Question

这是我的情况。

在此屏幕中，我点击评论按钮。

评论活动打开，我输入我想要的内容。

评论在firebase中成功添加，它将我带回细节活动。

到目前为止一切都很棒！现在让我们添加另一条评论。现在你看到我得到了重复的评论。

我希望你也能看到。现在在 DetailActivity 中，我有一个名为queryFirebaseDb()的方法，该方法在onCreate()和onResume()方法中都被调用。如果我不使用onResume（）方法，则在单击CommentActivity中的后退按钮后，将不会显示数据。你看我现在去哪里了吗？问题是如何从CommentActivity返回后避免重复数据。这是我的代码。

public class DetailActivity extends AppCompatActivity {

ArrayList<Comment> commentArrayList;

ImageView mImageView;
TextView mTitle;
TextView mDate;
TextView mDescription;
TextView mAuthor;
ToggleButton mFavBtn;
private TextView noCommentsTextView;
private TextView commentsTextView;

private ImageButton imageButton;

private FloatingActionButton mShareBtn;

private String newsTitle;
private String newsImage;
private String newsDate;
private String newsDescription;
private static String NEWS_SHARE_HASHTAG = "#EasyNewsApp";
private String date1;
private String date2;
private String newsUrl;
private String newsAuthor;

private Cursor favoriteCursor;

private DatabaseReference mDatabase;

private static Bundle bundle = new Bundle();

private Uri uri;

private RecyclerView mRecyclerView;
private DisplayCommentsAdapter displayCommentsAdapter;

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

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

    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    Intent i = getIntent();

    mAuthor = (TextView) findViewById(R.id.detail_author);

    mImageView = (ImageView) findViewById(R.id.detail_image_view);
    mTitle = (TextView) findViewById(R.id.detail_title);
    mDate = (TextView) findViewById(R.id.detail_publish_date);
    mDescription = (TextView) findViewById(R.id.detail_description);
    noCommentsTextView = (TextView)findViewById(R.id.noCommentsTextView);
    commentsTextView = (TextView)findViewById(R.id.commentsTextView);
    mShareBtn = (FloatingActionButton) findViewById(R.id.share_floating_btn);
    mFavBtn = (ToggleButton) findViewById(R.id.fav_news_btn);
    imageButton = (ImageButton)findViewById(R.id.detail_comment_image_btn);

    mRecyclerView = (RecyclerView)findViewById(R.id.recycler_comments);

    LinearLayoutManager manager = new LinearLayoutManager(this);
    mRecyclerView.setLayoutManager(manager);
    mRecyclerView.setHasFixedSize(true);
    mRecyclerView.addItemDecoration(new SimpleDividerItemDecoration(this));

    commentArrayList = new ArrayList<>();


    mDatabase = FirebaseDatabase.getInstance().getReference();


    mFavBtn.setTextOn(null);
    mFavBtn.setText(null);
    mFavBtn.setTextOff(null);

    newsAuthor = i.getStringExtra("author");
    newsImage = i.getStringExtra("image");
    newsTitle = i.getStringExtra("newsTitle");
    newsDate = i.getStringExtra("date");
    newsDescription = i.getStringExtra("description");
    newsUrl = i.getStringExtra("url");




        date1 = newsDate.substring(0, 10);
        date2 = newsDate.substring(11, 19);

    Picasso.with(this).load(newsImage)
            .placeholder(R.drawable.ic_broken_image)
            .into(mImageView);

    mTitle.setText(newsTitle);
    mAuthor.setText("Author: " + newsAuthor);
    mDescription.setText(newsDescription);
    mDate.setText(date2 + ", " + date1);

    mShareBtn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View view) {
            Intent shareIntent = createShareNewsIntent();
            startActivity(shareIntent);
        }
    });
    imageButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Intent commentIntent = new Intent(DetailActivity.this, CommentActivity.class);
            commentIntent.putExtra("newsTitle",newsTitle);
            startActivity(commentIntent);
        }
    });

    /**
     * Handling the add/remove news part. We check if the specific news article
     * exists in favourite.db.
     */
    favoriteCursor = getContentResolver().query(FavouriteContract.FavouriteEntry.CONTENT_URI,
            null,
            FavouriteContract.FavouriteEntry.COLUMN_NEWS_TITLE + "=?",
            new String[]{newsTitle},
            null);

    /**
     * If yes then set the toggle button to true
     */
    if (favoriteCursor.getCount() > 0) {
        try {
            mFavBtn.setChecked(true);
        } finally {
            favoriteCursor.close();
        }
    }

    /**
     * Else click the toggle button to add the news article as favourite
     */
    mFavBtn.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

        @Override
        public void onCheckedChanged(CompoundButton compoundButton, final boolean isChecked) {
            /**
             * If checked the add the news article as favourite.
             */
            if (isChecked) {
                new AsyncTask<Void, Void, Void>() {
                    @Override
                    protected Void doInBackground(Void... voids) {
                        ContentValues contentValues = new ContentValues();

