android - 在 RecyclerView 中删除最后一项时应用程序崩溃

Question

我正在使用 RecyclerView 并从数据库填充数据并将其存储到 arrayLists 中。我还在回收器 View 中添加了一个 onLongClickListener() ，它删除了长按的行。一切正常，但当我删除最后一个应用程序时，应用程序崩溃，并且出现 Java.Lang.IndexOutOfBoundsException 索引:0 大小:0。

这是我的代码

public class MainActivity extends AppCompatActivity implements AlarmRecyclerViewInterface {

    FloatingActionButton mAlarmAddButton;
    RecyclerView mRecyclerView;
    SQLiteDatabase db;
    AlarmsDBhelperClass mAlarmsDBhelperClass;
    ArrayList<String> nameArrayList = new ArrayList<>();
    ArrayList <String> modeArrayList = new ArrayList<>();
    ArrayList<String> repeatArrayList = new ArrayList<>();
    ArrayList<String> hoursArrayList = new ArrayList<>();
    ArrayList<String> minArrayList = new ArrayList<>();
    Switch mSwitch;
    AlarmAdapter alarmAdapter = new AlarmAdapter(hoursArrayList,minArrayList,modeArrayList,repeatArrayList,nameArrayList,this);
    ImageView emptyImageView;

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

        //Initializing RecyclerView, DatabaseHelperClass, FAB button, The ON OFF switch & the empty ImageView
        mAlarmsDBhelperClass = new AlarmsDBhelperClass(getApplicationContext());
        mAlarmAddButton = findViewById(R.id.btnAlarmADD);
        mRecyclerView = findViewById(R.id.alarmList);
        mSwitch = findViewById(R.id.switchONOFF);
        emptyImageView = findViewById(R.id.empty_view);

        //DividerItemDecoration class is used for getting a vertical line between rows of RecyclerView
        DividerItemDecoration itemDecoration = new DividerItemDecoration(this,DividerItemDecoration.VERTICAL);
        mRecyclerView.addItemDecoration(itemDecoration);

        //Getting a writable reference of the Database.
        db = mAlarmsDBhelperClass.getWritableDatabase();

        //Retrieving values from the database and storing them in custom ArrayLists
        boolean isDataEmpty = getAlarm(db);

        //Checking if our arrayList is empty? if yes then display some empty list text or an image
        if (!isDataEmpty){
            mRecyclerView.setVisibility(View.GONE);
            emptyImageView.setImageResource(R.drawable.no_alarm_black_white);
            emptyImageView.setVisibility(View.VISIBLE);
        }
        else {
            mRecyclerView.setVisibility(View.VISIBLE);
            emptyImageView.setVisibility(View.GONE);
        }

        //FAB Event handling
        mAlarmAddButton.setImageResource(R.drawable.addalarm);
        mAlarmAddButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent mIntent = new Intent(getApplicationContext(), AddAlarm.class);
                startActivity(mIntent);
            }
        });

       //Warping up with the recyclerView
        mRecyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
        mRecyclerView.setAdapter(alarmAdapter);
        mRecyclerView.setHasFixedSize(true);
    }

    public boolean getAlarm(SQLiteDatabase db) {
        Cursor cursor = db.rawQuery("SELECT * FROM alarms", new String[]{});
        boolean rowExists;
        if (cursor.moveToFirst()) {
            do {
                nameArrayList.add(cursor.getString(2));
                modeArrayList.add(cursor.getString(3));
                repeatArrayList.add(cursor.getString(4));
                hoursArrayList.add(Integer.toString(cursor.getInt(5)));
                minArrayList.add(Integer.toString(cursor.getInt(6)));
                rowExists = true;
            } while (cursor.moveToNext());
        }else {
            rowExists = false;
        }
        cursor.close();
        return rowExists;
    }

    //RecyclerView's onClick()
    @Override
    public void onItemClick(int position) {
        Toast.makeText(this, "Alarm Clicked !", Toast.LENGTH_SHORT).show();
    }

    //RecyclerView's onLongClick()
    @Override
    public void onLongItemClick(int position) {
        hoursArrayList.remove(position);
        //Updating the recyclerView
        alarmAdapter.notifyItemRemoved(position);
        //Deleting the row from the database
        db.delete("alarms","hours=?",new String[]{hoursArrayList.get(position)});
        Toast.makeText(this,"Alarm Deleted !", Toast.LENGTH_SHORT).show();
    }
}

