java - 添加新记录时 ListView 不刷新

Question

似乎无法弄清楚这一点，我已经浏览了所有代码但没有成功。当我将新的投球手添加到空列表时，它会正确显示，当我向列表中添加第二个或更多投球手时，投球手的名称显示为添加的第一个投球手的名称。我在下面添加了几张屏幕截图来说明我的意思。

显然这些图像的顺序是从左到右。我也将我的 BowlerActivity 包含在这篇文章中。这是我创建和更新新的和现有的保龄球手的地方。

private BowlerAdapter mAdapter;
    private List<Bowler> bowlersList = new ArrayList<>();
    private CoordinatorLayout coordinatorLayout;
    private RecyclerView recyclerView;
    private TextView noBowlersView;

    private DatabaseHelper db;

    private TextView leagueId;
    private String savedLeagueId;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bowler);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setDisplayShowHomeEnabled(true);

        toolbar.setNavigationOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startActivity(new Intent(getApplicationContext(),MainActivity.class));
                finish();
            }
        });

        savedLeagueId = String.valueOf(getIntent().getIntExtra("leagueId",2));
        leagueId = (TextView) findViewById(R.id.tvLeagueId);

        coordinatorLayout = findViewById(R.id.coordinator_layout);
        recyclerView = findViewById(R.id.recycler_view);
        noBowlersView = findViewById(R.id.empty_bowlers_view);

        db = new DatabaseHelper(this);

        bowlersList.addAll(db.getAllBowlers(savedLeagueId));

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.add_bowler_fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showBowlerDialog(false, null, -1);
            }
        });

        mAdapter = new BowlerAdapter(this, bowlersList);
        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(mLayoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        recyclerView.addItemDecoration(new MyDividerItemDecoration(this, LinearLayoutManager.VERTICAL, 16));
        recyclerView.setAdapter(mAdapter);

        toggleEmptyBowlers();

        //On Long Click On The RecyclerView Item An Alert Dialog Is Opened With The Option To Choose Edit/Delete
        recyclerView.addOnItemTouchListener(new RecyclerTouchListener(this,
                recyclerView, new RecyclerTouchListener.ClickListener() {
            @Override
            public void onClick(View view, final int position) {

                String seriesLeagueId = bowlersList.get(position).getLeagueId();
                int seriesBowlerId = bowlersList.get(position).getId();
                Intent myIntent = new Intent(BowlerActivity.this, SeriesActivity.class);
                myIntent.putExtra("seriesLeagueId", seriesLeagueId);
                myIntent.putExtra("seriesBowlerId", seriesBowlerId);
                startActivity(myIntent);

            }

            @Override
            public void onLongClick(View view, int position) {
                showActionsDialog(position);
            }
        }));
    }

    //Inserting New Bowler In The Database And Refreshing The List
    private void createBowler(String leagueId,  String bowlerName) {
        //Inserting Bowler In The Database And Getting Newly Inserted Bowler Id
        long id = db.insertBowler(leagueId, bowlerName);

        //Get The Newly Inserted Bowler From The Database
        Bowler n = db.getBowler(leagueId);

        if (n != null) {
            //Adding New Bowler To The Array List At Position 0
            bowlersList.add(0, n);

            //Refreshing The List
            mAdapter.notifyDataSetChanged();

            toggleEmptyBowlers();
        }
    }

    //Updating Bowler In The Database And Updating The Item In The List By Its Position
    private void updateBowler(String bowlerName, int position) {
        Bowler n = bowlersList.get(position);

        //Updating Bowler Text
        n.setLeagueId(savedLeagueId);
        n.setName(bowlerName);

        //Updating The Bowler In The Database
        db.updateBowler(n);

        //Refreshing The List
        bowlersList.set(position, n);
        mAdapter.notifyItemChanged(position);

        toggleEmptyBowlers();
    }

    //Deleting Bowler From SQLite Database And Removing The Bowler Item From The List By Its Position
    private void deleteBowler(int position) {
        //Deleting The Bowler From The Database
        db.deleteBowler(bowlersList.get(position));

        //Removing The Bowler From The List
        bowlersList.remove(position);
        mAdapter.notifyItemRemoved(position);

        toggleEmptyBowlers();
    }

    //Opens Dialog With Edit/Delete Options
    //Edit - 0
    //Delete - 0
    private void showActionsDialog(final int position) {
        CharSequence colors[] = new CharSequence[]{"Edit", "Delete"};

