android项目中的空指针异常
在我的项目中，我在下面显示的类中得到了nullpointerexception，我还附加了下面的logcat和java类。在if的情况下，我给出了类似“if（name==null）”的条件，我不确定它是正确的还是错误的if-Error意味着建议我使用正确的代码来解决NPE 先谢谢你android项目中的空指针异常,android,android-layout,android-fragments,android-intent,android-activity,Android,Android Layout,Android Fragments,Android Intent,Android Activity,在我的项目中，我在下面显示的类中得到了nullpointerexception，我还附加了下面的logcat和java类。在if的情况下，我给出了类似“if（name==null）”的条件，我不确定它是正确的还是错误的if-Error意味着建议我使用正确的代码来解决NPE 先谢谢你 public void onClick(DialogInterface dialog,int id) { // yes(); Intent tablewise = n
public void onClick(DialogInterface dialog,int id)
{
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,LoginForm.class);
startActivity(tablewise);
finish();
}
})
10-13 10:25:33.914 24201-24201/com.sentientit.theiWedplanner E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
at com.sentientit.theiWedplanner.Seating_Engagement$2.onClick(Seating_Engagement.java:77)
at android.view.View.performClick(View.java:4421)
at android.view.View$PerformClick.run(View.java:18190)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:175)
at android.app.ActivityThread.main(ActivityThread.java:5279)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
at dalvik.system.NativeStart.main(Native Method)
10-13 10:25:45.445 24201-24206/com.sentientit.theiWedplanner I/dalvikvm﹕ threadid=3: reacting to signal 3
10-13 10:25:45.578 24201-24206/com.sentientit.theiWedplanner I/dalvikvm﹕ Wrote stack traces to '/data/anr/traces.txt'
import android.app.AlertDialog;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import android.widget.Button;
import com.bugsense.trace.BugSenseHandler;
import java.util.StringTokenizer;
public class Seating_Engagement extends FragmentActivity{
ProgressDialog myProgressDialog = null;
String username=welcomeuser1.usernamevalue;
String result=null;
String nameresult=null;
String Table,Chart=null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState); BugSenseHandler.initAndStartSession(this, "68640bea");
setContentView(R.layout.seatingchart);
Button familywise=(Button)findViewById(R.id.familywise);
Button tablewisesummary=(Button)findViewById(R.id.tableclassify);
Button assignedguest=(Button)findViewById(R.id.assignedguest);
Button notassignedguest=(Button)findViewById(R.id.notassignedguest);
Button tablechair=(Button)findViewById(R.id.tableclass);
Button groupwise=(Button)findViewById(R.id.groupwise);
Button tablewise=(Button)findViewById(R.id.tablewisesummary);
Button familywisesummary=(Button)findViewById(R.id.familywisesummary);
Button groupwisesummary=(Button)findViewById(R.id.groupwisesummary);
Button arrangementsummary=(Button)findViewById(R.id.totaltables);
Button back=(Button)findViewById(R.id.back);
Button seatingoverview =(Button)findViewById(R.id.seatingview);
back.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
finish();
}
});
seatingoverview.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(username.equals("null"))
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setTitle("Message!")
.setPositiveButton(R.string.ok1,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
(77) Intent tablewise = new Intent(Seating_Engagement.this,LoginForm.class);
startActivity(tablewise);
finish();
}
})
.setMessage("Registered users can access this page. Click 'Yes' to login")
.setNegativeButton(R.string.no,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
}
})
.create();
locationError.show();
}
else
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setPositiveButton("Table",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
Seating_EngagementTable.class);
startActivity(tablewise);
// finish();
}
})
.setNegativeButton("Chart",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
Intent tab=new Intent(Seating_Engagement.this,Seating_Engagementviewtable.class);
startActivity(tab);
finish();
}
})
.create();
locationError.show();
}
}
});
notassignedguest.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent tablewise=new Intent(Seating_Engagement.this,Engagement_Notyetseated.class);
startActivity(tablewise);
// finish();
}
});
assignedguest.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent tablewise=new Intent(Seating_Engagement.this,Engagement_AssignedGuest.class);
startActivity(tablewise);
//finish();
}
});
tablechair.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent tablewise=new Intent(Seating_Engagement.this,Engagement_TableClassify.class);
startActivity(tablewise);
// finish();
}
});
tablewisesummary.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(username.equals("null"))
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setTitle("Message!")
.setPositiveButton(R.string.ok1,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
LoginForm.class);
startActivity(tablewise);
finish();
}
})
.setMessage("Registered users can access this page. Click 'Yes' to login")
.setNegativeButton(R.string.no,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
}
})
.create();
locationError.show();
}
else
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setPositiveButton("Table",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
Engagement_TableChairSummary.class);
startActivity(tablewise);
//finish();
}
})
.setNegativeButton("Chart",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
Intent tab=new Intent(Seating_Engagement.this,Engagement_ViewTable.class);
startActivity(tab);
finish();
}
})
.create();
locationError.show();
}
}
});
familywisesummary.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(username.equals("null"))
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setTitle("Message!")
.setPositiveButton(R.string.ok1,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
LoginForm.class);
startActivity(tablewise);
finish();
}
})
.setMessage("Registered users can access this page. Click 'Yes' to login")
.setNegativeButton(R.string.no,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
}
})
.create();
locationError.show();
}
else
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setPositiveButton("Table",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
Engagement_Familywisesummary.class);
startActivity(tablewise);
//finish();
}
})
.setNegativeButton("Chart",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
Intent tab=new Intent(Seating_Engagement.this,Engagement_Familyviewtable.class);
startActivity(tab);
finish();
}
})
.create();
locationError.show();
}
}
});
groupwisesummary.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(username.equals("null"))
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setTitle("Message!")
.setPositiveButton(R.string.ok1,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
LoginForm.class);
startActivity(tablewise);
finish();
}
})
.setMessage("Registered users can access this page. Click 'Yes' to login")
.setNegativeButton(R.string.no,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
}
})
.create();
locationError.show();
}
else
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setPositiveButton("Table",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
Engagement_Groupwisesummary.class);
startActivity(tablewise);
//finish();
}
})
.setNegativeButton("Chart",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
Intent tab=new Intent(Seating_Engagement.this,Engagement_Groupviewtable.class);
startActivity(tab);
finish();
}
})
.create();
locationError.show();
}
}
});
familywise.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
// String user_url ="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/tabledisplay.aspx?unme="+username+"&occasion=Engagement";
String user_url ="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/version21/seating-table-display.aspx?unme="+username+"&occasion=Engagement";
httpclass obj = new httpclass();
result = obj.server_conn(user_url);
StringTokenizer st = new StringTokenizer(result, "|");
result = st.nextToken();
// String user ="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/Notallocated_familywise.aspx?unme="+username+"&occasion=Engagement";
String user="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/version21/notallocated_familywise.aspx?unme="+username+"&occasion=Engagement";
httpclass objg = new httpclass();
nameresult = objg.server_conn(user);
StringTokenizer s = new StringTokenizer(nameresult, "|");
nameresult = s.nextToken();
if(result.equals("There is no table"))
{
alertbox("Assignment", "None of the table has been created");
}
else if(nameresult.equals("No Guests"))
{
alertbox("Assignment", "No Guest invited");
}
else
{
boolean netvalue = false;
ConnectivityManager cm = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo info = cm.getActiveNetworkInfo();
if (info != null && info.isAvailable()) {
netvalue = true;
Intent tablewise=new Intent(Seating_Engagement.this,Engagement_FamilwiseAllocation.class);
startActivity(tablewise);
// finish();
}
else
{
alertbox("Message!", "No Internet Connection!");
}
}
}
});
groupwise.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
// String user_url ="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/tabledisplay.aspx?unme="+username+"&occasion=Engagement";
String user_url ="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/version21/tabledisplay.aspx?unme="+username+"&occasion=Engagement";
httpclass obj = new httpclass();
result = obj.server_conn(user_url);
StringTokenizer st = new StringTokenizer(result, "|");
result = st.nextToken();
// String user ="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/Not_allocated_notfamily.aspx?unme="+username+"&occasion=Engagement";
String user="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/version21/Not_allocated_notfamily.aspx?unme="+username+"&occasion=Engagement";
httpclass objg = new httpclass();
nameresult = objg.server_conn(user);
StringTokenizer s = new StringTokenizer(nameresult, "|");
nameresult = s.nextToken();
if(result.equals("There is no table"))
{
alertbox("Summary", "None of the table has been created");
}
else if(nameresult.equals("No Guests"))
{
alertbox("Assignment", "No Guest invited");
}
else
{
Intent tablewise=new Intent(Seating_Engagement.this,Engagement_GroupWiseAllocation.class);
startActivity(tablewise);
//finish();
}
}
});
tablewise.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(username.equals("null"))
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setTitle("Message!")
.setPositiveButton(R.string.ok1,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
LoginForm.class);
startActivity(tablewise);
finish();
}
})
.setMessage("Registered users can access this page. Click 'Yes' to login")
.setNegativeButton(R.string.no,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
}
})
.create();
locationError.show();
}
else
{
Dialog locationError = new AlertDialog.Builder(
Seating_Engagement.this)
.setIcon(0)
.setPositiveButton("Table",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
// yes();
Intent tablewise = new Intent(Seating_Engagement.this,
Engagement_TableWiseSummary.class);
startActivity(tablewise);
//finish();
}
})
.setNegativeButton("Chart",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int id) {
Intent tab=new Intent(Seating_Engagement.this,Engagement_Tableviewtable.class);
startActivity(tab);
finish();
}
})
.create();
locationError.show();
}
}
});
arrangementsummary.setOnClickListener(new View.OnClickListener() {
//@Override
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
// String user_url ="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/tabledisplay.aspx?unme="+username+"&occasion=Engagement";
String user_url ="http://mobileapps.iwedplanner.com/mobileapps/iwedplanner/mobile/version21/tabledisplay.aspx?unme="+username+"&occasion=Engagement";
httpclass obj = new httpclass();
result = obj.server_conn(user_url);
StringTokenizer st = new StringTokenizer(result, "|");
result = st.nextToken();
if(result.equals("There is no table"))
{
alertbox("Summary", "None of the table has been created");
}
else
{
Intent tablewise=new Intent(Seating_Engagement.this,Engagement_TotalSeatingStatus.class);
startActivity(tablewise);
// finish();
}
}
});
}
protected void alertbox(String title, String mymessage)
{
new AlertDialog.Builder(this)
.setMessage(mymessage)
.setTitle(title)
.setCancelable(true)
.setNeutralButton(android.R.string.ok,
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int whichButton){}
})
.show();
}
@Override
public void onStart() {
super.onStart();
// The rest of your onStart() code.
// EasyTracker.getInstance(this).activityStart(this); // Add this method.
}
@Override
public void onStop() {
super.onStop();
// The rest of your onStop() code.
// EasyTracker.getInstance(this).activityStop(this); // Add this method.
}
}
您没有正确检查用户名是否为空。这就是您的NPE所在的位置，用户名为null，但您对其调用“equals（）”方法 将其更改为：
if(username == null){
(...)
}
if (TextUtils.isEmpty(username)) {
//code here
} else{
//code here
}
getActivity（）.startActivity（表级） 不要使用
username.equals（“null”）username==null if(username.equals("")){
Toast.makeText(getApplicationContext(), "Please Enter Username", Toast.LENGTH_SHORT).show();
}
else{
//code here
}
final String user= username.getText().toString();
if (user.matches("")) {
username.setError("Please Enter Name");
}