Android类型不匹配的帮助。将ArrayList转换为列表？

Question

好的..这可能很难遵循..

应用程序将联系人保存到名为CONTACTS的SQLite数据库。

ContactActivity应该在SQLite数据库中加载并创建一个自定义的ListView，允许通过切换按钮选择多个联系人。

我之前创建自定义LV允许多选的示例有一个本地Contact类。我遇到了从外部DAO Contact类转换为本地Contact类的问题。

Contact.java DAO类：

package dto; 

/** 
* This DTO describes a Contact that can create and respond to a Survey 
* @author Barnitek, Bosticsa 
* 
*/ 

public class Contact { 

private int id; 
private String firstName; 
private String lastName; 
private String phoneNumber; 

public Contact(){ 

} 

public Contact(int id, String firstName, String lastName, String phoneNumber){ 
    this.id = id; 
    this.firstName = firstName; 
    this.lastName = lastName; 
    this.phoneNumber = phoneNumber; 
} 

public Contact(String firstName, String lastName, String phoneNumber){ 
    this.firstName = firstName; 
    this.lastName = lastName; 
    this.phoneNumber = phoneNumber; 
} 

public int getID(){ 
    return id; 
} 

public void setID(int id){ 
    this.id = id; 
} 

public String getFirstName() { 
    return firstName; 
} 
public void setFirstName(String firstName) { 
    this.firstName = firstName; 
} 
public String getLastName() { 
    return lastName; 
} 
public void setLastName(String lastName) { 
    this.lastName = lastName; 
} 
public String getPhoneNumber() { 
    return phoneNumber; 
} 
public void setPhoneNumber(String phoneNumber) { 
    this.phoneNumber = phoneNumber; 
} 
} 

的ContactActivity类：

package edu.uc.pollyo; 

import java.util.ArrayList; 
import java.util.List; 

import android.app.Activity; 
import android.content.Context; 
import android.content.Intent; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.MenuItem; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.AdapterView; 
import android.widget.ArrayAdapter; 
import android.widget.CheckBox; 
import android.widget.ListView; 
import android.widget.TextView; 
import dao.PollyoBaseDAO; 

/** 
* 
* @author Barnitek 
* 
*   This activity builds a custom list view that lists an array of names 
*   and phone numbers with checkable boxes. When a box is checks the 
*   name+number from that row is added to a string that will then be 
*   returned to the MainActivity and placed in the contacts text view. 
* 
*/ 

public class ContactActivity extends MainActivity { 
private ListView mainListView; 
private ArrayAdapter<Contact> listAdapter; 
private List<Contact> contactList; 
private ArrayList<dto.Contact> contactArrayList; 

public static String listContacts = ""; 
PollyoBaseDAO mydb; 


// when activity is created 
@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_contact); 

    //contactList = new ArrayList<dto.Contact>(); 
    mydb = new PollyoBaseDAO(this); 
    contactArrayList = mydb.getAllContacts(); 


    //**************PROBBLEM HERE*************** 
    // The problem is: Type mismatch: cannot convert from ArrayList<Contact> to 
    // List<ContactActivity.Contact> 
    contactList = contactArrayList; 

    // Set our custom array adapter as the ListView's adapter. 
    listAdapter = new ContactArrayAdapter(getApplicationContext(), contactList); 
    // Find the ListView resource. 
    mainListView = (ListView) findViewById(R.id.lvContactView); 
    mainListView.setAdapter(listAdapter); 

    // When item is tapped, toggle checked properties of CheckBox and 
    // Contact. 
    mainListView 
      .setOnItemClickListener(new AdapterView.OnItemClickListener() { 
       @Override 
       public void onItemClick(AdapterView<?> parent, View item, 
         int position, long id) { 
        Contact contact = listAdapter.getItem(position); 
        contact.toggleChecked(); 
        ContactViewHolder viewHolder = (ContactViewHolder) item 
          .getTag(); 
        viewHolder.getCheckBox() 
          .setChecked(contact.isChecked()); 

        // build a string of selected contacts when one is 
        // checked 
        listContacts += contact.getFirstName() + " " + contact.getLastName() + " | "; 
        System.out.println("listContacts: (ContactActivity) " 
          + listContacts); 

       } 
      }); 

    mainListView.setAdapter(listAdapter); 
} 

// Holds contact data 
private static class Contact { 
    private String firstName = ""; 
    private String lastName = ""; 

    private boolean checked = false; 

    public Contact(){}; 

    public Contact(String firstName, String lastName){ 
     this.firstName = firstName; 
     this.lastName = lastName; 
    } 

    public Contact (String firstName, String lastName, boolean checked){ 
     this.firstName = firstName; 
     this.lastName = lastName; 
     this.checked = checked; 
    } 

    public String getFirstName() { 
     return firstName; 
    } 

    public String getLastName(){ 
     return lastName; 
    } 

    public boolean isChecked() { 
     return checked; 
    } 

    public void setChecked(boolean checked) { 
     this.checked = checked; 
    } 

    public String toString() { 
     return firstName; 
    } 

    public void toggleChecked() { 
     checked = !checked; 
    } 
} 

// Holds child views for each row 
private static class ContactViewHolder { 
    private CheckBox checkBox; 
    private TextView textView; 

    public ContactViewHolder(){}; 

    public ContactViewHolder(TextView textView, CheckBox checkBox) { 
     this.checkBox = checkBox; 
     this.textView = textView; 
    } 

    public CheckBox getCheckBox() { 
     return checkBox; 
    } 

    public TextView getTextView() { 
     return textView; 
    } 

    public void setTextView(TextView textView){ 
     this.textView = textView; 
    } 
} 

/** Custom adapter for displaying an array of Contact objects. */ 
private static class ContactArrayAdapter extends ArrayAdapter<Contact> { 

    private LayoutInflater inflater; 

    public ContactArrayAdapter(Context context, List<Contact> contactList) { 
     super(context, R.layout.simplerow, R.id.rowTextView, contactList); 
     // Cache the LayoutInflate to avoid asking for a new one each time. 
     inflater = LayoutInflater.from(context); 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     // contact to display 
     Contact contact = (Contact) this.getItem(position); 

     // The child views in each row. 
     CheckBox checkBox; 
     TextView textView; 

     // Create a new row view 
     if (convertView == null) { 
      convertView = inflater.inflate(R.layout.simplerow, parent); 

      // Find the child views. 
      textView = (TextView) convertView 
        .findViewById(R.id.rowTextView); 
      checkBox = (CheckBox) convertView.findViewById(R.id.CheckBox01); 

      // Optimization: Tag the row with it's child views, so we don't 
      // have to 
      // call findViewById() later when we reuse the row. 
      convertView.setTag(new ContactViewHolder(textView, checkBox)); 

      // If CheckBox is toggled, update the contact it is tagged with. 
      checkBox.setOnClickListener(new View.OnClickListener() { 
       public void onClick(View v) { 
        CheckBox cb = (CheckBox) v; 
        Contact contact = (Contact) cb.getTag(); 
        contact.setChecked(cb.isChecked()); 
       } 
      }); 
     } 
     // Reuse existing row view 
     else { 
      // Because we use a ViewHolder, we avoid having to call 
      // findViewById(). 
      ContactViewHolder viewHolder = (ContactViewHolder) convertView 
        .getTag(); 
      checkBox = viewHolder.getCheckBox(); 
      textView = viewHolder.getTextView(); 
     } 

     // Tag the CheckBox with the Contact it is displaying, so that we 
     // can 
     // access the contact in onClick() when the CheckBox is toggled. 
     checkBox.setTag(contact); 

     // Display contact data 
     checkBox.setChecked(contact.isChecked()); 
     textView.setText(contact.getFirstName() + " " + contact.getLastName()); 

     return convertView; 
    } 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    // Handle item selection 
    switch (item.getItemId()) { 
    case R.id.help: 
     showHelp(); 
     return true; 
    case R.id.about: 
     showAbout(); 
     return true; 
    default: 
     return super.onOptionsItemSelected(item); 
    } 
} 

// launch the about activity 
private void showAbout() { 
    Intent about = new Intent(this, AboutActivity.class); 
    startActivity(about); 
} 

// launch the help activity 
private void showHelp() { 
    Intent help = new Intent(this, HelpActivity.class); 
    startActivity(help); 
} 

// when the user clicks OK, send the list of selected contacts back 
public void onOkClicked(View v) { 
    Intent output = new Intent(); 
    output.putExtra("selectedContacts", listContacts); 
    setResult(Activity.RESULT_OK, output); 
    finish(); 
} 

// when the user clicks New Contact, start a new activity to add a new 
// contact to the list 
public void onNewContactClicked(View v) { 
    Intent newContact = new Intent(this, AddContactActivity.class); 
    startActivity(newContact); 

} 
} 

的getAllContacts（）方法，它柜面需要：

public ArrayList<Contact> getAllContacts() 
     { 
      ArrayList<Contact> array_list = new ArrayList<Contact>(); 

      String selectQuery = "SELECT * FROM " + CONTACTS; 

      SQLiteDatabase db = this.getWritableDatabase(); 

      Cursor res = db.rawQuery(selectQuery, null); 

      if (res.moveToFirst()) { 
       do { 
        Contact contact = new Contact(); 
        contact.setID(Integer.parseInt(res.getString(0))); 
        contact.setFirstName(res.getString(1)); 
        contact.setLastName(res.getString(2)); 
        contact.setPhoneNumber(res.getString(3)); 
        // Adding contact to list 
        array_list.add(contact); 
       } while (res.moveToNext()); 
      } 

      // return contact list 
      return array_list; 
     } 

没有人有一个想办法做到这一点？或者更简单的方法来读取SQLite数据库并从中选择多个对象？

Answer 1

你必须写在你ContactActivity的方法，看起来像这样：

我写dto.Contact和ContactActiviy.Contact做出明确，哪个是哪个

private List<ContactActivity.Contact> transformListFromDB(List<dto.Contact> listFromDb) { 
    List<ContactActivity.Contact> result = new ArrayList<ContactActivity.Contact>(); 
    for (dto.Contact con : listFromDb) { 
     result.add(new ContactActivity.Contact(con.firstName, con.lastName); 
    } 
    return result; 
} 

然后使用：contactList = transformListFromDB（contactArrayList）;