After creating inserting username and password signup.java , my app suddenly stop when I login ( in emulator) , and i moves to signup page in (bluestack). Not sure if data is actually being entered in database in signing up.<\/p>\n
DBManager.java<\/p>\n
package com.example.student_project;\n\nimport com.example.student_project.*;\n\nimport android.content.ContentValues;\nimport android.content.Context;\nimport android.database.Cursor;\nimport android.database.SQLException;\nimport android.database.sqlite.SQLiteDatabase;\nimport android.database.sqlite.SQLiteException;\nimport android.database.sqlite.SQLiteOpenHelper;\n\n\npublic class DBManager {\n public static final String KEY_ROWID = \"_id\";\n public static final String KEY_USERNAME = \"username\";\n public static final String KEY_PASSWORD = \"password\";\n\n\n private static final String DATABASE_NAME= \"LOGIN.db\";\n private static final int DATABASE_VERSION = 4;\n private static final String DATABASE_TABLE = \"LOGIN_TABLE\";\n\n private static DbHelper ourHelper;\n private final Context ourContext;\n private static SQLiteDatabase ourDatabase;\n\n class DbHelper extends SQLiteOpenHelper {\n\n public DbHelper(Context context) {\n super(context, DATABASE_NAME, null, DATABASE_VERSION);\n \/\/ TODO Auto-generated constructor stub\n }\n\n @Override\n public void onCreate(SQLiteDatabase db) {\n\n \/\/ TODO Auto-generated method stub\n db.execSQL(\"CREATE TABLE \" + DATABASE_TABLE + \" ( \" + \n KEY_ROWID + \" INTEGER PRIMARY KEY AUTOINCREMENT , \" +\n KEY_USERNAME + \" TEXT NOT NULL , \" + \n KEY_PASSWORD + \" TEXT NOT NULL );\" \n );\n }\n\n @Override\n public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {\n \/\/ TODO Auto-generated method stub\n db.execSQL(\"DROP TABLE IF EXISTS \" + DATABASE_TABLE);\n onCreate(db);\n }\n\n }\n\n\n public DBManager(Context c) {\n ourContext = c;\n }\n\n public DBManager open() throws SQLException{\n ourHelper = new DbHelper(ourContext);\n try\n {\n ourDatabase = ourHelper.getWritableDatabase();\n }\n catch(SQLException ex)\n {\n ourDatabase = ourHelper.getReadableDatabase();\n }\n return this;\n }\n\n public void close() {\n ourHelper.close();\n }\n\n public long createEntry(String username, String password) throws SQLException\n {\n \/\/ TODO Auto-generated method stub\n ContentValues cv = new ContentValues();\n cv.put(KEY_USERNAME, username);\n cv.put(KEY_PASSWORD, password);\n return ourDatabase.insert(DATABASE_TABLE, null, cv);\n\n }\n\n public static boolean verifyUser(String username , String password) \n {\n\n String columns[] = new String[2];\n columns[0] = username;\n columns[1] = password;\n Cursor c= null;\n int count=0;\n try\n {\n\n \/\/ TODO Auto-generated method stub\n c = ourDatabase.query(DATABASE_TABLE, columns,null , null, null, null, null);\n count = c.getCount();\n\n }\n catch (SQLException e)\n {\n \/\/ TODO: handle exception\n e.printStackTrace();\n }\n finally\n {\n c.close();\n }\n if(count>0)\n {\n return true;\n }\n else\n {\n return false;\n }\n\n }\n}\n<\/code><\/pre>\nMainActivity.java<\/p>\n
package com.example.student_project;\n\nimport com.example.student_project.*;\n\nimport android.os.Bundle;\nimport android.app.Activity;\nimport android.content.Intent;\nimport android.text.InputFilter.LengthFilter;\nimport android.util.Log;\nimport android.view.Menu;\nimport android.view.View;\nimport android.view.View.OnClickListener;\nimport android.widget.Button;\nimport android.widget.EditText;\nimport android.widget.Toast;\n\npublic class MainActivity extends Activity implements OnClickListener\n{\n private Button btn_signup;\n private Button btn_login;\n private EditText et_lusername;\n private EditText et_lpassword;\n\n @Override\n protected void onCreate(Bundle savedInstanceState)\n {\n super.onCreate(savedInstanceState);\n setContentView(R.layout.activity_main);\n\n Log.i(\"mytag\",\"this is my tag\");\n et_lusername = (EditText) findViewById(R.id.et_lusername);\n et_lpassword = (EditText) findViewById(R.id.et_lpassword);\n btn_signup = (Button) findViewById(R.id.btn_signup);\n btn_login = (Button) findViewById(R.id.btn_login);\n\n btn_login.setOnClickListener(this);\n btn_signup.setOnClickListener(this);\n\n }\n\n @Override\n public boolean onCreateOptionsMenu(Menu menu)\n {\n \/\/ Inflate the menu; this adds items to the action bar if it is present.