我还在学习java，所以如果这个问题太明显，我很抱歉。我正在尝试启动我的应用程序，它会抛出此错误。问题似乎出现在OnCreate()方法中，但我无法弄清楚是什么导致了它。
import java.util.Calendar;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.DatePickerDialog;
import android.app.Dialog;
import android.app.DialogFragment;
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.CheckBox;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.RadioGroup;
import android.widget.Toast;
public class MainActivity extends Activity {
public final static String NAME = "nick.miros.famous.problems.MESSAGE";
public final static String EMAIL = "nick.miros.famous.problems.MESSAGE1";
public final static String STUFFSEX = "nick.miros.famous.problems.MESSAGE2";
public final static String BIRTHDAY = "nick.miros.famous.problems.MESSAGE3";
private boolean agreed;
private String sex;
public static String bornDate;
public EditText emailEdit;
public EditText nameEdit;
public EditText passwordEdit;
// public EditText passwordRepeatEdit;
public RadioGroup radioSex;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
nameEdit = (EditText) findViewById(R.id.name);
emailEdit = (EditText) findViewById(R.id.email);
passwordEdit = (EditText) findViewById(R.id.password);
// passwordRepeatEdit = (EditText) findViewById(R.id.passwordRepeat);
emailEdit.addTextChangedListener(new GenericTextWatcher(emailEdit));
nameEdit.addTextChangedListener(new GenericTextWatcher(nameEdit));
passwordEdit
.addTextChangedListener(new GenericTextWatcher(passwordEdit));
// passwordRepeatEdit.addTextChangedListener(new
// GenericTextWatcher(passwordRepeatEdit));
Button Go = (Button) findViewById(R.id.sendButton);
Go.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
sendAndCheck();
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
private String getSex(int id) {
switch (id) {
case R.id.radioMale:
sex = "Male";
break;
case R.id.radioFemale:
sex = "Female";
break;
}
return sex;
}
public void showThanks() {
Toast.makeText(this.getApplicationContext(), R.string.thank_you,
Toast.LENGTH_LONG).show();
}
public void onCheckBoxClicked(View view) {
// Is the view now checked?
agreed = ((CheckBox) findViewById(R.id.agreementBox)).isChecked();
}
public final static boolean isValidEmail(CharSequence target) {
if (target == null) {
return false;
} else {
return android.util.Patterns.EMAIL_ADDRESS.matcher(target)
.matches();
}
}
public static class DatePickerFragment extends DialogFragment implements
DatePickerDialog.OnDateSetListener {
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// Use the current date as the default date in the picker
final Calendar c = Calendar.getInstance();
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH);
int day = c.get(Calendar.DAY_OF_MONTH);
// Create a new instance of DatePickerDialog and return it
return new DatePickerDialog(getActivity(), this, year, month, day);
}
public void onDateSet(DatePicker view, int year, int month, int day) {
// Do something with the date chosen by the user
bornDate = Integer.toString(year) + "/" + Integer.toString(month)
+ "/" + Integer.toString(day);
}
}
public void showDatePickerDialog(View v) {
DialogFragment newFragment = new DatePickerFragment();
newFragment.show(getFragmentManager(), "datePicker");
}
/** Called when the user clicks the Send button */
public void sendAndCheck() {
CharSequence emailToCheck = ((EditText) findViewById(R.id.email))
.getText().toString();
if (agreed) {
// Do something in response to button
if (isValidEmail(emailToCheck)) {
Intent intent = new Intent(this, DisplayMessageActivity.class);
String sent_name = ((EditText) findViewById(R.id.name))
.getText().toString();
String sent_email = ((EditText) findViewById(R.id.email))
.getText().toString();
int id = ((RadioGroup) findViewById(R.id.radioSex))
.getCheckedRadioButtonId();
String sent_sex = getSex(id);
String sent_birthday = bornDate;
intent.putExtra(NAME, sent_name);
intent.putExtra(EMAIL, sent_email);
intent.putExtra(STUFFSEX, sent_sex);
intent.putExtra(BIRTHDAY, sent_birthday);
startActivity(intent);
showThanks();
} else {
((EditText) findViewById(R.id.email)).setError("wrong email!");
}
} else {
AlertDialog.Builder Alert = new AlertDialog.Builder(this);
Alert.setMessage("Please agree with the terms and conditions first");
Alert.setTitle("Notice");
Alert.setPositiveButton("OK", null);
Alert.setCancelable(true);
Alert.create().show();
}
}
}
这是GenericTextWatcher：
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.EditText;
public class GenericTextWatcher implements TextWatcher{
private View view;
private PasswordValidator passwordValidator = new PasswordValidator();
String password = ((EditText) view).getText().toString();
GenericTextWatcher(View view) {
this.view = view;
}
public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {}
public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {}
public void afterTextChanged(Editable editable) {
String text = editable.toString();
switch(view.getId()){
case R.id.name:
if (!(text.equals("")))
{
}
else
{
((EditText) view).setError("wrong name!");
}
break;
case R.id.email:
CharSequence emailToCheck = ((EditText) view).getText().toString();
if (isValidEmail(emailToCheck))
{
}
else
{
((EditText) view).setError("wrong email!");
}
break;
case R.id.password:
if (passwordValidator.isValidPassword(text))
{
}
else
{
((EditText) view).setError("must have 1 uppercase letter, 1 number and be 6 characters long");
}
break;
/* case R.id.passwordRepeat:
String password = (((EditText) view) findViewById(R.id.password).getText().toString();
if (text.equals(password))
{
}
else
{
((EditText) view).setError("passwords don't match");
}
break;*/
}
}
public final static boolean isValidEmail(CharSequence target) {
if (target == null) {
return false;
} else {
return android.util.Patterns.EMAIL_ADDRESS.matcher(target)
.matches();
}
}
public class PasswordValidator{
private Pattern pattern;
private Matcher matcher;
private static final String PASSWORD_PATTERN =
"((?=.*\\d)(?=.*[A-Z]).{6,20})";
public PasswordValidator(){
pattern = Pattern.compile(PASSWORD_PATTERN);
}
/**
* Validate password with regular expression
* @param password password for validation
* @return true valid password, false invalid password
*/
public boolean isValidPassword(String password){
matcher = pattern.matcher(password);
return matcher.matches();
}
}
}
这是LogCat：
02-04 03:59:14.267: D/dalvikvm(2400): GC_FOR_ALLOC freed 37K, 7% free 2640K/2820K, paused 1ms, total 34ms
02-04 03:59:14.267: I/dalvikvm-heap(2400): Grow heap (frag case) to 3.319MB for 635808-byte allocation
02-04 03:59:14.277: D/dalvikvm(2400): GC_FOR_ALLOC freed 2K, 6% free 3258K/3444K, paused 10ms, total 10ms
02-04 03:59:14.377: D/AndroidRuntime(2400): Shutting down VM
02-04 03:59:14.377: W/dalvikvm(2400): threadid=1: thread exiting with uncaught exception (group=0xb2eb7648)
02-04 03:59:14.377: E/AndroidRuntime(2400): FATAL EXCEPTION: main
02-04 03:59:14.377: E/AndroidRuntime(2400): java.lang.RuntimeException: Unable to start activity ComponentInfo{nick.miros.famous.problems/nick.miros.famous.problems.MainActivity}: java.lang.NullPointerException
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.app.ActivityThread.access$600(ActivityThread.java:141)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.os.Handler.dispatchMessage(Handler.java:99)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.os.Looper.loop(Looper.java:137)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.app.ActivityThread.main(ActivityThread.java:5103)
02-04 03:59:14.377: E/AndroidRuntime(2400): at java.lang.reflect.Method.invokeNative(Native Method)
02-04 03:59:14.377: E/AndroidRuntime(2400): at java.lang.reflect.Method.invoke(Method.java:525)
02-04 03:59:14.377: E/AndroidRuntime(2400): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
02-04 03:59:14.377: E/AndroidRuntime(2400): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-04 03:59:14.377: E/AndroidRuntime(2400): at dalvik.system.NativeStart.main(Native Method)
02-04 03:59:14.377: E/AndroidRuntime(2400): Caused by: java.lang.NullPointerException
02-04 03:59:14.377: E/AndroidRuntime(2400): at nick.miros.famous.problems.GenericTextWatcher.<init>(GenericTextWatcher.java:15)
02-04 03:59:14.377: E/AndroidRuntime(2400): at nick.miros.famous.problems.MainActivity.onCreate(MainActivity.java:46)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.app.Activity.performCreate(Activity.java:5133)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
02-04 03:59:14.377: E/AndroidRuntime(2400): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
02-04 03:59:14.377: E/AndroidRuntime(2400): ... 11 more
答案 0 :(得分：0)
第15行NullPointerException初始化（GenericTextWatcher）中有<init>。
在那里你有一个成员变量：
String password = ((EditText) view).getText().toString();
view为null，您只需稍后在构造函数中指定它。将此代码移动到构造函数或更高版本。