Adding a Crime :: Tapping the back button doesnt update the Crime List but tapping the Hierarchical Up button does it

asett · May 10, 2017, 1:51am

When I tap the + button to add a new crime, the new crime layout shows up. I then type something in the new crime view and then tap the back button and it does not update the Crime List.
However if I tap the Show Subtitle Toolbar Menu option it does show that the new crime is there.

If I repeated the above and instead of tapping the back button I tap the Hierarchical Up button I am taken back to the Crime List showing the newly added crime.

Any idea why this is happening?

Here are some code snippets from my project:

CrimeListFragment.java

package com.bignerdranch.android.criminalintent;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.List;

public class CrimeListFragment extends Fragment {
    private int clickedCrimePosition;
    private static final String CLICKED_CRIME_POSITION_ID = "clicked_crime_position_id";
    private static final String SAVED_SUBTITLE_VISIBLE = "subtitle";

    private static final int REQUEST_CRIME = 1;

    private RecyclerView mCrimeRecyclerView;
    private CrimeAdapter mAdapter;
    private boolean mSubtitleVisible;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }

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

        mCrimeRecyclerView = (RecyclerView) view.findViewById(R.id.crime_recycler_view);
        mCrimeRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));

        if (savedInstanceState != null) {
            clickedCrimePosition = savedInstanceState.getInt(CLICKED_CRIME_POSITION_ID);
            mSubtitleVisible = savedInstanceState.getBoolean(SAVED_SUBTITLE_VISIBLE);
        }

        return view;
    }

    @Override
    public void onResume() {
        super.onResume();
        updateUI();
    }

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        super.onCreateOptionsMenu(menu, inflater);
        inflater.inflate(R.menu.fragment_crime_list, menu);

        MenuItem subtitleItem = menu.findItem(R.id.show_subtitle);
        if (mSubtitleVisible) {
            subtitleItem.setTitle(R.string.hide_subtitle);
        } else {
            subtitleItem.setTitle(R.string.show_subtitle);
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.new_crime:
                Crime crime = new Crime();
                CrimeLab.get(getActivity()).addCrime(crime);
                Intent intent = CrimePagerActivity
                        .newIntent(getActivity(), crime.getID());
                startActivity(intent);
                return true;
            case R.id.show_subtitle:
                mSubtitleVisible = !mSubtitleVisible;
                getActivity().invalidateOptionsMenu();
                updateSubtitle();
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }

    private void updateSubtitle() {
        CrimeLab crimeLab = CrimeLab.get(getActivity());
        int crimeCount = crimeLab.getCrimes().size();
        String subtitle = getString(R.string.subtitle_format, crimeCount);

        if (!mSubtitleVisible) {
            subtitle = null;
        }

        AppCompatActivity activity = (AppCompatActivity) getActivity();
        activity.getSupportActionBar().setSubtitle(subtitle);
    }

    private void updateUI() {
        CrimeLab crimeLab = CrimeLab.get(getActivity());
        List<Crime> crimes = crimeLab.getCrimes();

        if (mAdapter == null) {
            mAdapter = new CrimeAdapter(crimes);
            mCrimeRecyclerView.setAdapter(mAdapter);
        } else {
            mAdapter.notifyItemChanged(clickedCrimePosition);
        }

        updateSubtitle();
    }

    private class CrimeHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        private TextView mTitleTextView;
        private TextView mDateTextView;
        private ImageView mSolvedImageView;
        private Crime mCrime;

        public CrimeHolder(LayoutInflater inflater, ViewGroup parent) {
            super(inflater.inflate(R.layout.list_item_crime, parent, false));
            itemView.setOnClickListener(this);

            mTitleTextView = (TextView) itemView.findViewById(R.id.crime_title);
            mDateTextView = (TextView) itemView.findViewById(R.id.crime_date);
            mSolvedImageView = (ImageView) itemView.findViewById(R.id.crime_solved);
        }

        public void bind(Crime crime) {
            mCrime = crime;
            mTitleTextView.setText(mCrime.getTitle());
            DateFormat dateFormat = new SimpleDateFormat(CrimeFragment.DATE_FORMAT);
            DateFormat timeFormat = new SimpleDateFormat(CrimeFragment.TIME_FORMAT);
            mDateTextView.setText(dateFormat.format(mCrime.getDate()) + " " + timeFormat.format(mCrime.getTime()));
            mSolvedImageView.setVisibility(crime.isSolved() ? View.VISIBLE : View.GONE);
        }