\n getMenuInflater().inflate(R.menu.main, menu);\n return true;\n }\n\n\n @Override\n public void onClick(View v)\n {\n \/\/ TODO Auto-generated method stub\n switch(v.getId())\n {\n case R.id.btn_login :\n {\n String un = et_lusername.getText().toString();\n String pw = et_lusername.getText().toString();\n\n boolean success = DBManager.verifyUser(un,pw);\n if (success)\n {\n Intent i = new Intent(MainActivity.this,AdminMenu.class);\n startActivity(i); \n }\n else\n {\n Toast.makeText(getApplicationContext(), \"wrong username or password\",Toast.LENGTH_LONG);\n }\n\n\n }\n case R.id.btn_signup:\n {\n Intent i = new Intent(MainActivity.this,Signup.class);\n startActivity(i); \n }\n }\n }\n\n\n }\n<\/code><\/pre>\nSignup.java<\/p>\n
package com.example.student_project;\n\n\nimport com.example.student_project.*;\n\nimport android.os.Bundle;\nimport android.app.Activity;\nimport android.app.Dialog;\nimport android.content.Intent;\nimport android.view.Menu;\nimport android.view.View;\nimport android.view.View.OnClickListener;\nimport android.widget.Button;\nimport android.widget.EditText;\nimport android.widget.TextView;\nimport android.widget.Toast;\n\npublic class Signup extends Activity implements OnClickListener {\nprivate Button btn_add;\nprivate EditText et_username;\nprivate EditText et_password;\nprivate EditText et_confirmpassword;\n@Override\nprotected void onCreate(Bundle savedInstanceState) {\n super.onCreate(savedInstanceState);\n setContentView(R.layout.signup);\n\n et_username = (EditText) findViewById(R.id.et_username);\n et_password = (EditText) findViewById(R.id.et_password);\n et_confirmpassword = (EditText) findViewById(R.id.et_confirmpassword);\n btn_add = (Button) findViewById(R.id.btn_add);\n\n btn_add.setOnClickListener(this);\n}\n\n@Override\npublic boolean onCreateOptionsMenu(Menu menu) {\n \/\/ Inflate the menu; this adds items to the action bar if it is present.\n getMenuInflater().inflate(R.menu.main, menu);\n\n return true;\n}\n\n@Override\npublic void onClick(View v)\n{\n \/\/ TODO Auto-generated method stub\n switch(v.getId())\n {\n case R.id.btn_add :\n\n boolean diditwork = true; \n try \n {\n String username = et_username.getText().toString();\n String password = et_password.getText().toString();\n String cpassword = et_confirmpassword.getText().toString();\n\n if(password.equalsIgnoreCase(cpassword))\n {\n DBManager empty = new DBManager(Signup.this);\n empty.open();\n empty.createEntry(username,password);\n empty.close(); \n\n Intent addintent = new Intent(Signup.this,MainActivity.class);\n startActivity(addintent);\n }\n else \n {\n Toast.makeText(getApplicationContext(), \"passwords does not match\", Toast.LENGTH_LONG);\n }\n } \n catch (Exception e)\n {\n diditwork = false;\n Dialog d = new Dialog(this);\n String error = e.toString();\n d.setTitle(\"dang\");\n TextView tv = new TextView(this);\n tv.setText(error);\n d.setContentView(tv);\n d.show();\n }\n \/* finally\n {\n if(diditwork)\n {\n Dialog d = new Dialog(this);\n d.setTitle(\"hech ya\");\n TextView tv = new TextView(this);\n tv.setText(\"success\");\n d.setContentView(tv);\n d.show();\n }\n\n } *\/\n\n\n }\n}\n<\/code><\/pre>\n}<\/p>\n
Admin.java<\/p>\n