                        contentValues.put(FavouriteContract.FavouriteEntry.COLUMN_NEWS_TITLE, newsTitle);
                        contentValues.put(FavouriteContract.FavouriteEntry.COLUMN_NEWS_AUTHOR, newsAuthor);
                        contentValues.put(FavouriteContract.FavouriteEntry.COLUMN_NEWS_DESCRIPTION, newsDescription);
                        contentValues.put(FavouriteContract.FavouriteEntry.COLUMN_NEWS_URL, newsUrl);
                        contentValues.put(FavouriteContract.FavouriteEntry.COLUMN_NEWS_URL_TO_IMAGE, newsImage);
                        contentValues.put(FavouriteContract.FavouriteEntry.COLUMN_NEWS_PUBLISHED_AT, newsDate);

                        //The actual insertion in the db.
                        uri = getContentResolver().insert(FavouriteContract.FavouriteEntry.CONTENT_URI, contentValues);
                        return null;
                    }

                    @Override
                    protected void onPostExecute(Void aVoid) {
                        super.onPostExecute(aVoid);
                        Toast.makeText(DetailActivity.this, "Article with title:  " + newsTitle + " was added", Toast.LENGTH_SHORT).show();

                    }
                }.execute();
            } else {
                /**
                 * If you uncheck the toggle button then delete the news article from the favourite db.
                 */
                Uri newsTitleOfFavNews = FavouriteContract.FavouriteEntry.buildNewsUriWithTitle(newsTitle);
                //String title = uri.getPathSegments().get(1);// Get the task ID from the URI path

                getContentResolver().delete(
                        newsTitleOfFavNews,
                        null,
                        null);
                Toast.makeText(DetailActivity.this, "News article deleted from favourites ", Toast.LENGTH_SHORT).show();

            }
        }
    });


    queryFirebaseDb();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    getMenuInflater().inflate(R.menu.detail_menu, menu);

    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
   super.onOptionsItemSelected(item);

   if(item.getItemId() == R.id.detail_browser_btn){
        Intent browserIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(newsUrl));
        startActivity(browserIntent);
    } if(item.getItemId() == android.R.id.home){
        NavUtils.navigateUpFromSameTask(this);
        return true;
    }

    return true;
}

private Intent createShareNewsIntent() {
    Intent shareIntent = ShareCompat.IntentBuilder.from(this)
            .setType("text/plain")
            .setText(NEWS_SHARE_HASHTAG + "\n\n\n" + newsTitle
                    + "\n\n\n" + newsDescription
                    + "\n\n\n" + newsDate)
            .getIntent();

    return shareIntent;
}


@Override
protected void onStart() {
    super.onStart();
    //queryFirebaseDb();
}

@Override
protected void onRestart() {
    super.onRestart();
    queryFirebaseDb();
    //displayCommentsAdapter.notifyDataSetChanged();
}


public void queryFirebaseDb(){

    /**
     * Querying the database to check if the specific article has comments.
     */

    mDatabase = FirebaseDatabase.getInstance().getReference();

    Query query = mDatabase.child("comments").orderByChild("newsTitle").equalTo(newsTitle);

    query.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            if(dataSnapshot.exists()){
                for(DataSnapshot dataSnapshots : dataSnapshot.getChildren()){
                    Comment comment = dataSnapshots.getValue(Comment.class);

                    //mUserDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(userId);

                    commentArrayList.add(comment);

                    displayCommentsAdapter = new DisplayCommentsAdapter(this,commentArrayList);

                    mRecyclerView.setAdapter(displayCommentsAdapter);

                    displayCommentsAdapter.setCommentsData(commentArrayList);

                    //Log.d(LOG_TAG, String.valueOf(commentArrayList.size()));

                }
                noCommentsTextView.setVisibility(View.GONE);

                //commentsTextView.setVisibility(View.VISIBLE);

            }else{
                //Toast.makeText(DisplayComments.this,"There are no comments posted",Toast.LENGTH_LONG).show();
                noCommentsTextView.setVisibility(View.VISIBLE);

            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}
/*
@Override
protected void onPause() {
    super.onPause();
    bundle.putBoolean("ToggleButtonState", mFavBtn.isChecked());
}

@Override
public void onResume() {
    super.onResume();
    mFavBtn.setChecked(bundle.getBoolean("ToggleButtonState",false));
}
*/
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
    mFavBtn.setChecked(savedInstanceState.getBoolean("ToggleButtonState",false));
    savedInstanceState.putParcelableArrayList("newsList",commentArrayList);
}

@Override
protected void onSaveInstanceState(Bundle outState) {
    super.onSaveInstanceState(outState);
    outState.putBoolean("ToggleButtonState",mFavBtn.isChecked());
    outState.getParcelableArrayList("newsList");

  }
 }

和

public class CommentActivity extends AppCompatActivity {

private static final String REQUIRED = "Required";
private static final String TAG = CommentActivity.class.getSimpleName();

Toolbar toolbar;

DatabaseReference mDatabase;
EditText titleEt;
EditText bodyEt;
Button commentBtn;
String newsTitle;
Intent i;
String name;

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

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

    setSupportActionBar(toolbar);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setTitle("Add comment");

    mDatabase = FirebaseDatabase.getInstance().getReference();

    titleEt = (EditText) findViewById(R.id.comment_title);
    bodyEt = (EditText) findViewById(R.id.comment_body);
    commentBtn = (Button) findViewById(R.id.comment_btn);

    i = getIntent();

    newsTitle = i.getStringExtra("newsTitle");




    commentBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            submitPost();
        }
    });

}

private void submitPost() {
    final String title = titleEt.getText().toString();
    final String body = bodyEt.getText().toString();

    // Title is required
    if (TextUtils.isEmpty(title)) {
        titleEt.setError(REQUIRED);
        return;
    }

    // Body is required
    if (TextUtils.isEmpty(body)) {
        bodyEt.setError(REQUIRED);
        return;
    }

    // Disable button so there are no multi-posts
    setEditingEnabled(false);
    Toast.makeText(this, "Posting...", Toast.LENGTH_SHORT).show();

    // [START single_value_read]
    final String userId = FirebaseAuth.getInstance().getCurrentUser().getUid();


    mDatabase.child("Users").child(userId).addListenerForSingleValueEvent(
            new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    // Get user value
                    User user = dataSnapshot.getValue(User.class);


                    // [START_EXCLUDE]
                    if (user == null) {
                        // User is null, error out
                        Log.e(TAG, "User " + userId + " is unexpectedly null");
                        Toast.makeText(CommentActivity.this,
                                "Error: could not fetch user.",
                                Toast.LENGTH_SHORT).show();
                    } else {
                        // Write new post
                        name = dataSnapshot.child("name").getValue().toString();

                        Calendar c = Calendar.getInstance();
                        SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy hh:mm:ss");
                        String strDate = sdf.format(c.getTime());

                        writeNewPost(userId,strDate,name,newsTitle, title, body);
                    }

                    // Finish this Activity, back to the stream
                    setEditingEnabled(true);
                    finish();
                    // [END_EXCLUDE]
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {
                    Log.w(TAG, "getUser:onCancelled", databaseError.toException());
                    // [START_EXCLUDE]
                    setEditingEnabled(true);
                    // [END_EXCLUDE]
                }
            });
    // [END single_value_read]
}

 private void writeNewPost(String userId,String date,String 
 commentAuthor, String newsTitle, String commentTitle, String 
 commentBody){
   String key = mDatabase.child("comments").push().getKey();
   Comment comment = new Comment(userId, date, 
   commentAuthor,newsTitle,commentTitle,commentBody);
   Map<String, Object> commentValues = comment.toMap();

   Map<String, Object> childUpdates = new HashMap<>();
   childUpdates.put("/comments/" + key, commentValues);

   mDatabase.updateChildren(childUpdates);
   }

private void setEditingEnabled(boolean enabled) {
    titleEt.setEnabled(enabled);
    bodyEt.setEnabled(enabled);
    if (enabled) {
        commentBtn.setVisibility(View.VISIBLE);
    } else {
        commentBtn.setVisibility(View.GONE);
    }
  } 
}

更新

我用过这个

@Override
protected void onRestart() {
    super.onRestart();
    finish();
    startActivity(getIntent());
}

瞧！

Answer 1

我认为你在做Android时会知道的一些东西：

基本上，在android中，你需要了解生命周期是如何工作的。因此，当您从queryFirebaseDb()和onCreate致电onResume时，您的应用最初会在活动开始时同时进行两次查询。

生命周期就像这样OnCreate -> onResume。因此，有意义的是，当活动开始时，查询会根据您的逻辑在onCreate上执行一次而不是在onResume上执行。

答案就在这里

我注意到您使用的是ArrayList<Comment> commentArrayList; ArrayList结构，它允许您拥有重复数据。而且，如果你研究Firebase的行为以及你的查询是如何构建的，就像这样，

Query query = mDatabase.child("comments").orderByChild("newsTitle").equalTo(newsTitle);

此查询意味着您收集所有评论，之前的评论和新评论（不仅仅是新评论），我认为您只是希望（1）最近添加评论或（2）用新的评论替换旧的评论。

这样做的第一种方式听起来很复杂，尽管这并非不可能。但是，第二种做法很容易。

因此，要解决这个问题，简单地说，用这个数据替换你拥有的arrayList。

if(dataSnapshot.exists()){
            ArrayList<Comment> tempComments = new ArrayList();

            for(DataSnapshot dataSnapshots : dataSnapshot.getChildren()){
                Comment comment = dataSnapshots.getValue(Comment.class);

                //mUserDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(userId);

                tempComments.add(comment);

                //Log.d(LOG_TAG, String.valueOf(commentArrayList.size()));

            }

            commentArrayList = tempComments; //assuming you want to store the data in the class fields 
            displayCommentsAdapter = new DisplayCommentsAdapter(this,commentArrayList);
            mRecyclerView.setAdapter(displayCommentsAdapter);
            displayCommentsAdapter.setCommentsData(commentArrayList);

            noCommentsTextView.setVisibility(View.GONE);

            //commentsTextView.setVisibility(View.VISIBLE);

        }

单击后退按钮时复制值 - 已修复

1 个答案: