以下是例外的 logcat ：
05-09 15:03:37.623: D/AndroidRuntime(25205): Shutting down VM 05-09 15:03:37.643: W/dalvikvm(25205): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
05-09 15:03:37.763: E/AndroidRuntime(25205): FATAL EXCEPTION: main
05-09 15:03:37.763: E/AndroidRuntime(25205): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.bugs3.munishgupta.cabup/com.bugs3.munishgupta.cabup.Profile}: java.lang.NullPointerException
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.app.ActivityThread.access$600(ActivityThread.java:141)
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.os.Handler.dispatchMessage(Handler.java:99)
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.os.Looper.loop(Looper.java:137)
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.app.ActivityThread.main(ActivityThread.java:5041)
05-09 15:03:37.763: E/AndroidRuntime(25205): at java.lang.reflect.Method.invokeNative(Native Method)
05-09 15:03:37.763: E/AndroidRuntime(25205): at java.lang.reflect.Method.invoke(Method.java:511)
05-09 15:03:37.763: E/AndroidRuntime(25205): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-09 15:03:37.763: E/AndroidRuntime(25205): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-09 15:03:37.763: E/AndroidRuntime(25205): at dalvik.system.NativeStart.main(Native Method)
05-09 15:03:37.763: E/AndroidRuntime(25205): Caused by: java.lang.NullPointerException
05-09 15:03:37.763: E/AndroidRuntime(25205): at com.bugs3.munishgupta.cabup.Profile.onCreate(Profile.java:29)
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.app.Activity.performCreate(Activity.java:5104) \
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-09 15:03:37.763: E/AndroidRuntime(25205): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-09 15:03:37.763: E/AndroidRuntime(25205): ... 11 more
05-09 15:04:07.774: I/Process(25205): Sending signal. PID: 25205 SIG: 9
以下是有错误的代码（Login.java）
package com.bugs3.munishgupta.cabup;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONException;
import org.json.JSONObject;
import com.bugs3.munishgupta.cabup.R;
import com.bugs3.munishgupta.cabup.JSONParser;
import com.bugs3.munishgupta.cabup.Login;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.text.method.HideReturnsTransformationMethod;
import android.text.method.PasswordTransformationMethod;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;
public class Login extends Activity {
CheckBox ocbShowPass;
RadioGroup type;
RadioButton rbType;
EditText oetEmail,oetPassword;
Button obtSignup, obtSubmit;
private ProgressDialog pDialog;
JSONParser jsonParser = new JSONParser();
String stre,strp, radio;
private static final String LOGIN_URL = "http://10.0.2.2/android_login_api/max.php";
Intent iprofile;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.login);
ocbShowPass=(CheckBox)findViewById(R.id.showPassCB);
oetEmail=(EditText)findViewById(R.id.eUserName);
type=(RadioGroup)findViewById(R.id.logType);
oetPassword=(EditText)findViewById(R.id.ePassword);
obtSignup=(Button)findViewById(R.id.btnRegister);
obtSubmit=(Button)findViewById(R.id.btnSubmit);
ocbShowPass.setOnCheckedChangeListener(new OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
// TODO Auto-generated method stub
if(isChecked)
{
oetPassword.setTransformationMethod(HideReturnsTransformationMethod.getInstance());
}
else
{
oetPassword.setTransformationMethod(PasswordTransformationMethod.getInstance());
}
}
});
obtSignup.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent regIntent=new Intent(Login.this, Registration.class);
startActivity(regIntent);
}
});
obtSubmit.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
stre=oetEmail.getText().toString();
strp=oetPassword.getText().toString();
if(stre.equals("")||stre.length()!=10)//(android.util.Patterns.PHONE.matcher("+91"+stre).matches()==false)||
{
oetEmail.setError("Enter valid Mobile no.");
}
else if(strp.equals(""))
{
oetPassword.setError("Enter Password");
}
else
{
rbType=(RadioButton)findViewById(type.getCheckedRadioButtonId());
radio=rbType.getText().toString();
new AttemptLogin().execute();
/* if(loginForm(stre,strp,rbType.getText().toString().toLowerCase()))
{
iprofile=new Intent(Login.this,Profile.class);
startActivity(iprofile);
}
else
{
Toast.makeText(getApplicationContext(), "Login Failed ", Toast.LENGTH_SHORT).show();
Toast.makeText(getApplicationContext(), "Email or Password not matched ", Toast.LENGTH_SHORT).show();
}
*/
}
}
});
}
/* public boolean loginForm(String mob, String password, String UserType)
{
new AttemptLogin().execute();
return true;
}*/
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.taxi_pool, menu);
return true;
}
class AttemptLogin extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
boolean failure = false;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(Login.this);
pDialog.setMessage("Attempting login...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... args) {
// TODO Auto-generated method stub
// Check for success tag
String username = oetEmail.getText().toString();
String password = oetPassword.getText().toString();
try {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("op", "select"));
params.add(new BasicNameValuePair("query","select * from "+ radio
+ " where `mob`='" + username + "' and `password`='" + password +"'" ));
Log.d("request!", "starting");
// getting product details by making HTTP request
JSONObject json = jsonParser.makeHttpRequest(
LOGIN_URL, "GET", params);
// check your log for json response
Log.d("Login attempt", json.toString());
// json success tag
if (json.getString("mob").toString().equalsIgnoreCase(username)) {
Log.d("Login Successful!", json.getString("mob"));
pDialog.dismiss();
//Toast.makeText(getApplicationContext(), "Logging in...", Toast.LENGTH_SHORT).show();
Intent i = new Intent(Login.this, Profile.class);
i.putExtra("mob", username);
if(radio.equalsIgnoreCase("driver"))
{
Log.d("putting Car no",json.getString("carNo"));
i.putExtra("carno",json.getString("carNo"));
}
finish();
startActivity(i);
return json.getString("mob");
}
else{
Log.d("Login Failure!", "no info exits");
return null;
}
} catch (Exception e) {
Log.d("JSON Error",e.getMessage());
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog once product deleted
pDialog.dismiss();
if (file_url != null){
Toast.makeText(Login.this, file_url, Toast.LENGTH_LONG).show();
}
}
}
}
}
这是Profile.java代码
package com.bugs3.munishgupta.cabup;
import com.bugs3.munishgupta.cabup.R;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
public class Profile extends Activity {
Button obhier, obshare, obsettings;
Intent info;
String mob;
Bundle b;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.profile);
obhier=(Button) findViewById(R.id.btnHier);
obshare=(Button) findViewById(R.id.btnShare);
obsettings=(Button) findViewById(R.id.btnSetting);
info = getIntent();
b = info.getExtras();
if( ! (b.getString("carno").equals(null) ) )
Toast.makeText(getApplicationContext(), b.get("carno").toString(), Toast.LENGTH_SHORT).show();
obshare.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent wshare=new Intent(Profile.this,WannaShare.class);
if(b.getString("mob")!=null)
{
mob = b.getString("mob");
wshare.putExtra("mob", mob);
}
startActivity(wshare);
}
});
obhier.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent whier=new Intent(Profile.this,WannaHier.class);
if(b.getString("mob")!=null)
{
mob = b.getString("mob");
whier.putExtra("mob", mob);
}
startActivity(whier);
}
});
obsettings.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent isetting = new Intent(Profile.this,ChangeSetting.class);
if(b.getString("mob")!=null)
{
mob = b.getString("mob");
isetting.putExtra("mob", mob);
}
startActivity(isetting);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.profile, menu);
return true;
}
}
答案 0 :(得分：1)
在Login.java中，传递给intent的String处于if条件
if(radio.equalsIgnoreCase("driver"))
{
Log.d("putting Car no",json.getString("carNo"));
i.putExtra("carno",json.getString("carNo"));
}
所以在Profile.java的onCreate（）中，
b.get("carno").toString()
会在未通过值时抛出NPE，我认为这是这种情况。
把吐司放在里面
if(b.get("carno").getString!=null)
OR
在if条件之前，在Login.java中，默认情况下传递一些东西，如：
i.putExtra("carno","!(radio equals driver)");
需要检查一下，检查吐司内部的修正：
if((b.getString("carno")!=null) ){
Toast.makeText(this, b.getString("carno").toString(), Toast.LENGTH_SHORT).show();}