这是我的 RecyclerView 适配器

public class AlarmAdapter extends RecyclerView.Adapter<AlarmAdapter.AlarmView> {
    //Variables for the main recycler view
    private ArrayList<String> hoursArrayList;
    private ArrayList<String> minArrayList;
    private ArrayList<String> modeArrayList;
    private ArrayList<String> repeatArrayList;
    private ArrayList<String> nameArrayList;
    private AlarmRecyclerViewInterface mInterface;

    public AlarmAdapter(ArrayList<String> hours,ArrayList<String> mins,ArrayList<String> mode,ArrayList<String> repeat,ArrayList<String> name,AlarmRecyclerViewInterface mInterface){
        this.hoursArrayList = hours;
        this.minArrayList = mins;
        this.modeArrayList = mode;
        this.nameArrayList = name;
        this.repeatArrayList = repeat;
        this.mInterface = mInterface;
    }

    @NonNull
    @Override
    public AlarmView onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
        View view = layoutInflater.inflate(R.layout.alarm_profile,parent,false);
        return new AlarmView(view);
    }

    @Override
    public void onBindViewHolder(@NonNull AlarmView holder, int position) {
        if(Integer.parseInt(hoursArrayList.get(position)) < 10 ){
            holder.hours.setText("0"+hoursArrayList.get(position));
        }else {
            holder.hours.setText(hoursArrayList.get(position));
        }
        if (Integer.parseInt(minArrayList.get(position)) < 10){
            holder.mins.setText("0"+minArrayList.get(position));
        }else {
            holder.mins.setText(minArrayList.get(position));
        }
        holder.repeat.setText(repeatArrayList.get(position));
        holder.mode.setText(modeArrayList.get(position));
        holder.name.setText(nameArrayList.get(position));
    }

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

    /*ItemTouchHelper.SimpleCallback itemTouchHelperCallback = new ItemTouchHelper.SimpleCallback(0,ItemTouchHelper.RIGHT) {
        @Override
        public boolean onMove(@NonNull RecyclerView recyclerView, @NonNull RecyclerView.ViewHolder viewHolder, @NonNull RecyclerView.ViewHolder target) {
            return false;
        }

        @Override
        public void onSwiped(@NonNull RecyclerView.ViewHolder viewHolder, int direction) {
            nameArrayList.remove(viewHolder.getAdapterPosition());
            modeArrayList.remove(viewHolder.getAdapterPosition());
            repeatArrayList.remove(viewHolder.getAdapterPosition());
            hoursArrayList.remove(viewHolder.getAdapterPosition());
            minArrayList.remove(viewHolder.getAdapterPosition());
        }
    };*/

    public class AlarmView extends RecyclerView.ViewHolder{
        TextView hours,mins,repeat,name,mode;
        public AlarmView(@NonNull View itemView) {
            super(itemView);
            hours = itemView.findViewById(R.id.txtHOUR);
            mins = itemView.findViewById(R.id.txtMins);
            repeat = itemView.findViewById(R.id.txtRepeatDays);
            name = itemView.findViewById(R.id.txtName);
            mode = itemView.findViewById(R.id.txtMode);

            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    mInterface.onItemClick(getAdapterPosition());
                }
            });

            itemView.setOnLongClickListener(new View.OnLongClickListener() {
                @Override
                public boolean onLongClick(View view) {
                    mInterface.onLongItemClick(getAdapterPosition());
                    return true;
                }
            });

        }
    }

}

感谢您的帮助!

Answer 1

• 崩溃:- IndexOutOfBoundsException

  • 原因:- 您从列表中删除了数据，之后您再次从列表中提取该值以从数据库中删除数据，此时数据库会崩溃，因为删除数据时它没有任何值。

  • 解决方案:- 您可以先从数据库中删除，然后再从列表中删除。

• Example :-

  Replace below onLongClick() Override method in your class.

//RecyclerView's onLongClick()
@Override
public void onLongItemClick(int position) {

    // Best way to remove data from list
    if(hoursArrayList != null && hoursArrayList.size() > 0){

        //Deleting the row from the database
        db.delete("alarms","hours=?",new String[]{hoursArrayList.get(position)});

        //Delete from your list if you successfully removed data from your database.
        hoursArrayList.remove(position);

        //Updating the recyclerView
        if(alarmAdapter){
            alarmAdapter.notifyItemRemoved(position);
        }

        //Message to show User.
        Toast.makeText(this,"Alarm Deleted !", Toast.LENGTH_SHORT).show();
    }

}