嘿，我的 sharedpreferences 有点问题，它在 Editor edit = prefs.edit(); 行给了我一个空指针异常。
你明白我为什么会收到错误吗？
我在网上搜索过这个错误，很多人都遇到过类似的问题，但我没有找到和我在同一行有同样错误的人，而且解决方案不是我可以使用的。
谢谢你的帮助。
这是我的 Main 类的代码：
public class Main extends Activity{
Button bStart, bStop;
TextView tvView;
Spinner spinner1;
boolean stopValue;
int startkilometer;
String date;
SharedPreferences prefs;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
bStart = (Button) findViewById(R.id.bStart);
tvView = (TextView) findViewById(R.id.tvView);
spinner1 = (Spinner) findViewById(R.id.spinner1);
date = getIntent().getStringExtra("datoen");
startkilometer = getIntent().getIntExtra("startkm", 0);
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
prefs.getBoolean("stopper", true);
prefs.getInt("startkm", startkilometer);
prefs.getString("datoen", date);
stopValue = getIntent().getBooleanExtra("stopper", stopValue);
if(stopValue){
bStart.setText("Start");
bStart.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
Intent start = new Intent("com.uniqueapps.runner.START");
startActivity(start);
}
});
}
if(stopValue == false){
bStart.setText("Stop");
bStart.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
Intent stop = new Intent("com.uniqueapps.runner.STOP");
stop.putExtra("startkm", startkilometer);
stop.putExtra("datoen", date);
startActivity(stop);
}
});
}
KilometerSQL info = new KilometerSQL(this);
info.open();
String data = info.getData();
info.close();
tvView.setText(data);
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
}
@Override
protected void onPause() {
// TODO Auto-generated method stub
Editor edit = prefs.edit();
edit.putBoolean("stopper", stopValue);
edit.putInt("startkm", startkilometer);
edit.putString("datoen", date);
edit.commit();
super.onPause();
}
我的开始课：
public class Start extends Main implements OnClickListener {
Button bStartTur;
EditText etDate, etKm;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.start);
bStartTur = (Button) findViewById(R.id.bStartTur);
bStartTur.setOnClickListener(this);
etDate = (EditText) findViewById(R.id.etdate);
etKm = (EditText) findViewById(R.id.etKm);
Calendar cal = Calendar.getInstance();
SimpleDateFormat format = new SimpleDateFormat("dd/MM/yyyy");
etDate.setText(format.format(new Date()));
}
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
String date = etDate.getText().toString();
int startkilometer;
switch (v.getId()) {
case R.id.bStartTur:
startkilometer = Integer.valueOf(etKm.getText().toString());
Intent menu = new Intent("com.uniqueapps.runner.MENU");
menu.putExtra("stopper", false);
menu.putExtra("startkm", startkilometer);
menu.putExtra("datoen", date);
startActivity(menu);
break;
}
}
}
我的停止课：
public class Stop extends Main implements OnClickListener {
Button bStop;
EditText sqllocations, kilometer;
int startkilometer;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.stop);
bStop = (Button) findViewById(R.id.bstopTur);
bStop.setOnClickListener(this);
sqllocations = (EditText) findViewById(R.id.locations);
kilometer = (EditText) findViewById(R.id.Kilometer);
sqllocations.setText("Unknown");
}
@Override
public void onClick(View v) {
int startkilometer;
int slutkilometer;
startkilometer = getIntent().getIntExtra("startkm", 0);
date = getIntent().getStringExtra("datoen");
// TODO Auto-generated method stub
switch(v.getId()){
case R.id.bstopTur:
slutkilometer = Integer.valueOf(kilometer.getText().toString());
int kortekm = (slutkilometer - startkilometer);
try{
String locations = sqllocations.getText().toString();
KilometerSQL entry = new KilometerSQL(this);
entry.open();
entry.createEntry(date, kortekm, locations);
entry.close();
}catch(Exception e){
e.printStackTrace();
}
Intent menu = new Intent("com.uniqueapps.runner.MENU");
menu.putExtra("stopper", true);
startActivity(menu);
break;
}
}
}
还有我的 SQL：
公共类公里SQL {
public static final String KEY_ROWID = "date";
public static final String KEY_KILOMETER = "kilometer";
public static final String KEY_LOCATIONS = "locations";
private static final String DATABASE_NAME = "Kilometerdb";
private static final String DATABASE_TABLE = "kilometertable";
private static final int DATABASE_VERSION = 1;
private DbHelper ourHelper;
private final Context ourContext;
private SQLiteDatabase ourDatabase;
private static class DbHelper extends SQLiteOpenHelper{
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" +
KEY_ROWID + " TEXT NOT NULL, " +
KEY_KILOMETER + " INTEGER, " +
KEY_LOCATIONS + " TEXT NOT NULL);"
);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
public KilometerSQL (Context c){
ourContext = c;
}
public KilometerSQL open(){
ourHelper = new DbHelper(ourContext);
ourDatabase = ourHelper.getWritableDatabase();
return this;
}
public void close(){
ourHelper.close();
}
public long createEntry(String date, int kortekm, String locations) {
// TODO Auto-generated method stub
ContentValues cv = new ContentValues();
cv.put(KEY_ROWID, date);
cv.put(KEY_KILOMETER, kortekm);
cv.put(KEY_LOCATIONS, locations);
return ourDatabase.insert(DATABASE_TABLE, null, cv);
}
public String getData() {
// TODO Auto-generated method stub
String [] columns = new String []{ KEY_ROWID, KEY_KILOMETER, KEY_LOCATIONS};
Cursor c = ourDatabase.query(DATABASE_TABLE, columns, null, null, null, null, null);
String result = "";
int iDate = c.getColumnIndex(KEY_ROWID);
int iKilometer = c.getColumnIndex(KEY_KILOMETER);
int iLocations = c.getColumnIndex(KEY_LOCATIONS);
for (c.moveToFirst();!c.isAfterLast();c.moveToNext()){
result = result + c.getString(iDate) + " " + c.getString(iKilometer) + " " + c.getString(iLocations) + "\n";
}
return result;
}
}