完成部分中的计数器会自动更新。有谁也知道该怎么做？也许使用 protected void onHandleIntent(Intent intent)？您是否也知道在 Debug模式下是否有模拟流逝时间的选项？

代码如下:

主 Activity .java

public class MainActivity extends AppCompatActivity implements ToOtherFragmentCommunicator {


private ViewPagerAdapter mViewPagerAdapter;
private ViewPager mViewPager;
private static final int DONE = 1;
private static final int TODO = 0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);


    mViewPagerAdapter = new ViewPagerAdapter(getSupportFragmentManager());
    mViewPager = (ViewPager) findViewById(R.id.container);
    mViewPager.setAdapter(mViewPagerAdapter);

    TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
    tabLayout.setupWithViewPager(mViewPager);
    tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
        @Override
        public void onTabSelected(TabLayout.Tab tab) {
            mViewPager.setCurrentItem(tab.getPosition());
        }

        @Override
        public void onTabUnselected(TabLayout.Tab tab) {

        }

        @Override
        public void onTabReselected(TabLayout.Tab tab) {

        }
    });

    RealmConfiguration configuration = new RealmConfiguration.Builder(this).build();
    Realm.setDefaultConfiguration(configuration);
}

@Override
public void itemToOtherFragment(String data, int fragment) {
    if (DONE == fragment) {
        Done done = (Done) mViewPagerAdapter.getItem(fragment);
        done.createDoneItem(data);
    } else if (TODO == fragment) {
        ToDo toDo = (ToDo) mViewPagerAdapter.getItem(fragment);
        toDo.createToDoItem(data);
    }
}
}

ToDo.java

public class ToDo extends Fragment {

private RecyclerView mRecyclerView;
private ToDoAdapter mAdapter;
private EditText taskInput;
private String taskName;
private Realm mRealm;
private RealmResults<ListItems> mResults;


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View toDoView = inflater.inflate(R.layout.todo_layout, container, false);

    mRecyclerView = (RecyclerView) toDoView.findViewById(R.id.todo_rv);


    mRealm = Realm.getDefaultInstance();
    mResults = mRealm.where(ListItems.class).equalTo("fragment", 0).findAllAsync();

    setRecyclerView();

    mRecyclerView.setItemAnimator(null);

    //TODO add product to shopping list
    final Handler handler = new Handler();
    taskInput = (EditText) toDoView.findViewById(R.id.task_input);
    taskInput.setOnKeyListener(new View.OnKeyListener() {
        @Override
        public boolean onKey(View v, int keyCode, KeyEvent event) {
            if (taskInput.getText().length() > 0 && (event.getAction() == KeyEvent.ACTION_DOWN) &&
                    (keyCode == KeyEvent.KEYCODE_ENTER)) {
                // Perform action on key press
                taskName = taskInput.getText().toString();

                //Problem 2.1
                //Code for adding item at the top with mRealm?
                mRealm.beginTransaction();
                createToDoItem(taskName);
                mRealm.commitTransaction();


//                    mRecyclerView.scrollToPosition(0);
                taskInput.setText(null);

                handler.postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        taskInput.setFocusableInTouchMode(true);
                        taskInput.setFocusable(true);
                        taskInput.requestFocus();
                    }
                }, 200);

                return true;

            } else if (taskInput.length() == 0 && (event.getAction() == KeyEvent.ACTION_DOWN) &&
                    (keyCode == KeyEvent.KEYCODE_ENTER)) {
                taskInput.clearFocus();
                InputMethodManager imm = (InputMethodManager) getActivity().getSystemService(Context.INPUT_METHOD_SERVICE);
                imm.hideSoftInputFromWindow(taskInput.getWindowToken(), 0);
                return true;
            }

            return false;

        }
    });

    return toDoView;
}


//TODO creates the shopping list item in DB
public void createToDoItem(String taskName) {

    ListItems item = mRealm.createObject(ListItems.class);

    long now = System.currentTimeMillis();
    item.setAddedTime(now);
    item.setFragment(0);

    item.setTaskName(taskName);

    mRealm.copyToRealmOrUpdate(item);
}

public void setRecyclerView() {
    mRecyclerView.setHasFixedSize(true);
    LinearLayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
    mRecyclerView.setLayoutManager(mLayoutManager);
    mAdapter = new ToDoAdapter(getActivity(), mRealm, mResults);
    mRecyclerView.setAdapter(mAdapter);

    //Problem 2.3.
    //Produces "java.lang.IllegalStateException: Cannot change whether this adapter has stable IDs while the adapter has registered observers."
//        mAdapter.setHasStableIds(true);
}

private RealmChangeListener mChangeListener = new RealmChangeListener() {
    @Override
    public void onChange() {
        mAdapter.updateItems(mResults);
    }
};

@Override
public void onStart() {
    super.onStart();
    mResults.addChangeListener(mChangeListener);
}

