我是新手编码所以在尝试创建一个接受一个布局“我的个人资料”中的值的应用程序并替换另一个布局“预订表单”中的edittext字段时。
即。在我的个人资料中，它将存储姓名，电子邮件，电话。因此，在预订页面，它应该从共享偏好中填写这些值。
我可以将这些值存储到共享首选项，但无法显示它们。代码如下，已经超过13小时，无法通过NPE尝试setText的第一部分。
我的活动档案
package com.buses;
import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;
import javax.mail.AuthenticationFailedException;
import javax.mail.MessagingException;
import javax.mail.internet.InternetAddress;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.NavUtils;
import android.text.format.Time;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.TimePicker;
import android.widget.Toast;
public class DetailActivity extends FragmentActivity {
//Variables for Storing Message & Button objects
/*final EditText name= (EditText)findViewById(R.id.prof_uname);
final EditText phone= (EditText)findViewById(R.id.prof_mob_num);
final EditText email= (EditText)findViewById(R.id.prof_email);
final EditText dob= (EditText)findViewById(R.id.prof_dob);
final EditText bname= (EditText)findViewById(R.id.uname);
final EditText bphone= (EditText)findViewById(R.id.mob_num);
final EditText bemail= (EditText)findViewById(R.id.email);*/
// EditText from_loc= null;
// EditText to_loc= null;
CheckBox today, tomorrow;
TimePicker pickup;
public static final String MyPREFERENCES = "MyPrefs";
public static final String Name = "nameKey";
public static final String Phone = "phoneKey";
public static final String Email = "emailKey";
public static final String DOB = "dobKey";
SharedPreferences sharedpreferences;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_cab_detail);
// Show the Up button in the action bar.
getActionBar().setDisplayHomeAsUpEnabled(true);
// Profile Layout Display
/*
* name = (EditText)findViewById(R.id.prof_uname); phone =
* (EditText)findViewById(R.id.prof_mob_num); email =
* (EditText)findViewById(R.id.prof_email); dob =
* (EditText)findViewById(R.id.prof_dob);
*/
sharedpreferences = this.getSharedPreferences(MyPREFERENCES,
Context.MODE_PRIVATE);
if (sharedpreferences.contains(Name)) {
// Value below prints on logcat output
System.out.println(sharedpreferences.getString(Name, ""));
// NPE error is shown as Caught at the line below
((EditText) findViewById(R.id.prof_uname))
.setText(sharedpreferences.getString(Name, null));
}
if (sharedpreferences.contains(Phone)) {
((EditText) findViewById(R.id.prof_mob_num))
.setText(sharedpreferences.getString(Phone, ""));
}
if (sharedpreferences.contains(Email)) {
((EditText) findViewById(R.id.prof_email))
.setText(sharedpreferences.getString(Email, ""));
}
if (sharedpreferences.contains(DOB)) {
((EditText) findViewById(R.id.prof_dob)).setText(sharedpreferences
.getString(DOB, ""));
}
// Book Layout
/*
* bname = (EditText)findViewById(R.id.uname); bphone =
* (EditText)findViewById(R.id.mob_num); bemail =
* (EditText)findViewById(R.id.email);
*/
if (sharedpreferences.contains(Name)) {
((EditText) findViewById(R.id.uname)).setText(sharedpreferences
.getString(Name, ""));
}
if (sharedpreferences.contains(Phone)) {
((EditText) findViewById(R.id.mob_num)).setText(sharedpreferences
.getString(Phone, ""));
}
if (sharedpreferences.contains(Email)) {
((EditText) findViewById(R.id.email)).setText(sharedpreferences
.getString(Email, ""));
}
// savedInstanceState is non-null when there is fragment state
// saved from previous configurations of this activity
// (e.g. when rotating the screen from portrait to landscape).
// In this case, the fragment will automatically be re-added
// to its container so we don't need to manually add it.
// For more information, see the Fragments API guide at:
//
// http://developer.android.com/guide/components/fragments.html
//
if (savedInstanceState == null) {
// Create the detail fragment and add it to the activity
// using a fragment transaction.
