java – 在.setOnClickListener上的空指针异常
发布时间:2020-12-15 00:21:31 所属栏目:Java 来源:网络整理
导读:我遇到一个点击监听器的登录模式提交按钮的问题. 这是错误. Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object referen
我遇到一个点击监听器的登录模式提交按钮的问题.
这是错误. Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference 我有一个合理的理解,一个空指针异常是什么,我有一个类似于我的问题彻底搜索.我已经尝试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. 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); } }); } 显而易见,但与我认为的话题无关. <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. 解决方法
Submit是null,因为它不是activity_main.xml的一部分
当您在Activity中调用findViewById时,将在Activity的布局中查找一个View. 改为: Submit = (Button)loginDialog.findViewById(R.id.Submit); 另一件事:你使用 android:layout_below="@+id/LoginTitle" 但你想要的是可能的 android:layout_below="@id/LoginTitle" 请参阅this question关于@id和@ id之间的区别. (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |