Question

我一直在设计我的应用的登录和注册屏幕。在我的主要活动中更改操作栏设置后，我似乎无法登录到应用程序。登录和注册屏幕完美加载。但后来它说“不幸的是，____已停止”这是我得到的错误，我还包括我的LoginActivity.java，因为它说错误在哪里。但是我不知道要引用哪个其他文件，所以如果你需要另一个文件让我知道，我会更新它。谢谢！

 1493-1493/com.example.aalok.chirp E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.aalok.chirp, PID: 1493
java.lang.NullPointerException
        at com.example.aalok.chirp.LoginActivity$2.onClick(LoginActivity.java:58)
        at android.view.View.performClick(View.java:4438)
        at android.view.View$PerformClick.run(View.java:18422)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        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:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)


    package com.example.aalok.chirp;

import android.app.ActionBar;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.parse.LogInCallback;
import com.parse.Parse;
import com.parse.ParseException;
import com.parse.ParseUser;
import com.parse.SignUpCallback;


public class LoginActivity extends Activity {

    protected EditText mUsername;
    protected EditText mPassword;
    protected Button mLoginButton;
    protected TextView mSignUpTextView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
        setContentView(R.layout.activity_login);

        ActionBar actionBar = getActionBar();
        actionBar.hide();

        //Set up SignUp text
        mSignUpTextView = (TextView) findViewById(R.id.signUpText);
        mSignUpTextView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(LoginActivity.this, SignUpActivity.class);
                startActivity(intent);
            }
        });

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

        //Set up Login button
        mLoginButton = (Button) findViewById(R.id.loginButton);
        mLoginButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String username = mUsername.getText().toString();
                String password = mPassword.getText().toString();

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

                if (username.isEmpty() || password.isEmpty()) {
                    AlertDialog.Builder builder = new AlertDialog.Builder(LoginActivity.this);
                    builder.setMessage(R.string.login_error_message)
                            .setTitle(R.string.login_error_title)
                            .setPositiveButton(android.R.string.ok, null);
                    AlertDialog dialog = builder.create();
                    dialog.show();
                } else {
                    //LOGIN
                    setProgressBarIndeterminateVisibility(true);

                    ParseUser.logInInBackground(username, password, new LogInCallback() {
                        @Override
                        public void done(ParseUser user, ParseException e) {
                            setProgressBarIndeterminateVisibility(false);
                            if (e == null) {
                                //SUCCESS!
                                Intent intent = new Intent(LoginActivity.this, MainActivity.class);
                                intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                                intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);
                                startActivity(intent);
                            } else {
                                AlertDialog.Builder builder = new AlertDialog.Builder(LoginActivity.this);
                                builder.setMessage(e.getMessage())
                                        .setTitle(R.string.login_error_title)
                                        .setPositiveButton(android.R.string.ok, null);
                                AlertDialog dialog = builder.create();
                                dialog.show();
                            }
                        }
                    });
                }

            }
        });
    }
}

Answer 1

Process: com.example.aalok.chirp, PID: 1493
java.lang.NullPointerException
        at com.example.aalok.chirp.LoginActivity$2.onClick(LoginActivity.java:58)
        at android.view.View.performClick(View.java:4438)
        at android.view.View$PerformClick.run(View.java:18422)

这意味着第58行的某些内容为空。

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

//Set up Login button
mLoginButton = (Button) findViewById(R.id.loginButton);
mLoginButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        String username = mUsername.getText().toString();
        String password = mPassword.getText().toString(); //this is line 58

但根据您的代码，您初始化mPassword，因此如果它存在于布局中，则不能是null。因此，我怀疑R.id.passwordField

中不存在R.layout.activity_login

获得致命异常：主要错误

1 个答案: