我正在尝试构建一个小项目，该项目使用带有两个不同片段的标签，具体取决于选择了哪个标签。这两个片段都包含EditText字段，当我单击按钮时，我想从中保存值。问题是当我单击按钮时，我得到一个空指针异常。 Logcat在尝试获取片段的onClick(View v)方法中的EditText字段的值时抛出异常
与encrypt.setSaveEntry(getActivity(), "uname", edit_username.getText().toString())。
我非常感谢提前对这个问题的贡献
这是我的fragment_registry.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<EditText
android:id="@+id/edit_username1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_marginTop="25dp"
android:ems="10"
android:inputType="text"
android:text="@string/edit_username" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/edit_username1"
android:layout_below="@+id/edit_username1"
android:layout_marginTop="15dp"
android:text="@string/choose_gender"
android:textAppearance="?android:attr/textAppearanceMedium" />
<RadioGroup
android:id="@+id/radioGroup1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView3"
android:layout_below="@+id/textView3"
android:layout_marginTop="15dp"
android:orientation="vertical" >
<RadioButton
android:id="@+id/radio_male"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onRadioButtonClicked"
android:text="@string/male" />
<RadioButton
android:id="@+id/radio_female"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:onClick="onRadioButtonClicked"
android:text="@string/female" />
</RadioGroup>
<EditText
android:id="@+id/edit_password1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/radioGroup1"
android:layout_below="@+id/radioGroup1"
android:layout_marginTop="15dp"
android:ems="10"
android:inputType="text"
android:text="@string/edit_password" />
<EditText
android:id="@+id/edit_confirm"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/edit_password2"
android:layout_below="@+id/edit_password2"
android:layout_marginTop="15dp"
android:ems="10"
android:inputType="text"
android:text="@string/confirm_password" />
<Button
android:id="@+id/btn_registry"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignRight="@+id/edit_confirm"
android:layout_below="@+id/edit_confirm"
android:layout_marginTop="15dp"
android:onClick="register"
android:text="@string/btn_register" />
</RelativeLayout>
这是我的UserAccount_Activity的代码：
public class UserAccount_Activity extends ActionBarActivity implements
ActionBar.TabListener {
/**
* The {@link android.support.v4.view.PagerAdapter} that will provide
* fragments for each of the sections. We use a {@link FragmentPagerAdapter}
* derivative, which will keep every loaded fragment in memory. If this
* becomes too memory intensive, it may be best to switch to a
* {@link android.support.v4.app.FragmentStatePagerAdapter}.
*/
SectionsPagerAdapter mSectionsPagerAdapter;
/**
* The {@link ViewPager} that will host the section contents.
*/
ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.user_account);
// Set up the action bar.
final ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// Create the adapter that will return a fragment for each of the three
// primary sections of the activity.
mSectionsPagerAdapter = new SectionsPagerAdapter(
getSupportFragmentManager());
// Set up the ViewPager with the sections adapter.
mViewPager = (ViewPager) findViewById(R.id.pager);
mViewPager.setAdapter(mSectionsPagerAdapter);
// When swiping between different sections, select the corresponding
// tab. We can also use ActionBar.Tab#select() to do this if we have
// a reference to the Tab.
mViewPager
.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
actionBar.setSelectedNavigationItem(position);
}
});
// For each of the sections in the app, add a tab to the action bar.
for (int i = 0; i < mSectionsPagerAdapter.getCount(); i++) {
// Create a tab with text corresponding to the page title defined by
// the adapter. Also specify this Activity object, which implements
// the TabListener interface, as the callback (listener) for when
// this tab is selected.
actionBar.addTab(actionBar.newTab()
.setText(mSectionsPagerAdapter.getPageTitle(i))
.setTabListener(this));
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.user_account_, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public void onTabSelected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
// When the given tab is selected, switch to the corresponding page in
// the ViewPager.
mViewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
@Override
public void onTabReselected(ActionBar.Tab tab,
FragmentTransaction fragmentTransaction) {
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return new RegistryFragment();
case 1:
return new LoginFragment();
}
return null;
}
@Override
public int getCount() {
// Show 3 total pages.
return 2;
}
@Override
public CharSequence getPageTitle(int position) {
Locale l = Locale.getDefault();
switch (position) {
case 0:
return getString(R.string.title_section1).toUpperCase(l);
case 1:
return getString(R.string.title_section2).toUpperCase(l);
}
return null;
}
}
public static class RegistryFragment extends Fragment {
private Encryptor encrypt;
private EditText edit_username;
private EditText edit_password;
private EditText edit_confirm;
private Button registry;
public RegistryFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_registry,
container, false);
encrypt=new Encryptor();
edit_username = (EditText) rootView
.findViewById(R.id.edit_username1);
edit_password = (EditText) rootView
.findViewById(R.id.edit_password1);
edit_confirm = (EditText) rootView.findViewById(R.id.edit_confirm);
registry = (Button) rootView.findViewById(R.id.btn_registry);
registry.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
encrypt.setSaveEntry(getActivity(), "uname",
edit_username
.getText().toString());
encrypt.setSaveEntry(getActivity(), "upass",
edit_password
.getText().toString());
Context context
getActivity().getApplicationContext();
CharSequence text
encrypt.getSaveEntry(getActivity(),
"uname")
+ " "
+
encrypt.getSaveEntry(getActivity(), "upass");
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, text,
duration);
toast.show();
}
});
return rootView;
}
}
public static class LoginFragment extends Fragment {
public LoginFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_login,
container, false);
return rootView;
}
}
}
抱歉，我忘记了Logcat输出，所以这里是：
04-14 09:24:56.969: I/InputMethodManager(26111): startInput,
mServedView=android.widget.EditText{417f4d58 VFED..CL .F.P..ID 0,396-720,475 #7f050044
app:id/edit_password2}, inputType=0x1
04-14 09:25:00.444: I/InputMethodManager(26111): startInput,
mServedView=android.widget.EditText{417f69b0 VFED..CL .F.P..ID 0,505-720,584 #7f050045
app:id/edit_confirm}, inputType=0x1
04-14 09:25:04.479: W/dalvikvm(26111): threadid=1: thread exiting with uncaught
exception (group=0x413b8a08)
04-14 09:25:04.494: E/AndroidRuntime(26111): FATAL EXCEPTION: main
04-14 09:25:04.494: E/AndroidRuntime(26111): java.lang.NullPointerException
04-14 09:25:04.494: E/AndroidRuntime(26111): at
com.mHealth.screeningApp2.activities.UserAccount_Activity$RegistryFragment$1.onClick
(UserAccount_Activity.java:213)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
android.view.View.performClick(View.java:4231)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
android.view.View$PerformClick.run(View.java:17537)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
android.os.Handler.handleCallback(Handler.java:725)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
android.os.Handler.dispatchMessage(Handler.java:92)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
android.os.Looper.loop(Looper.java:158)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
android.app.ActivityThread.main(ActivityThread.java:5751)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
java.lang.reflect.Method.invokeNative(Native Method)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
java.lang.reflect.Method.invoke(Method.java:511)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1083)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:850)
04-14 09:25:04.494: E/AndroidRuntime(26111): at
dalvik.system.NativeStart.main(Native Method)
04-14 09:25:06.384: D/Process(26111): killProcess, pid=26111
这里也是包含get-和setSaveEntry方法的Encryptor类：
package com.mHealth.screeningApp2.helperClasses;
import android.content.Context;
import android.content.SharedPreferences;
public class Encryptor {
public Encryptor() {
}
/**
* Save a String value persistent on the smartphone indentified by a key
* @param context Activity context
* @param key String identifier for the saved value
* @param name String value which to save persistent
*/
public void setSaveEntry(Context context, String key, String name) {
// encrypt values
String crypt_key = null;
String crypt_name = null;
try {
crypt_key = SimpleCrypto.encrypt(
"das22ist3das1passwort98mit1demallesumgerechnetwird", key);
crypt_name = SimpleCrypto.encrypt(
"das22ist3das1passwort98mit1demallesumgerechnetwird", name);
} catch (Exception e) {
e.printStackTrace();
}
// save the entry name as SharedPreference at the Smartphone, in the
// filename "prefs.xml"
SharedPreferences entry = context.getSharedPreferences("prefs", 0);
SharedPreferences.Editor editor = entry.edit();
editor.putString(crypt_key, crypt_name);
editor.commit();
}
/**
* Returns the persistent saved value of an asked key identifier
*
* @param context Activity context
* @param key String identifier under which name the value was saved
* @return decrypted String key
*/
public String getSaveEntry(Context context, String key) {
String crypt_entry = null;
// encrypt the checked field again to get the encrypted String and
// retrieve the stored checks
try {
crypt_entry = SimpleCrypto.encrypt(
"das22ist3das1passwort98mit1demallesumgerechnetwird", key);
} catch (Exception e) {
e.printStackTrace();
}
// Restore preferences
SharedPreferences entry;
// tell the correct preference file to be read
try {
entry = context.getSharedPreferences("prefs", 0);
} catch (Exception e) {
return "The SharedPreferences File does not exist.";
}
// first check whether the Key exist
if (entry.contains(crypt_entry)) {
// returns false if there is no saved value
String entry_name = entry.getString(crypt_entry, "false");
// abort if no value
if (entry_name.equals("false")) {
return "No Entry";
}
// decrypt the last saved datas at the smartphone
String crypt_entry_name = null;
try {
crypt_entry_name = SimpleCrypto.decrypt(
"das22ist3das1passwort98mit1demallesumgerechnetwird",
entry_name);
} catch (Exception e) {
// e.printStackTrace();
crypt_entry_name = "No Entry";
}
return crypt_entry_name;
} else {
return "notExist";
}
}
}
答案 0 :(得分：1)
您永远不会初始化encrypt变量：
private Encryptor encrypt;
但是在onClick()。
如何初始化：
encrypt = new Encryptor();
答案 1 :(得分：0)
检查您的EditText 用户名和密码他们有id edit_username2 和 edit_password2 并且您的RegistryFragment更改了 edit_username1 和 edit_password1 。