我正在制作一个简单的 Android 应用程序,它获取用户的姓名、电子邮件和联系电话,并将这些(包括 ID)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。它像这样运行:
它在行之间留下这些空间。如何删除这些空格? 此外,从数据库中检索时,详细信息会混淆。就像第一行以正确的格式显示(如我所愿)。但是第二个细节混淆了。我该如何纠正这个问题?
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();
}
}
此应用程序还显示 ArrayIndexOutOfBounds
异常:
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)
我该如何纠正这个问题?
最佳答案
修改你的这两个文件:
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();
}
}
采用此方法也不会导致您出现“ArrayIndexOutOfBounds”异常
关于java - 如何在 Android 中自定义适配器?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33464781/