Question

我的SignUpActivity课程在NullPointerException的{{1}}处显示getText().toString()。

SignUpActivity：

mSignUpButton.setOnClickListener

这是我的logcat文件

        import android.app.Activity;
        import android.app.AlertDialog;
        import android.os.Bundle;
        import android.view.Menu;
        import android.view.View;
        import android.widget.Button;
        import android.widget.EditText;


        public class SignUpActivity extends Activity {

            protected EditText mUsername;
            protected EditText mPassword;
            protected EditText mEmail;
            protected Button mSignUpButton;


            @Override
            protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_sign_up);

            mUsername = (EditText)findViewById(R.id.usenameField);
            mPassword = (EditText)findViewById(R.id.passwordField);
            mEmail = (EditText)findViewById(R.id.emailField);
            mSignUpButton = (Button)findViewById(R.id.signupButton);



            mSignUpButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    String username = mUsername.getText().toString();
                    String password = mPassword.getText().toString();
                    String email = mEmail.getText().toString();

                    username = username.trim();
                    password = password.trim();
                    email = email.trim();

                    if (username.isEmpty() || password.isEmpty() || email.isEmpty()) {
                    AlertDialog.Builder builder = new AlertDialog.Builder(SignUpActivity.this);
                        builder.setMessage(R.string.sign_up_error_message)
                            .setTitle(R.string.sign_up_error_title)
                            .setPositiveButton(android.R.string.ok, null);
                        AlertDialog dialog = builder.create();
                        dialog.show();
                    }
                    else {
                        // create the new user!
                    }
                }
            });
        }




        @Override
        public boolean onCreateOptionsMenu(Menu menu) {
            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.sign_up, menu);
            return true;
        }

    }

我的布局文件

02-26 14:00:26.288: D/AndroidRuntime(19215): Shutting down VM
02-26 14:00:26.289: W/dalvikvm(19215): threadid=1: thread exiting with uncaught exception (group=0x414589a8)
02-26 14:00:26.295: E/AndroidRuntime(19215): FATAL EXCEPTION: main
02-26 14:00:26.295: E/AndroidRuntime(19215): java.lang.NullPointerException
02-26 14:00:26.295: E/AndroidRuntime(19215):    at com.turtalabs.bagit.SignUpActivity$1.onClick(SignUpActivity.java:32)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at android.view.View.performClick(View.java:4243)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at android.view.View$PerformClick.run(View.java:17520)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at android.os.Handler.handleCallback(Handler.java:725)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at android.os.Handler.dispatchMessage(Handler.java:92)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at android.os.Looper.loop(Looper.java:153)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at android.app.ActivityThread.main(ActivityThread.java:5297)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at java.lang.reflect.Method.invokeNative(Native Method)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at java.lang.reflect.Method.invoke(Method.java:511)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
02-26 14:00:26.295: E/AndroidRuntime(19215):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

你应该替换这个

mUsername = (EditText)findViewById(R.id.usenameField);

使用

mUsername = (EditText)findViewById(R.id.usernameField);

由于这个愚蠢的错误Activity没有找到EditText mUsername。

Answer 2

在你的布局文件中，这个元素被称为“use * r * nameField”吗？

mUsername = (EditText)findViewById(R.id.usenameField);

Edittext gettext tostring在setOnClickListener上显示错误

2 个答案: