这是我的片段活动我在访问数据库时遇到错误我的代码是：
public class RainfallFragment extends Fragment {
public static final String KEY_DIVISION_ID="division_id";
public static final String KEY_DIVISION_NAME="division_name";
ListView listCollege;
ProgressBar proCollageList;
public Context context;
private MySQLiteHelper dbHelper;
public RainfallFragment() {}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
dbHelper = new MySQLiteHelper(getActivity());
// dbHelper = new MySQLiteHelper(this);
dbHelper.getReadableDatabase();
}
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
// Inflate the layout for this fragment
getActivity().setTitle("Rainfall Report");
getActivity().setTitleColor(0000000);
View v =inflater.inflate(R.layout.fragment_rainfall, container, false);
context = v.getContext();
v.setFocusableInTouchMode(true);
v.requestFocus();
v.setOnKeyListener(new View.OnKeyListener() {
@Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction() == KeyEvent.ACTION_DOWN) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
getActivity().finish();
Intent intent = new Intent(getActivity(), MainActivity.class);
startActivity(intent);
return true;
}
}
return false;
}
});
//DISINI BATAS NYA//
listCollege = (ListView)v.findViewById(R.id.listCollege);
proCollageList = (ProgressBar)v.findViewById(R.id.proCollageList);
new GetHttpResponse().execute();
listCollege.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> arg0, View view, int arg2, long arg3) {
// On selecting single row to get detail information
final String division_id = ((TextView) view.findViewById(R.id.adapter_text_id)).getText().toString();
final String division_name = ((TextView) view.findViewById(R.id.adapter_text_estate)).getText().toString();
AlertDialog.Builder b = new AlertDialog.Builder(getActivity());
b.setIcon(android.R.drawable.ic_dialog_alert);
b.setMessage("Sure for choosing this estate");
b.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
Intent i = new Intent(getActivity(), RainfallReport.class);
i.putExtra(KEY_DIVISION_ID, division_id);
i.putExtra(KEY_DIVISION_NAME, division_name);
getActivity().startActivity(i);
dialog.dismiss();
}
});
b.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int whichButton) {
}
});
b.show();
}
});
return v;
}
private class GetHttpResponse extends AsyncTask<Void, Void, Void> {
private Context context;
String result;
List<HashMap<String, String>> collegeList;
@Override
protected void onPreExecute()
{
super.onPreExecute();
}
@Override
protected Void doInBackground(Void... arg0)
{
List<Estate> estates = new LinkedList<Estate>();
estates= dbHelper.getAllEstate();
//Syntax for sort Listview Array by Id Ascending
Collections.sort(estates, new Comparator<Estate>(){
@Override
public int compare(Estate id1,Estate id2) {
return id1.getDivision_id() - id2.getDivision_id();
}
});
// looping through All data
for(Estate temp_vg: estates){
temp_vg.getDivision_id();
temp_vg.getDivision_name();
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put("division_id", String.valueOf(temp_vg.getDivision_id()));
map.put("division_estate", temp_vg.getDivision_name());
// adding HashList to ArrayList
collegeList.add(map);
}
return null;
}
@Override
protected void onPostExecute(Void result)
{
proCollageList.setVisibility(View.GONE);
listCollege.setVisibility(View.VISIBLE);
if(collegeList != null)
{
//adapter = new ListAdapterEstate(LihatDataEstate.this, map);
ListAdapterEstate adapter = new ListAdapterEstate(collegeList, context);
listCollege.setAdapter(adapter);
//adapter=new LazyAdapter(Lihat_Data.this, dataList);
//list.setAdapter(adapter);
}
}
}
MySQLiteHelper.java
public class MySQLiteHelper extends SQLiteOpenHelper {
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "AARIDB.db";
private SQLiteDatabase database;
public MySQLiteHelper(Context context) {
super(context, "/mnt/sdcard/AARIDB/DBAARI.db", null, DATABASE_VERSION);
//super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
String RAINFALL_TABLE = "CREATE TABLE rainfall ( " +
"division_id INTEGER PRIMARY KEY, " +
"year_rainfall VARCHAR (5), "+
"jan VARCHAR (10), "+
"feb VARCHAR (10),"+
"mar VARCHAR (10),"+
"apr VARCHAR (10),"+
"may VARCHAR (10),"+
"jun VARCHAR (10),"+
"jul VARCHAR (10),"+
"aug VARCHAR (10),"+
"sep VARCHAR (10),"+
"oct VARCHAR (10),"+
"nov VARCHAR (10),"+
"dec VARCHAR (10),"+
" FOREIGN KEY division_id REFERENCES "+ESTATE_TABLE+"division_id;";
// create table
db.execSQL(RAINFALL_TABLE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// Drop older books table if existed
db.execSQL("DROP TABLE IF EXISTS rainfall");
// create fresh books table
this.onCreate(db);
}
//---------------------------------------------------------------------
/**
* CRUD operations (create "add", read "get", update, delete) book + get all + delete all
*/
private static final String TABLE_RAINFALL = "rainfall";
// assesment Table Columns names
public static final String KEY_DIVISION_ID_RAINFALL= "division_id";
public static final String KEY_YEAR_RAINFALL= "year_rainfall";
public static final String KEY_JAN_RAINFALL = "jan";
public static final String KEY_FEB_RAINFALL = "feb";
public static final String KEY_MAR_RAINFALL = "mar";
public static final String KEY_APR_RAINFALL = "apr";
public static final String KEY_MAY_RAINFALL = "may";
public static final String KEY_JUN_RAINFALL = "jun";
public static final String KEY_JUL_RAINFALL = "jul";
public static final String KEY_AUG_RAINFALL = "aug";
public static final String KEY_SEP_RAINFALL = "sep";
public static final String KEY_OCT_RAINFALL = "oct";
public static final String KEY_NOV_RAINFALL = "nov";
public static final String KEY_DEC_RAINFALL = "dec";
private static final String[] COLUMN_RAINFALL = {
KEY_DIVISION_ID_RAINFALL,
KEY_YEAR_RAINFALL,
KEY_JAN_RAINFALL,
KEY_FEB_RAINFALL ,
KEY_MAR_RAINFALL ,
KEY_APR_RAINFALL,
KEY_MAY_RAINFALL,
KEY_JUN_RAINFALL,
KEY_JUL_RAINFALL,
KEY_AUG_RAINFALL,
KEY_SEP_RAINFALL,
KEY_OCT_RAINFALL ,
KEY_NOV_RAINFALL ,
KEY_DEC_RAINFALL};
public void addRAINFALL(Rainfall rainfall){
Log.d("addRAINFALL", rainfall.toString());
// 1. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
// 2. create ContentValues to add key "column"/value
ContentValues values = new ContentValues();
values.put(KEY_DIVISION_ID_RAINFALL, rainfall.getDivision_id()); // get est
values.put(KEY_YEAR_RAINFALL, rainfall.getYear_rainfall());
values.put(KEY_JAN_RAINFALL , rainfall.getJan());
values.put(KEY_FEB_RAINFALL, rainfall.getFeb());
values.put(KEY_MAR_RAINFALL, rainfall.getMar()); // get estate name
values.put(KEY_APR_RAINFALL, rainfall.getApr());
values.put(KEY_MAY_RAINFALL, rainfall.getMay());
values.put(KEY_JUN_RAINFALL, rainfall.getJun());
values.put(KEY_JUL_RAINFALL, rainfall.getJul()); // get estate name
values.put(KEY_AUG_RAINFALL, rainfall.getAug());
values.put(KEY_SEP_RAINFALL, rainfall.getSep());
values.put(KEY_OCT_RAINFALL , rainfall.getOct()); // get estate name
values.put(KEY_NOV_RAINFALL,rainfall.getNov());
values.put(KEY_DEC_RAINFALL, rainfall.getDec());
// 3. insert
db.insert(TABLE_RAINFALL, // table
null, //nullColumnHack
values); // key/value -> keys = column names/ values = column values
// 4. close
db.close();
}
public List<Rainfall> getAllRainfall() {
List<Rainfall> rainfall = new LinkedList<Rainfall>();
// 1. build the query
String query = "SELECT * FROM " + TABLE_RAINFALL+" ORDER BY "+KEY_DIVISION_ID_RAINFALL;
// 2. get reference to writable DB
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(query, null);
// 3. go over each row, build book and add it to list
Rainfall rainfall1 = null;
if (cursor.moveToFirst()) {
do {
rainfall1 = new Rainfall();
rainfall1.setDivision_id(Integer.parseInt(cursor.getString(0)));
rainfall1.setYear_rainfall(cursor.getString(1));
rainfall1.setJan(cursor.getString(2));
rainfall1.setFeb(cursor.getString(3));
rainfall1.setMar(cursor.getString(4));
rainfall1.setApr(cursor.getString(5));
rainfall1.setMay(cursor.getString(6));
rainfall1.setJun(cursor.getString(7));
rainfall1.setJul(cursor.getString(8));
rainfall1.setAug(cursor.getString(9));
rainfall1.setSep(cursor.getString(10));
rainfall1.setOct(cursor.getString(11));
rainfall1.setNov(cursor.getString(12));
rainfall1.setDec(cursor.getString(13));
// Add vgm
rainfall.add(rainfall1);
} while (cursor.moveToNext());
}
return rainfall;
}
public Cursor getAllDataRainfall() {
SQLiteDatabase db=this.getWritableDatabase();
Cursor mCursor = db.query("SELECT year_rainfall, jan, feb,mar,apr,may,jun,jul,aug,sep,oct,nov,dec FROM rainfall",
new String[] {KEY_YEAR_RAINFALL,KEY_JAN_RAINFALL,KEY_FEB_RAINFALL,KEY_MAR_RAINFALL,KEY_APR_RAINFALL,KEY_MAY_RAINFALL,
KEY_JUN_RAINFALL,KEY_JUL_RAINFALL,KEY_AUG_RAINFALL,KEY_SEP_RAINFALL,KEY_OCT_RAINFALL,KEY_NOV_RAINFALL,KEY_DEC_RAINFALL},
null, null, null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
db.close();
return mCursor;
}
我只需要片段访问数据库。任何人都会帮助我，我会很感激。错误的log cat低于。
请注意！ at com.test.myapplication.RainfallFragment.onCreate(RainfallFragment.java:40)是指dbHelper.getReadableDatabase();
09-14 22:20:16.387 1247-1247/com.test.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.test.myapplication, PID: 1247
java.lang.NullPointerException
at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
at android.database.sqlite.SQLiteOpenHelper.getReadableDatabase(SQLiteOpenHelper.java:188)
at com.test.myapplication.RainfallFragment.onCreate(RainfallFragment.java:40)
at android.support.v4.app.Fragment.performCreate(Fragment.java:2068)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1055)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1290)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:801)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1677)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:536)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：0)
我无法设置你的MySQLiteHelper的onCreate。你需要把
String RAINFALL_TABLE = "CREATE TABLE rainfall ( " +
"division_id INTEGER PRIMARY KEY, " +
"year_rainfall VARCHAR (5), "+
"jan VARCHAR (10), "+
"feb VARCHAR (10),"+
"mar VARCHAR (10),"+
"apr VARCHAR (10),"+
"may VARCHAR (10),"+
"jun VARCHAR (10),"+
"jul VARCHAR (10),"+
"aug VARCHAR (10),"+
"sep VARCHAR (10),"+
"oct VARCHAR (10),"+
"nov VARCHAR (10),"+
"dec VARCHAR (10),"+
" FOREIGN KEY division_id REFERENCES "+ESTATE_TABLE+"division_id;";
// create table
db.execSQL(RAINFALL_TABLE);
在你的MySQLiteHelper的onCreate中创建像这样的表
@Override
public void onCreate(SQLiteDatabase db) {
String RAINFALL_TABLE = "CREATE TABLE rainfall ( " +
"division_id INTEGER PRIMARY KEY, " +
"year_rainfall VARCHAR (5), "+
"jan VARCHAR (10), "+
"feb VARCHAR (10),"+
"mar VARCHAR (10),"+
"apr VARCHAR (10),"+
"may VARCHAR (10),"+
"jun VARCHAR (10),"+
"jul VARCHAR (10),"+
"aug VARCHAR (10),"+
"sep VARCHAR (10),"+
"oct VARCHAR (10),"+
"nov VARCHAR (10),"+
"dec VARCHAR (10),"+
" FOREIGN KEY division_id REFERENCES "+ESTATE_TABLE+"division_id;";
// create table
db.execSQL(RAINFALL_TABLE);
}
答案 1 :(得分：0)
我已经解决了这个问题.. 只需在RainfallFragment中更改我的代码
从：
List<HashMap<String, String>> collegeList;
为：
ArrayList<HashMap<String, String>> collegeList = new ArrayList<HashMap<String, String>>();
进入我的Asynctask RainfallFargment。
答案 2 :(得分：-1)
在MySQLiteHelper：
public class MySQLiteHelper {
private SQLiteDatabase db;
private Context context;
private DBHelper dbHelper;
public MySQLiteHelper(Context context) {
dbHelper = new DBHelper(context);
}
public MySQLiteHelper open() throws SQLException {
db = dbHelper.getWritableDatabase();
return this;
}
public void close() {
dbHelper.close();
}
public class DBHelper extends SQLiteOpenHelper {
public DBHelper(Context context) {
super(context, "/mnt/sdcard/AARIDB/DBAARI.db", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(RAINFALL_TABLE);//create tables
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS rainfall"); //drop tables if exists and than create or alter
this.onCreate(db);
}
}
}
从其他activity拨打电话：
MySQLiteHelper db = new MySQLiteHelper(MainActivity.this);