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Choose option");
        builder.setItems(colors, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                if (which == 0) {
                    showBowlerDialog(true, bowlersList.get(position), position);
                } else {
                    deleteBowler(position);
                }
            }
        });
        builder.show();
    }

    //Show Alert Dialog With EditText Options to Enter/Edit A League
    //When shouldUpdate = true, It Will Automatically Display Old Bowler Name And Change The Button Text To UPDATE
    private void showBowlerDialog(final boolean shouldUpdate, final Bowler bowler, final int position) {
        LayoutInflater layoutInflaterAndroid = LayoutInflater.from(getApplicationContext());
        View view = layoutInflaterAndroid.inflate(R.layout.dialog_bowler, null);

        AlertDialog.Builder alertDialogBuilderUserInput = new AlertDialog.Builder(BowlerActivity.this);
        alertDialogBuilderUserInput.setView(view);

        leagueId.setText(savedLeagueId);
        final EditText inputBowlerName = view.findViewById(R.id.etBowlerNameInput);
        TextView dialogTitle = view.findViewById(R.id.dialog_title);
        dialogTitle.setText(!shouldUpdate ? getString(R.string.lbl_new_bowler_title) : getString(R.string.lbl_edit_bowler_title));

        if (shouldUpdate && bowler != null) {
            leagueId.setText(bowler.getLeagueId());
            inputBowlerName.setText(bowler.getName());

        }
        alertDialogBuilderUserInput
                .setCancelable(false)
                .setPositiveButton(shouldUpdate ? "update" : "save", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialogBox, int id) {

                    }
                })
                .setNegativeButton("cancel",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialogBox, int id) {
                                dialogBox.cancel();
                            }
                        });

        final AlertDialog alertDialog = alertDialogBuilderUserInput.create();
        alertDialog.show();

        alertDialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                //Show Toast Message When No Text Is Entered
                if (TextUtils.isEmpty(inputBowlerName.getText().toString())) {
                    Toast.makeText(BowlerActivity.this, "Enter Bowler!", Toast.LENGTH_SHORT).show();
                    return;
                } else {
                    alertDialog.dismiss();
                }

                //Check If User Is Updating Bowler
                if (shouldUpdate && bowler != null) {

                    //Updating Bowler By Its Id
                    updateBowler(inputBowlerName.getText().toString(), position);

                } else {
                    //Creating New Bowler
                    createBowler(leagueId.getText().toString(), inputBowlerName.getText().toString());

                }
            }
        });
    }

    //Toggling List And Empty Bowler View
    private void toggleEmptyBowlers() {
        //You Can Check bowlerList.size() > 0

        if (db.getBowlersCount() > 0) {
            noBowlersView.setVisibility( View.GONE);
        } else {
            noBowlersView.setVisibility( View.VISIBLE);
        }
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate( R.menu.menu_main, menu );
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected( item );
    }
}

我还包含了包含 Bowler 方法的 DatabaseHelper 部分。

public long insertBowler(String leagueId, String bowlerName) {
        //Get Writable Database That We Want To Write Data Too
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        //`id` and `timestamp` Will Be Inserted Automatically
        values.put(Bowler.COLUMN_LEAGUE_ID, leagueId);
        values.put(Bowler.COLUMN_NAME, bowlerName);

         //Insert Row
        long id = db.insert( Bowler.TABLE_NAME, null, values );

        //Close Database Connection
        db.close();

        //Return Newly Inserted Row Id
        return id;
    }

    public Bowler getBowler(String leagueId) {
        //Get Readable Database If We Are Not Inserting Anything
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(Bowler.TABLE_NAME,
                new String[]{Bowler.COLUMN_ID, Bowler.COLUMN_LEAGUE_ID, Bowler.COLUMN_NAME, Bowler.COLUMN_TIMESTAMP},
                Bowler.COLUMN_LEAGUE_ID + "=?",
                new String[]{String.valueOf(leagueId)}, null, null, null, null);

        if (cursor.moveToFirst()) {

            //Prepare Bowler Object
        Bowler bowler = new Bowler(
                cursor.getInt(cursor.getColumnIndex(Bowler.COLUMN_ID)),
                cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_LEAGUE_ID)),
                cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_NAME)),
                cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_TIMESTAMP)));

        //Close Database Connection
        cursor.close();
        return bowler;
    } else {return null;}
}
    public List<Bowler> getAllBowlers(String leagueId) {
        List<Bowler> bowlers = new ArrayList<>();

