Question

我尽力解决这个问题，但它仍然给我一个错误。希望有人在这里帮助我。我不知道代码中的问题是什么。

public class StudentListActivity extends AppCompatActivity implements View.OnClickListener {
private View scanqr, viewqr;
final Context context = this;
private ListView studentlist;
private DatabaseReference mDatabase, mDatabase1;
private ArrayList<String> mUsername = new ArrayList<>();
private ArrayList<String> mUserId = new ArrayList<>();
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
String message, qrcodevalue, selectedItem, value, values;
private IntentIntegrator qrScan;
private DatabaseReference ref, ref0, ref1;
private FirebaseAuth.AuthStateListener authListener;
private FirebaseAuth auth;
LstViewAdapter1 adapter;
private String value3;
private EditText inputSearch;
ArrayAdapter<String> arrayAdapter;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_student_list);
    getSupportActionBar().setHomeButtonEnabled(true);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    scanqr = findViewById(R.id.scanqr);
    //viewqr = findViewById(R.id.viewqr);
    studentlist = (ListView) findViewById(R.id.studentlist);
    inputSearch = (EditText) findViewById(R.id.inputSearch);

    inputSearch.setVisibility(View.GONE);

    message = getIntent().getStringExtra("secname").toString(); // Now, message has Drawer title
    setTitle(message);

    //get firebase auth instance
    auth = FirebaseAuth.getInstance();

    //get current user
    final FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();

    authListener = new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull final FirebaseAuth firebaseAuth) {
            final FirebaseUser user = firebaseAuth.getCurrentUser();

            if (user != null) {

                // user auth state is changed - user is null
                // launch login activity
            } else {
                //user auth state is not existed or closed, return to Login activity
                startActivity(new Intent(StudentListActivity.this, LoginActivity.class));
                finish();
            }
        }
    };


    //intializing scan object
    qrScan = new IntentIntegrator(this);

    //attaching onclick listener
    scanqr.setOnClickListener(this);

    adapter= new LstViewAdapter1(this, R.layout.listitem1,R.id.id, mUsername, mUserId);
    studentlist.setAdapter(adapter);

    mDatabase = FirebaseDatabase.getInstance().getReference().child("users").child("teacher").child(user.getUid().toString().trim()).child("class").child(message).child("Listofstudents");
    mDatabase.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            value = dataSnapshot.getKey().toString().trim();
            mUserId.add(value);

            ref = FirebaseDatabase.getInstance().getReference();
            ref.child("users").child("student").child(value).addValueEventListener(new ValueEventListener() {

                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {

                    String value0 = dataSnapshot.child("firstname").getValue().toString().trim();
                    String value1 = dataSnapshot.child("middlename").getValue().toString().trim();
                    String value2 = dataSnapshot.child("lastname").getValue().toString().trim();
                    mUsername.add(value0+" "+value1+" "+value2);
                    studentlist.invalidateViews();
                    adapter.notifyDataSetChanged();
                }
                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });


        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {

        }

        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    studentlist.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            selectedItem = (String) parent.getItemAtPosition(position);
            TextView userId=(TextView) view.findViewById(R.id.id);
            TextView userName=(TextView) view.findViewById(R.id.txt);
            String name = userName.getText().toString().trim();
            String uid = userId.getText().toString().trim();

            Intent intent = new Intent(StudentListActivity.this, StudentAttendanceDetailsActivity.class);
            intent.putExtra("name", name);
            intent.putExtra("secsub", uid);
            startActivity(intent);

        }
    });

    inputSearch.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
            // When user changed the Text
            adapter.getFilter().filter(cs.toString());            }

        @Override
        public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
                                      int arg3) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable arg0) {
            // TODO Auto-generated method stub
        }
    });
}

@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) {
    int id = item.getItemId();
    switch (item.getItemId()) {
        case android.R.id.home:

            // app icon in action bar clicked; goto parent activity.
            this.finish();
            return true;
        default:

            if (id == R.id.refresh) {
                restartThis();
                //Do something
                return true;
            } else if (id == R.id.add) {   //<------- CODE FOR BUTTON IN ADDING STUDENT
                Intent intent = new Intent(StudentListActivity.this, AddsStudentActivity.class);
                intent.putExtra("secname", message);
                intent.putExtra("arraylist", mUsername);
                intent.putExtra("useridvalue", mUserId);
                startActivity(intent);
                return true;
            } else if (id == R.id.search) {
                inputSearch.setVisibility(View.VISIBLE);
                inputSearch.requestFocus();
                return true;
            } else if (id == R.id.view) {
                MultiFormatWriter multiFormatWriter = new MultiFormatWriter();
                try {
                    qrcodevalue = "{"+"\"userid\""+":"+"\""+user.getUid().toString().trim()+"\""+","+"\"secsub\""+":"+"\""+message+"\""+"}";
                    Intent intent = new Intent(StudentListActivity.this, GenerateQrCodeActivity.class);
                    ByteArrayOutputStream stream = new ByteArrayOutputStream();
                    BitMatrix bitMatrix = multiFormatWriter.encode(qrcodevalue, BarcodeFormat.QR_CODE,500,500);
                    BarcodeEncoder barcodeEncoder = new BarcodeEncoder();
                    Bitmap bitmap = barcodeEncoder.createBitmap(bitMatrix);
                    bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
                    byte[] bytes = stream.toByteArray();
                    intent.putExtra("bitmap",bytes);
                    startActivity(intent);
                } catch (WriterException e) {
                    e.printStackTrace();
                }
                return true;
            }
            return super.onOptionsItemSelected(item);
    }
}

//Getting the scan results
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    IntentResult result = IntentIntegrator.parseActivityResult(requestCode, resultCode, data);
    String content = result.getContents();
    if (result != null && resultCode == RESULT_OK) {
        //if qrcode has nothing in it
        if (content == null || content =="") {
            Toast.makeText(this, "Result Not Found", Toast.LENGTH_SHORT).show();
        } else if (!content.contains("useridcontent")) {
            Toast.makeText(this, "Unregistered QR Code", Toast.LENGTH_SHORT).show();
        } else {
            //if qr contains data
            try {
                //converting the data to json
                JSONObject obj = new JSONObject(result.getContents());
                //setting values to textviews
                final String qrcodecontent = obj.getString("useridcontent");
                final String date = new SimpleDateFormat("MMM d, yyyy").format(new Date());
                final String datetime = DateFormat.getDateTimeInstance().format(new Date());

                ref1 = FirebaseDatabase.getInstance().getReference();
                ref1.child("users").child("teacher").child(user.getUid().toString().trim()).child("class").child(message).child("Listofstudents").child(qrcodecontent).addListenerForSingleValueEvent(new ValueEventListener() {

                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        if (dataSnapshot.exists()) {
                            ref1 = FirebaseDatabase.getInstance().getReference();
                            ref1.child("users").child("teacher").child(user.getUid().toString().trim()).child("class").child(message).child("Listofstudents").child(qrcodecontent).child("attendance").child(date).addListenerForSingleValueEvent(new ValueEventListener() {

                                @Override
                                public void onDataChange(DataSnapshot dataSnapshot) {
                                    if (dataSnapshot.exists()) {
                                        Toast.makeText(StudentListActivity.this, "Your already took attendance", Toast.LENGTH_SHORT).show();
                                    } else {
                                        DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference().child("users").child("teacher").child(user.getUid().toString().trim()).child("class").child(message).child("Listofstudents").child(qrcodecontent).child("attendance").child(date);
                                        mDatabase.child("date&time").setValue(datetime);
                                        mDatabase.child("status").setValue("present");
                                        Toast.makeText(StudentListActivity.this, "Time come in: "+datetime, Toast.LENGTH_SHORT).show();
                                    }
                                }
                                @Override
                                public void onCancelled(DatabaseError databaseError) {

                                }
                            });

                        } else {
                            android.support.v7.app.AlertDialog.Builder builder2=new android.support.v7.app.AlertDialog.Builder(StudentListActivity.this);
                            builder2.setTitle("Add Student");
                            builder2.setMessage("This student is not yet added in this class"+"\n"+"\n"+"Add this student in this class?");
                            builder2.setIcon(R.drawable.add);
                            builder2.setPositiveButton("Yes",new DialogInterface.OnClickListener() {

                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    DatabaseReference mDatabase1 = FirebaseDatabase.getInstance().getReference().child("users").child("teacher").child(user.getUid().toString().trim()).child("class").child(message).child("Listofstudents").child(qrcodecontent);
                                    mDatabase1.child("date&timejoin").setValue(datetime);