Bundle arguments = new Bundle();
arguments.putString(CabDetailFragment.ARG_ITEM_ID, getIntent()
.getStringExtra(CabDetailFragment.ARG_ITEM_ID));
CabDetailFragment fragment = new CabDetailFragment();
fragment.setArguments(arguments);
getSupportFragmentManager().beginTransaction()
.add(R.id.cab_detail_container, fragment).commit();
}
}
void onCreateContextMenu() {}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// This ID represents the Home or Up button. In the case of this
// activity, the Up button is shown. Use NavUtils to allow users
// to navigate up one level in the application structure. For
// more details, see the Navigation pattern on Android Design:
//
// http://developer.android.com/design/patterns/navigation.html#up-vs-back
//
NavUtils.navigateUpTo(this, new Intent(this, ListActivity.class));
return true;
}
return super.onOptionsItemSelected(item);
}
// When Book Button is clicked
public void send(View v) {
new SendEmailAsyncTask().execute();
}
class SendEmailAsyncTask extends AsyncTask<Void, Void, Boolean> {
// Email Code
// if (BuildConfig.DEBUG) Log.v(SendEmailAsyncTask.class.getName(),
// "SendEmailAsyncTask()");
// email Code
@Override
protected Boolean doInBackground(Void... params) {
if (BuildConfig.DEBUG)
Log.v(SendEmailAsyncTask.class.getName(), "doInBackground()");
try {
m.send();
return true;
} catch (AuthenticationFailedException e) {
Log.e(SendEmailAsyncTask.class.getName(), "Bad account details");
e.printStackTrace();
return false;
} catch (MessagingException e) {
Log.e(SendEmailAsyncTask.class.getName(), m.getTo(null)
+ "failed");
e.printStackTrace();
return false;
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
}
// Save Option use here
public void save(View v) {
new SaveEmailAsyncTask().execute();
}
class SaveEmailAsyncTask extends AsyncTask<Void, Void, Boolean> {
// Email Code
// if (BuildConfig.DEBUG) Log.v(SaveEmailAsyncTask.class.getName(),
// "SaveEmailAsyncTask()");
// email code
// }
@Override
protected Boolean doInBackground(Void... params) {
if (BuildConfig.DEBUG)
Log.v(SaveEmailAsyncTask.class.getName(), "doInBackground()");
try {
m.send();
return true;
} catch (AuthenticationFailedException e) {
Log.e(SaveEmailAsyncTask.class.getName(), "Bad account details");
e.printStackTrace();
return false;
} catch (MessagingException e) {
Log.e(SaveEmailAsyncTask.class.getName(), m.getTo(null)
+ "failed");
e.printStackTrace();
return false;
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
}
}
Log.cat文件
E/Trace(2222): error opening trace file: No such file or directory (2)
D/dalvikvm(2222): GC_FOR_ALLOC freed 86K, 8% free 2670K/2880K, paused 73ms, total 77ms
I/dalvikvm-heap(2222): Grow heap (frag case) to 3.329MB for 635812-byte allocation
D/dalvikvm(2222): GC_FOR_ALLOC freed 3K, 7% free 3288K/3504K, paused 198ms, total 198ms
D/dalvikvm(2222): GC_CONCURRENT freed <1K, 7% free 3289K/3504K, paused 14ms+92ms, total 162ms
D/libEGL(2222): loaded /system/lib/egl/libEGL_emulation.so
D/(2222): HostConnection::get() New Host Connection established 0x2a147768, tid 2222
D/libEGL(2222): loaded /system/lib/egl/libGLESv1_CM_emulation.so
D/libEGL(2222): loaded /system/lib/egl/libGLESv2_emulation.so
W/EGL_emulation(2222): eglSurfaceAttrib not implemented
D/OpenGLRenderer(2222): Enabling debug mode 0
I/Choreographer(2222): Skipped 174 frames! The application may be doing too much work on its main thread.
I/System.out(2222): Jasneet
D/AndroidRuntime(2222): Shutting down VM
W/dalvikvm(2222): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
E/AndroidRuntime(2222): FATAL EXCEPTION: main
E/AndroidRuntime(2222): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.primecabs/com.primecabs.CabDetailActivity}: java.lang.NullPointerException
E/AndroidRuntime(2222): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
E/AndroidRuntime(2222): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
E/AndroidRuntime(2222): at android.app.ActivityThread.access$600(ActivityThread.java:141)
E/AndroidRuntime(2222): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
E/AndroidRuntime(2222): at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(2222): at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime(2222): at android.app.ActivityThread.main(ActivityThread.java:5041)
E/AndroidRuntime(2222): at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(2222): at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(2222): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
E/AndroidRuntime(2222): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
E/AndroidRuntime(2222): at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(2222): Caused by: java.lang.NullPointerException
E/AndroidRuntime(2222): at com.primecabs.CabDetailActivity.onCreate(CabDetailActivity.java:110)
E/AndroidRuntime(2222): at android.app.Activity.performCreate(Activity.java:5104)