        //Select All Query
        String selectQuery = "SELECT  * FROM " + Bowler.TABLE_NAME + " WHERE " + Bowler.COLUMN_LEAGUE_ID + " = '" + leagueId + "'" + " ORDER BY " +
                Bowler.COLUMN_TIMESTAMP + " DESC";

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        //Looping Through All Rows And Adding To The List
        if (cursor.moveToFirst()) {
            do {
                Bowler bowler = new Bowler();
                bowler.setId(cursor.getInt(cursor.getColumnIndex(Bowler.COLUMN_ID)));
                bowler.setLeagueId(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_LEAGUE_ID)));
                bowler.setName(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_NAME)));
                bowler.setTimestamp(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_TIMESTAMP)));
                bowlers.add(bowler);
            } while (cursor.moveToNext());
        }
        cursor.close();
        //Close Database Connection
        db.close();

        //Return Bowlers List
        return bowlers;
    }

    public int getBowlersCount() {
        String countQuery = "SELECT  * FROM " + Bowler.TABLE_NAME;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);

        int count = cursor.getCount();
        cursor.close();

        //Return The Count
        return count;
    }

    public int updateBowler(Bowler bowler) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(Bowler.COLUMN_LEAGUE_ID, bowler.getLeagueId());
        values.put(Bowler.COLUMN_NAME, bowler.getName());

        //Updating Row
        return db.update(Bowler.TABLE_NAME, values, Bowler.COLUMN_ID + " = ?",
                new String[]{String.valueOf(bowler.getId())});
    }

    public void deleteBowler(Bowler bowler) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete( Bowler.TABLE_NAME, Bowler.COLUMN_ID + " = ?",
                new String[]{String.valueOf( bowler.getId())});
        db.close();
    }

为了以防万一，我也发布了 BowlerAdapter 代码。

public class BowlerAdapter extends RecyclerView.Adapter<BowlerAdapter.MyViewHolder> {

    private Context context;
    private List<Bowler> bowlersList;

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView bowlerLeagueId;
        public TextView name;
        public TextView timestamp;

        public MyViewHolder(View view) {
            super(view);
            bowlerLeagueId = view.findViewById( R.id.tvLeagueId);
            name = view.findViewById(R.id.tvBowlerName );
            timestamp = view.findViewById(R.id.timestamp);
        }
    }


    public BowlerAdapter(Context context, List<Bowler> bowlersList) {
        this.context = context;
        this.bowlersList = bowlersList;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.listview_bowler, parent, false);

        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        Bowler bowler = bowlersList.get(position);

        holder.bowlerLeagueId.setText(bowler.getLeagueId());
        holder.name.setText(bowler.getName());

        //Formatting And Displaying Timestamp
        holder.timestamp.setText(formatDate(bowler.getTimestamp()));
    }

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

    //Formatting TimeStamp to 'EEE MMM dd yyyy (HH:mm:ss)'
    //Input  : 2018-05-23 9:59:01
    //Output : Wed May 23 2018 (9:59:01)
    private String formatDate(String dateStr) {
        try {
            SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Date date = fmt.parse(dateStr);
            SimpleDateFormat fmtOut = new SimpleDateFormat("EEE MMM dd yyyy (HH:mm:ss)");
            return fmtOut.format(date);
        } catch (ParseException e) { }

        return "";
    }

我确信这是非常明显的事情，但我已经查看代码几个小时了，但我只是没有看到问题。

如有任何帮助，我们将不胜感激。

我已经按照您的指示修改了我的代码，但是当我添加一个新的 Bowler 时，屏幕会返回空白，直到我离开 BowlerActivity 并返回其中，此时列表已更新。

//Inserting New Bowler In The Database And Refreshing The List
    private void createBowler(String leagueId,  String bowlerName) {
        //Inserting Bowler In The Database And Getting Newly Inserted Bowler Id
        long id = db.insertBowler(leagueId, bowlerName);

        //Get The Newly Inserted Bowler From The Database
        Bowler n = db.getBowler(leagueId);

        if (n != null) {
            //Adding New Bowler To The Array List At Position 0
            bowlersList.add(0, n);

            //Refreshing The List
            mAdapter.notifyDataSetChanged(bowlersList);

            toggleEmptyBowlers();
        }
    }

BowlerAdapter 的notifyDataSetChanged 方法

private List<Bowler> bowlersList;

    public void notifyDataSetChanged(List<Bowler> newbowlersList) {
        bowlersList.clear();
        bowlersList.addAll( newbowlersList );
        super.notifyDataSetChanged();
    }

调试日志

this = {BowlerActivity@5027} 
leagueId = "1"
bowlerName = "Robert"
id = 6
n = {Bowler@5032} 
 id = 1
 league_id = "1"
 name = "b1"
 timestamp = "2018-06-07 20:03:19"
 shadow$_klass_ = {Class@4839} "class ca.rvogl.tpbcui.database.models.Bowler"
 shadow$_monitor_ = -2106571381
mAdapter = {BowlerAdapter@5033} 
 bowlersList = {ArrayList@5037}  size = 0
 mHasStableIds = false
 mObservable = {RecyclerView$AdapterDataObservable@5088} 
 shadow$_klass_ = {Class@4930} "class ca.rvogl.tpbcui.views.BowlerAdapter"
 shadow$_monitor_ = -2088753560

log.d 日志文件 fragment

06-08 13:00:53.807 29879-29879/ca.rvogl.tpbcui D/INSERTBOWLER: Number of bowlers in db = 4
06-08 13:00:53.814 29879-29884/ca.rvogl.tpbcui I/art: Do partial code cache collection, code=30KB, data=29KB
06-08 13:00:53.815 29879-29884/ca.rvogl.tpbcui I/art: After code cache collection, code=30KB, data=29KB
    Increasing code cache capacity to 128KB
06-08 13:00:53.815 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:00:53.831 29879-29879/ca.rvogl.tpbcui W/IInputConnectionWrapper: finishComposingText on inactive InputConnection
06-08 13:01:00.552 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:02.336 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:04.023 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:04.040 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:04.050 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:04.059 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:04.534 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:04.542 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:05.034 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:11.363 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:11.373 29879-29879/ca.rvogl.tpbcui D/INSERTBOWLER: Number of bowlers in db = 5
06-08 13:01:11.380 29879-29895/ca.rvogl.tpbcui D/EGL_emulation: eglMakeCurrent: 0x9e6fa300: ver 3 0 (tinfo 0xa068a610)
06-08 13:01:11.393 29879-29879/ca.rvogl.tpbcui W/IInputConnectionWrapper: finishComposingText on inactive InputConnection

Answer 1

我认为您的问题是您没有更新适配器内的实际源列表。

• 阅读 Is Java “pass-by-reference” or “pass-by-value”?可以解释一下。

解决方案可能是向 BowlerAdapter 添加一个方法，例如:-

public void notifyDatasetChanged(List<Bowler> newbowlerlist) {
    bowlersList.clear();
    bowlersList.addAll(newbowlerlist);
    super.notifyDataSetChanged();
}

然后使用这个新方法，传递修改后的bowlerlist，而不是库存的notifyDatasetChanged 方法。

例如而不是:-

    if (n != null) {
        //Adding New Bowler To The Array List At Position 0
        bowlersList.add(0, n);

        //Refreshing The List
        mAdapter.notifyDataSetChanged();

        toggleEmptyBowlers();
    }

使用:-

    if (n != null) {
        //Adding New Bowler To The Array List At Position 0
        bowlersList.add(0, n);

        //Refreshing The List
        mAdapter.notifyDataSetChanged(bowlerList);

        toggleEmptyBowlers();
    }

根据您使用上述代码的代码，获得以下结果:-

初始显示

• 应用启动时最初添加了 2 个保龄球手。
• 添加了按钮，而不是对所有对话框处理进行编码(因此，如果 EditText 不为空，单击按钮将添加一个新的圆顶礼帽)。

添加新投球手后

添加了一个新的投球手:-

1. 在 EditText 中输入 Howard。
2. 点击“添加投球手”按钮。
3. 列表将刷新，显示添加的投球手。

:-

添加评论:-

OK, insert is happening OK (you can remove the changes). Now make the following changes to the getAllBowlers method (1 write the selectQuery sql to the log, 2 write the number of rows retrieved to the log and 3 write the size of the bowlers ArrayList to the log). Run and report or fix.

public List<Bowler> getAllBowlers(String leagueId) {
    List<Bowler> bowlers = new ArrayList<>();

    //Select All Query
    String selectQuery = "SELECT  * FROM " + Bowler.TABLE_NAME + " WHERE " + Bowler.COLUMN_LEAGUE_ID + " = '" + leagueId + "'" + " ORDER BY " +
            Bowler.COLUMN_TIMESTAMP + " DESC";

    Log.d("GETALLBOWLERS-SQL","SQL used = >>>>" +selectQuery + "<<<<");

