通过在另一个活动上调用DBAdapter插入方法将记录添加到DB 没有运行时错误，数据似乎正确地添加到数据库中，但是当运行应用程序时，listview对象不会出现
主要活动
public class MainScreen extends ActionBarActivity implements View.OnClickListener
{
Button addNewButton;
Button sortByNameButton;
Button sortByBusinessButton;
Button sortByPhoneButton;
DBAdapter userDB;
ListView cardList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(layout.activity_main_screen);
//declare buttons
addNewButton= (Button)findViewById(R.id.addNewButton);
sortByNameButton= (Button)findViewById(R.id.sortByNameButton);
sortByBusinessButton= (Button)findViewById(R.id.sortByBusinessButton);
sortByPhoneButton= (Button)findViewById(R.id.sortByPhoneButton);
//set onclick listeners
addNewButton.setOnClickListener(this);
//set button to font
addNewButton.setText("Add New");
sortByNameButton.setText("Sort by Name");
sortByBusinessButton.setText("Sort by Business");
sortByPhoneButton.setText("Sort by Phone #");
userDB = new DBAdapter(this);
userDB.open();
cardList=(ListView) findViewById(id.cardList);
populateListViewFromDB();
}
@Override
public void onDestroy(){
userDB.close();
}
private void populateListViewFromDB() {
Cursor cursor = userDB.getAllRows();
//allow activity to manage cursor lifetime (dont want memory leak)
startManagingCursor(cursor);
//map from cursor to view fields
String[] fromFieldNames = new String[]{DBAdapter.KEY_BUS_NAME};
int[] toViewIDs = new int[]{R.id.business_name};
//adapter to map out columns and rows of DB (deprecated, but it's okay)
SimpleCursorAdapter cursorAdapter = new SimpleCursorAdapter(
this, //context
R.layout.item_layout, //layout template
cursor, //cursor
fromFieldNames, //information
toViewIDs //where to put information
);
//String[] vals = {"me","you","he","she"};
//ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, layout.activity_main_screen, vals);
//set adapter to list view element
cardList.setAdapter(cursorAdapter);
}
}
DBAdapter类：
public class DBAdapter {
private static final String TAG = "DBAdapter";
// DB Fields
public static final String KEY_ROWID = "_id";
public static final int COL_ROWID = 0;
/*
* CHANGE 1:
*/
// TODO: Setup your fields here:
public static final String KEY_BUS_NAME = "BusinessName";
public static final String KEY_PERS_NAME = "PersonalName";
public static final String KEY_ADDRESS = "Address";
public static final String KEY_PHONE_NUM = "PhoneNum";
public static final String KEY_EMAIL = "Email";
// TODO: Setup your field numbers here (0 = KEY_ROWID, 1=...)
public static final int COL_BUS_NAME = 1;
public static final int COL_PERS_NAME = 2;
public static final int COL_ADDRESS = 3;
public static final int COL_PHONE_NUM = 4;
public static final int COL_EMAIL = 5;
public static final String[] ALL_KEYS = new String[] {KEY_ROWID, KEY_BUS_NAME, KEY_PERS_NAME, KEY_ADDRESS, KEY_PHONE_NUM, KEY_EMAIL};
// DB info: its name, and the table we are using (just one).
public static final String DATABASE_NAME = "LocalCards";
public static final String DATABASE_TABLE = "CardInfo";
// Track DB version if a new version of your app changes the format.
public static final int DATABASE_VERSION = 3;
private static final String DATABASE_CREATE_SQL =
"create table " + DATABASE_TABLE
+ " (" + KEY_ROWID + " integer primary key autoincrement, "
/*
* CHANGE 2:
*/
// TODO: Place your fields here!
// + KEY_{...} + " {type} not null"
// - Key is the column name you created above.
// - {type} is one of: text, integer, real, blob
// (http://www.sqlite.org/datatype3.html)
// - "not null" means it is a required field (must be given a value).
// NOTE: All must be comma separated (end of line!) Last one must have NO comma!!
+ KEY_BUS_NAME + " text, "
+ KEY_PERS_NAME + " text, "
+ KEY_ADDRESS + " text, "
+ KEY_PHONE_NUM + " text, "
+ KEY_EMAIL + " text"
// Rest of creation:
+ ");";
// Context of application who uses us.
private final Context context;
private DatabaseHelper myDBHelper;
private SQLiteDatabase db;
/////////////////////////////////////////////////////////////////////
// Public methods:
/////////////////////////////////////////////////////////////////////
public DBAdapter(Context ctx) {
this.context = ctx;
myDBHelper = new DatabaseHelper(context);
//Cursor x = db.rawQuery("SELECT "+KEY_BUS_NAME+" FROM " + DATABASE_TABLE,null);
}
// Open the database connection.
public DBAdapter open() {
db = myDBHelper.getWritableDatabase();
//db.execSQL(DATABASE_CREATE_SQL);
return this;
}
// Close the database connection.
public void close() {
myDBHelper.close();
}
// Add a new set of values to the database.
public void insertRow(String bus_name, String pers_name, String address, String phone, String email) {
/*
* CHANGE 3:
// TODO: Update data in the row with new fields.
// TODO: Also change the function's arguments to be what you need!
// Create row's data:
ContentValues values = new ContentValues();
values.put(KEY_BUS_NAME, bus_name);
values.put(KEY_PERS_NAME, pers_name);
values.put(KEY_ADDRESS, address);
values.put(KEY_PHONE_NUM, phone);
values.put(KEY_EMAIL, email);*/
// Insert it into the database.
//return db.insert(DATABASE_TABLE, null, values);
db.rawQuery("INSERT INTO " + DATABASE_TABLE + " (" + KEY_BUS_NAME + "," + KEY_PERS_NAME + "," +
KEY_ADDRESS + "," + KEY_PHONE_NUM + "," + KEY_EMAIL + ") VALUES (" + "'" + bus_name +
"','" + pers_name + "','" + address + "','" + phone + "','" + email + "');",null);
}
// Delete a row from the database, by rowId (primary key)
public boolean deleteRow(long rowId) {
String where = KEY_ROWID + "=" + rowId;
return db.delete(DATABASE_TABLE, where, null) != 0;
}
public void deleteAll() {
Cursor c = getAllRows();
long rowId = c.getColumnIndexOrThrow(KEY_ROWID);
if (c.moveToFirst()) {
do {
deleteRow(c.getLong((int) rowId));
} while (c.moveToNext());
}
c.close();
}
// Return all data in the database.
public Cursor getAllRows() {
String where = null;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null);
//Cursor c = db.rawQuery("SELECT * FROM " + DATABASE_TABLE, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
// Get a specific row (by rowId)
public Cursor getRow(long rowId) {
String where = KEY_ROWID + "=" + rowId;
Cursor c = db.query(true, DATABASE_TABLE, ALL_KEYS,
where, null, null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
// Change an existing row to be equal to new data.
public boolean updateRow(long rowId, String bus_name, String pers_name, String address, String phone, String email) {
String where = KEY_ROWID + "=" + rowId;
/*
* CHANGE 4:
*/
// TODO: Update data in the row with new fields.
// TODO: Also change the function's arguments to be what you need!
// Create row's data:
ContentValues newValues = new ContentValues();
newValues.put(KEY_BUS_NAME, bus_name);
newValues.put(KEY_PERS_NAME, pers_name);
newValues.put(KEY_ADDRESS, address);
newValues.put(KEY_PHONE_NUM, phone);
newValues.put(KEY_EMAIL, email);
// Insert it into the database.
return db.update(DATABASE_TABLE, newValues, where, null) != 0;
}
/////////////////////////////////////////////////////////////////////
// Private Helper Classes:
/////////////////////////////////////////////////////////////////////
/**
* Private class which handles database creation and upgrading.
* Used to handle low-level database access.
*/
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase _db) {
_db.execSQL(DATABASE_CREATE_SQL);
}
@Override
public void onUpgrade(SQLiteDatabase _db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading application's database from version " + oldVersion
+ " to " + newVersion + ", which will destroy all old data!");
// Destroy old database:
_db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
// Recreate new database:
onCreate(_db);
}
}
}
item_layout.xml：
<?xml version="1.0" encoding="utf-8"?>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceLarge"
android:text="Large Text"
android:id="@+id/business_name"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:text="Medium Text"
android:id="@+id/personal_name"
android:layout_below="@+id/business_name"
android:layout_alignParentLeft="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:text="Small Text"
android:id="@+id/phone_number"
android:layout_below="@+id/business_name"
android:layout_alignParentRight="true" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceSmall"
android:text="Small Text"
android:id="@+id/email"
android:layout_below="@+id/phone_number"
android:layout_alignParentRight="true" />
activity_main_screen.xml：
<?xml version="1.0" encoding="utf-8"?>
<Button
android:layout_width="75dp"
android:layout_height="50dp"
android:text="Sort by Name"
android:id="@+id/sortByNameButton"
android:layout_alignParentTop="true"
android:layout_alignParentLeft="true" />
<Button
android:layout_width="100dp"
android:layout_height="50dp"
android:text="Sort by Business"
android:id="@+id/sortByBusinessButton"
android:layout_alignParentTop="true"
android:layout_toRightOf="@+id/sortByNameButton" />
<Button
android:layout_width="100dp"
android:layout_height="50dp"
android:text="Sort by Phone"
android:id="@+id/sortByPhoneButton"
android:layout_alignParentTop="true"
android:layout_toRightOf="@+id/sortByBusinessButton" />
<Button
android:layout_width="75dp"
android:layout_height="50dp"
android:text="Add New"
android:id="@+id/addNewButton"
android:layout_alignBottom="@+id/sortByPhoneButton"
android:layout_toRightOf="@+id/sortByPhoneButton" />
<SearchView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/searchBox"
android:layout_below="@+id/sortByNameButton"
android:layout_alignParentLeft="true"
android:layout_alignRight="@+id/addNewButton"
/>
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/cardList"
android:layout_alignParentRight="true"
android:layout_below="@+id/searchBox" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Text"
android:id="@+id/textView"
android:layout_below="@+id/searchBox"
android:layout_alignBottom="@+id/cardList"
android:layout_alignRight="@+id/searchBox"
android:layout_alignParentLeft="true" />