我正试图在Dialog中像这样使用这个好的教程用于Login action:
public class MainActivity extends AppCompatActivity {
private SQLiteHandler db;
public ProgressDialog pDialog;
public SessionManager session;
private DrawerLayout drawerLayout;
private static final String TAG = MainActivity.class.getSimpleName();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Displaying the user details on the screen
TextView txtName = (TextView) findViewById(R.id.usernamehd);
TextView txtEmail = (TextView) findViewById(R.id.emailuserr);
db = new SQLiteHandler(getApplicationContext());
HashMap<String, String> user = db.getUserDetails();
String name = user.get("name");
String email = user.get("email");
txtName.setText(name);
txtEmail.setText(email);
TextView sgnin = (TextView) findViewById(R.id.signinbtn);
sgnin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
final Dialog d = new Dialog(MainActivity.this);
d.setContentView(R.layout.dialog);
String title = getResources().getString(R.string.dialog_title);
d.setTitle(title);
d.show();
// first dialog for showing that dialog Login-register
final EditText inusremail = (EditText) d.findViewById(R.id.emailuserr);
final EditText inpass = (EditText) d.findViewById(R.id.passworduser);
final Button btnLogin = (Button) d.findViewById(R.id.Login);
pDialog = new ProgressDialog(MainActivity.this);
pDialog.setCancelable(false);
btnLogin.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String email = inusremail.getText().toString();
String password = inpass.getText().toString();
if (email.trim().length() > 0 && password.trim().length() > 0) {
checkLogin(email, password);
} else {
Toast.makeText(getApplicationContext(), "Please enter the credentials!", Toast.LENGTH_LONG).show();
}
}
});
//end the Login button
}
});
这是CheckLogin:的函数
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_REGISTER, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
Log.d(TAG, "Login Response: " + response.toString());
hideDialog();
try {
JSONObject jObj = new JSONObject(response);
boolean error = jObj.getBoolean("error");
// Check for error node in json
if (!error) {
// user successfully logged in
// Create login session
session.setLogin(true);
// Launch main activity
Intent intent = new Intent(MainActivity.this,
MainActivity.class);
startActivity(intent);
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();
}
}
}, 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("tag", "login");
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();
}
但是，有一个问题，我不知道是什么：
java.lang.NullPointerException: Attempt to invoke virtual method 'void client.package.helper.SessionManager.setLogin(boolean)' on a null object reference
at client.package.MainActivity$6.onResponse(MainActivity.java:257)
at client.package.MainActivity$6.onResponse(MainActivity.java:242)
at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:60)
at com.android.volley.toolbox.StringRequest.deliverResponse(StringRequest.java:30)
at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
i just change the package name
当然，Register正在工作，我可以将用户凭据保存在服务器端，但这也有类似的问题，我不知道如何在一个Acttivity中解决这个问题。
任何帮助都会很棒。
session.setLogin(true);
您必须确保session已初始化。。
要格外小心：
if(session!=null)
session.setLogin(true);
错误显示SessionManager的Object为null。您尚未在声明后初始化对象。
SessionManager session; //declared
session = New SessionManager(Arguments); //Intialized