    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    Log.d("GETALLBOWLERS-CNT","Number of rows retrieved = " + String.valueOf(cursor.getCount()));


    //Looping Through All Rows And Adding To The List
    if (cursor.moveToFirst()) {
        do {
            Bowler bowler = new Bowler();
            bowler.setId(cursor.getInt(cursor.getColumnIndex(Bowler.COLUMN_ID)));
            bowler.setLeagueId(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_LEAGUE_ID)));
            bowler.setName(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_NAME)));
            bowler.setTimestamp(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_TIMESTAMP)));
            bowlers.add(bowler);
        } while (cursor.moveToNext());
    }
    cursor.close();
    //Close Database Connection
    db.close();
    Log.d("GETALLBOWLERS-CNT","Number of elements in bowlerslist = " + String.valueOf(bowlers.size()));

    //Return Bowlers List
    return bowlers;
}

<小时/>

工作示例

我实际上无法指出您的问题，尽管我确实相信它与原始答案有关，因为适配器在投球手列表的副本上工作/与投球手列表的副本一起工作，这与传递给它的投球手列表不同。因此，更改 Activity 中的投球手列表不会更改适配器中的投球手列表。因此发布 onNotifyDatasetChanged更改 Bowlerlist 后，就是向适配器表明您已更改适配器中的列表(即，它是副本，尚未更改)。

因此，投球手列表上的副本必须更改，然后 onNotifyDatasetChanged应发出。我的猜测是您没有正确实现上述内容。

因此，我几乎重新创建了您的代码并拥有一个可以工作的版本:-

• 使用按钮来添加投球手，而不是使用操作栏。
• LeagueID 是硬编码的，而不是由花药 Activity 调用并从 Intent Extra 获取 LeagueID。
• 为了方便起见，ClickListener 接口(interface)包含在 Activity 中。

Activity (我称之为 BowlerActivity)

public class BowlerActivity extends AppCompatActivity {

    private BowlerAdapter mAdapter;
    private List<Bowler> bowlersList = new ArrayList<>();
    private RecyclerView recyclerView;
    private DatabaseHelper db;
    private Button addbowler;
    private EditText newbowler;
    private TextView leagueId, noBowlersView;
    private String savedLeagueId;
    Context mContext;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = this;
        addbowler = this.findViewById(R.id.addbowler); // For testing
        leagueId = this.findViewById(R.id.tvLeagueId);
        noBowlersView = this.findViewById(R.id.noBowlersView);
        recyclerView = this.findViewById(R.id.recycler_view);
        db = new DatabaseHelper(this);

        savedLeagueId = "0"; //<<<< HARD CODED rather than get from IntentExtra
        leagueId.setText(savedLeagueId);
        bowlersList = db.getAllBowlers(leagueId.getText().toString());
        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(this);
        mAdapter = new BowlerAdapter(this,bowlersList);
        recyclerView.setLayoutManager(mLayoutManager);
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        //recyclerView.addItemDecoration(new MyDividerItemDecoration(this, LinearLayoutManager.VERTICAL, 16));
        recyclerView.setAdapter(mAdapter);

        addbowler.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showBowlerDialog(false, null, -1);
            }
        });

        recyclerView.addOnItemTouchListener(new RecyclerTouchListener(this, recyclerView, new ClickListener() {
            @Override
            public void onClick(View view, int position) {
                Toast.makeText(mContext,"You clicked me", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onLongClick(View view, int position) {
                Toast.makeText(mContext,"You long clicked me", Toast.LENGTH_SHORT).show();
                showActionsDialog(position);

            }
        }));
    }

    //Opens Dialog With Edit/Delete Options
    //Edit - 0
    //Delete - 0
    private void showActionsDialog(final int position) {
        CharSequence colors[] = new CharSequence[]{"Edit", "Delete"};

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Choose option");
        builder.setItems(colors, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                if (which == 0) {
                    showBowlerDialog(true, bowlersList.get(position), position);
                } else {
                    deleteBowler(position);
                }
            }
        });
        builder.show();
    }

    //Toggling List And Empty Bowler View
    private void toggleEmptyBowlers() {
        //You Can Check bowlerList.size() > 0

        if (db.getBowlersCount() > 0) {
            noBowlersView.setVisibility( View.GONE);
        } else {
            noBowlersView.setVisibility( View.VISIBLE);
        }
    }

    //Inserting New Bowler In The Database And Refreshing The List
    private void createBowler(String leagueId,  String bowlerName) {
        //Inserting Bowler In The Database And Getting Newly Inserted Bowler Id
        long id = db.insertBowler(leagueId, bowlerName);

