在我的主要活动中，名为EditText的{{1}}获得了date
这是我的NullPointerException：
MainActivity这是我的第二个活动，应该在public class MainActivity extends AppCompatActivity implements View.OnClickListener {
Spinner menuList;
EditText menu;
EditText date;
EditText time;
CheckBox dailyAlarm;
CheckBox reminder;
String item;
String setTime;
String setDate;
String menuDetails;
String spItem;
private int mYear,mMonth,mDay,mHour,mMinute;
ArrayList<String> a= new ArrayList<String>();
String[] from = {DBHelper.COLUMN_DATE,DBHelper.COLUMN_TIME,DBHelper.COLUMN_MENU};
int[] to = {R.id.spList,R.id.date,R.id.time,R.id.menu};
private ListView listView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
date = (EditText) findViewById(R.id.datePicker);
time = (EditText) findViewById(R.id.timePicker);
listView = (ListView) findViewById(R.id.listView);
menuList = (Spinner) findViewById(R.id.menuList);
//spItem = menuList.getSelectedItem().toString();
menu = (EditText) findViewById(R.id.menuET);
DBHelper2 helper2 = new DBHelper2(this);
menuDetails = menu.getText().toString();
helper2.insert(setDate,setTime,menuDetails);
a = (ArrayList<String>) helper2.getAllInfo();
/* ArrayAdapter adp = new ArrayAdapter(this,android.R.layout.simple_list_item_1,a);
listView.setAdapter(adp);
*/
//ArrayList<String> getInfo = (ArrayList<String>) helper2.getAllInfo();
//SimpleAdapter info = new SimpleAdapter(this,R.layout.activity_show_result,getInfo,from,to,0);
DBSpinner dbSpinner = new DBSpinner(this);
dbSpinner.insert("Breakfast");
dbSpinner.insert("Lunch");
dbSpinner.insert("Dinner");
ArrayList<String> list = dbSpinner.getAll();
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,R.layout.spinner,R.id.spinnerID,list);
menuList.setAdapter(adapter);
menuList.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
item = parent.getItemAtPosition(position).toString();
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
date.setOnClickListener(this);
time.setOnClickListener(this);
}
public void onClick(View v){
if (v == date){
final Calendar c = Calendar.getInstance();
mYear = c.get(Calendar.YEAR);
mMonth = c.get(Calendar.MONTH);
mDay = c.get(Calendar.DAY_OF_MONTH);
DatePickerDialog datePickerDialog = new DatePickerDialog(this, new DatePickerDialog.OnDateSetListener() {
@Override
public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
date.setText(dayOfMonth +"-"+(monthOfYear+1)+"-"+year);
}
},mYear, mMonth,mDay);
datePickerDialog.show();
setDate = date.getText().toString();
}
else if (v == time){
final Calendar c = Calendar.getInstance();
mHour = c.get(Calendar.HOUR_OF_DAY);
mMinute = c.get(Calendar.MINUTE);
TimePickerDialog timePickerDialog = new TimePickerDialog(this, new TimePickerDialog.OnTimeSetListener() {
@Override
public void onTimeSet(TimePicker view, int hourOfDay, int minute) {
time.setText(hourOfDay +" : "+minute);
}
},mHour,mMinute,false);
timePickerDialog.show();
setTime = time.getText().toString();
}
}
public void save(View view){
Intent intent = new Intent(getApplicationContext(),ShowResult.class);
intent.putExtra("menuList",item);
intent.putExtra("menu",menuDetails);
intent.putExtra("date",setDate);
intent.putExtra("time",setTime);
startActivity(intent);
}
}
中显示结果。它没有：
TextView要将 public class ShowResult extends AppCompatActivity {
TextView menulist;
TextView menu;
TextView date;
TextView time;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show_result);
menulist = (TextView) findViewById(R.id.spList);
menu = (TextView) findViewById(R.id.menu);
date = (TextView) findViewById(R.id.date);
time = (TextView) findViewById(R.id.time);
Bundle intent = getIntent().getExtras();
String menuListS = intent.getString("menuList");
String menuS = intent.getString("menu");
String dateS = intent.getString("date");
String timeS = intent.getString("time");
menulist.setText(menuListS);
menu.setText(menuS);
date.setText(dateS);
time.setText(timeS);
}
}
数据存储在Spinner中，请执行以下操作：
SQLiteDatabase要将其他数据存储在 public class DBSpinner extends SQLiteOpenHelper {
public static final String DATABASE_NAME = "spinner.db";
public static final String TABLE_NAME = "spinner";
public static final int DATABASE_VERSION = 1;
public static final String CREATE_TABLE = " CREATE TABLE " + TABLE_NAME +" (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT NULL UNIQUE )";
public DBSpinner(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(CREATE_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
public void insert(String name){
SQLiteDatabase db = this.getWritableDatabase();
db.beginTransaction();
ContentValues values;
try{
values = new ContentValues();
values.put("name",name);
db.insert(TABLE_NAME,null,values);
db.setTransactionSuccessful();
}catch (Exception ex){
ex.printStackTrace();
}finally {
db.endTransaction();
db.close();
}
}
public ArrayList<String> getAll(){
ArrayList<String> list = new ArrayList<String>();
SQLiteDatabase db = this.getReadableDatabase();
db.beginTransaction();
try{
String query = "SELECT * FROM "+ TABLE_NAME;
Cursor cursor =db.rawQuery(query,null);
if(cursor.getCount() > 0){
while (cursor.moveToNext()){
String name = cursor.getString(cursor.getColumnIndex("name"));
list.add(name);
}
}
db.setTransactionSuccessful();
}catch (Exception ex){
ex.printStackTrace();
}finally {
db.endTransaction();
db.close();
}
return list;
}
}
中，请执行以下操作：
SQLiteDatabase我是Android新手。关于如何解决这个问题的任何建议？