验证空白 EditText 显示错误

Question

当我验证 EditText 登录时，我收到 NullPointerException

            public boolean onMenuItemClick( MenuItem item )
                {

                if(item.getTitle().equals("Login"))
                    {

                        final String Usname;
                        final String Pswd;
                        Status=(TextView)findViewById(R.id.tvStatus);
                        Uname=(EditText)findViewById(R.id.etLUsername);
                        Pwd=(EditText)findViewById(R.id.etLPassword);
                        LayoutInflater li = LayoutInflater.from(MainActivity.this);
                        View promptsView = li.inflate(R.layout.login, null);
                        //Usname=Uname.getText().toString();
                        //Pswd=Pwd.getText().toString();

                        AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(MainActivity.this);

                        // set dialog message
                        alertDialogBuilder
                            .setCancelable(true)
                            .setPositiveButton("Login",
                                 new DialogInterface.OnClickListener() {
                                      public void onClick(DialogInterface dialog,int id) {
                                        if(Uname!=null&&Pwd!=null){
                                            new Asynctask_Login().execute();

                                        }
                                        else if(Pwd!=null){
                                            Status.setText("No Username");
                                            Status.setVisibility(View.VISIBLE); 

                                        }
                                        else if(Uname!=null){


                                            Status.setText("No Password");
                                            Status.setVisibility(View.VISIBLE);
                                        }
                                        else{

                                            Status.setText("No Username and Password");
                                            Status.setVisibility(View.VISIBLE);
                                        }


                                      }
                                 })
                                .setNegativeButton("Register",
                                 new DialogInterface.OnClickListener() {
                                 public void onClick(DialogInterface dialog,int id) {

                                try {
                                        Intent tvi = new Intent("com.takebestloan.action.REGISTER");                        
                                        startActivity(tvi);

                                    } catch (Exception e) {
                                        // TODO: handle exception
                                    }
                                    dialog.cancel();
                                       }
                                  });
                            AlertDialog alertDialog = alertDialogBuilder.create();
                            alertDialog.setView(promptsView,0,0,0,0);
                            alertDialog.show();
             }else if(item.getItemId()==R.id.mRegister)
                    {
                        try {
                            Intent tvi = new Intent("com.takebestloan.action.REGISTER");                        
                            startActivity(tvi);

                        } catch (Exception e) {
                            // TODO: handle exception
                        }
                    }else if(item.getTitle().equals("Nearby ATM"))
                    {
                        //Toast.makeText( MainActivity.this, "Comming soon..", Toast.LENGTH_SHORT ).show();

                        try {
                            Intent in = new Intent(Intent.ACTION_VIEW,Uri.parse("https://maps.google.co.in/maps?q=atm&z=16"));
                            in.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK& Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
                            in.setClassName("com.google.android.apps.maps","com.google.android.maps.MapsActivity");
                            startActivity(in);
                           } catch (Exception e) {
                           // tm.showToast(R.string.tm_gmap_not_detected);
                            e.printStackTrace();
                           }
                    }
                    else  if(item.getTitle().equals("Nearby Banks"))
                    {
                        //Toast.makeText( MainActivity.this, "Comming soon..", Toast.LENGTH_SHORT ).show();

                        try {
                            Intent in = new Intent(Intent.ACTION_VIEW,Uri.parse("https://maps.google.co.in/maps?q=bank&z=16"));
                            in.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK& Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
                            in.setClassName("com.google.android.apps.maps","com.google.android.maps.MapsActivity");
                            startActivity(in);
                           } catch (Exception e) {
                           // tm.showToast(R.string.tm_gmap_not_detected);
                            e.printStackTrace();
                           }
                    }
                    else  if(item.getTitle().equals("Home Loans"))
                    {
                        try {
                            Intent tvi = new Intent(getApplicationContext(),HL.class);  
                            startActivity(tvi);
                        } catch (Exception e) {
                            // TODO: handle exception
                        }               
                    }
                    else  if(item.getTitle().equals("Loan Against Property"))
                    {
                        try {
                            Intent tvi = new Intent(getApplicationContext(),LAP.class); 
                            startActivity(tvi);

                        } catch (Exception e) {
                            // TODO: handle exception
                        }               
                    }

                    else
                    {
                        Toast.makeText( MainActivity.this, "Romba NOT", Toast.LENGTH_SHORT ).show();

                    }


                    return true;
                }
            } );

            menu.show();

        }
    });

Check if EditText is empty.

中的所有方法我都试过了

Logcat:

06-17 18:34:04.019: E/AndroidRuntime(24618): FATAL EXCEPTION: main
06-17 18:34:04.019: E/AndroidRuntime(24618): java.lang.NullPointerException
06-17 18:34:04.019: E/AndroidRuntime(24618):    at com.takebestloan.IFSC.MainActivity.onMenuItemClick(MainActivity.java:241)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at com.takebestloan.mainMenu.HoneycombHelper.onMenuItemClick(HoneycombHelper.java:52)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.widget.PopupMenu.onMenuItemSelected(PopupMenu.java:142)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:149)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at com.android.internal.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:874)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at com.android.internal.view.menu.MenuPopupHelper.onItemClick(MenuPopupHelper.java:156)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.widget.AdapterView.performItemClick(AdapterView.java:292)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.widget.AbsListView.performItemClick(AbsListView.java:1394)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.widget.AbsListView$PerformClick.run(AbsListView.java:3024)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.widget.AbsListView.run(AbsListView.java:3830)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.os.Handler.handleCallback(Handler.java:605)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.os.Handler.dispatchMessage(Handler.java:92)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.os.Looper.loop(Looper.java:137)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at android.app.ActivityThread.main(ActivityThread.java:4517)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at java.lang.reflect.Method.invokeNative(Native Method)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at java.lang.reflect.Method.invoke(Method.java:511)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:993)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:760)
06-17 18:34:04.019: E/AndroidRuntime(24618):    at dalvik.system.NativeStart.main(Native Method)

错误出现在行Usname=Uname.getText().toString(); 应用强制关闭

Answer 1

通过此检查 Null

if (myString != null && !myString.isEmpty()) {
  // doSomething
}

并解决错误

Usname=Uname.text.toString();

Answer 2

关于为什么会出现空指针异常，有两种可能。首先Uname=(EditText)findViewById(R.id.etLUsername); 如果找不到视图 edLUsername，实际上可能会为 Uname 分配 null。

其次，Uname.getText() 可能会返回 null，因此当您调用 toString() 时，它会导致空指针异常。你应该添加一些错误检查

Editable text = Uname.getText();
if (text != null) {
    Uname = text.toString();
}

Answer 3

我弄错了。在我的例子中，我在设置布局之前设置了 EditTexts。我做了以下更改：

Status=(TextView)promptsView.findViewById(R.id.tvStatus);                                   
Uname=(EditText)promptsView.findViewById(R.id.etLUsername);
Pwd=(EditText)promptsView.findViewById(R.id.etLPassword);

我得到了以下帮助：NullPointerException thrown on TextView setText()

验证空白 EditText 显示错误

Validating Blank EditText shows error

android

nullpointerexception

android-edittext

android-alertdialog