java - 将 SQLite 数据库中的数据显示到自定义 ListView

Question

我正在尝试将 SQLite 数据库中的数据显示到自定义 ListView ，但它没有显示。当我使用带有单个数据的简单 ListView 时，它可以正常工作，但当我尝试在自定义 ListView 上显示时它不起作用。

主 Activity .java

package com.example.addressbook;
public class MainActivity extends Activity {
public final static String EXTRA_MESSAGE = "com.example.AddressBook.MESSAGE";

private ListView lv;
List<Listcollection> collectionlist;
DBHelper mydb;
private Context context = this;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    lv = (ListView) findViewById(R.id.listView1);
    mydb = new DBHelper(this);

    // CustomListAdapter customListAdapter = new
    // CustomListAdapter(MainActivity.this, );
    lv.setAdapter(new ViewAdapter(mydb.listfromdb()));
    // lv.setAdapter(ViewAdapter);
    // adding it to the list view.

    lv.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                long arg3) {
            // TODO Auto-generated method stub
            int id_To_Search = arg2 + 1;
            Bundle dataBundle = new Bundle();
            dataBundle.putInt("id", id_To_Search);
            Intent intent = new Intent(getApplicationContext(),
                    com.example.addressbook.Display.class);
            intent.putExtras(dataBundle);
            startActivity(intent);
        }
    });
}

public class ViewAdapter extends BaseAdapter {
    LayoutInflater mInflater;
    List<Listcollection> collectionlist;

    public ViewAdapter(List<Listcollection> c) {
        collectionlist = c;
        mInflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        // TODO Auto-generated method stub
        return collectionlist.size();
    }

    @Override
    public Object getItem(int position) {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public long getItemId(int position) {
        // TODO Auto-generated method stub
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // TODO Auto-generated method stub

        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater)                     getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = mInflater.inflate(R.layout.list_item, null);
        }
        Listcollection o = collectionlist.get(position);

        if (o != null) {
            TextView idText = (TextView) convertView
                    .findViewById(R.id.lvid);
            TextView nameText = (TextView) convertView
                    .findViewById(R.id.lvname);

            TextView dateText = (TextView) convertView
                    .findViewById(R.id.lvdate);
            TextView phoneText = (TextView) convertView
                    .findViewById(R.id.lvphone);

            if (idText != null) {
                idText.setText(Integer.toString(o.getId()));
            }
            if (nameText != null) {
                nameText.setText("Name : "
                        + collectionlist.get(position).getName());
            }
            if (dateText != null) {
                dateText.setText("Date: "
                        + collectionlist.get(position).getDate());
            }
            if (phoneText != null) {
                phoneText.setText("Phone: "
                        + collectionlist.get(position).getPhone());
            }
        }

        return convertView;
    }

}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.mainmenu, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    super.onOptionsItemSelected(item);
    switch (item.getItemId()) {
    case R.id.item1:
        Bundle dataBundle = new Bundle();
        dataBundle.putInt("id", 0);
        Intent intent = new Intent(getApplicationContext(),
                com.example.addressbook.Display.class);
        intent.putExtras(dataBundle);
        startActivity(intent);
        return true;
    default:
        return super.onOptionsItemSelected(item);

    }

}

public boolean onKeyDown(int keycode, KeyEvent event) {
    if (keycode == KeyEvent.KEYCODE_BACK) {
        moveTaskToBack(true);
    }
    return super.onKeyDown(keycode, event);
}}

DBHelper.java

      public class DBHelper extends SQLiteOpenHelper {

  public static final String DATABASE_NAME = "MyDBName.db";
  public static final String CONTACTS_TABLE_NAME = "contacts";
  public static final String CONTACTS_COLUMN_ID = "id";
  public static final String C_NAME = "name";
  public static final String C_TYPE = "type";
  public static final String C_ADDRESS = "address";
  public static final String C_DATE = "date";
  public static final String C_PHONE = "phone";

  private HashMap hp;

public DBHelper(Context context) {
    super(context, DATABASE_NAME, null, 1);
}

@Override
public void onCreate(SQLiteDatabase db) {
    // TODO Auto-generated method stub
    db.execSQL("create table contacts "
            + "(id integer primary key, name text,phone text,type text, address text,date       text)");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub
    db.execSQL("DROP TABLE IF EXISTS contacts");
    onCreate(db);
}

public boolean insertContact(String name, String phone, String type,
        String address, String date) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();

    contentValues.put("name", name);
    contentValues.put("phone", phone);
    contentValues.put("type", type);
    contentValues.put("address", address);
    contentValues.put("date", date);

    db.insert("contacts", null, contentValues);
    return true;
}

public Cursor getData(int id) {
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor res = db.rawQuery("select * from contacts where id=" + id + "",
            null);
    return res;
}

public int numberOfRows() {
    SQLiteDatabase db = this.getReadableDatabase();
    int numRows = (int) DatabaseUtils.queryNumEntries(db,
            CONTACTS_TABLE_NAME);
    return numRows;
}

public boolean updateContact(Integer id, String name, String phone,
        String type, String address, String date) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put("name", name);
    contentValues.put("phone", phone);
    contentValues.put("type", type);
    contentValues.put("address", address);
    contentValues.put("date", date);
    db.update("contacts", contentValues, "id = ? ",
            new String[] { Integer.toString(id) });
    return true;
}

public Integer deleteContact(Integer id) {
    SQLiteDatabase db = this.getWritableDatabase();
    return db.delete("contacts", "id = ? ",
            new String[] { Integer.toString(id) });
}


public ArrayList<Listcollection> listfromdb() {
    SQLiteDatabase db = this.getReadableDatabase();

    Listcollection lcollection;
    Listcollection list = new Listcollection();
    ArrayList<Listcollection> results = new ArrayList<Listcollection>();
    Cursor crs = db.rawQuery("select * from contacts", null);

    crs.moveToFirst();

    list.setId(crs.getInt(crs.getColumnIndex(CONTACTS_COLUMN_ID)));
    list.setName(crs.getString(crs.getColumnIndex(C_NAME)));
    list.setDate(crs.getString(crs.getColumnIndex(C_DATE)));
    list.setPhone(crs.getString(crs.getColumnIndex(C_PHONE)));

    db.close();
    return results;

}

enter code here

列表集合.java

  public class Listcollection {

// private variables
int id;
String name;
String type;
String address;
String date;
String phone;

// Empty constructor
public Listcollection(Parcel in) {

}

// constructor
public Listcollection(int id, String name, String type, String address,
        String date, String phone) {
    this.id = id;
    this.name = name;
    this.type = type;
    this.address = address;
    this.phone = phone;
    this.date = date;
}

public Listcollection() {
    // TODO Auto-generated constructor stub
}

// getting id
public int getId() {
    return this.id;
}

// setting id
public void setId(int id) {
    this.id = id;
}

// getting name
public String getName() {
    return this.name;
}

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

public String getType() {
    return this.type;
}

public void setType(String type) {
    this.type = type;
}

public String getAddress() {
    return this.address;
}

public void setAddress(String address) {
    this.address = address;
}

public String getDate() {
    return this.date;
}

public void setDate(String date) {
    this.date = date;
}

public String getPhone() {
    return this.phone;
}

public void setPhone(String phone) {
    this.phone = phone;
}

public String toString() {
    return "Complain [id=" + id + ", name=" + name + ", type=" + type
            + ", address=" + address + ", date=" + date + ", phone="
            + phone + ",";
}

@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + id;
    return result;
}

@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    Listcollection other = (Listcollection) obj;
    if (id != other.id)
        return false;
    return true;
}

public int describeContents() {
    return 0;
}

public void writeToParcel(Parcel parcel, int flags) {
    parcel.writeInt(getId());
    parcel.writeString(getName());
    parcel.writeString(getType());
    parcel.writeString(getAddress());
    parcel.writeString(getPhone());
    parcel.writeString(getDate());
}

public static final Parcelable.Creator<Listcollection> CREATOR = new Parcelable.Creator<Listcollection>() {
    public Listcollection createFromParcel(Parcel in) {
        return new Listcollection(in);

    }

    public Listcollection[] newArray(int size) {
        return new Listcollection[size];
    }
};

Answer 1

您实际上并没有将数据库记录添加到 listfromdb() 中的 results 集合中。

应该是这样的:

public ArrayList<Listcollection> listfromdb() {
    SQLiteDatabase db = this.getReadableDatabase();
    ArrayList<Listcollection> results = new ArrayList<Listcollection>();

    Cursor crs = db.rawQuery("select * from contacts", null);
    while (crs.moveToNext()) {
        Listcollection item = new Listcollection();
        item.setId(crs.getInt(crs.getColumnIndex(CONTACTS_COLUMN_ID)));
        item.setName(crs.getString(crs.getColumnIndex(C_NAME)));
        item.setDate(crs.getString(crs.getColumnIndex(C_DATE)));
        list.setPhone(crs.getString(crs.getColumnIndex(C_PHONE)));
        results.add(item);
    }

    db.close();
    return results;
}