从ArrayList提取字符串，该字符串从listview获取项目

Question

I want to extract string from the arraylist of String which is filled by the selected items from the listView.
The result of the array list is:

     {studentName=XXX,studentID=SF10001}
     {studentName=YYYY,studentID=SF10002}

I want only get the studentID which are SF10001 and SF10002. Below is my code:

     SparseBooleanArray checked = list.getCheckedItemPositions();
     ArrayList<String> selectedItems = new ArrayList<String>();

    for (int i = 0; i < checked.size(); i++) {
        // Item position in adapter
        int position = checked.keyAt(i);
        // Add sport if it is checked i.e.) == TRUE!
        if (checked.valueAt(i))
            selectedItems.add(adapter.getItem(position));
    }

    String[] outputStrArr = new String[selectedItems.size()];

    for (int i = 0; i < selectedItems.size(); i++) {

            outputStrArr[i] = selectedItems.get(i);

    }

    Intent intent = new Intent(getApplicationContext(),
            ResultActivity.class);

    // Create a bundle object
    Bundle b = new Bundle();
    b.putStringArray("selectedItems", outputStrArr);

    // Add the bundle to the intent.
    intent.putExtras(b);

    // start the ResultActivity
    startActivity(intent);
    }

And this the Result Activity.java

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_result);
    Bundle b = getIntent().getExtras();
    String[] resultArr = b.getStringArray("selectedItems");

    ListView lv = (ListView) findViewById(R.id.outputList);

    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1, resultArr);
    lv.setAdapter(adapter);


}

@SoulRayder So, I had created a StudentData Class:

public class StudentData implements Serializable {
String studentName;
String studentID;

public String getStudentNameStudentData() {
    return studentName;

}

public String getStudentID()
{
    return studentID;
}

And I change the code like tis：

    SparseBooleanArray checked = list.getCheckedItemPositions();

    ArrayList<StudentData> selectedItems = new ArrayList<StudentData>();

    for (int i = 0; i < checked.size(); i++) {
        // Item position in adapter
        int position = checked.keyAt(i);
        // Add sport if it is checked i.e.) == TRUE!
       if (checked.valueAt(i))

            selectedItems.add(adapter.getItem(position));
    }

    String[] outputStrArr = new String[selectedItems.size()];

    for (int i = 0; i < selectedItems.size(); i++) {

            outputStrArr[i] = selectedItems.get(i).getStudentID();

    }

    Intent intent = new Intent(getApplicationContext(),
            ResultActivity.class);

    // Create a bundle object
    Bundle b = new Bundle();
    b.putStringArray("selectedItems", outputStrArr);

    // Add the bundle to the intent.
    intent.putExtras(b);

    // start the ResultActivity
    startActivity(intent);
    }

But this code show me error:

 selectedItems.add(adapter.getItem(position));

which is ArrayList cannot applied to (java.lang.String). How to solve the problem. BTW, thanks your immediate respond :D

Answer 1

Two ways of solving your problem :

1) Simpler way , but not efficient : (You can use this if all your strings are guaranteed to use that exact template, or add further validations to the below function)

 public string extractStudentID(string input)
 {
      string [] parts = input.substring(1,input.length-1).split(",");

      return parts[1].split("=")[1];
 }

and use it in your code as follows

 for (int i = 0; i < checked.size(); i++) {
    // Item position in adapter
    int position = checked.keyAt(i);
    // Add sport if it is checked i.e.) == TRUE!
    if (checked.valueAt(i))
        selectedItems.add(extractStudentID(adapter.getItem(position)));
}

2) Create a class for you student data

class StudentData
{
       public string studentName;
       public string studentID;
}

Use an arraylist of these objects, instead of an arraylist of strings and modify your code in all other places accordingly:

 ArrayList<StudentData> selectedItems = new ArrayList<StudentData>();

Then, at any point, you can access the student ID easily by

 selectedItems.get(index).studentID;