您好我对java和android开发的了解非常充分，但这个错误给我带来了大约三个星期的麻烦。我已经尝试了所有关于堆栈溢出的解决方案，比如我改变初始化editText变量的方式，但仍然没有运气。任何帮助都会非常感激，因为它似乎不应该有任何错误。
这是我的mainActivity类代码：
`public class MainActivity extends AppCompatActivity实现了View.OnClickListener {
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
public String email;
public String password;
private EditText emailedittext;
private EditText passwordedittext;
private TextView mStatusTextView;
private TextView mDetailTextView;
private static final String TAG = "EmailPassword";
SharedPreferences sharedpref;
private SharedPreferences.Editor loginStateEditor;
ProgressDialog progressdialog;
Handler handler = new Handler();
int status = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
TwitterAuthConfig authConfig = new TwitterAuthConfig(TWITTER_KEY, TWITTER_SECRET);
Fabric.with(this, new Twitter(authConfig));
setContentView(R.layout.activity_main);
EditText emailedittext = (EditText)findViewById(R.id.emailedittext);
EditText passwordedittext = (EditText)findViewById(R.id.passwordedittext);
final TextView mStatusTextView = (TextView) findViewById(R.id.mStatus);
TextView mDetailTextView = (TextView) findViewById(R.id.mDetail);
Button loginbutton = (Button)findViewById(R.id.login);
Button signupbutton = (Button)findViewById(R.id.signup);
Button signoutbutton = (Button)findViewById(R.id.signout);
findViewById(R.id.login).setOnClickListener(this);
findViewById(R.id.signup).setOnClickListener(this);
findViewById(R.id.signout).setOnClickListener(this);
CreateProgressDialog();
sharedpref = getSharedPreferences("myPref", Context.MODE_PRIVATE);
loginStateEditor = sharedpref.edit();
if (sharedpref.getBoolean("success_login", false)) {
// Start Your Menu Activity
Intent i = new Intent(MainActivity.this, Menu.class);
i.putExtra(EXTRA_MESSAGE, email);
i.putExtra(EXTRA_MESSAGE, password);
startActivity(i);
mAuth = FirebaseAuth.getInstance();
mAuthListener = new FirebaseAuth.AuthStateListener() {
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
FirebaseUser user = firebaseAuth.getCurrentUser();
if (user != null) {
// User is signed in
Log.d(TAG, "onAuthStateChanged:signed_in:" + user.getUid());
Intent i = new Intent(MainActivity.this, Menu.class);
i.putExtra(EXTRA_MESSAGE, email);
i.putExtra(EXTRA_MESSAGE, password);
startActivity(i);
} else {
// User is signed out
Log.d(TAG, "onAuthStateChanged:signed_out");
}
updateUI(user);
}
};}}
@SuppressLint("StringFormatInvalid")
private void updateUI(FirebaseUser user) {
final TextView mStatusTextView = (TextView) findViewById(R.id.mStatus);
TextView mDetailTextView = (TextView) findViewById(R.id.mDetail);
Button loginbutton = (Button)findViewById(R.id.login);
Button signupbutton = (Button)findViewById(R.id.signup);
Button signoutbutton = (Button)findViewById(R.id.signout);
findViewById(R.id.login).setOnClickListener(this);
findViewById(R.id.signup).setOnClickListener(this);
findViewById(R.id.signout).setOnClickListener(this);
hideProgressDialog();{
if (user != null) {
mStatusTextView.setText(getString(R.string.emailpassword_status_fmt, user.getEmail()));
mDetailTextView.setText(getString(R.string.firebase_status_fmt, user.getUid()));
this.findViewById(R.id.login).setVisibility(View.GONE);
this.findViewById(R.id.signup).setVisibility(View.GONE);
this.findViewById(R.id.mStatus).setVisibility(View.GONE);
this.findViewById(R.id.mDetail).setVisibility(View.GONE);
this.findViewById(R.id.signout).setVisibility(View.VISIBLE);
} else {
mStatusTextView.setText(R.string.signed_out);
mDetailTextView.setText(null);
this.findViewById(R.id.login).setVisibility(View.VISIBLE);
this.findViewById(R.id.signup).setVisibility(View.VISIBLE);
this.findViewById(R.id.mStatus).setVisibility(View.GONE);
this.findViewById(R.id.mDetail).setVisibility(View.GONE);
this.findViewById(R.id.signout).setVisibility(View.GONE);
}
}
}
private void createAccount(final String email, final String password){
Log.d(TAG, "createAccount:" + email);
if (!validateForm()) {
return;
}
showProgressDialog();
mAuth.createUserWithEmailAndPassword(email, password)
.addOnCompleteListener(this, new OnCompleteListener<AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
Log.d(TAG, "createUserWithEmail:onComplete:" + task.isSuccessful());
// If sign in fails, display a message to the user. If sign in succeeds
// the auth state listener will be notified and logic to handle the
// signed in user can be handled in the listener.
