[英]Button click causing null pointer
Every time I click on the button, the app crashes.
每次我单击按钮时,应用程序都会崩溃。 I have trouble finding the bug, but I'm sure it has to do something with either the onClickListener, or the onClick function.
我很难找到该错误,但是我确定它必须与onClickListener或onClick函数一起执行某些操作。
Note: I'm using Parse API for some back end stuff. 注意:我正在使用Parse API来处理一些后端内容。 But I highly doubt it has anything to do with any of the Parse stuff.
但是我非常怀疑这与任何Parse东西有关系。
Here's what my code looks like: 这是我的代码:
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);
requestWindowFeature(Window.FEATURE_INDETERMINATE_PROGRESS);
setContentView(R.layout.activity_sign_up);
mUserName = (EditText) findViewById(R.id.usernameField);
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.signup_error_message)
.setTitle(R.string.signup_error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
else{
setProgressBarIndeterminateVisibility(true);
ParseUser newUser = new ParseUser();
newUser.setUsername(username);
newUser.setPassword(password);
newUser.setEmail(email);
newUser.signUpInBackground(new SignUpCallback() {
@Override
public void done(ParseException e) {
setProgressBarIndeterminateVisibility(false);
if(e == null){
// success
Intent intent = new Intent(SignUpActivity.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(SignUpActivity.this);
builder.setMessage(e.getMessage())
.setTitle(R.string.signup_error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
}
});
}
}
});
}
@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;
}
}
Here's my Log Cat: 这是我的原木猫:
04-14 14:19:05.881: E/AndroidRuntime(1156): FATAL EXCEPTION: main 04-14 14:19:05.881:
E/AndroidRuntime(1156): Process: com.ebad.ribbit, PID: 1156 04-14 14:19:05.881:
E/AndroidRuntime(1156): java.lang.NullPointerException 04-14 14:19:05.881:
E/AndroidRuntime(1156): at com.ebad.ribbit.SignUpActivity$1.onClick(SignUpActivity.java:40) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at android.view.View.performClick(View.java:4438) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at android.view.View$PerformClick.run(View.java:18422) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at android.os.Handler.handleCallback(Handler.java:733) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at android.os.Handler.dispatchMessage(Handler.java:95) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at android.os.Looper.loop(Looper.java:136) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at android.app.ActivityThread.main(ActivityThread.java:5017) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at java.lang.reflect.Method.invokeNative(Native Method) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at java.lang.reflect.Method.invoke(Method.java:515) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) 04-14 14:19:05.881:
E/AndroidRuntime(1156): at dalvik.system.NativeStart.main(Native Method)
EDIT: 编辑:
As requested, here is line 40: 根据要求,这是第40行:
String username = mUserName.getText().toString();
EDIT 2: 编辑2:
Here is the log cat after adding Log.i(TAG, mUserName == null ? "mUserName is null" : mUserName.getText() == null ? "mUserName.getText() is null" : "nothing is null");
这是添加
Log.i(TAG, mUserName == null ? "mUserName is null" : mUserName.getText() == null ? "mUserName.getText() is null" : "nothing is null");
后的日志猫Log.i(TAG, mUserName == null ? "mUserName is null" : mUserName.getText() == null ? "mUserName.getText() is null" : "nothing is null");
: :
04-14 15:21:47.955: E/AndroidRuntime(1318): FATAL EXCEPTION: main
04-14 15:21:47.955: E/AndroidRuntime(1318): Process: com.ebad.ribbit, PID: 1318
04-14 15:21:47.955: E/AndroidRuntime(1318): java.lang.NullPointerException
04-14 15:21:47.955: E/AndroidRuntime(1318): at com.ebad.ribbit.SignUpActivity$1.onClick(SignUpActivity.java:43)
04-14 15:21:47.955: E/AndroidRuntime(1318): at android.view.View.performClick(View.java:4438)
04-14 15:21:47.955: E/AndroidRuntime(1318): at android.view.View$PerformClick.run(View.java:18422)
04-14 15:21:47.955: E/AndroidRuntime(1318): at android.os.Handler.handleCallback(Handler.java:733)
04-14 15:21:47.955: E/AndroidRuntime(1318): at android.os.Handler.dispatchMessage(Handler.java:95)
04-14 15:21:47.955: E/AndroidRuntime(1318): at android.os.Looper.loop(Looper.java:136)
04-14 15:21:47.955: E/AndroidRuntime(1318): at android.app.ActivityThread.main(ActivityThread.java:5017)
04-14 15:21:47.955: E/AndroidRuntime(1318): at java.lang.reflect.Method.invokeNative(Native Method)
04-14 15:21:47.955: E/AndroidRuntime(1318): at java.lang.reflect.Method.invoke(Method.java:515)
04-14 15:21:47.955: E/AndroidRuntime(1318): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-14 15:21:47.955: E/AndroidRuntime(1318): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-14 15:21:47.955: E/AndroidRuntime(1318): at dalvik.system.NativeStart.main(Native Method)
EDIT 3: 编辑3:
Upon Request, here is my activity_sign_up.xml: 根据要求,这是我的activity_sign_up.xml:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".SignUpActivity" >
<EditText
android:id="@+id/userNameField"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:hint="@string/username_hint"
android:ems="10" >
<requestFocus />
</EditText>
<EditText
android:id="@+id/passwordField"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/userNameField"
android:ems="10"
android:hint="@string/password_hint"
android:inputType="textPassword" />
<EditText
android:id="@+id/emailField"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_below="@+id/passwordField"
android:ems="10"
android:hint="@string/email_hint"
android:inputType="textEmailAddress" />
<Button
android:id="@+id/signupButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/emailField"
android:layout_below="@+id/emailField"
android:layout_marginTop="50dp"
android:text="@string/sign_up_button_label" />
</RelativeLayout>
If mUsername
is null
, calling getText()
on it will cause a NullPointerException
. 如果
mUsername
为null
,则对其调用getText()
将导致NullPointerException
。 You should check that it's not null before doing this. 在执行此操作之前,应检查它是否不为null。 Try changing to the following:
尝试更改为以下内容:
if(mUserName == null || mPassword == null || mEmail == null){
AlertDialog.Builder builder = new AlertDialog.Builder(SignUpActivity.this);
builder.setMessage(R.string.signup_error_message)
.setTitle(R.string.signup_error_title)
.setPositiveButton(android.R.string.ok, null);
AlertDialog dialog = builder.create();
dialog.show();
}
String username = mUserName.getText().toString();
String password = mPassword.getText().toString();
String email = mEmail.getText().toString();
username = username.trim();
password = password.trim();
email = email.trim();
Do this please: 请这样做:
@Override
public void onClick(View v) {
if(mUserName != null && mPassword != null && mEmail != null && mUserName.getText() != null && mPassword.getText() != null && mEmail.getText() != null)
{
Your original code here.
}
}
Update: Typo 更新:错字
mUserName = (EditText) findViewById(R.id.usernameField); should be userNameField?
<EditText android:id="@+id/userNameField" ...
Try 尝试
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
https://developer.android.com/guide/topics/ui/dialogs.html https://developer.android.com/guide/topics/ui/dialogs.html
Also make sure that SignUpActivity is declared in the app manifest. 还要确保在应用清单中声明了SignUpActivity。 I guess make sure that all activities are set up in the manifest.
我想确保清单中设置了所有活动。
EDIT 1 If line 40 is the issue, then mUserName is null or mUserName.getText() is null. 编辑1如果第40行是问题,则mUserName为null或mUserName.getText()为null。 So create a couple checks before hand and also add some debug logs to just verify that they are not null.
因此,请事先创建一些检查,并添加一些调试日志以仅验证它们是否不为空。
Make sure that R.layout.activity_sign_up has usernameField as an id. 确保R.layout.activity_sign_up具有usernameField作为ID。 Also make sure in any other app/res/layout folders (ie layout-v14), that all R.layout.activity_sign_up has the edittext as well.
还要确保在任何其他app / res / layout文件夹(即layout-v14)中,所有R.layout.activity_sign_up也都具有edittext。
If this errors occurred in your line 40, that means your are getting null from your EditText. 如果此错误发生在您的第40行中,则意味着您将从EditText中获取空值。
Try it in every place you are getting a string. 在得到字符串的每个地方尝试一下。 At least it will save you from getting null pointer exception from EditText.
至少它将避免您从EditText获取空指针异常。
String username = String.valueOf(mUserName.getText());
String password = String.valueOf(mPassword.getText());
String email = String.valueOf(mEmail.getText());
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