        @Override
        public void onClick(View v) {
            clickedCrimePosition = getAdapterPosition();
            Intent intent = CrimePagerActivity.newIntent(getActivity(), mCrime.getID());
            startActivityForResult(intent, REQUEST_CRIME);
        }
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (requestCode == REQUEST_CRIME) {
            // Handle result
        }
    }

    private class CrimeAdapter extends RecyclerView.Adapter<CrimeHolder> {
        private List<Crime> mCrimes;

        public CrimeAdapter(List<Crime> crimes) {
            mCrimes = crimes;
        }

        @Override
        public CrimeHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
            return new CrimeHolder(layoutInflater, parent);
        }

        @Override
        public void onBindViewHolder(CrimeHolder holder, int position) {
            Crime crime = mCrimes.get(position);
            holder.bind(crime);
        }

        @Override
        public int getItemCount() {
            return mCrimes.size();
        }
    }

    @Override
    public void onSaveInstanceState(Bundle onSavedInstanceState) {
        super.onSaveInstanceState(onSavedInstanceState);
        onSavedInstanceState.putSerializable(CLICKED_CRIME_POSITION_ID, clickedCrimePosition);
        onSavedInstanceState.putBoolean(SAVED_SUBTITLE_VISIBLE, mSubtitleVisible);
    }
}

CrimeFragment.java

package com.bignerdranch.android.criminalintent;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.EditText;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.UUID;

import static android.widget.CompoundButton.*;

public class CrimeFragment extends Fragment {

    public static final String DATE_FORMAT = "EEE MMM dd yyyy";
    public static final String TIME_FORMAT = "hh:mm a z";

    private static final String ARG_CRIME_ID = "crime_id";
    private static final String DIALOG_DATE = "DialogDate";
    private static final String DIALOG_TIME = "DialogTime";

    private static final int REQUEST_DATE = 0;
    private static final int REQUEST_TIME = 1;

    private Crime mCrime;
    private EditText mTitleField;
    private Button mDateButton;
    private Button mTimeButton;
    private CheckBox mSolvedCheckBox;

    public static CrimeFragment newInstace(UUID crimeId) {
        Bundle args = new Bundle();
        args.putSerializable(ARG_CRIME_ID, crimeId);

        CrimeFragment fragment = new CrimeFragment();
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        UUID crimeId = (UUID) getArguments().getSerializable(ARG_CRIME_ID);
        mCrime = CrimeLab.get(getActivity()).getCrime(crimeId);
    }

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

        mTitleField = (EditText) v.findViewById(R.id.crime_title);
        mTitleField.setText(mCrime.getTitle());
        mTitleField.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                // This space intentionally left blank
            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                mCrime.setTitle(s.toString());
            }

            @Override
            public void afterTextChanged(Editable s) {
                // This one too
            }
        });

        mDateButton = (Button) v.findViewById(R.id.crime_date);
        updateDate();
        mDateButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (Utils.getInstance(getActivity()).isPhone()) {
                    Intent intent = DatePickerActivity.newIntent(getActivity(), mCrime.getDate());
                    startActivityForResult(intent, REQUEST_DATE);
                } else { // DEVICE_IS_A_TABLET
                    FragmentManager manager = getFragmentManager();
                    DatePickerFragment dialog = DatePickerFragment.newInstance(mCrime.getDate());
                    dialog.setTargetFragment(CrimeFragment.this, REQUEST_DATE);
                    dialog.show(manager, DIALOG_DATE);
                }
            }
        });

        mTimeButton = (Button) v.findViewById(R.id.crime_time);
        updateTime();
        mTimeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                FragmentManager manager = getFragmentManager();
                TimePickerFragment dialog = TimePickerFragment.newInstance(mCrime.getTime());
                dialog.setTargetFragment(CrimeFragment.this, REQUEST_TIME);
                dialog.show(manager, DIALOG_TIME);
            }
        });

        mSolvedCheckBox = (CheckBox) v.findViewById(R.id.crime_solved);
        mSolvedCheckBox.setChecked(mCrime.isSolved());
        mSolvedCheckBox.setOnCheckedChangeListener(new OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                mCrime.setSolved(isChecked);
            }
        });

        return v;
    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if (resultCode != Activity.RESULT_OK) {
            return;
        }

        if (requestCode == REQUEST_DATE) {
            Date date = (Date) data.getSerializableExtra(DatePickerFragment.EXTRA_DATE);
            mCrime.setDate(date);
            updateDate();
        }

        if (requestCode == REQUEST_TIME) {
            Date time = (Date) data.getSerializableExtra(TimePickerFragment.EXTRA_TIME);
            mCrime.setTime(time);
            updateTime();
        }
    }

    private void updateDate() {
        DateFormat dateFormat = new SimpleDateFormat(DATE_FORMAT);
        mDateButton.setText(dateFormat.format(mCrime.getDate()));
    }

    private void updateTime() {
        DateFormat timeFormat = new SimpleDateFormat(TIME_FORMAT);
        mTimeButton.setText(timeFormat.format(mCrime.getTime()));
    }

    public void returnResult() {
        getActivity().setResult(Activity.RESULT_OK, null);
    }


}

CrimeLab.java

package com.bignerdranch.android.criminalintent;

import android.content.Context;

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.UUID;

public class CrimeLab {
    public static CrimeLab sCrimeLab;

    private Map<UUID, Crime> mCrimes;

    public static CrimeLab get(Context context) {
        if (sCrimeLab == null) {
            sCrimeLab = new CrimeLab(context);
        }
        return sCrimeLab;
    }

    private CrimeLab(Context context) {
        mCrimes = new LinkedHashMap<>();
    }

    public void addCrime(Crime c) {
        mCrimes.put(c.getID(), c);
    }

    public List<Crime> getCrimes() {
        return new ArrayList<>(mCrimes.values());
    }

    public Crime getCrime(UUID id) {
        return mCrimes.get(id);
    }
}

Crime.java

package com.bignerdranch.android.criminalintent;

import java.util.Date;
import java.util.UUID;

public class Crime {
    private UUID mID;
    private String mTitle;
    private Date mDate;
    private Date mTime;
    private boolean mSolved;

    public Crime() {
        mID = UUID.randomUUID();
        mDate = new Date();
        mTime = new Date();
    }

    public UUID getID() {
        return mID;
    }

    public String getTitle() {
        return mTitle;
    }

    public void setTitle(String title) {
        mTitle = title;
    }

    public Date getDate() {
        return mDate;
    }

    public void setDate(Date date) {
        mDate = date;
    }

    public Date getTime() {
        return mTime;
    }

    public void setTime(Date time) {
        mTime = time;
    }

    public boolean isSolved() {
        return mSolved;
    }

    public void setSolved(boolean solved) {
        mSolved = solved;
    }
}

Appreciate your help on this @cstewart

cstewart · May 15, 2017, 2:01pm

I am not sure what the problem is but I suspect that there is some issue with your refresh performance optimization:

mAdapter.notifyItemChanged(clickedCrimePosition);

A few ideas:

Does the problem happen if you change this line to use notifyDataSetChanged? That could give us a hint about the cause.
Break out the debugger and see what happens when onResume is called.

Try those out and let me know what you find.

asett · May 16, 2017, 1:04am

Hi @cstewart,

Changing the line: mAdapter.notifyItemChanged(clickedCrimePosition); to mAdapter.notifyDataSetChanged(); in CrimeListFragment.java did not solve the issue

I then tried your other suggestion to break out the debugger and see what happens when onResume() is called and I did notice a difference in the FrameStacks when the Back button is pressed in comparison to the case where the Hierarchical Up button is pressed. Pressing the Back button does not show the following FrameStacks:
> handleLaunchActivity:2392, ActivityThread (android.app)
> access$800:151, ActivityThread (android.app)

If I tapped the Back button after adding a new crime the app would take me back to the CrimeListFragment showing everything except the newly added crime. The mAdapter object in CrimeListFragment as expected did not have the newly added crime in its copy of mCrimes. As you mentioned this could be an issue related to refresh performance optimization and I am not sure how to test that hypothesis.

Below is a screenshot of the FrameStack when the Back button was pressed after adding a new crime:

Below is a screenshot of the FrameStack when the Hierarchical Up button was pressed after adding a new crime:

cstewart · May 22, 2017, 2:03pm

The difference between the back button and the up button is expected. When you hit back, you pop back to the previous activity/fragment and onStart then onResume will be called. When you tap on the up/home button, you are popped back in the backstack, but the previous activity is recreated from scratch (there’s a discussion about why this is in the book).