if (!task.isSuccessful()) {
Toast.makeText(MainActivity.this, "Authentication failed.",
Toast.LENGTH_SHORT).show();
loginStateEditor.putBoolean("success_login", true);
loginStateEditor.commit();
Intent i = new Intent(MainActivity.this, Menu.class);
i.putExtra(EXTRA_MESSAGE, email);
i.putExtra(EXTRA_MESSAGE, password);
startActivity(i);
}
hideProgressDialog();
loginStateEditor.putBoolean("success_login", true);
loginStateEditor.commit();
Intent i = new Intent(MainActivity.this, Menu.class);
startActivity(i);
}
});
}
private void hideProgressDialog() {
progressdialog.dismiss();
}
private boolean validateForm() {
boolean valid = true;
String email = emailedittext.getText().toString();
if (TextUtils.isEmpty(email)) {
emailedittext.setError("Required.");
valid = false;
} else {
emailedittext.setError(null);
}
String password = passwordedittext.getText().toString();
if (TextUtils.isEmpty(password)) {
passwordedittext.setError("Required.");
valid = false;
} else {
passwordedittext.setError(null);
}
return valid;
}
public void showProgressDialog() {
status = 0;
new Thread(new Runnable() {
@Override
public void run() {
while(status < 100){
status +=1;
try{
Thread.sleep(200);
}catch(InterruptedException e){
e.printStackTrace();
}
handler.post(new Runnable() {
@Override
public void run() {
progressdialog.setProgress(status);
if(status == 100){
progressdialog.dismiss();
}
}
});
}
}
}).start();
}
@Override
public void onClick(View v) {
EditText emailedittext = (EditText)MainActivity.this.findViewById(R.id.emailedittext);
EditText passwordedittext = (EditText)MainActivity.this.findViewById(R.id.passwordedittext);
int i = v.getId();
try {
if (i == R.id.signup && emailedittext.getText() != null && passwordedittext.getText() != null) {
createAccount(emailedittext.getText().toString(), passwordedittext.getText().toString());
String email = emailedittext.getText().toString();
String password = passwordedittext.getText().toString();
} else if (i == R.id.login && emailedittext.getText() != null && passwordedittext.getText() != null) {
signIn(emailedittext.getText().toString(), passwordedittext.getText().toString());
String email = emailedittext.getText().toString();
String password = passwordedittext.getText().toString();
} else if (i == R.id.signout) {
signOut();
}
}catch(Exception e){
e.printStackTrace();
}
}
public void CreateProgressDialog()
{
progressdialog = new ProgressDialog(MainActivity.this);
progressdialog.setIndeterminate(false);
progressdialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressdialog.setCancelable(true);
progressdialog.setMax(100);
progressdialog.show();
}
private void signIn(final String email, final String password){
Log.d(TAG, "signIn:" + email);
if (!validateForm()) {
return;
}
showProgressDialog();
mAuth.signInWithEmailAndPassword(email, password)
.addOnCompleteListener(MainActivity.this, new OnCompleteListener<com.google.firebase.auth.AuthResult>() {
@Override
public void onComplete(@NonNull Task<AuthResult> task) {
Log.d(TAG, "signInWithEmail:onComplete:" + task.isSuccessful());
// If sign in fails, display a message to the user. If sign in succeeds
// the auth state listener will be notified and logic to handle the
// signed in user can be handled in the listener.
if (!task.isSuccessful()) {
onSuccess();
{
Log.w(TAG, "signInWithEmail", task.getException());
Toast.makeText(MainActivity.this, "Authentication failed.",
Toast.LENGTH_SHORT).show();
loginStateEditor.putBoolean("success_login", true);
loginStateEditor.commit();
Intent i = new Intent(MainActivity.this, Menu.class);
i.putExtra(EXTRA_MESSAGE, email);
i.putExtra(EXTRA_MESSAGE, password);
startActivity(i);
}
if (!task.isSuccessful()) {
mStatusTextView.setText(R.string.auth_failed);
}
hideProgressDialog();
}
}
});
}
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
{
if (user != null) {
// Name, email address, and profile photo Url
String name = user.getDisplayName();
String email = user.getEmail();
Uri photoUrl = user.getPhotoUrl();
// The user's ID, unique to the Firebase project. Do NOT use this value to
// authenticate with your backend server, if you have one. Use
// FirebaseUser.getToken() instead.
String uid = user.getUid();
}
}
private void signOut() {
mAuth.signOut();
updateUI(null);
}
@Override
protected void onStart() {
super.onStart();
}
@Override
protected void onStop() {
super.onStop();
}
public void onSuccess(){
sharedpref.getBoolean("success_login", true);
loginStateEditor.commit();
Intent i = new Intent(MainActivity.this, Menu.class);
i.putExtra(EXTRA_MESSAGE, email);
i.putExtra(EXTRA_MESSAGE, password);
startActivity(i);
}
} `
以下是导致错误的具体部分：
@Override
public void onClick(View v) {
EditText emailedittext = (EditText)MainActivity.this.findViewById(R.id.emailedittext);
EditText passwordedittext = (EditText)MainActivity.this.findViewById(R.id.passwordedittext);
int i = v.getId();
try {
if (i == R.id.signup && emailedittext.getText() != null && passwordedittext.getText() != null) {
createAccount(emailedittext.getText().toString(), passwordedittext.getText().toString());
String email = emailedittext.getText().toString();
String password = passwordedittext.getText().toString();
} else if (i == R.id.login && emailedittext.getText() != null && passwordedittext.getText() != null) {
signIn(emailedittext.getText().toString(), passwordedittext.getText().toString());
String email = emailedittext.getText().toString();
String password = passwordedittext.getText().toString();
} else if (i == R.id.signout) {
signOut();
}
}catch(Exception e){
e.printStackTrace();
}
}
这是logcat：
ittouch W/System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
03-26 16:15:57.401 5772-5772/com.example.littouchinc.littouch W/System.err: at com.example.littouchinc.littouch.MainActivity.validateForm(MainActivity.java:202)
03-26 16:15:57.401 5772-5772/com.example.littouchinc.littouch W/System.err: at com.example.littouchinc.littouch.MainActivity.createAccount(MainActivity.java:153)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at com.example.littouchinc.littouch.MainActivity.onClick(MainActivity.java:242)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at android.view.View.performClick(View.java:5610)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at android.view.View$PerformClick.run(View.java:22265)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at android.os.Handler.handleCallback(Handler.java:751)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at android.os.Handler.dispatchMessage(Handler.java:95)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at android.os.Looper.loop(Looper.java:154)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at android.app.ActivityThread.main(ActivityThread.java:6077)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at java.lang.reflect.Method.invoke(Native Method)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865)
03-26 16:15:57.402 5772-5772/com.example.littouchinc.littouch W/System.err: at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
非常感谢任何帮助。谢谢。
答案 0 :(得分：0)
你为什么一次又一次地使用这些线？
EditText emailedittext = (EditText)findViewById(R.id.emailedittext);
EditText passwordedittext = (EditText)findViewById(R.id.passwordedittext);
EditText emailedittext，passworditext已经声明了变量。 所以，只需使用
emailedittext = (EditText)findViewById(R.id.emailedittext);
passwordedittext = (EditText)findViewById(R.id.passwordedittext);
另外，从onCreate（）中删除这些行。你不需要在这里定义它们，因为它们已经在OnCreate（）中定义了
EditText emailedittext = (EditText)MainActivity.this.findViewById(R.id.emailedittext);
EditText passwordedittext = (EditText)MainActivity.this.findViewById(R.id.passwordedittext);
答案 1 :(得分：0)
错误消息表示您尝试在null对象上调用getText（）。在MainActivity.java:202行之前检查emailedittext或passwordedittext是否为null。
答案 2 :(得分：0)
您是否有任何具体原因要添加以下行：
EditText emailedittext = (EditText)MainActivity.this.findViewById(R.id.emailedittext);
EditText passwordedittext = (EditText)MainActivity.this.findViewById(R.id.passwordedittext);
因为您已在OnCreate中初始化它们，所以不需要这些。这总是问题。它是否在您第一次启动应用程序时有效？如果它第一次工作并在暂停应用程序后崩溃，那么最好初始化OnResume中的所有视图。
答案 3 :(得分：0)
将所有Button，EditText和TextView声明为全球。
............
private EditText emailedittext;
private EditText passwordedittext;
private TextView mStatusTextView;
private TextView mDetailTextView;
private Button loginbutton;
private Button signupbutton;
private Button signoutbutton;
.........
...............
将活动OnCreate()方法更新为：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
...................
......................
emailedittext = (EditText) findViewById(R.id.emailedittext);
passwordedittext = (EditText) findViewById(R.id.passwordedittext);
mStatusTextView = (TextView) findViewById(R.id.mStatus);
mDetailTextView = (TextView) findViewById(R.id.mDetail);
loginbutton = (Button) findViewById(R.id.login);
signupbutton = (Button) findViewById(R.id.signup);
signoutbutton = (Button) findViewById(R.id.signout);
loginbutton .setOnClickListener(this);
signupbutton .setOnClickListener(this);
signoutbutton .setOnClickListener(this);
.................
......................
}
将您的updateUI()方法更新为：
@SuppressLint("StringFormatInvalid")
private void updateUI(FirebaseUser user) {
hideProgressDialog();
if (user != null) {
mStatusTextView.setText(getString(R.string.emailpassword_status_fmt, user.getEmail()));
mDetailTextView.setText(getString(R.string.firebase_status_fmt, user.getUid()));
loginbutton.setVisibility(View.GONE);
signupbutto.setVisibility(View.GONE);
mStatusTextView.setVisibility(View.GONE);
mDetailTextView.setVisibility(View.GONE);
signoutbutton.setVisibility(View.VISIBLE);
} else {
mStatusTextView.setText(R.string.signed_out);
mDetailTextView.setText(null);
loginbutton.setVisibility(View.VISIBLE);
signupbutton.setVisibility(View.VISIBLE);
mStatusTextView.setVisibility(View.GONE);
mStatusTextView.setVisibility(View.GONE);
signoutbutton.setVisibility(View.GONE);
}
}
将onClick()方法更新为：
@Override
public void onClick(View v) {
int i = v.getId();
try {
if (i == R.id.signup && emailedittext.getText() != null && passwordedittext.getText() != null) {
createAccount(emailedittext.getText().toString(), passwordedittext.getText().toString());
String email = emailedittext.getText().toString();
String password = passwordedittext.getText().toString();
} else if (i == R.id.login && emailedittext.getText() != null && passwordedittext.getText() != null) {
signIn(emailedittext.getText().toString(), passwordedittext.getText().toString());
String email = emailedittext.getText().toString();
String password = passwordedittext.getText().toString();
} else if (i == R.id.signout) {
signOut();
}
}catch(Exception e){
e.printStackTrace();
}
}
希望这会有所帮助！