以下是我在 sqlite 中创建数据库的方式：
public class DBAdapter {
public static final String KEY_ROWID = "_id";
public static final String KEY_FIRST = "first_name";
public static final String KEY_SECOND = "second_name";
public static final String KEY_SALARY = "salary";
public static final String KEY_OVERTIME = "overtime";
public static final String KEY_TOTAL = "total";
private static final String TAG = "DBAdapter";
private static final String DATABASE_NAME = "myDatabase";
private static final String DATABASE_TABLE = "Info";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE = "create table Info (_id integer primary key autoincrement, "
+ "first_name text not null, last_name text not null, salary real not null, overtime real null, total real not null);";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
public DBAdapter(Context ctx)
{
this.context = ctx;
DBHelper = new DatabaseHelper(context);
}
private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db)
{
try {
db.execSQL(DATABASE_CREATE);
} catch (SQLException e) {
e.printStackTrace();
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS history");
onCreate(db);
}
}
//---opens the database---
public DBAdapter open() throws SQLException
{
db = DBHelper.getWritableDatabase();
return this;
}
//---closes the database---
public void close()
{
DBHelper.close();
}
//---insert a History into the database---
public long insertHistory(String source, String destination, String distance, String charge_day, String charge_night)
{
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_FIRST, first_name);
initialValues.put(KEY_SECOND, last_name);
initialValues.put(KEY_SALARY, salary);
initialValues.put(KEY_OVERTIME, overtime);
initialValues.put(KEY_TOTAL, total);
return db.insert(DATABASE_TABLE, null, initialValues);
}
//---deletes a particular History---
public boolean deleteHistory(long rowId)
{
return db.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
//---retrieves all the history---
public Cursor getAllHistory()
{
return db.query(DATABASE_TABLE, new String[] {KEY_ROWID, KEY_FIRST,KEY_SECOND, KEY_SALARY, KEY_OVERTIME, KEY_TOTAL}, null, null, null, null, null);
}
//---retrieves a particular History---
public Cursor getHistory(String first_name, String last_name) throws SQLException
{
//SQLiteDatabase db = this.getReadableDatabase();
Cursor mCursor = db.query(true, DATABASE_TABLE, new String[] {KEY_ROWID,KEY_FIRST, KEY_SECOND, KEY_SALARY, KEY_OVERTIME, KEY_TOTAL}, KEY_ROWID + "=" + destination, null,null, null, null, null);
if (mCursor != null)
{
mCursor.moveToFirst();
}
return mCursor;
}
}
现在我从 mainActivity 插入输入。代码如下：
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText et1 = (EditText) findViewById(R.id.editText1);
final EditText et2 = (EditText) findViewById(R.id.editText2);
Button b = (Button) findViewById(R.id.button1);
b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, Second.class);
intent.putExtra("first_name", et1.getText().toString());
intent.putExtra("second_name", et2.getText().toString());
startActivity(intent);
}
});
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
}
现在，我必须根据在下一个活动的列表视图中作为输入给出的 first_name 和 last_name 显示项目。我使用的代码如下：
public class Second extends Activity{
String first_name, last_name;
protected void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
setContentView(R.layout.second);
DBAdapter db = new DBAdapter(this);
ListView listView = (ListView) findViewById(R.id.listView1);
db.open();
first_name = getIntent().getExtras().getString("first_name");
last_name = getIntent().getExtras().getString("last_name");
Cursor c;
String select = "SELECT * FROM Info WHERE first_name = ? AND last_name = ?";
String[] whereArgs = {first_name, last_name};
c = db.rawQuery(select, whereArgs); //this statement is not accepted. Why?
final ArrayList<String> temparr = new ArrayList<String>();
if (c.moveToFirst())
{
do{
temparr.add("Your details are as follows:" + '\n' + '\n' + "First_name: " +c.getString(1)+ '\n' + "Second_name: " + c.getString(2) + '\n' + "Salary: "+ c.getString(3)+ "\n" + "Overtime: "+ c.getString(4) +'\n'+ "Total: " +c.getString(5));
}while(c.moveToNext());
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, temparr);
listView.setAdapter(adapter);
}else{
temparr.add("NO DETAILS!!!");
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, temparr);
listView.setAdapter(adapter);
}
db.close();
}
}
为什么不使用 rawQuery？请解释原因。我是android的初学者，刚刚开始。我发现我需要使用 SQLiteDatabase 进行实例化，但如何？