@Override
public void onStop() {
    super.onStop();
    mResults.removeChangeListener(mChangeListener);
}


}

ToDoAdapter.java

public class ToDoAdapter extends RecyclerView.Adapter<ListItemsViewHolder> {

private Context mContext;
private Realm mRealm;
private RealmResults<ListItems> mResults;
private int focusedItem = 0;
ToOtherFragmentCommunicator comm;

ToDoAdapter(Context context, Realm realm, RealmResults<ListItems> mResults) {
    this.mContext = context;
    this.mRealm = realm;
    updateItems(mResults);
}

public void updateItems(RealmResults<ListItems> mResults) {
    this.mResults = mResults;
    notifyDataSetChanged();
}

//Problem 2.3.
//needed for mAdapter.setHasStableIds(true); in ToDo.java
//    @Override
//    public long getItemId(int position) {
//        if (position < mResults.size()) {
//            return mResults.get(position).getAddedTime();
//        } else {
//            return RecyclerView.NO_ID;
//        }
//    }

@Override
public ListItemsViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.todo_item, parent, false);
    comm = (ToOtherFragmentCommunicator) mContext;
    return new ListItemsViewHolder(v);

}

@Override
public void onBindViewHolder(final ListItemsViewHolder holder, final int position) {
    final ListItems items = mResults.get(position);


    holder.taskName.setText(items.getTaskName());

    holder.itemView.setSelected(focusedItem == position);
    holder.getLayoutPosition();

    holder.itemCheckbox.setOnCheckedChangeListener(null);
    holder.itemCheckbox.setChecked(items.isSelected());

    holder.itemCheckbox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            mRealm.beginTransaction();
            items.setSelected(isChecked);

            //send item to Done
            comm.itemToOtherFragment(items.getTaskName(), 1);

            removeItem(position);
            mRealm.commitTransaction();

        }
    });


}


@Override
public int getItemCount() {
    return (mResults != null ? mResults.size() : 0);
}

private void removeItem(int position) {
    mResults.get(position).removeFromRealm();
    notifyDataSetChanged();
}

}

完成.java

public class Done extends Fragment {

private RecyclerView mRecyclerView;
private DoneAdapter mAdapter;
private Calendar calendar = Calendar.getInstance();
private Date date = new Date();
private SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd.MM.yyyy");
private Realm mRealm;
private RealmResults<ListItems> mResults;


@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View doneView = inflater.inflate(R.layout.done_layout, container, false);

    mRecyclerView = (RecyclerView) doneView.findViewById(R.id.done_rv);

    mRealm = Realm.getDefaultInstance();
    mResults = mRealm.where(ListItems.class).equalTo("fragment", 1).findAllAsync();

    setRecyclerView();
    mRecyclerView.setItemAnimator(null);


    return doneView;
}


//TODO creates the fridge item in DB
public void createDoneItem(String taskName) {
    TimeZone.getDefault();


    ListItems item = mRealm.createObject(ListItems.class);

    long now = System.currentTimeMillis();
    item.setAddedTime(now);
    item.setFragment(1);

    item.setTaskName(taskName);
    item.setInputDate(simpleDateFormat.format(calendar.getTime()));

    calendar.add(Calendar.DATE, 2);
    item.setRenewDate(simpleDateFormat.format(calendar.getTime()));


    //reset time to current date after adding days
    calendar.setTime(date);

    item.getRenewDate();

    mRealm.copyToRealmOrUpdate(item);
}


public void setRecyclerView() {
    mRecyclerView.setHasFixedSize(true);
    LinearLayoutManager mLayoutManager = new LinearLayoutManager(getActivity());
    mRecyclerView.setLayoutManager(mLayoutManager);
    mAdapter = new DoneAdapter(getActivity(), mRealm, mResults, Done.this);
    mRecyclerView.setAdapter(mAdapter);
}


private RealmChangeListener mChangeListener = new RealmChangeListener() {
    @Override
    public void onChange() {
        mAdapter.updateItems(mResults);
    }
};

@Override
public void onStart() {
    super.onStart();
    mResults.addChangeListener(mChangeListener);
}

@Override
public void onStop() {
    super.onStop();
    mResults.removeChangeListener(mChangeListener);
}
}

完成适配器.java

public class DoneAdapter extends RecyclerView.Adapter<ListItemsViewHolder> {

private Context mContext;
private Done done;
private Realm mRealm;
private RealmResults<ListItems> mResults;
private int focusedItem = 0;
protected ToOtherFragmentCommunicator comm;


DoneAdapter(Context context, Realm realm, RealmResults<ListItems> results, Done done) {
    this.mContext = context;
    this.mRealm = realm;
    this.done = done;

    updateItems(results);
}

public void updateItems(RealmResults<ListItems> mResults) {
    this.mResults = mResults;
    notifyDataSetChanged();
}

@Override
public ListItemsViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.done_item, parent, false);
    comm = (ToOtherFragmentCommunicator) mContext;
    return new ListItemsViewHolder(v);
}

@TargetApi(Build.VERSION_CODES.JELLY_BEAN)
@Override
public void onBindViewHolder(final ListItemsViewHolder holder, final int position) {
    final ListItems items = mResults.get(position);

    holder.taskName.setText(items.getTaskName());

    try {
        if (items.getRenewCounter() == 1) {
            holder.renewCounter.setText(mContext.getString(R.string.show_days_till_renew, items.getRenewCounter(), mContext.getString(R.string.day)));
        } else {
            holder.renewCounter.setText(mContext.getString(R.string.show_days_till_renew, items.getRenewCounter(), mContext.getString(R.string.days)));
        }

        holder.renewCounter.setTextColor(ContextCompat.getColor(mContext, R.color.colorAccent));
        if (items.getRenewCounter() <= 0) {
            mRealm.beginTransaction();

            //Problem 1.1.
            //send item back to todo list
            comm.itemToOtherFragment(items.getTaskName(), 0);
            // Produces "java.lang.IllegalStateException: Cannot call this method while RecyclerView is computing a layout or scrolling" if there is no Handler
            Handler handler = new Handler();
            final Runnable r = new Runnable() {
                public void run() {

                    mRealm.beginTransaction();
                    removeItem(position);
                    mRealm.commitTransaction();

                }
            };
            handler.post(r);
            mRealm.commitTransaction();
        }


    } catch (ParseException e) {
        e.printStackTrace();
    }


    holder.itemView.setSelected(focusedItem == position);
    holder.getLayoutPosition();

}


@Override
public int getItemCount() {
    return (mResults != null ? mResults.size() : 0);
}

private void removeItem(int position) {
    mResults.get(position).removeFromRealm();
    notifyDataSetChanged();
}


}

列表项.java

public class ListItems extends RealmObject {

public ListItems(long addedTime, String taskName, String inputDate, String renewDate, int fragment) {
    this.addedTime = addedTime;
    this.taskName = taskName;
    this.inputDate = inputDate;
    this.renewDate = renewDate;
    this.fragment = fragment;
}

@PrimaryKey
private long addedTime;
private int fragment;
@Ignore
private long renewCounter;
private String taskName, inputDate, renewDate;
private boolean selected;

public ListItems() {
}

public long getAddedTime() {
    return addedTime;
}

public void setAddedTime(long addedTime) {
    this.addedTime = addedTime;
}

public int getFragment() {
    return fragment;
}

public void setFragment(int fragment) {
    this.fragment = fragment;
}

public String getTaskName() {
    return taskName;
}

public void setTaskName(String taskName) {
    this.taskName = taskName;
}

public String getInputDate() {
    return inputDate;
}

public void setInputDate(String inputDate) {
    this.inputDate = inputDate;
}

public String getRenewDate() {
    return renewDate;
}

public void setRenewDate(String renewDate) {
    this.renewDate = renewDate;
}

public boolean isSelected() {
    return selected;
}

public void setSelected(boolean selected) {
    this.selected = selected;
}

public long getRenewCounter() throws ParseException {
    TimeZone.getDefault();

    SimpleDateFormat dateFormat = new SimpleDateFormat("dd.MM.yyyy");
    Date todayDate = new Date();
    Date exDate = dateFormat.parse(renewDate);

    this.renewCounter = daysBetween(todayDate, exDate);
    return renewCounter;

}

private static long daysBetween(Date startDate, Date endDate) {
    Calendar sDate = getDatePart(startDate);
    Calendar eDate = getDatePart(endDate);

    long daysBetween = 0;
    while (sDate.before(eDate)) {
        sDate.add(Calendar.DAY_OF_MONTH, 1);
        daysBetween++;
    }

    while (eDate.before(sDate)) {
        eDate.add(Calendar.DAY_OF_MONTH, 1);
        daysBetween--;
    }

    return daysBetween;
}

private static Calendar getDatePart(Date date) {
    Calendar cal = Calendar.getInstance();       // get calendar instance
    cal.setTime(date);
    cal.set(Calendar.HOUR_OF_DAY, 0);            // set hour to midnight
    cal.set(Calendar.MINUTE, 0);                 // set minute in hour
    cal.set(Calendar.SECOND, 0);                 // set second in minute
    cal.set(Calendar.MILLISECOND, 0);            // set millisecond in second

    return cal;                                  // return the date part
}

}

这是应用程序外观的屏幕截图: DailyTaskRepeater

就是这样!如果有人可以帮助我解决所有这些问题(尤其是问题 1.1!)，这对我来说意义重大。

谢谢!

Answer 1

目前 Realm 支持的做法是添加一个索引(例如时间戳)并反向排序您的列表，以使最新项目位于顶部并实现您正在寻求的重新排列效果。

请考虑引用 an adapter example在官方存储库中提供。