        //Get The Newly Inserted Bowler From The Database
       bowlersList = db.getAllBowlers(leagueId);
       mAdapter.notifyDatasetChanged(bowlersList);
       //mAdapter.notifyDataSetChanged();
    }

    //Updating Bowler In The Database And Updating The Item In The List By Its Position
    private void updateBowler(String bowlerName, int position) {
        Bowler n = bowlersList.get(position);

        //Updating Bowler Text
        n.setLeagueId(savedLeagueId);
        n.setName(bowlerName);

        //Updating The Bowler In The Database
        db.updateBowler(n);

        //Refreshing The List
        bowlersList.set(position, n); //<<<<< does not change the bowlerlist in the adapter
        //mAdapter.notifyItemChanged(position); // Saying that nothing has changed
        mAdapter.notifyDatasetChanged(db.getAllBowlers(savedLeagueId)); //<<<<< rebuilds adapter bowler list
        toggleEmptyBowlers();
    }

    //Deleting Bowler From SQLite Database And Removing The Bowler Item From The List By Its Position
    private void deleteBowler(int position) {
        //Deleting The Bowler From The Database
        db.deleteBowler(bowlersList.get(position));


        //Removing The Bowler From The List
        bowlersList.remove(position);
        //mAdapter.notifyItemRemoved(position); // Saying that nothing has changed
        mAdapter.notifyDatasetChanged(db.getAllBowlers(savedLeagueId));
        toggleEmptyBowlers();
    }

    public interface ClickListener{
        void onClick(View view,int position);
        void onLongClick(View view,int position);
    }

    //Show Alert Dialog With EditText Options to Enter/Edit A League
    //When shouldUpdate = true, It Will Automatically Display Old Bowler Name And Change The Button Text To UPDATE
    private void showBowlerDialog(final boolean shouldUpdate, final Bowler bowler, final int position) {
        LayoutInflater layoutInflaterAndroid = LayoutInflater.from(getApplicationContext());
        View view = layoutInflaterAndroid.inflate(R.layout.dialog_bowler, null);

        AlertDialog.Builder alertDialogBuilderUserInput = new AlertDialog.Builder(BowlerActivity.this);
        alertDialogBuilderUserInput.setView(view);

        leagueId.setText(savedLeagueId);
        final EditText inputBowlerName = view.findViewById(R.id.etBowlerNameInput);
        TextView dialogTitle = view.findViewById(R.id.dialog_title);
        dialogTitle.setText(!shouldUpdate ? getString(R.string.lbl_new_bowler_title) : getString(R.string.lbl_edit_bowler_title));

        if (shouldUpdate && bowler != null) {
            leagueId.setText(bowler.getLeagueId());
            inputBowlerName.setText(bowler.getName());

        }
        alertDialogBuilderUserInput
                .setCancelable(false)
                .setPositiveButton(shouldUpdate ? "update" : "save", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialogBox, int id) {

                    }
                })
                .setNegativeButton("cancel",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialogBox, int id) {
                                dialogBox.cancel();
                            }
                        });

        final AlertDialog alertDialog = alertDialogBuilderUserInput.create();
        alertDialog.show();

        alertDialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                //Show Toast Message When No Text Is Entered
                if (TextUtils.isEmpty(inputBowlerName.getText().toString())) {
                    Toast.makeText(BowlerActivity.this, "Enter Bowler!", Toast.LENGTH_SHORT).show();
                    return;
                } else {
                    alertDialog.dismiss();
                }

                //Check If User Is Updating Bowler
                if (shouldUpdate && bowler != null) {

                    //Updating Bowler By Its Id
                    updateBowler(inputBowlerName.getText().toString(), position);

                } else {
                    //Creating New Bowler
                    createBowler(leagueId.getText().toString(), inputBowlerName.getText().toString());
                }
            }
        });
    }
}

• 唯一的变化是使用 onNotifyDatasetChanged(List<Bowler>)方法而不是股票onNotifyDatabsetChanged()

圆顶礼帽适配器

public class BowlerAdapter extends RecyclerView.Adapter<BowlerAdapter.MyViewHolder> {

    private Context context;
    private List<Bowler> bowlersList;

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView bowlerLeagueId;
        public TextView name;
        public TextView timestamp;


        public MyViewHolder(View view) {
            super(view);
            bowlerLeagueId = view.findViewById(R.id.tvLeagueId);
            name = view.findViewById(R.id.tvBowlerName);
            timestamp = view.findViewById(R.id.timestamp);
        }
    }


    public BowlerAdapter(Context context, List<Bowler> bowlersList) {
        this.context = context;
        this.bowlersList = bowlersList;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        int fakeid = android.R.layout.simple_list_item_1;
        int realid = R.layout.listview_boweler;

        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(realid, parent, false);

        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {
        Bowler bowler = bowlersList.get(position);

        holder.bowlerLeagueId.setText(bowler.getLeagueId());
        holder.name.setText(bowler.getName());

        //Formatting And Displaying Timestamp
        holder.timestamp.setText(formatDate(bowler.getTimestamp()));
    }

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

    //<<<<<<<<<< Added >>>>>>>>>>
    // This will get the actual bowler from the list
    public Bowler getItemAtPosition(int position) {
        return bowlersList.get(position);
    }

    //Formatting TimeStamp to 'EEE MMM dd yyyy (HH:mm:ss)'
    //Input  : 2018-05-23 9:59:01
    //Output : Wed May 23 2018 (9:59:01)
    private String formatDate(String dateStr) {
        try {
            SimpleDateFormat fmt = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            Date date = fmt.parse(dateStr);
            SimpleDateFormat fmtOut = new SimpleDateFormat("EEE MMM dd yyyy (HH:mm:ss)");
            return fmtOut.format(date);
        } catch (ParseException e) {
        }
        return "";
    }

    public void notifyDatasetChanged(List<Bowler> newbowlerlist) {
        bowlersList.clear();
        bowlersList.addAll(newbowlerlist);
        super.notifyDataSetChanged();
    }
}

• 注意notifyDatasetChanged(List<Bowler)方法，这会获取更改后的投球手列表并重建与其配合使用的适配器的副本，然后调用适配器的 notfiydatasetChanged方法。

• 已添加但未使用的是 getItemAtPosition可用于在给定位置从适配器返回投球手的方法(这可用于避免更改 Activity 的投球手列表副本)。

数据库助手

这仅包括一些更改，这些更改记录了一些信息，但其他方面没有变化(尽管添加了一些缺失的代码)。

public class DatabaseHelper extends SQLiteOpenHelper {

    public static final String DBNAME = "leagueapp.db";
    public static final int DBVERSION = 1;

    SQLiteDatabase mDB;

    public DatabaseHelper(Context context) {
        super(context, DBNAME, null, DBVERSION);
        mDB = this.getWritableDatabase();
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(Bowler.CRTSQL);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

    public long insertBowler(String leagueId, String bowlerName) {
        //Get Writable Database That We Want To Write Data Too
        SQLiteDatabase db = this.getWritableDatabase();

        Log.d("INSERTBOWLER","Number of bowlers in db = " + String.valueOf(DatabaseUtils.queryNumEntries(db,Bowler.TABLE_NAME)));

        ContentValues values = new ContentValues();
        //`id` and `timestamp` Will Be Inserted Automatically
        values.put(Bowler.COLUMN_LEAGUE_ID, leagueId);
        values.put(Bowler.COLUMN_NAME, bowlerName);

        //Insert Row
        long id = db.insertOrThrow( Bowler.TABLE_NAME, null, values );

        //Close Database Connection
        db.close();

        //Return Newly Inserted Row Id
        return id;
    }

    public Bowler getBowler(String leagueId) {
        //Get Readable Database If We Are Not Inserting Anything
        SQLiteDatabase db = this.getReadableDatabase();

        Cursor cursor = db.query(Bowler.TABLE_NAME,
                new String[]{Bowler.COLUMN_ID, Bowler.COLUMN_LEAGUE_ID, Bowler.COLUMN_NAME, Bowler.COLUMN_TIMESTAMP},
                Bowler.COLUMN_LEAGUE_ID + "=?",
                new String[]{String.valueOf(leagueId)}, null, null, null, null);

        if (cursor.moveToFirst()) {

            //Prepare Bowler Object
            Bowler bowler = new Bowler(
                    cursor.getLong(cursor.getColumnIndex(Bowler.COLUMN_ID)),
                    cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_LEAGUE_ID)),
                    cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_NAME)),
                    cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_TIMESTAMP)));

            //Close Database Connection
            cursor.close();
            return bowler;
        } else {return null;}
    }
    public List<Bowler> getAllBowlers(String leagueId) {
        List<Bowler> bowlers = new ArrayList<>();

        //Select All Query
        String selectQuery = "SELECT  * FROM " + Bowler.TABLE_NAME + " WHERE " + Bowler.COLUMN_LEAGUE_ID + " = '" + leagueId + "'" + " ORDER BY " +
                Bowler.COLUMN_TIMESTAMP + " DESC";

        Log.d("GETALLBOWLERS-SQL","SQL used = >>>>" +selectQuery + "<<<<");

        SQLiteDatabase db = this.getWritableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        Log.d("GETALLBOWLERS-CNT","Number of rows retrieved = " + String.valueOf(cursor.getCount()));


        //Looping Through All Rows And Adding To The List
        if (cursor.moveToFirst()) {
            do {
                Bowler bowler = new Bowler();
                bowler.setId(cursor.getInt(cursor.getColumnIndex(Bowler.COLUMN_ID)));
                bowler.setLeagueId(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_LEAGUE_ID)));
                bowler.setName(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_NAME)));
                bowler.setTimestamp(cursor.getString(cursor.getColumnIndex(Bowler.COLUMN_TIMESTAMP)));
                bowlers.add(bowler);
            } while (cursor.moveToNext());
        }
        cursor.close();
        //Close Database Connection
        db.close();
        Log.d("GETALLBOWLERS-CNT","Number of elements in bowlerslist = " + String.valueOf(bowlers.size()));

        //Return Bowlers List
        return bowlers;
    }

    public int getBowlersCount() {
        String countQuery = "SELECT  * FROM " + Bowler.TABLE_NAME;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);

        int count = cursor.getCount();
        cursor.close();

        //Return The Count
        return count;
    }

    public int updateBowler(Bowler bowler) {
        SQLiteDatabase db = this.getWritableDatabase();

        ContentValues values = new ContentValues();
        values.put(Bowler.COLUMN_LEAGUE_ID, bowler.getLeagueId());
        values.put(Bowler.COLUMN_NAME, bowler.getName());

        //Updating Row
        return db.update(Bowler.TABLE_NAME, values, Bowler.COLUMN_ID + " = ?",
                new String[]{String.valueOf(bowler.getId())});
    }

    public void deleteBowler(Bowler bowler) {
        SQLiteDatabase db = this.getWritableDatabase();
        db.delete( Bowler.TABLE_NAME, Bowler.COLUMN_ID + " = ?",
                new String[]{String.valueOf( bowler.getId())});
        db.close();
    }

    public int deleteBowlerChecked(Bowler bowler) {
        SQLiteDatabase db = this.getWritableDatabase();
        Log.d("DELETEBOWLER","Attempting to DELETE bowler " + bowler.getName());
        int rv = db.delete(Bowler.TABLE_NAME,Bowler.COLUMN_ID + "=?",
                new String[]{String.valueOf(bowler.getId())});
        if (rv < 1) {
            Log.d("DELETEBOWLER", "Bowler with an id of " + String.valueOf(bowler.getId()) + " was not deleted, as it didn't exist.");
        }
        return rv;
    }
}

RecyclerTouchListener

此wad已添加，它可能与您的相同，也可能不同。

public class RecyclerTouchListener implements RecyclerView.OnItemTouchListener{

    private BowlerActivity.ClickListener clicklistener;
    private GestureDetector gestureDetector;

    public RecyclerTouchListener(Context context, final RecyclerView recycleView, final BowlerActivity.ClickListener clicklistener){

        this.clicklistener=clicklistener;
        gestureDetector=new GestureDetector(context,new GestureDetector.SimpleOnGestureListener(){
            @Override
            public boolean onSingleTapUp(MotionEvent e) {
                return true;
            }

            @Override
            public void onLongPress(MotionEvent e) {
                View child=recycleView.findChildViewUnder(e.getX(),e.getY());
                if(child!=null && clicklistener!=null){
                    clicklistener.onLongClick(child,recycleView.getChildAdapterPosition(child));
                }
            }
        });
    }

    @Override
    public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
        View child=rv.findChildViewUnder(e.getX(),e.getY());
        if(child!=null && clicklistener!=null && gestureDetector.onTouchEvent(e)){
            clicklistener.onClick(child,rv.getChildAdapterPosition(child));
        }

        return false;
    }

    @Override
    public void onTouchEvent(RecyclerView rv, MotionEvent e) {

    }

    @Override
    public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {

    }

}

结果/测试

初始屏幕(空数据库):-

点击添加投球手按钮:-

进入Bowler B1并点击“保存”:-

添加了更多投球手:-

Bowler B5 更新:-

保龄球手 B1 和 B6 已删除:-