As you navigate with back, onResume will get called and you are refreshing the UI. With the debugger, check to see that the list of crimes has changed when this happens (and your new crime is there). Also verify that the adapter is refreshed with notifyDataSetChanged or notifyItemChanged.

It’s hard for me to say what the problem is without seeing all of your code. The code you posted here looks correct to me. If you’d like for me to take a closer look, can you attach a zip of your whole project?

asett · May 23, 2017, 1:21am

Certainly. Attached please find a link to the zip file of the project

cstewart · May 23, 2017, 2:18pm

Thanks for uploading your project (nice work on the challenges!).

The problem comes from this line in CrimeLab.java:

public List<Crime> getCrimes() {
  return new ArrayList<>(mCrimes.values());
}

When you create your adapter, you give it a List. The notifyDataSetChanged/notifyItemChanged methods rely on the adapter’s same instance of the list changing. In your case, once you set up the adapter, the list you gave the adapter never changes. So when you tell it to refresh, it does, but it still has an empty list. So, our code is pretty brittle because it does rely on that same list instance existing in a few places.

To fix this problem, you can create a new method on your adapter to accept a new list. Something like this:

public void replaceList(List<Crime> crimes) {
  mCrimes = crimes;
}

After you call this method, your notify calls should refresh the list and show the new content.

asett · May 24, 2017, 12:50am

Thank you very much @cstewart . Your analysis was spot on and the suggestion certainly helped resolve the issue:
Here’s are the modified versions of the updateUI() method and the CrimeAdapter class:

updateUI()

private void updateUI() {
CrimeLab crimeLab = CrimeLab.get(getActivity());
List crimes = crimeLab.getCrimes();

    if (mAdapter == null) {
        mAdapter = new CrimeAdapter(crimes);
        mCrimeRecyclerView.setAdapter(mAdapter);
    } else {
        mAdapter.replaceList(crimes);
        mAdapter.notifyItemChanged(clickedCrimePosition);
    }

    if (crimes.size() > 0) {
        mEmptyCrimeListLinearLayout.setVisibility(View.GONE);
        mCrimeRecyclerView.setVisibility(View.VISIBLE);
    } else {
        mEmptyCrimeListLinearLayout.setVisibility(View.VISIBLE);
        mCrimeRecyclerView.setVisibility(View.GONE);

        mEmptyCrimeListAddButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                addCrime();
            }
        });
    }

    updateSubtitle();
}

CrimeAdapter

private class CrimeAdapter extends RecyclerView.Adapter<CrimeHolder> {
    private List<Crime> mCrimes;

    public CrimeAdapter(List<Crime> crimes) {
        mCrimes = crimes;
    }

    @Override
    public CrimeHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(getActivity());
        return new CrimeHolder(layoutInflater, parent);
    }

    @Override
    public void onBindViewHolder(CrimeHolder holder, int position) {
        Crime crime = mCrimes.get(position);
        holder.bind(crime);
    }

    @Override
    public int getItemCount() {
        return mCrimes.size();
    }

    public void replaceList(List<Crime> crimes) {
        mCrimes = crimes;
    }
}

cstewart · May 24, 2017, 1:03pm

Great! I’m glad I could help.

asett · May 25, 2017, 1:05am

I see the exact same method in Chapter 14 Listing 20 only it is called setCrimes instead of replaceList. Wish I had read ahead

cstewart · May 25, 2017, 1:15pm

Ha. I forgot that we had that in the book! Thanks for the follow up.

Vannessa · July 7, 2017, 3:51pm

this a little difficult for me…but it is helpful for me!thank you!

vladcrash · July 17, 2017, 12:02pm

I had the same problem. Thank you very much @cstewart for your help =)

crystalDf · October 29, 2017, 5:55am

Hi @cstewart,

Same issue for me and it’s a perfect solution from your answer.

My suggestion is moving the solution from Chapter 14 to Chapter 13 and letting it be a new challenge with some tips in next release.

Thanks.

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Adding a Crime :: Tapping the back button doesnt update the Crime List but tapping the Hierarchical Up button does it

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