مشکل در ListView

دوستان سلام و خسته نباشید.

من یک پروژه بر اساس آموزش ListView استاد نوشتم، ولی یه مشکلی دارم که وقتی برنامه رو کاملا میبندم هر چی که داخل برنامه بود از بین میره و پاک میشه(منظورم اطلاعاتی هست که کاربر وارد میکنه) و دقیقا نمیدونم باید از چه مبحثی استفاده کنم برای حل این مشکل.

آموزش بخش 14 رو نگاه کردم اما متوجه نشدم که چجوری میتونم موقع باز کردن مجدد برنامه اطلاعاتی که قبلا ذخیره کردم رو باز کنم.
کد های برنامه رو قرار میدم:

ActivityMain.java

 public class ActivityMain extends AppCompatActivity {
public ArrayAdapter adapter;
public Button btnAdd;
@Override
protected void onResume() {
G.currentActivity = this;
super.onResume();
if (adapter != null) {
adapter.notifyDataSetChanged();
        }
    }
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView lstContent = (ListView) findViewById(R.id.lstContent);
btnAdd = (Button) findViewById(R.id.btnAdd);
adapter = new AdapterWord(G.words);
lstContent.setAdapter(adapter);
btnAdd.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
StructWord word = new StructWord();
G.words.add(word);
adapter.notifyDataSetChanged();
            }
        });
adapter.notifyDataSetChanged();
    }
}

G.java

 public class G extends Application {

public static Context context;
public static LayoutInflater inflater;
public static Activity currentActivity;
public static ArrayList<StructWord> words = new ArrayList<StructWord>();

public static SQLiteDatabase database;

public static final String DIR_SDCARD = Environment.getExternalStorageDirectory().getAbsolutePath();
public static final String DIR_DATABASE = DIR_SDCARD + "/database-test/";

@Override
public void onCreate() {
super.onCreate();
context = getApplicationContext();
inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

File file = new File(DIR_DATABASE);
file.mkdirs();
database = SQLiteDatabase.openOrCreateDatabase(DIR_DATABASE + "/database.sqlite", null);
G.database.execSQL("CREATE  TABLE  IF NOT EXISTS wordtable (" +
"word_id INTEGER PRIMARY KEY  AUTOINCREMENT  NOT NULL  UNIQUE , " +
"word_word TEXT," +
"word_translate TEXT," +
"word_synonym TEXT, " +
"word_oposite TEXT, " +
"word_noun BOOL, " +
"word_verb BOOL, " +
"word_adj BOOL, " +
"word_adv BOOL," +
" word_example TEXT" +
")");
G.database.execSQL("CREATE  TABLE  IF NOT EXISTS listviewtable (" +
"list_id INTEGER PRIMARY KEY  AUTOINCREMENT  NOT NULL  UNIQUE ," +
"list_word TEXT, " +
"list_translate TEXT)");
    }
}

AdapterWord.java

public class AdapterWord extends ArrayAdapter<StructWord> {
public AdapterWord(ArrayList<StructWord> array) {
super(G.context, R.layout.adapter_words, array);
    }
public static class ViewHolder {
public TextView txtWord;
public TextView txtTranslate;
public ViewGroup layoutRoot;
public ImageView imgDelete;

public ViewHolder(View view) {
txtWord = (TextView) view.findViewById(R.id.txtWord);
txtTranslate = (TextView) view.findViewById(R.id.txtTranslate);
layoutRoot = (ViewGroup) view.findViewById(R.id.layoutRoot);
imgDelete = (ImageView) view.findViewById(R.id.imgDelete);
        }

public void fill(final ArrayAdapter<StructWord> adapter, final StructWord item, final int position) {
txtWord.setText(item.word);
txtTranslate.setText(item.translate);
layoutRoot.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent = new Intent(G.currentActivity, ActivityEdit.class);
intent.putExtra("POSITION", position);
G.currentActivity.startActivity(intent);
                }
            });
imgDelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
adapter.remove(item);
                }
            });
        }
    }
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder;
StructWord item = getItem(position);
if (convertView == null) {
convertView = G.inflater.inflate(R.layout.adapter_words, parent, false);
holder = new ViewHolder(convertView);
convertView.setTag(holder);
        } else {
holder = (ViewHolder) convertView.getTag();
        }
holder.fill(this, item, position);
return convertView;
    }
}

 public class ActivityEdit extends Activity {
@Override
protected void onResume() {
G.currentActivity = this;
super.onResume();
    }
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_edit);
final EditText edtWord = (EditText) findViewById(R.id.edtWord);
final EditText edtTranslate = (EditText) findViewById(R.id.edtTranslate);
final EditText edtSynonym = (EditText) findViewById(R.id.edtSynonym);
final EditText edtOposite = (EditText) findViewById(R.id.edtOposite);
final EditText edtExample = (EditText) findViewById(R.id.edtExample);
final Button btnOk = (Button) findViewById(R.id.btnOk);
final CheckBox chkNoun = (CheckBox) findViewById(R.id.chkNoun);
final CheckBox chkVerb = (CheckBox) findViewById(R.id.chkVerb);
final CheckBox chkadj = (CheckBox) findViewById(R.id.chkadj);
final CheckBox chkadv = (CheckBox) findViewById(R.id.chkadv);

Bundle extras = getIntent().getExtras();
int position = 0;
if (extras != null) {
position = extras.getInt("POSITION");
        }
final StructWord word = G.words.get(position);
edtWord.setText(word.word);
edtTranslate.setText(word.translate);
edtSynonym.setText(word.synonym);
edtOposite.setText(word.oposite);
edtExample.setText(word.example);
chkNoun.setChecked(word.doneNoun);
chkVerb.setChecked(word.doneVerb);
chkadj.setChecked(word.doneadj);
chkadv.setChecked(word.doneadv);

btnOk.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
word.word = edtWord.getText().toString();
word.translate = edtTranslate.getText().toString();
word.synonym = edtSynonym.getText().toString();
word.oposite = edtOposite.getText().toString();
word.example = edtExample.getText().toString();
word.doneNoun = chkNoun.isChecked();
word.doneVerb = chkVerb.isChecked();
word.doneadj = chkadj.isChecked();
word.doneadv = chkadv.isChecked();
finish();
G.database.execSQL("INSERT INTO wordtable (word_word,word_translate,word_translate) VALUES('" + edtWord.getText() + "','" + edtTranslate.getText() + "','" + edtSynonym.getText() + "');");
            }
        });
    }
}

public class StructWord {
public String word;
public String translate;
public String synonym;
public String oposite;
public String example;
public boolean doneNoun;
public boolean doneVerb;
public boolean doneadj;
public boolean doneadv;
}