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我知道這是一個非常常見的話題，但我得到這個錯誤，不知道爲什麼。該代碼在Eclipse中運行得非常好，但在Studio中按下按鈕時會崩潰。我可以想到的唯一區別是Request.Method而不是像Eclipse中的Method。之前我認爲它是因爲edittext的值沒有得到。但它顯示在吐司。爲什麼它顯示nullpointerexception？
Error
01-13 11:13:34.242 14427-14427/com.sam.sports E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.sam.sports, PID: 14427
java.lang.NullPointerException
at com.sam.sports.LoginPage.checkLogin(LoginPage.java:180)
at com.sam.sports.LoginPage.access$200(LoginPage.java:28)
at com.sam.sports.LoginPage$1.onClick(LoginPage.java:80)
at android.view.View.performClick(View.java:4562)
at android.view.View$PerformClick.run(View.java:18918)
at android.os.Handler.handleCallback(Handler.java:808)
at android.os.Handler.dispatchMessage(Handler.java:103)
at android.os.Looper.loop(Looper.java:193)
at android.app.ActivityThread.main(ActivityThread.java:5388)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:655)
at dalvik.system.NativeStart.main(Native Method)
01-13 11:13:38.996 14427-14427/com.sam.sports I/Process: Sending signal. PID: 14427 SIG: 9public class LoginPage extends AppCompatActivity {
private static final String TAG = RegisterPage.class.getSimpleName();
private Button btnLogin;
private Button btnLinkToRegister;
private EditText inputEmail;
private EditText inputPassword;
private ProgressDialog pDialog;
private SessionManager session;
private SQLiteHandler db;
String name;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.loginpage);
inputEmail = (EditText) findViewById(R.id.email_login);
inputPassword = (EditText) findViewById(R.id.password_login);
btnLogin = (Button) findViewById(R.id.login_btn);
btnLinkToRegister = (Button) findViewById(R.id.btnLinktoRegd);
// Progress dialog
pDialog = new ProgressDialog(this);
pDialog.setCancelable(false);
// SQLite database handler
db = new SQLiteHandler(getApplicationContext());
// Session manager
session = new SessionManager(getApplicationContext());
// Check if user is already logged in or not
if (session.isLoggedIn()) {
// User is already logged in. Take him to main activity
Intent intent = new Intent(LoginPage.this, HomePage.class);
startActivity(intent);
finish();
}
// Login button Click Event
btnLogin.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
String email = inputEmail.getText().toString().trim();
String password = inputPassword.getText().toString().trim();
// Check for empty data in the form
if (!email.isEmpty() && !password.isEmpty()) {
// login user
checkLogin(email, password);
//Toast.makeText(getApplicationContext(), email + "\n" + password, Toast.LENGTH_LONG).show();
} else {
// Prompt user to enter credentials
Toast.makeText(getApplicationContext(), "Please enter the credentials!", Toast.LENGTH_LONG).show();
}
}
});
// Link to Register Screen
btnLinkToRegister.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
startActivity(new Intent(LoginPage.this, RegisterPage.class));
finish();
}
});
}
/**
* function to verify login details in mysql db
* */
private void checkLogin(final String email, final String password) {
// Tag used to cancel the request
String tag_string_req = "req_login";
pDialog.setMessage("Logging in ...");
showDialog();
StringRequest strReq = new StringRequest(Request.Method.POST,
AppConfig.URL_LOGIN, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.d(TAG, "Login Response: " + response.toString());
hideDialog();
try {
JSONObject jObj = new JSONObject(response);
String status = jObj.getString("status");
// Now check status value
if (status.equals("0")) {
Toast.makeText(getApplicationContext(), "Email or Password may be incorrect! Please try again.", Toast.LENGTH_LONG).show();
}else if(status.equals("1")){
// user successfully logged in
// Create login session
session.setLogin(true);
// Now store the user in SQLite
JSONObject userData = jObj.getJSONObject("userData");
String uid = userData.getString("id");
String name = userData.getString("name");
String email = userData.getString("email");
String created_at = userData.getString("created_at");
// Inserting row in users table
db.addUser(name, email, uid, created_at);
// Launch main activity
startActivity(new Intent(LoginPage.this, HomePage.class));
finish();
} else {
// Error in login. Get the error message
String errorMsg = jObj.getString("error_msg");
Toast.makeText(getApplicationContext(), errorMsg, Toast.LENGTH_LONG).show();
}
} catch (JSONException e) {
// JSON error
e.printStackTrace();
Toast.makeText(getApplicationContext(), "Json error: " + e.getMessage(), Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Log.e(TAG, "Login Error: " + error.getMessage());
Toast.makeText(getApplicationContext(), error.getMessage(), Toast.LENGTH_LONG).show();
hideDialog();
}
}) {
@Override
protected Map<String, String> getParams() {
// Posting parameters to login url
Map<String, String> params = new HashMap<String, String>();
params.put("email", email);
params.put("password", password);
return params;
}
};
// Adding request to request queue
AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
}
private void showDialog() {
if (!pDialog.isShowing())
pDialog.show();
}
private void hideDialog() {
if (pDialog.isShowing())
pDialog.dismiss();
}
}
提及您在哪條線上獲得例外。 –
其中'checkLogin（email，password）;'在'btnLogin.setOnClickListener'中有' – Sam
其中checkLogin方法？ –