HashSet ArrayList不在列表視圖中顯示

Question

所以這個項目讓我瘋狂。感謝Ahmed Aeon Axan提供的最後答案。我從來沒有使用HashTables之前，但從我看過的所有代碼應該工作。請告訴我爲什麼這不顯示在我的listview中。

在model.java創建以下

public class Model implements Serializable { 
public static final int END_MORNING = 11; // 11:00AM, inclusive 
public static final int END_AFTERNOON = 16; // 4:00PM, inclusive 

private GregorianCalendar startDate; 

private ArrayList<GregorianCalendar> datesSmoked = new ArrayList<GregorianCalendar>(); 
private ArrayList<String> locationsSmoked = new ArrayList<String>(); 
private ArrayList<String> locations = new ArrayList<String>(); 
private ArrayList<String> allIncidents = new ArrayList<String>(); 
private Set<String> newLocArr = new HashSet<String>(locations); 
private SimpleDateFormat sdf = new SimpleDateFormat("E, MMM dd"); 
private ArrayList<String> times = new ArrayList<String>(); 

public String [] defaultLocations = {"Home", "Work", "Commuting", "School", "Bar", "Restaurant", "Social Gathering", "Other"}; 
public String [] eachSmoked; 


public Model(GregorianCalendar date){ 
    startDate = date; 

    for (String s : this.defaultLocations) {    
     locations.add(s); 
    } 
} 

public Model(){ 
    this(new GregorianCalendar()); // now 
} 

public ArrayList<String> getDates() { 
    for (int i = 0; i < datesSmoked.size(); i++) { 
     String s = (sdf.format(i)); 
     times.add(s); 
    } 
    return times; 
} 

public List<String> getPlacesSmoked() { 

    for (String key : locations) { 

    newLocArr.add(key+ ": " + Collections.frequency(locationsSmoked, key)); 

    }  
    return new ArrayList<String>(newLocArr); 
} 

public ArrayList<String> getAllIncidentsArray() { 

    for (int i = 0; i < datesSmoked.size(); i++) { 
     allIncidents.add(getDates().get(i) + ", " + locationsSmoked.get(i)); 
    } 

    return allIncidents; 
} 

public ArrayList<String> getlocationsArray() { 
    return this.locations; 
} 

public ArrayList<String> getLocationsSmokedArray() { 
    return this.locationsSmoked; 
} 

public ArrayList<GregorianCalendar> getDatesSmokedArray() { 
    return this.datesSmoked; 
} 

結束對model.java

相關的代碼中調用到了活動地點如下它沒有顯示

列表視圖

public class LocationActivity extends Activity { 

public static final String SMOKIN_DATA_FILE = "smokin.dat"; 

public static Model model = null; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    setContentView(R.layout.activity_location); 

    restoreModel(); 

    ListView listView = (ListView) findViewById(R.id.location_listview_Id); 
    ArrayAdapter<String> listAdapter = new ArrayAdapter<String>(this, 
      android.R.layout.simple_list_item_1, model.getPlacesSmoked());  
    listView.setAdapter(listAdapter); 
    listAdapter.notifyDataSetChanged(); 
} 

本質上我試圖得到ArrayList locationsSmoked這顯示
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Answer 1

locTest您的locTest列表爲空，因爲它在Model創建時初始化爲空HashSettest1這是用空locations列表初始化的。

的List(Collection<?>)構造函數的值複製，而不是指向集合，據我記得

快速的解決方案（如果它做的伎倆居然不知道）：

public Model(GregorianCalendar date){ 
    startDate = date; 
    for (String s : this.defaultLocations) {    
     locations.add(s); 
    }   
    // calling setPlacesSmoked to process data 
    setPlacesSmoked(); 
} 

public void setPlacesSmoked() { 
    // assuming that locations list holds the data needed to process 
    for (String key : locations) { 
     test1.add(key+ ": " + Collections.frequency(locations, key));   
    } 
} 


public List<String> getPlacesSmoked() {    
    //return locTest; 
    return new ArrayList<String>(test1); 
} 

預期產出：

Home: 1 
Work: 1 
Commuting: 1 
School: 1 
Bar: 1 
Restaurant: 1 
Social Gathering: 1 
Other: 1 

但這取決於locations內容