Question

我想将ArrayList转换为逗号分隔的String，这是我的代码。我在本地数据库中保存纬度，经度和日期时间并单独获取它们。

添加到本地数据库：

    db = new DatabaseHandler(context);
                   // db.open();


                /**
                 * CRUD Operations
                 * */
                // Inserting Contacts
                    Log.d("Insert: ", "Inserting ..");
                    db.addLocation(new Location2(latitude, longitude, city + "," + state, strDate));
                    db.close();

并单独获取：

public List<String> getLattitude(){
        List<String> labels = new ArrayList<String>();

        // Select All Query
        String selectQuery = " SELECT " + LATTITUDE + " FROM "+ TABLE_CONTACTS;

        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                labels.add(cursor.getString(0));
            } while (cursor.moveToNext());
        }

        // closing connection
        cursor.close();
        db.close();

        // returning lables
        return labels;
    }

    public List<String> getLongitude(){
        List<String> labels = new ArrayList<String>();

        // Select All Query
        String selectQuery = " SELECT " + LONGITUDE + " FROM "+ TABLE_CONTACTS;

        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                labels.add(cursor.getString(0));
            } while (cursor.moveToNext());
        }

        // closing connection
        cursor.close();
        db.close();

        // returning lables
        return labels;
    }


    public List<String> getAllDate(){
        List<String> labels = new ArrayList<String>();

        // Select All Query
        String selectQuery = " SELECT " + DATE + " FROM "+ TABLE_CONTACTS;

        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);

        // looping through all rows and adding to list
        if (cursor.moveToFirst()) {
            do {
                labels.add(cursor.getString(0));
            } while (cursor.moveToNext());
        }

        // closing connection
        cursor.close();
        db.close();

        // returning lables
        return labels;
    }

从本地db获取数据：

List<String> data = new ArrayList<>();
List<String> data2 = new ArrayList<>();
List<String> data3 = new ArrayList<String>();
String lattitute5 = String.valueOf(db.getAllLabels());
Log.d("database lattitude",lattitute5);


data.add(lattitute5);
Log.d("database to list lattitude", lattitute5);

String longitude5 = String.valueOf(db.getAllLabels2());
Log.d("database to list Longitude", longitude5);

data2.add(longitude5);

String Date3 = String.valueOf(db.getAllLabels3());
Log.d("database to list  date",Date3);

data3.add(Date3);

Latti = TextUtils.join(",", data);
Log.d("lattitu", Latti);
Longi = TextUtils.join(",", data2);
Log.d("longiii", Longi);
Date = TextUtils.join(",", data3);
Log.d("dattttt", Date);

logcat的：

database to list lattitude﹕ [23.1069556, 23.1069556] 
database to list Longitude﹕ [72.605684, 72.605684] 
database to list  date﹕ [20150810233842, 20150810233846]

longiii﹕ [72.605684],[72.605684, 72.605684] 

lattitu﹕ [23.1069556],[23.1069556, 23.1069556]

dattttt﹕ [20150810233842],[20150810233842, 20150810233846]

我想要类似的东西：

longiii : 72.605684,72.605684,72.605684
lattitu : 23.1069556,23.1069556,23.1069556
dattttt : 20150810233842,20150810233842,20150810233846

我该怎么做？

Answer 1

这两种方法很有用

 public static String listToString(List<String> list)
 {
     return TextUtils.join(",", list);
 }

 public static List<String> stringToList(String string)
 {
    if(string==null)
        return new ArrayList<String>();
    else
        return new ArrayList<String>(Arrays.asList(TextUtils.split(string, ",")));
 }

Answer 2

首先将ArrayList转换为数组：String myNewArr[] = mylist.toArray();

然后你可以通过简单的for循环加入它们：

StringBuilder sb = new StringBuilder();
for (int i = 0; i < myNewArr.length; i++)
    sb.append(myNewArr[i]);
String str = sb.toString();

或者您可以使用Apache Commons StringUtils class加入：

String str = StringUtils.join(myNewArr, ',');

Answer 3

试试这个......

public String getLattitude(){
            String labels = "";

            // Select All Query
            String selectQuery = " SELECT " + LATTITUDE + " FROM "+ TABLE_CONTACTS;

            SQLiteDatabase db = this.getReadableDatabase();
            Cursor cursor = db.rawQuery(selectQuery, null);

            // looping through all rows and adding to list
            if (cursor.getCount()>0) {
               cursor.moveToFirst();
               for(int i=0;i<cursor.getCount();i++){
                 labels+=cursor.getString(0);
                 if(i<(cursor.getCount()-1)){
                   labels+=",";
                 }
                 cursor.moveToNext();
               }
            }

            // closing connection
            cursor.close();
            db.close();

            // returning lables
            return labels;
        }

将ArrayList转换为逗号分隔的String

3 个答案: