.setOnClickListener上的空指针异常 [英] Null pointer Exception on .setOnClickListener
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问题描述
我遇到登录模式提交按钮的点击监听器问题。
I am having an issue with a click listener for a login modal submit button.
这是错误。
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
我对空指针异常是什么有合理的理解，我已经彻底搜索了一个问题与我的相似。我试图以多种方式重新格式化点击监听器，确保我有正确的视图ID等。
I have a reasonable understanding of what a null pointer exception is and I have search thoroughly for an issue similar to mine. I have tried to reformat the click listener in several ways, made sure I have the correct view ID etc.
package...
import...
public class MainActivity extends ActionBarActivity implements NavigationDrawerFragment.NavigationDrawerCallbacks {
//Variables
String currentPage = "";
Stack<String> crumbs = new Stack<String>();
//Fragment managing the behaviors, interactions and presentation of the navigation drawer.
private NavigationDrawerFragment mNavigationDrawerFragment;
// Used to store the last screen title. For use in {@link #restoreActionBar()}.
public CharSequence mTitle;
//temp
AuthenticateUserTokenResult authenticateUserTokenResult;
String loginErrorMessage = "";
String loginErrorTitle = "";
Boolean logonSuccessful = false;
Dialog loginDialog;
// Login EditTexts
EditText Username;
EditText CompanyID;
EditText Password;
Button Submit;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mNavigationDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
mTitle = getTitle(); // Set up the drawer.
mNavigationDrawerFragment.setUp(R.id.navigation_drawer, (DrawerLayout) findViewById(R.id.drawer_layout));
if(authenticateUserTokenResult == null) {
attemptLogin();
}
}
public void attemptLogin() {
loginDialog = new Dialog(this,android.R.style.Theme_Translucent_NoTitleBar);
loginDialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
loginDialog.setContentView(R.layout.login_modal);
loginDialog.setCancelable(false);
//loginDialog.setOnCancelListener(cancelListener);
loginDialog.show();
Submit = (Button)findViewById(R.id.Submit);
Submit.setOnClickListener(new View.OnClickListener() // the error is on this line (specifically the .setOnClickListener)
{
@Override
public void onClick(View v)
{
ClyxUserLogin user = new ClyxUserLogin();
Username = (EditText)findViewById(R.id.Username);
user.logon = Username.getText().toString();
CompanyID = (EditText)findViewById(R.id.CompanyID);
user.idCompany = Integer.parseInt(CompanyID.getText().toString());
Password = (EditText)findViewById(R.id.Password);
user.password = Password.getText().toString();
user.idApplication = 142;
authenticate(user);
}
});
}
显然，我认为有更多与此主题无关。
这是包含按钮的对话框的XML文件。
There is more, obviously, but not relevant to the topic I think. Here is the XML file for the dialog that has the button on it.
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="#3366FF">
<RelativeLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:background="#FFFFFF" >
<TextView
android:id="@+id/LoginTitle"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:gravity="center_horizontal"
android:layout_marginTop="10dp"
android:layout_marginStart="10dp"
android:textColor="#000000"
android:textSize="20sp"
android:text="Login" />
<EditText
android:id="@+id/Username"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:layout_below="@+id/LoginTitle"
android:layout_margin="10dp"
android:hint="Username" />
<EditText
android:id="@+id/CompanyID"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:layout_below="@+id/Username"
android:layout_alignStart="@+id/Username"
android:inputType="number"
android:hint="Company ID" />
<EditText
android:id="@+id/Password"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:layout_below="@+id/CompanyID"
android:layout_alignStart="@+id/Username"
android:layout_marginTop="10dp"
android:layout_marginBottom="10dp"
android:inputType="textPassword"
android:hint="Password" />
<Button
android:id="@+id/Submit"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/Password"
android:layout_marginBottom="10dp"
android:layout_centerHorizontal="true"
android:text="Login" />
</RelativeLayout>
</RelativeLayout>
任何帮助将不胜感激。
Any help would be greatly appreciated.
推荐答案
提交 null 因为它不是 activity_main.xml的一部分
当你打电话给 findViewById 在活动中，它将在Activity的布局中寻找 View 。
When you call findViewById inside an Activity, it is going to look for a View inside your Activity's layout.
试试这个：
Submit = (Button)loginDialog.findViewById(R.id.Submit);
另一件事：你使用
android:layout_below="@+id/LoginTitle"
但是你想要的可能是
android:layout_below="@id/LoginTitle"
请参阅这个问题关于 @id 和 @ + id 之间的区别。
See this question about the difference between @id and @+id.
这篇关于.setOnClickListener上的空指针异常的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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