此处我已附上我的代码供您审核。
我的LoginActivity.java： -
login_btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
u_name = user_name.getText().toString();
p_word = password.getText().toString();
System.out.println("u_name==> "+u_name);
System.out.println("p_word==> "+p_word);
test(u_name,p_word);
}
});
测试方法： -
public void test(String u_name,String p_word)
{
New_SQLController dbHelper;
dbHelper=new New_SQLController(LoginActivity.this);
if (dbHelper.Login(u_name,p_word))
{
Intent i = new Intent(LoginActivity.this,GPS_Example.class);
startActivity(i);
}
else {
System.out.println("Login Failed");
}
}
我的SQLController.java： -
public boolean Login(String username, String password) throws SQLException
{
Cursor mCursor = database.rawQuery("SELECT * FROM " + New_MyDbHelper.TABLE_LOGIN + " WHERE _user_id=? AND _password=?", new String[]{username,password});
if (mCursor != null) {
if(mCursor.getCount() > 0)
{
return true;
}
}
return false;
}
我的DBHelper.java： -
public class New_MyDbHelper extends SQLiteOpenHelper{
// TABLE INFORMATTION FOR LOGIN
public static final String TABLE_LOGIN = "_login";
public static final String LOGIN_PKEY_ID = "_id";
public static final String USER_ID = "_user_id";
public static final String PASSWORD = "_password";
// DATABASE INFORMATION FOR LOGIN
static final String DATA_BASE_NAME = "EXAMPLE.DB";
static final int DATA_BASE_VERSION = 1;
// TABLE CREATION STATEMENT FOR LOGIN
private static final String CREATE_ADDRESS_TABLE = "create table " + TABLE_LOGIN
+ "(" + LOGIN_PKEY_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
+ USER_ID + " TEXT NOT NULL ," + PASSWORD + " TEXT NOT NULL);";
public New_MyDbHelper(Context context) {
super(context, DATA_BASE_NAME, null, DATA_BASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_ADDRESS_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + CREATE_ADDRESS_TABLE);
onCreate(db);
}
}
我的问题是当我点击登录按钮时，我的应用程序被强制关闭。
错误讯息： -
05-29 11:23:31.271: E/AndroidRuntime(23372): FATAL EXCEPTION: main
05-29 11:23:31.271: E/AndroidRuntime(23372): java.lang.NullPointerException
05-29 11:23:31.271: E/AndroidRuntime(23372): at com.testing.dbhelper.New_SQLController.Login(New_SQLController.java:50)
05-29 11:23:31.271: E/AndroidRuntime(23372): at com.testing.login_example.LoginActivity.test(LoginActivity.java:64)
05-29 11:23:31.271: E/AndroidRuntime(23372): at com.testing.login_example.LoginActivity$1.onClick(LoginActivity.java:40)
05-29 11:23:31.271: E/AndroidRuntime(23372): at android.view.View.performClick(View.java:4204)
05-29 11:23:31.271: E/AndroidRuntime(23372): at android.view.View$PerformClick.run(View.java:17355)
05-29 11:23:31.271: E/AndroidRuntime(23372): at android.os.Handler.handleCallback(Handler.java:725)
05-29 11:23:31.271: E/AndroidRuntime(23372): at android.os.Handler.dispatchMessage(Handler.java:92)
05-29 11:23:31.271: E/AndroidRuntime(23372): at android.os.Looper.loop(Looper.java:137)
05-29 11:23:31.271: E/AndroidRuntime(23372): at android.app.ActivityThread.main(ActivityThread.java:5041)
05-29 11:23:31.271: E/AndroidRuntime(23372): at java.lang.reflect.Method.invokeNative(Native Method)
05-29 11:23:31.271: E/AndroidRuntime(23372): at java.lang.reflect.Method.invoke(Method.java:511)
05-29 11:23:31.271: E/AndroidRuntime(23372): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-29 11:23:31.271: E/AndroidRuntime(23372): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-29 11:23:31.271: E/AndroidRuntime(23372): at dalvik.system.NativeStart.main(Native Method)
请让我知道我做了什么错误？即使我尝试使用硬编码的值。它也显示错误。请让我解决这个问题。
提前致谢。
我的New_SQLController： -
public class New_SQLController {
private New_MyDbHelper dbhelper;
private Context ourcontext;
private SQLiteDatabase database;
public New_SQLController(Context c) {
ourcontext = c;
}
public New_SQLController open() throws SQLException {
dbhelper = new New_MyDbHelper(ourcontext);
database = dbhelper.getWritableDatabase();
return this;
}
public void close() {
dbhelper.close();
}
public void insertData(String u_name, String p_word) {
ContentValues cv = new ContentValues();
cv.put(New_MyDbHelper.USER_ID, u_name);
cv.put(New_MyDbHelper.PASSWORD, p_word);
database.insert(New_MyDbHelper.TABLE_LOGIN, null, cv);
//rowCount();
}
public boolean validateUser(String username, String password){
Cursor c = database.rawQuery(
"SELECT * FROM " + New_MyDbHelper.TABLE_LOGIN + " WHERE "
+ New_MyDbHelper.USER_ID + "='" + username +"'AND "+New_MyDbHelper.PASSWORD+"='"+password+"'" , null);
if (c.getCount()>0)
return true;
return false;
}
public boolean Login(String username, String password) throws SQLException
{
Cursor mCursor = database.rawQuery("SELECT * FROM " + New_MyDbHelper.TABLE_LOGIN + " WHERE _user_id=? AND _password=?", new String[]{username,password});
if (mCursor != null) {
if(mCursor.getCount() > 0)
{
return true;
}
}
return false;
}
public void rowCount()
{
Cursor mCount= database.rawQuery("select count(*) from '"+New_MyDbHelper.TABLE_LOGIN+"'", null);
mCount.moveToFirst();
int count= mCount.getInt(0);
mCount.close();
System.out.println("Totoal Row Count==>"+count);
if(count>5)
deleteFirstRow();
}
public void deleteAll() {
database.execSQL("delete from " + New_MyDbHelper.TABLE_LOGIN);
database.close();
}
public void deleteFirstRow() {
Cursor cursor = database.query(New_MyDbHelper.TABLE_LOGIN, null, null,
null, null, null, null);
if (cursor.moveToFirst()) {
String rowId = cursor.getString(cursor
.getColumnIndex(New_MyDbHelper.LOGIN_PKEY_ID));
database.delete(New_MyDbHelper.TABLE_LOGIN, New_MyDbHelper.LOGIN_PKEY_ID
+ "=?", new String[] { rowId });
}
database.close();
}
public Cursor readEntry() {
String[] allColumns = new String[] { New_MyDbHelper.LOGIN_PKEY_ID,
New_MyDbHelper.USER_ID, New_MyDbHelper.PASSWORD };
Cursor c = database.query(New_MyDbHelper.TABLE_LOGIN, allColumns, null,
null, null, null, null);
if (c != null) {
c.moveToFirst();
}
return c;
}
}