E/AndroidRuntime(2222): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
E/AndroidRuntime(2222): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
E/AndroidRuntime(2222): ... 11 more
答案 0 :(得分：0)
if (sharedpreferences.contains(Name))
{
System.out.println(sharedpreferences.getString(Name, ""));
((EditText)findViewById(R.id.prof_uname)).setText(sharedpreferences.getString(Name, "")); <-------- NPE error is shown as Caught at this line
}
MD和wqrahd给出的答案是正确的。但只是为了解释用于检索首选项的语法sharedpreferences.getString("KEY", "DEFAULT VALUE")的概念
如果“KEY”不存在则返回“DEFAULT VALUE”，否则返回首选项中保存的最新值
答案 1 :(得分：0)
由于sharedpreferences.getString(Name, null)不为null，因此唯一可以为null的其他内容是(EditText)findViewById(R.id.prof_uname)。打印出来：
EditText et = (EditText)findViewById(R.id.prof_uname);
Log.w("DetailActivity", "EditText: " + et); // null I bet
原因：您处于FragmentActivity中。显然这些元素属于尚未加载的片段？不确定，让我知道我是否正确，我们会解决它
此外，我没有看到R import
重要提示：您的格式是非常糟糕，而您提供的内容甚至没有编译（您在课程中间有一些ifs（？！））。我编辑了它，但下次你会得到-1。这种糟糕的格式化会导致错误并使调试变得困难。没有人愿意阅读你的代码或认真对待你，相信我。
尝试没有水平滚动条，代码越少越好 - 尝试仅发布重要部分。 避免空行。 Logcat时间很少有用。
答案 2 :(得分：0)
已解决，结合多个问题，来自@Mr_and_Mrs_D的输入
1）对象具有空值
EditText et = (EditText)findViewById(R.id.prof_uname);
Log.w("DetailActivity", "EditText: " + et);
2）通过提供视图（当我在CabDetailActivity
时）来纠正它EditText et = (EditText)v.findViewById(R.id.prof_uname);
Log.w("DetailActivity", "EditText: " + et);
虽然一切都有值，但SetText在应用程序执行时没有反映出来。后来我发现它膨胀的视图与正在使用的视图不同。
因此经过几次环顾四周，并重新分析流程。我得出结论，因为我的观点在片段中被夸大，即CabDetailFragment;哪个无法读取getSharePreferences，绕过该错误需要时间，最终我的CabDetailFragment
package com.primecabs;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.CheckBox;
import android.widget.TextView;
import android.widget.TimePicker;
import com.primecabs.home.Content;
/**
* A fragment representing a single Cab detail screen. This fragment is either
* contained in a {@link CabListActivity} in two-pane mode (on tablets) or a
* {@link CabDetailActivity} on handsets.
*/
public class CabDetailFragment extends Fragment {
/**
* The fragment argument representing the item ID that this fragment
* represents.
*/
public static final String ARG_ITEM_ID = "item_id";
// Variables for Storing Message & Button objects
TextView name, from_loc, to_loc, phone, email, dob;
CheckBox today, tomorrow;
TimePicker pickup;
public static final String MyPREFERENCES = "MyPrefs";
public static final String Name = "nameKey";
public static final String Phone = "phoneKey";
public static final String Email = "emailKey";
public static final String DOB = "dobKey";
SharedPreferences sharedpreferences;
/**
* The dummy content this fragment is presenting.
*/
private Content.Item mItem;
/**
* Mandatory empty constructor for the fragment manager to instantiate the
* fragment (e.g. upon screen orientation changes).
*/
public CabDetailFragment() {}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments().containsKey(ARG_ITEM_ID)) {
// Load the content specified by the fragment
// arguments. In a real-world scenario, use a Loader
// to load content from a content provider.
mItem = Content.ITEM_MAP.get(getArguments().getString(ARG_ITEM_ID));
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = null;
sharedpreferences = this.getActivity().getSharedPreferences(
MyPREFERENCES, Context.MODE_PRIVATE);
if (mItem.id == "1") {
rootView = inflater.inflate(R.layout.fragment_cab_detail_book,
container, false);
TextView bname = (TextView) rootView.findViewById(R.id.uname);
TextView bphone = (TextView) rootView.findViewById(R.id.mob_num);
TextView bemail = (TextView) rootView.findViewById(R.id.email);
if (sharedpreferences.contains(Name)) {
bname.setText(sharedpreferences.getString(Name, ""));
}
if (sharedpreferences.contains(Phone)) {
bphone.setText(sharedpreferences.getString(Phone, ""));
}
if (sharedpreferences.contains(Email)) {
bemail.setText(sharedpreferences.getString(Email, ""));
}
}
if (mItem.id == "3") {
rootView = inflater.inflate(R.layout.fragment_user_profile,
container, false);
// Profile Layout Display
name = (TextView) rootView.findViewById(R.id.prof_uname);
phone = (TextView) rootView.findViewById(R.id.prof_mob_num);
email = (TextView) rootView.findViewById(R.id.prof_email);
dob = (TextView) rootView.findViewById(R.id.prof_dob);
if (sharedpreferences.contains(Name) == true) {
name.setText(sharedpreferences.getString(Name, ""));
}
if (sharedpreferences.contains(Phone)) {
(phone).setText(sharedpreferences.getString(Phone, ""));
}
if (sharedpreferences.contains(Email)) {
(email).setText(sharedpreferences.getString(Email, ""));
}
if (sharedpreferences.contains(DOB)) {
(dob).setText(sharedpreferences.getString(DOB, ""));
}
}
if (mItem.id == "2") {
rootView = inflater.inflate(R.layout.fragment_cab_detail_confirm,
container, false);
// Show the content as text in a TextView.
// if (mItem != null) {
// ((TextView) rootView.findViewById(R.id.cab_detail))
// .setText(mItem.content);
}
return rootView;
}
}
谢谢大家