如何在Android中自定义适配器？

我正在制作一个简单的Android应用程序，它接收用户的姓名，电子邮件和联系电话号码，并将这些（包括身份证）保存在手机内存中（通过sqlite）。 “显示全部”页面使用自定义适配器在ListView中显示数据库中所有用户的详细信息。它运行是这样的：如何在Android中自定义适配器？

它留下这些空间的行之间。我如何删除这些空间？此外，从数据库检索时，细节会混淆。就像第一行以正确的格式显示（如我所愿）。但是第二个细节混杂起来了。我该如何纠正？

MyDBHandler.java

public class MyDBHandler extends SQLiteOpenHelper{ 

    private static final int DATABASE_VERSION = 1; 
    private static final String DATABASE_NAME= "user.db"; 
    public static final String TABLE_NAME = "data"; 
    public static final String COLUMN_ID = "id"; 
    public static final String COLUMN_NAME = "name"; 
    public static final String COLUMN_email = "email"; 
    public static final String COLUMN_phno = "phno"; 

    public MyDBHandler(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) { 
     super(context, DATABASE_NAME, factory, DATABASE_VERSION); 
    } 

    @Override 
    public void onCreate(SQLiteDatabase db) { 

     String query = "CREATE TABLE "+TABLE_NAME+"("+ 
       COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT,"+ 
       COLUMN_NAME + " VARCHAR(20),"+ 
       COLUMN_email + " VARCHAR(20),"+ 
       COLUMN_phno + " VARCHAR(20)"+ 
       ");"; 

     db.execSQL(query); 

    } 

    @Override 
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 


     db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME); 
     onCreate(db); 
    } 

    public void addData(Data d){ 
     ContentValues values = new ContentValues(); 
     //values.put(COLUMN_ID, d.getId()); 
     values.put(COLUMN_NAME, d.getName()); 
     values.put(COLUMN_email, d.getEmail()); 
     values.put(COLUMN_phno, d.getPhno()); 

     SQLiteDatabase db = getWritableDatabase(); 
     db.insert(TABLE_NAME, null, values); 
     db.close(); 
    } 

    public ArrayList<String> retrieveData(){ 

     ArrayList<String> al = new ArrayList<>(); 

     SQLiteDatabase db = getWritableDatabase(); 
     String query = "SELECT * FROM "+TABLE_NAME+";"; 

     Cursor c = db.rawQuery(query,null); 

     c.moveToFirst(); 

     while(!c.isAfterLast()){ 
      if(c.getString(c.getColumnIndex("id"))!=null){ 

       al.add(c.getString(c.getColumnIndex("id"))); 
       al.add(c.getString(c.getColumnIndex("name"))); 
       al.add(c.getString(c.getColumnIndex("email"))); 
       al.add(c.getString(c.getColumnIndex("phno"))); 

      } 
      c.moveToNext(); 
     } 
     db.close(); 
     return al; 

    } 

}

CustomAdapter.java

public class CustomAdapter extends ArrayAdapter<String>{ 


    ArrayList<String>a = new ArrayList<>(); 


    public CustomAdapter(Context context, ArrayList<String>a){ 
     super(context,R.layout.custom_row,a); 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     LayoutInflater harshitsInflator = LayoutInflater.from(getContext()); 
     View customView = harshitsInflator.inflate(R.layout.custom_row, parent, false); 

     TextView textView3 = (TextView) customView.findViewById(R.id.textView3); 
     TextView textView4 = (TextView) customView.findViewById(R.id.textView4); 
     TextView textView5 = (TextView) customView.findViewById(R.id.textView5); 
     Button button4 = (Button) customView.findViewById(R.id.button4); 

     String Sid = getItem(position); 

     if(position%4==0 && position>0) 
     { 
      textView3.setText(a.get(1)); 
      textView4.setText(a.get(2)); 
      textView5.setText(a.get(3)); 
      button4.setText(a.get(0)); 
      a.clear(); 
      customView.setVisibility(View.VISIBLE); 
     } 
     else { 
      a.add(Sid); 
      customView.setVisibility(View.GONE); 
     } 
     return customView; 
    } 
}

listView.java

public class listView extends Activity { 

    protected void onCreate(Bundle savedInstanceState){ 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.list_view_layout); 

     ArrayList<String> n; 


     MyDBHandler db = new MyDBHandler(this, null, null, 1); 

     n=db.retrieveData(); 

     ListAdapter harshitsAdapter = new CustomAdapter(this, n); 

     ListView harshitsListView = (ListView) findViewById(R.id.harshitsListView); 
     harshitsListView.setAdapter(harshitsAdapter); 
     //((BaseAdapter)harshitsAdapter).notifyDataSetChanged(); 




    } 

    public void backToMain(View view){ 

     Intent i = new Intent(this, MainActivity.class); 
     startActivity(i); 
     finish(); 
    } 
}

这个应用程序还显示ArrayIndexOutOfBounds例外：

Process: com.example.h8pathak.dilliheart, PID: 21258 
    java.lang.IndexOutOfBoundsException: Invalid index 3, size is 3 
      at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255) 
      at java.util.ArrayList.get(ArrayList.java:308)

我怎么也纠正这一个？

来源

2015-11-01 h8pathak

使用列表的长度来检查越界，所以你不会遇到这样的异常 –

尝试我的长度如@StanlyMoses所述，或者为什么不写你自己的RecyclerViewAdapter呢？ – sud007

我没有看到数组列表'a'的目的。如果这也是存储数据的列表，那么在getView（）中清除它。您无法修改用于显示视图的数据。 – Droidekas

-1

修改这两个文件你的：

CustomAdapter.java

public class CustomAdapter extends ArrayAdapter<String>{ 

    ArrayList<String> id, name, email, phno; 
    Context c; 


    public CustomAdapter(Context context, ArrayList<String>id, ArrayList<String>name , ArrayList<String>email , ArrayList<String> phno){ 
     super(context,R.layout.custom_row, id); 

     this.c=context; 
     this.id = id; 
     this.name=name; 
     this.email=email; 
     this.phno=phno; 

    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     LayoutInflater harshitsInflator = LayoutInflater.from(getContext()); 
     View customView = harshitsInflator.inflate(R.layout.custom_row, parent, false); 

     TextView textView3 = (TextView) customView.findViewById(R.id.textView3); 
     TextView textView4 = (TextView) customView.findViewById(R.id.textView4); 
     TextView textView5 = (TextView) customView.findViewById(R.id.textView5); 
     Button button4 = (Button) customView.findViewById(R.id.button4); 


      String Sid = id.get(position); 
      String Sname = name.get(position); 
      String Semail = email.get(position); 
      String Sphno = phno.get(position); 

      textView3.setText(Sname); 
      textView4.setText(Semail); 
      textView5.setText(Sphno); 
      button4.setText(Sid); 

     return customView; 
    } 
}

listView.java

public class listView extends Activity { 

    protected void onCreate(Bundle savedInstanceState){ 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.list_view_layout); 

     ArrayList<String> n; 
     ArrayList<String> id = new ArrayList<>(); 
     ArrayList<String> name = new ArrayList<>(); 
     ArrayList<String> email = new ArrayList<>(); 
     ArrayList<String> phno = new ArrayList<>(); 

     MyDBHandler db = new MyDBHandler(this, null, null, 1); 

     n=db.retrieveData(); 

     for(int i =0; i<n.size();i++){ 
      if(i%4==0) 
       id.add(n.get(i)); 
      else if (i%4==1) 
       name.add(n.get(i)); 
      else if (i%4==2) 
       email.add(n.get(i)); 
      else 
       phno.add(n.get(i)); 
     } 

     System.out.println(n); 


     ListAdapter harshitsAdapter = new CustomAdapter(this, id, name, email, phno); 

     ListView harshitsListView = (ListView) findViewById(R.id.harshitsListView); 
     harshitsListView.setAdapter(harshitsAdapter); 




    } 

    public void backToMain(View view){ 

     Intent i = new Intent(this, MainActivity.class); 
     startActivity(i); 
     finish(); 
    } 





}

适应这种方法也不会导致你“的ArrayIndexOutOfBounds “例外

来源

2015-11-05 11:12:00 TheHardRock

@TheHardRock感谢这个方法真的工作:) – h8pathak

好吧，将所有数据存储在模型类Data中，并将数据对象添加到ListView。更改数据库方法以获得所有类似的数据

public ArrayList<Data> retrieveData(){ 

     ArrayList<Data> al = new ArrayList<>(); 

     SQLiteDatabase db = getWritableDatabase(); 
     String query = "SELECT * FROM "+TABLE_NAME+";"; 

     Cursor c = db.rawQuery(query,null); 

     c.moveToFirst(); 

     while(!c.isAfterLast()){ 
      if(c.getString(c.getColumnIndex("id"))!=null){ 

       Data dt = new Data(); 
       dt.setId(c.getString(c.getColumnIndex("id"))); 
       dt.setName(c.getString(c.getColumnIndex("name"))); 
       dt.setEmail(c.getString(c.getColumnIndex("email"))); 
       dt.setPhno(c.getString(c.getColumnIndex("phno"))); 

       al.add(dt); 

      } 
      c.moveToNext(); 
     } 
     db.close(); 
     return al; 

    }

使用getter方法检索数据。希望可能适合你。

来源

2015-11-05 11:59:46

首先，我应该创建一个Value Object来处理。例如：

public class UserVO { 

    private long id; 
    private String name, 
        email, 
        contactNumber; 

    public long getId() { 
     return id; 
    } 

    public void setId(long id) { 
     this.id = id; 
    } 

    public String getName() { 
     return name; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    public String getEmail() { 
     return email; 
    } 

    public void setEmail(String email) { 
     this.email = email; 
    } 

    public String getContactNumber() { 
     return contactNumber; 
    } 

    public void setContactNumber(String contactNumber) { 
     this.contactNumber = contactNumber; 
    } 

}

然后你可以使用到你的类，如下列：

public class CustomAdapter extends ArrayAdapter<UserVO>{ 

    private UserVO mUser; 
    private Context mContext; 
    private LayoutInflater mLayoutInflater; 
    private ViewHolder mHolder; 

    public CustomAdapter(Context context, UserVO user){ 

     mContext = context; 
     mUser = user; 

    } 

    static class ViewHolder { 

     private TextView textView3, 
         textView4, 
         textView5; 

    } 

    @Override 
    public View getView(int position, View view, ViewGroup parent) { 

     if (view == null) { 

      view = layoutInflater.inflate(R.layout.custom_row, parent, false); 

      mHolder = new ViewHolder(); 

      mHolder.textView3 = (TextView) view.findViewById(R.id.textView3); 
      mHolder.textView4 = (TextView) view.findViewById(R.id.textView4); 
      mHolder.textView5 = (TextView) view.findViewById(R.id.textView5); 

      view.setTag(mHolder); 

     } 
     else { 

      mHolder = (ViewHolder) view.getTag(); 

     } 

     mUser = getItem(position); 

     mHolder.textView3.setText(mUser.getId()); 
     mHolder.textView4.setText(mUser.getEmail()); 
     mHolder.textView5.setText(mUser.getContactNumber()); 

     return view; 
    } 

}

在你MyDBHandler你并不需要将光标移动到第一位置。这可能是你说的异常错误。此外，您还可以返回用户喜欢的列表：

public ArrayList<UserVO> retrieveData(){ 

    ArrayList<UserVO> userList = new ArrayList<>(); 

    SQLiteDatabase db = getWritableDatabase(); 
    String query = "SELECT * FROM " + TABLE_NAME + ";"; 

    Cursor c = db.rawQuery(query, null); 

    while(c.moveToNext()) { 

     if(c.getString(c.getColumnIndex("id")) != null) { 

      UserVO _user = new UserVO(); 

      _user.setId(c.getLong(c.getColumnIndex("id"))); 
      _user.setName(c.getString(c.getColumnIndex("name"))); 
      _user.setEmail(c.getString(c.getColumnIndex("email"))); 
      _user.setContactNumber(c.getString(c.getColumnIndex("phno"))); 

      userList.add(_user); 

     } 

    } 

    db.close(); 

    return userList; 

}

终于可以加载ListView：

public class listView extends Activity { 

    protected void onCreate(Bundle savedInstanceState){ 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.list_view_layout); 

     ArrayList<UserVO> userList; 


     MyDBHandler db = new MyDBHandler(this, null, null, 1); 

     userList = db.retrieveData(); 

     ListAdapter harshitsAdapter = new CustomAdapter(this, userList); 

     ListView harshitsListView = (ListView) findViewById(R.id.harshitsListView); 

     harshitsListView.setAdapter(harshitsAdapter); 

    } 

    public void backToMain(View view){ 

     Intent i = new Intent(this, MainActivity.class); 
     startActivity(i); 
     finish(); 
    } 

}

这些类只是一个例子。而你将不得不编辑一些东西来使它成为诅咒。无论如何，随意问任何你想要的。

来源

2015-11-05 12:20:36

如何在Android中自定义适配器？

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