Android java.lang.NullPointerException：println需要一条消息[重复]
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【中文标题】Android java.lang.NullPointerException：println需要一条消息[重复]【英文标题】：Android java.lang.NullPointerException: println needs a message [duplicate] 【发布时间】：2013-10-24 02:23:06 【问题描述】：当我尝试登录时，我的应用出现问题。
事实上，如果我先注册（如果复选框remerberMe isChecked() 注册操作，在下一个连接时会显示主要活动，否则会出现登录活动），它工作正常。
但是，Login Activity 在注册操作后在下一个连接上调用时不起作用。
登录活动
public void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
setTitle(R.string.loginTitle);
// Importing all assets like buttons, text fields
inputUsername = (EditText) findViewById(R.id.username_value);
inputPassword = (EditText) findViewById(R.id.password_value);
btnLogin = (Button) findViewById(R.id.loginButton);
btnExit = (Button) findViewById(R.id.exitButton);
btnLinkToRegister = (Button) findViewById(R.id.btnLinkToRegister);
rememberMe = (CheckBox) findViewById(R.id.rememberNameRegister);
// Login button Click Event
btnLogin.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
LoginAction();
);
// Link to Register Screen
btnLinkToRegister.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View view)
Intent i = new Intent(getApplicationContext(),
RegisterActivity.class);
startActivity(i);
finish();
);
btnExit.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
finish();
);
public void LoginAction()
Log.i("Login", "Login Action");
progressDialog = ProgressDialog.show(LoginActivity.this, null,
getResources().getString(R.string.loginProgressMessage), true);
// try
runOnUiThread(new Runnable()
String username = inputUsername.getText().toString();
String password = inputPassword.getText().toString();
@Override
public void run()
Log.i("Login Run", "username " + username);
switch (username.length())
case 0:
blankUserName();
break;
switch (password.length())
case 0:
blankPassWord();
// thread.stop();
break;
try
if (username.length() > 0 && password.length() > 0)
Log.i("Login Run", "password " + password);
// Password pass = new Password(username, password);
DatabaseHelper db = new DatabaseHelper(
getApplicationContext());
int count = db.getRowCount();
Log.i("Login", "getRowCompte " + count);
if (count == 1)
Log.i("Login","getLogin1 ");
// if (db.getLogin(username, password) == 1)
if (db.Login(username, password)== true)
Log.i("Login", "rememberMe.isChecked()");
if (rememberMe.isChecked() == true)
statut = "on";
else if (rememberMe.isChecked() == false)
statut = "off";
Log.i("Login", "ok ischecked");
Log.i("Login","getRowCompteStat "+ db.getRowCountStat());
if (db.getRowCountStat() == 1)
db.UpdateStatut(statut);
Log.i("Login", "getRowCompte " + count);
Toast.makeText(getApplicationContext(),
"Student Moyenne \n Bienvenu!",
Toast.LENGTH_LONG).show();
Log.i("Login Run", "Connecté");
Intent moy = new Intent(
getApplicationContext(),
MoyenneMain.class);
// Close all views before launching
// Dashboard
moy.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(moy);
finish();
db.close();
else if (db.Login(username, password)==false)
// if (db.getLogin(username, password) == 0)
// Log.i("Login Run", "faux password");
Toast.makeText(LoginActivity.this,"Invalid Username/Password",Toast.LENGTH_LONG).show();
Intent login = new Intent(getApplicationContext(),LoginActivity.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
finish();
db.close();
else if (count == 0)
Log.i("Login Run", "Enregistrez vous");
Toast.makeText(LoginActivity.this,
"Enregistrez vous!", Toast.LENGTH_SHORT)
.show();
Intent register = new Intent(
getApplicationContext(),
RegisterActivity.class);
register.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(register);
finish();
db.close();
catch (Exception e)
Log.i("Login Error1", e.getMessage());
Toast.makeText(LoginActivity.this, e.getMessage(),
Toast.LENGTH_LONG).show();
);
// catch (Exception e)
// Thread.currentThread().destroy();
// Log.i("Login Error2", e.getMessage());
// Toast.makeText(LoginActivity.this, e.getMessage(),
// Toast.LENGTH_LONG).show();
//
private void blankUserName()
Toast.makeText(LoginActivity.this, "Entrez un nom Utilisateur SVP!",
Toast.LENGTH_SHORT).show();
Intent login = new Intent(getApplicationContext(), LoginActivity.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
finish();
private void blankPassWord()
Toast.makeText(LoginActivity.this, "Entrez un mot de passe SVP!",
Toast.LENGTH_SHORT).show();
Intent login = new Intent(getApplicationContext(), LoginActivity.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
finish();
DatabaseHelper 的一部分
public int getRowCountStat()
String countQuery = "SELECT * FROM " + TABLE_STATUT;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(countQuery, null);
int rowCount = cursor.getCount();
db.close();
cursor.close();
// return row count
return rowCount;
public int getRowCount()
String countQuery = "SELECT * FROM " + TABLE_LOGIN;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(countQuery, null);
int rowCount = cursor.getCount();
db.close();
cursor.close();
// return row count
return rowCount;
public boolean Login(String username, String password) throws SQLException
Cursor mCursor = db.rawQuery("SELECT * FROM " + TABLE_LOGIN + " WHERE username=? AND password=?"
, new String[]username,password);
if (mCursor != null)
if(mCursor.getCount() > 0)
return true;
return false;
public int UpdateStatut(String statut)
final static int idStat = 1;
SQLiteDatabase db = this.getWritableDatabase();
ContentValues cv = new ContentValues();
cv.put(STATUT, statut);
return db.update(TABLE_STATUT, cv, ID_STAT + "=?",
new String[] String.valueOf(idStat) );
Logcat
10-24 01:48:08.819: E/androidRuntime(29242): FATAL EXCEPTION: main
10-24 01:48:08.819: E/AndroidRuntime(29242): java.lang.NullPointerException: println needs a message
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.util.Log.println_native(Native Method)
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.util.Log.i(Log.java:143)
10-24 01:48:08.819: E/AndroidRuntime(29242): at com.android.moyenne.activity.LoginActivity$4.run(LoginActivity.java:163)
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.app.Activity.runOnUiThread(Activity.java:3707)
10-24 01:48:08.819: E/AndroidRuntime(29242): at com.android.moyenne.activity.LoginActivity.LoginAction(LoginActivity.java:78)
10-24 01:48:08.819: E/AndroidRuntime(29242): at com.android.moyenne.activity.LoginActivity$1.onClick(LoginActivity.java:46)
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.view.View.performClick(View.java:2408)
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.view.View$PerformClick.run(View.java:8816)
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.os.Handler.handleCallback(Handler.java:587)
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.os.Handler.dispatchMessage(Handler.java:92)
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.os.Looper.loop(Looper.java:123)
10-24 01:48:08.819: E/AndroidRuntime(29242): at android.app.ActivityThread.main(ActivityThread.java:4627)
10-24 01:48:08.819: E/AndroidRuntime(29242): at java.lang.reflect.Method.invokeNative(Native Method)
10-24 01:48:08.819: E/AndroidRuntime(29242): at java.lang.reflect.Method.invoke(Method.java:521)
10-24 01:48:08.819: E/AndroidRuntime(29242): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-24 01:48:08.819: E/AndroidRuntime(29242): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-24 01:48:08.819: E/AndroidRuntime(29242): at dalvik.system.NativeStart.main(Native Method)
10-24 01:48:12.260: I/Process(29242): Sending signal. PID: 29242 SIG: 9
【问题讨论】：
【参考方案1】：在catch 块中e.getMessage() 可能是null。试试这个：
String msg = (e.getMessage()==null)?"Login failed!":e.getMessage();
Log.i("Login Error1",msg);
【讨论】：
我已经完成了，但是现在消息“登录失败！”出现在 logcat 和 Toast 中（因此 e.getmessage 返回 null）并且线程不会自动销毁但是getRowCount() 返回 1 并且我输入的用户名和密码与我在注册时输入的相同。所以db.Login(username, password) 应该返回 true 但它返回 false。销毁线程我想使用Thread.currentThread().destroy(); 但destroy() 是删除线。请帮帮我
既然要进入catch块，首先你应该找出抛出了什么异常，在catch中做一个e.printStackTrace()并报告错误日志。此外，由于它与您之前提出的问题完全无关，您可能需要关闭此问题并提出新问题，以便更多人可以帮助您。【参考方案2】：
图片是你的imageView，imageurl是你从服务器加载图片的url。
try
InputStream in = new java.net.URL(imageURl).openStream();
this.image = BitmapFactory.decodeStream(in);
catch (Exception e)
String msg = (e.getMessage() == null) ? "image load failed!" :e.getMessage();
Log.i("image load error", msg);
【讨论】：
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