Question

我有各种各样的片段，但是我显示了有一个名为ShowItem.java的bug的片段。我在另一个片段中添加了数据，并在setter和getter的帮助下将其发送到另一个片段，并将其添加到ShowItem.java片段上的listview中。我有一个选项，当用户点击保存选项然后listview整个数据保存到数据库并清除数据库时，我回到showItem.java片段然后它显示listview中的数据库和列表视图数据。这是代码ShowItem.java

public class ShowItem extends Fragment {

// initialization and variable declaration
ArrayList<String> inventoryArray;
private ArrayAdapter<String> listAdapter;
public DBAdapter mDBAdapter;
String date_time = null;
 String invoice_number=null;
String quality=null;
String user;
ListView list_data;
String a,b,c,d;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                     Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_show_item, null, false);
// getting the listview and back button id
list_data = (ListView) view.findViewById(R.id.idata);
Button button_back = (Button) view.findViewById(R.id.iback);
mDBAdapter=new DBAdapter(getActivity());
inventoryArray = new ArrayList<>(Inventory.mInventoryModels.size());

// accessing the model and set on the list view
for(UseModel useModel: Home.mInventoryModels){
    user=useModel.getUser();
}
for (InventoryModel model : Inventory.mInventoryModels) {
    date_time = model.getDate();
    invoice_number = model.getInvoice_number();
    quality = model.getQuality();
    inventoryArray.add(0,user+" "+date_time + " " + invoice_number + " " + quality);
    listAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, inventoryArray);
    list_data.setAdapter(listAdapter);

}

// for showing the data on listview from the database

Cursor cursor=mDBAdapter.selectLogs();

if(cursor.moveToFirst()) {
do{
        a = cursor.getString(1);
        b = cursor.getString(2);
        c = cursor.getString(3);
        d=cursor.getString(4);
        inventoryArray.add(a + " " + b + " " + c+ " "+ d );
    }
while(cursor.moveToNext());
}


button_back.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {

        Inventory inventory = new Inventory();
        FragmentManager manager = getFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        transaction.replace(R.id.defaultFrame, inventory).commit();

    }
});

return view;
}

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

@Override
public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
// TODO Add your menu entries here
super.onCreateOptionsMenu(menu, inflater);
}

// menu option
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {

    case R.id.send:
        deletingData();

        return true;
    case R.id.save:
        savingData();
        listAdapter.clear();
        listAdapter.notifyDataSetChanged();
        return true;

    case R.id.profile:
        Profile profile = new Profile();
        FragmentManager manager = getFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        transaction.replace(R.id.defaultFrame, profile).commit();
        return true;

    default:
        break;
}

return true;
}


// method for saving the data into the database
public void savingData(){

boolean data=mDBAdapter.gettingValues(user,date_time,invoice_number,quality);
if(data){
    try{
            Toast.makeText(getActivity(), "Data saved", Toast.LENGTH_SHORT).show();
        }
    catch (Exception e){
        e.printStackTrace();
    }

}
else{
    Toast.makeText(getActivity(), "Data not saved",Toast.LENGTH_SHORT).show();
}
}

//deleting the data from the database
public void  deletingData(){
new AlertDialog.Builder(getActivity()).setMessage("Are you sure? This will delete all entries")
        .setPositiveButton("OK", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        mDBAdapter.clearData();
                        listAdapter.clear();
                        listAdapter.notifyDataSetChanged();
                        Toast.makeText(getActivity(), "Database cleared", Toast.LENGTH_SHORT).show();
                    }
                }).setNegativeButton("NO", new DialogInterface.OnClickListener() {
    @Override
    public void onClick(DialogInterface dialog, int which) {
        getActivity().finish();
    }
}).setIcon(R.mipmap.ic_launcher).show();


}



 }

在将数据添加到listview之后，在保存并清除listview后，它看起来像第一个截图，但是当我回到showItem.java片段时，它有listview，那么它看起来像第二个截图，我认为它同时显示数据库和listview值。的更新

public class DBAdapter extends SQLiteOpenHelper {
public static final String database_name="inventoryData";
public static final String table="dataTable";
public static final String id="_id";
public static final String userName="user";
public static final String datetime="date_time";
public static final String invoicenumber="invoice_number";
public static final String i_quality="quality";


public DBAdapter(Context context) {
    super(context, database_name, null, 1);
}

@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
// creation of table into a database
 String defaultTable="create table datatable (id integer primary key, user varchar(255), date_time varchar(255), invoice_number varchar(255), quality varchar(255));";
sqLiteDatabase.execSQL(defaultTable);
}

@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
    // if table exists then it will drop the table
    sqLiteDatabase.execSQL("drop table if exists dataTable");
    onCreate(sqLiteDatabase);
}


// saving the data into the table's column
public boolean gettingValues(String user,String date_time,String invoice_number,String quality) {
    SQLiteDatabase database = this.getWritableDatabase();
    ContentValues data = new ContentValues();
    data.put(userName,user);
    data.put(datetime, date_time);
    data.put(invoicenumber, invoice_number);
    data.put(i_quality, quality);
    // insert values
    long a = database.insert(table, null, data);
    if (a == -1) {
        return false;
    } else {
        return true;
    }
}

// deleting the data
    public void clearData(){
        SQLiteDatabase database=this.getWritableDatabase();
        database.delete(table,null,null);
}


// selecting the data from the database
public Cursor selectLogs(){
        SQLiteDatabase database=this.getWritableDatabase();
        Cursor cursor=database.rawQuery("select * from "+table,null);
        return cursor;
}

}

Answer 1

IndexError

这是正确的方法;清除arraylist，你传递给适配器，然后通知适配器数据已被切换（或清除）。

Answer 2

尝试在将所有数据添加到列表后创建适配器：

for (InventoryModel model : Inventory.mInventoryModels) {
    date_time = model.getDate();
    invoice_number = model.getInvoice_number();
    quality = model.getQuality();
    inventoryArray.add(0,user+" "+date_time + " " + invoice_number + " " + quality);
}
// for showing the data on listview from the database
Cursor cursor=mDBAdapter.selectLogs();
if(cursor.moveToFirst()) {
    do{
        a = cursor.getString(1);
        b = cursor.getString(2);
        c = cursor.getString(3);
        d=cursor.getString(4);
        inventoryArray.add(a + " " + b + " " + c+ " "+ d + " (DB)");
    }
    while(cursor.moveToNext());
}
listAdapter = new ArrayAdapter<String>(getActivity(), android.R.layout.simple_list_item_1, inventoryArray);
list_data.setAdapter(listAdapter);

在多次尝试清除列表视图后，我的数据未从列表视图中删除

2 个答案: