我试图从我的数据库中获取数据以显示在列表视图中。我遇到的问题是,似乎获取器不能正常工作。当我测试它们返回的数据时,它返回的是null。
任何见解都将是感激的,因为我在这里迷失了方向。先谢谢你。
这里是我初始化类的地方。
public ArrayList<GameStats> getAllData() {
ArrayList<GameStats> arrayList = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery("SELECT * FROM savedGamesTable", null);
while(cursor.moveToNext()){
int id = cursor.getInt(0);
String lName = cursor.getString(1);
int lScore = cursor.getInt(2);
String rName = cursor.getString(3);
int rScore = cursor.getInt(4);
String notes = cursor.getString(5);
GameStats gameStats = new GameStats(id, lName, lScore, rName, rScore, notes);
arrayList.add(gameStats);
}
return arrayList;
}
这里是我尝试使用getters的地方:
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
convertView = inflater.inflate(R.layout.activity_saved_games, null);
TextView lName = convertView.findViewById(R.id.lName);
TextView lScore = convertView.findViewById(R.id.lScore);
TextView rName = convertView.findViewById(R.id.rName);
TextView rScore = convertView.findViewById(R.id.rScore);
TextView notes = convertView.findViewById(R.id.notes);
GameStats gameStats = arrayList.get(position);
testVar = gameStats.getlName();
Log.d("MyAdaptor","gameStats = " + var);
lName.setText(gameStats.getlName());
lScore.setText(String.valueOf(gameStats.getlScore()));
rName.setText(gameStats.getrName());
rScore.setText(String.valueOf(gameStats.getrScore()));
notes.setText(gameStats.getNotes());
return convertView;
}
这里是模型类
public class GameStats {
int id, lScore, rScore;
String lName, rName, notes;
public GameStats(int id, String lName, int lScore, String rName, int rScore, String notes) {
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getlScore() {
return lScore;
}
public void setlScore(int lScore) {
this.lScore = lScore;
}
public int getrScore() {
return rScore;
}
public void setrScore(int rScore) {
this.rScore = rScore;
}
public String getlName() {
return lName;
}
public void setlName(String lName) {
this.lName = lName;
}
public String getrName() {
return rName;
}
public void setrName(String rName) {
this.rName = rName;
}
public String getNotes() {
return notes;
}
public void setNotes(String notes) {
this.notes = notes;
}
}
这里是我调用方法的地方。
public class SavedGameScreen extends AppCompatActivity {
ListView lv1;
ArrayList<GameStats> arrayList;
MyAdaptor myAdaptor;
DatabaseHelper databaseHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_saved_game_screen);
lv1 = findViewById(R.id.lv1);
databaseHelper = new DatabaseHelper(this);
arrayList = new ArrayList<>();
loadData();
}
private void loadData() {
arrayList = databaseHelper.getAllData();
myAdaptor = new MyAdaptor(this, arrayList);
lv1.setAdapter(myAdaptor);
myAdaptor.notifyDataSetChanged();
}
}
请更改以下构造函数,看看是否有效。
public GameStats(int id, String lName, int lScore, String rName, int rScore, String notes) {
this.id = id;
this.lName = IName;
this.lScore = IScore;
this.rName = rName;
this.rScore = rScore;
this.notes = notes;
}
在你的模型类中,使用constrtuctor初始化变量。我想这就是问题所在。因为你没有初始化模型类的属性,所以获取器会返回 "null "或任何垃圾值。
你把值传给了模型构造函数,但你没有把它分配给模型变量。你需要修改以下代码。
public GameStats(int id, String lName, int lScore, String rName, int rScore, String notes) {
this.id = id;
this.lName = IName;
this.lScore = IScore;
this.rName = rName;
this.rScore = rScore;
this.notes = notes;
}
Else通过以下方式初始化每个变量 setter()
方法。