package com.example.student_project;\n\nimport android.os.Bundle;\nimport android.app.Activity;\nimport android.content.Intent;\nimport android.view.Menu;\nimport android.view.View;\nimport android.view.View.OnClickListener;\nimport android.widget.Button;\nimport android.widget.EditText;\n\npublic class AdminMenu extends Activity\n{\n\n @Override\n protected void onCreate(Bundle savedInstanceState)\n {\n super.onCreate(savedInstanceState);\n setContentView(R.layout.admin_menu);\n\n\n\n}\n\n@Override\npublic boolean onCreateOptionsMenu(Menu menu)\n{\n \/\/ Inflate the menu; this adds items to the action bar if it is present.\n getMenuInflater().inflate(R.menu.main, menu);\n return true;\n}\n<\/code><\/pre>\n}<\/p>\n
logcat error<\/p>\n
W\/ActivityManager( 293): Unbind failed: could not find connection for android.os.BinderProxy@410ce000\n\nI\/Choreographer( 1994): Skipped 55 frames! The application may be doing too much work on its main thread.\n\nD\/AndroidRuntime( 1994): Shutting down VM\n\nW\/dalvikvm( 1994): threadid=1: thread exiting with uncaught exception (group=0x40a71930)\n\nE\/AndroidRuntime( 1994): FATAL EXCEPTION: main\n\nE\/AndroidRuntime( 1994): java.lang.NullPointerException\n\nE\/AndroidRuntime( 1994): at com.example.student_project.DBManager.verifyUser(DBManager.java:110)\n\nE\/AndroidRuntime( 1994): at com.example.student_project.MainActivity.onClick(MainActivity.java:61)\n\nE\/AndroidRuntime( 1994): at android.view.View.performClick(View.java:4204)\n\nE\/AndroidRuntime( 1994): at android.view.View$PerformClick.run(View.java:17355)\n\nE\/AndroidRuntime( 1994): at android.os.Handler.handleCallback(Handler.java:725)\n\nE\/AndroidRuntime( 1994): at android.os.Handler.dispatchMessage(Handler.java:92)\n\nE\/AndroidRuntime( 1994): at android.os.Looper.loop(Looper.java:137)\n\nE\/AndroidRuntime( 1994): at android.app.ActivityThread.main(ActivityThread.java:5041)\n\nE\/AndroidRuntime( 1994): at java.lang.reflect.Method.invokeNative(Native Method)\n\nE\/AndroidRuntime( 1994): at java.lang.reflect.Method.invoke(Method.java:511)\n\nE\/AndroidRuntime( 1994): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)\n\nE\/AndroidRuntime( 1994): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)\n\nE\/AndroidRuntime( 1994): at dalvik.system.NativeStart.main(Native Method)\n\nW\/ActivityManager( 293): Force finishing activity com.example.student_project\/.MainActivity\n\nW\/WindowManager( 293): Failure taking screenshot for (246x410) to layer 21020\n<\/code><\/pre>\n\n- \n
It is because your Cursor c<\/code> is null..and u have’nt caught the NullPointerException<\/code> in the catch<\/code> block in verifyUser()<\/code>..change the SQLException<\/code> in the catch to Exception<\/code> to catch all the exceptions..<\/p>\n<\/li>\n- \n
You are calling DBManager.verifyUser(un,pw);<\/code> which reqires database to be opened. Probably ourDatabase<\/code> variable is Null<\/code> and you got handled exception when trying to get cursor and unhandled when trying to access null cursor.<\/p>\nProbably you do not need verifyUser<\/code> to bee static as you need to call DBManager.open<\/code> before it<\/p>\n<\/li>\n<\/ol>\nOriginally posted 2013-11-26 18:03:36. <\/small><\/p>","protected":false},"excerpt":{"rendered":"
After creating inserting username and password signup.java , my app suddenly stop when I login ( in emulator) , and i moves to signup page in (bluestack). Not sure if data is actually being entered in database in signing up. DBManager.java package com.example.student_project; import com.example.student_project.*; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1522","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts\/1522","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/comments?post=1522"}],"version-history":[{"count":0,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/posts\/1522\/revisions"}],"wp:attachment":[{"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/media?parent=1522"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/categories?post=1522"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/unknownerror.org\/index.php\/wp-json\/wp\/v2\/tags?post=1522"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}