                                    DatabaseReference mDatabase2 = FirebaseDatabase.getInstance().getReference().child("users").child("teacher").child(user.getUid().toString().trim()).child("class").child(message).child("Listofstudents").child(qrcodecontent).child("attendance").child(date);
                                    mDatabase2.child("date&time").setValue(datetime);
                                    mDatabase2.child("status").setValue("present");
                                }
                            });

                            builder2.setNegativeButton("No", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog, int which) {
                                    dialog.dismiss();
                                }
                            });
                            android.support.v7.app.AlertDialog dialog = builder2.show();
                        }
                    }
                    @Override
                    public void onCancelled(DatabaseError databaseError) {

                    }
                });

                //Toast.makeText(this, obj.getString("userid")+obj.getString("secsub"), Toast.LENGTH_LONG).show();
            } catch (JSONException e) {
                e.printStackTrace();
                //if control comes here
                //that means the encoded format not matches
                //in this case you can display whatever data is available on the qrcode
                //to a toast
                Toast.makeText(this, result.getContents(), Toast.LENGTH_LONG).show();
            }
        }
    } else {
        super.onActivityResult(requestCode, resultCode, data);
    }
}

@Override
public void onClick(View view) {
    //initiating the qr code scan
    qrScan.initiateScan();

}

private void restartThis() {
    finish();
    overridePendingTransition(0, 0);
    startActivity(getIntent());
    overridePendingTransition(0, 0);
}
private static void doKeepDialog(Dialog dialog){
    WindowManager.LayoutParams lp = new WindowManager.LayoutParams();
    lp.copyFrom(dialog.getWindow().getAttributes());
    lp.width = WindowManager.LayoutParams.WRAP_CONTENT;
    lp.height = WindowManager.LayoutParams.WRAP_CONTENT;
    dialog.getWindow().setAttributes(lp);
}

class LstViewAdapter1 extends BaseAdapter implements Filterable {

    private Context context;
    private int resource;
    private int ids;
    private ArrayList arrayList;
    private List<String> originalData=null;
    private List<String>filteredData=null;
    List<String> title;;
    private FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
    private LstViewAdapter1.ItemFilter mFilter = new LstViewAdapter1.ItemFilter();
    private LayoutInflater inflater;

    public LstViewAdapter1(Context context, int resource, int id, ArrayList title, ArrayList userId){
        this.context = context;
        this.resource = resource;
        this.ids = id;
        this.title = title;
        this.arrayList = userId;
        this.filteredData = userId ;
        this.originalData = userId ;
        inflater = LayoutInflater.from(context);

    }

    public int getCount() {
        return filteredData.size();
    }

    public Object getItem(int position) {
        return filteredData.get(position);
    }

    public long getItemId(int position) {
        return position;
    }

    // Hold views of the ListView to improve its scrolling performance
    private class ViewHolder {
        public TextView type;
        public TextView uid;
        public ImageButton removeButton;

    }

    public View getView(final int position, final View convertView, ViewGroup parent) {

        View rowView = convertView;
        // Inflate the list_item.xml file if convertView is null
        if(rowView==null){
            rowView = inflater.inflate(R.layout.listitem, null);
            rowView= inflater.inflate(resource, parent, false);
            LstViewAdapter1.ViewHolder viewHolder = new LstViewAdapter1.ViewHolder();
            viewHolder.type= (TextView) rowView.findViewById(R.id.txt);
            viewHolder.uid= (TextView) rowView.findViewById(R.id.id);
            viewHolder.removeButton= (ImageButton) rowView.findViewById(btn_del);
            rowView.setTag(viewHolder);

        }

        final String x = (String) arrayList.get(position);
        final String y = arrayList.get(position).toString().trim();
        // Set text to each TextView of ListView item
        LstViewAdapter1.ViewHolder holder = (LstViewAdapter1.ViewHolder) rowView.getTag();
        holder.uid.setText(x);
        holder.removeButton.setBackgroundResource(R.drawable.deletes);
        holder.removeButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(final View v) {
                final AlertDialog.Builder builder2=new AlertDialog.Builder(context);
                final View dialogView = inflater.inflate(R.layout.customdialog, null);
                builder2.setView(dialogView);
                final EditText input = (EditText) dialogView.findViewById(R.id.edit1);
                final TextInputLayout inputs = (TextInputLayout) dialogView.findViewById(R.id.text_field);

                TextWatcher watcher = new TextWatcher() {

                    @Override
                    public void onTextChanged(CharSequence s, int start, int before, int count) {

                    }

                    @Override
                    public void beforeTextChanged(CharSequence s, int start, int count, int after) {

                    }

                    @Override
                    public void afterTextChanged(Editable s) {
                        inputs.setErrorEnabled(false);
                        inputs.setError(null);
                    }
                };

                input.addTextChangedListener(watcher);

                builder2.setTitle("Delete Class");
                builder2.setMessage("Do you want to delete "+y+" from this class?");
                builder2.setPositiveButton("ok", null);
                builder2.setNegativeButton("cancel", null);
                builder2.setIcon(R.drawable.deletes);
                final AlertDialog mAlertDialog = builder2.create();
                mAlertDialog.setOnShowListener(new DialogInterface.OnShowListener() {
                    @Override
                    public void onShow(final DialogInterface dialog) {
                        Button a = mAlertDialog.getButton(AlertDialog.BUTTON_POSITIVE);
                        a.setOnClickListener(new View.OnClickListener() {

                            @Override
                            public void onClick(View view) {
                                // TODO Do something
                                if (input.getText().toString().equalsIgnoreCase("delete")) {
                                    arrayList.remove(position);
                                    notifyDataSetChanged();
                                    Toast.makeText(v.getContext(), y + " has been deleted in this class", Toast.LENGTH_SHORT).show();

                                    ref0 = FirebaseDatabase.getInstance().getReference();
                                    ref0.child("users").child("student").orderByChild("name").equalTo(y).addListenerForSingleValueEvent(new ValueEventListener() {

                                        @Override
                                        public void onDataChange(DataSnapshot dataSnapshot) {

                                            for (DataSnapshot child: dataSnapshot.getChildren()) {
                                                String hello = child.getKey();
                                                DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference().child("users").child("teacher").child(user.getUid().toString().trim()).child("class").child(message).child("Listofstudents").child(hello);
                                                mDatabase.setValue(null);
                                                dialog.dismiss();
                                                notifyDataSetChanged();
                                                restartThis();
                                            }
                                        }
                                        @Override
                                        public void onCancelled(DatabaseError databaseError) {

                                        }
                                    });
                                } else {
                                    inputs.setError("Enter word \"DELETE\"");
                                }
                            }
                        });

                        Button b = mAlertDialog.getButton(AlertDialog.BUTTON_NEGATIVE);
                        b.setOnClickListener(new View.OnClickListener() {

                            @Override
                            public void onClick(View view) {
                                // TODO Do something
                                dialog.dismiss();
                            }
                        });
                    }
                });

                mAlertDialog.show();

            }
        });
        holder.type.setText(title.get(position));
        holder.uid.setText(filteredData.get(position));

        return rowView;
    }

    public Filter getFilter() {
        return mFilter;
    }

    private class ItemFilter extends Filter {
        @Override
        protected FilterResults performFiltering(CharSequence constraint) {

            String filterString = constraint.toString().toLowerCase();

            FilterResults results = new FilterResults();

            final List<String> list = originalData;

            int count = list.size();
            final ArrayList<String> nlist = new ArrayList<String>(count);

            String filterableString ;

            for (int i = 0; i < count; i++) {
                filterableString = list.get(i);
                if (filterableString.toLowerCase().contains(filterString)) {
                    nlist.add(filterableString);
                }
            }

            results.values = nlist;
            results.count = nlist.size();

            return results;
        }

        @SuppressWarnings("unchecked")
        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            filteredData = (ArrayList<String>) results.values;
            notifyDataSetChanged();
        }

    }

}

}

这是发生错误的部分。

Answer 1

您的问题从此时开始：title因为标题为空

=＆GT;试着找出它为什么空=＆gt; LstViewAdapter1是来自public LstViewAdapter1(Context context, int resource, int id, ArrayList title, ArrayList userId) adapter= new LstViewAdapter1(this, R.layout.listitem1,R.id.id, mUsername, mUserId);

的构造函数的init

=＆GT;您的构造函数来自：title =＆gt;与mUsername对应的是mUsername

=＆GT;在使用ArrayList时，您只需要mUsername，但不要在其中添加任何值，以免造成错误。

我看到你为mUsername增加了价值，但在你身后使用它。请更改您的代码：在尝试使用之前将值添加到items = [{key: 1, name: 'name1'}, {key: 2, name: 'name2'}, ... ]。

索引0无效，大小为0 getView Custom Listview

1 个答案: