我正在创建一个拥有数据库的应用程序，现在我正在尝试使用此方法存储数据并获取错误javanullpointer，
JSONParser jParser = new JSONParser();
JSONObject json = jParser.getJSONFromUrl(url);
// TODO Auto-generated method stub
JSONArray Erate= json.getJSONArray("Erates");
if(Erate!=null)
{
// looping through All Contacts
for(int i = 0; i < Erate.length(); i++){
JSONObject c = Erate.getJSONObject(i);
Cursor cr = db.rawQuery("select * from `rates` where `id`='"+c.getString("id")+"'",null);
String query=
"Insert into rates(id,kondisi,condition,tenor,erate,erateDB)"+
"values("+
c.getString("id")+",'"+
c.getString("....")
+"')";
db.execSQL(query);
Log.d("Insert",query);
cr.close();}
}
然后我尝试另一种方法（这也给出了相同的错误）
for (int i = 0; i < Erates.length(); i++) {
JSONObject c = Erates.getJSONObject(i);
int id = c.getInt(TAG_ER_ID);
int tenor = c.getInt(TAG_ER_TENOR);
String ko = c.getString(TAG_ER_K);
String co = c.getString(TAG_ER_C);
double rate = c.getDouble(TAG_ER_RATE);
double ratedb = c.getDouble(TAG_ER_RATE_DB);
Log.d("Response test: ", id + "\n" + tenor + "\n" + ko
+ "\n" + co + "\n" + rate + "\n" + ratedb);
/**
* Updating parsed JSON data into db
* */
db.saveEntryEffectiveRate(id, tenor,ko,co,
rate,ratedb);
}
数据库中的saveEntryEffectiveRate：
public void saveEntryEffectiveRate(int id, int tenor,String ko,String co, double rate,
double ratedb) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues valuesER = new ContentValues();
valuesER.put(KEY_ER_ID, id);
valuesER.put(KEY_ER_TENOR, tenor);
valuesER.put(KEY_ER_KO, ko);
valuesER.put(KEY_ER_CO, co);
valuesER.put(KEY_ER_RATE, rate);
valuesER.put(KEY_ER_RATE_DB, ratedb);
db.insert(TABLE_EFFECTIVE_RATE, null, valuesER);
}
更新：logcat：
04-23 16:44:14.044: E/AndroidRuntime(6752): FATAL EXCEPTION: main
04-23 16:44:14.044: E/AndroidRuntime(6752): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{www.mandiritunasfinancemobile.co.id.a1s2d3f4g5h6j7k8l9.p0.comcom/www.mandiritunasfinancemobile.co.id.a1s2d3f4g5h6j7k8l9.p0.comcom.MainActivity}: java.lang.NullPointerException
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1544)
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1638)
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:928)
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.os.Handler.dispatchMessage(Handler.java:99)
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.os.Looper.loop(Looper.java:123)
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.app.ActivityThread.main(ActivityThread.java:3647)
04-23 16:44:14.044: E/AndroidRuntime(6752): at java.lang.reflect.Method.invokeNative(Native Method)
04-23 16:44:14.044: E/AndroidRuntime(6752): at java.lang.reflect.Method.invoke(Method.java:507)
04-23 16:44:14.044: E/AndroidRuntime(6752): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-23 16:44:14.044: E/AndroidRuntime(6752): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-23 16:44:14.044: E/AndroidRuntime(6752): at dalvik.system.NativeStart.main(Native Method)
04-23 16:44:14.044: E/AndroidRuntime(6752): Caused by: java.lang.NullPointerException
04-23 16:44:14.044: E/AndroidRuntime(6752): at www.mandiritunasfinancemobile.co.id.a1s2d3f4g5h6j7k8l9.p0.comcom.MainActivity.<init>(MainActivity.java:55)
04-23 16:44:14.044: E/AndroidRuntime(6752): at java.lang.Class.newInstanceImpl(Native Method)
04-23 16:44:14.044: E/AndroidRuntime(6752): at java.lang.Class.newInstance(Class.java:1409)
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
04-23 16:44:14.044: E/AndroidRuntime(6752): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1536)
04-23 16:44:14.044: E/AndroidRuntime(6752): ... 11 more
更新：DB：
public class DatabaseMaster2 extends SQLiteOpenHelper {
SQLiteDatabase mydb;
// Database Version
private static final int DATABASE_VERSION = 7;
// Database Name
private static final String DATABASE_NAME = "Rates";
// Table Names
//effective_rate
public static final String KEY_ER_ID = "er_id";
public static final String KEY_ER_TENOR = "ER_tenor";
public static final String KEY_ER_KO = "ER_ko";
public static final String KEY_ER_CO = "ER_co";
public static final String KEY_ER_RATE = "ER_rate";
public static final String KEY_ER_RATE_DB = "ER_rate_DB" ;
//ER_Linker
public static final String KEY_ER_L_ID = "kondisi_id";
public static final String KEY_ER_L_K = "kondisi";
public static final String KEY_ER_L_C = "condition";
//AS_Linker
public static final String KEY_AS_L_ID = "asuransi_type_id";
public static final String KEY_AS_L_Ty = "asuransi_type";
//AS_linker_zona
public static final String KEY_AS_L_Z_ID = "aslz_id";
public static final String KEY_AS_L_Z_ZONA = "aslz_zona";
public static final String KEY_AS_L_Z_ZONE = "aslz_zone";
// Asuransi rate
public static final String KEY_AS_ID = "as_id";
public static final String KEY_AS_ZO = "AS_zona";
public static final String KEY_AS_TENOR = "AS_tenor";
public static final String KEY_AS_TLO = "TLO";
public static final String KEY_AS_COMPREHENSIVE = "Comprehensive";
public static final String KEY_AS_COMBINE = "Combine";
//the tables
public static final String TABLE_EFFECTIVE_RATE = "effective_rate";
public static final String TABLE_ASURANSI_RATE = "asuransi_rate";
public static final String TABLE_AS_LINKER = "as_linker";
public static final String TABLE_AS_L_ZONA= "as_l_zona";
public static final String TABLE_ER_LINKER = "er_linker";
public DatabaseMaster2(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
try {
db.beginTransaction();
db.execSQL("CREATE TABLE " + TABLE_ER_LINKER + " ("+ KEY_ER_L_K + " TEXT NOT NULL," + KEY_ER_L_C+ " TEXT NOT NULL)");
db.execSQL("CREATE TABLE " + TABLE_AS_LINKER + " ("+ KEY_AS_L_Ty + " TEXT NOT NULL)");
db.execSQL("CREATE TABLE " + TABLE_AS_L_ZONA + " ("+ KEY_AS_L_Z_ZONA + " TEXT NOT NULL, " + KEY_AS_L_Z_ZONE + " TEXT NOT NULL)");
db.execSQL("CREATE TABLE " + TABLE_EFFECTIVE_RATE + " ("+ KEY_ER_ID + " INTEGER PRIMARY KEY, " + KEY_ER_TENOR+" INTEGER," +KEY_ER_KO+" TEXT NOT NULL, "+KEY_ER_CO+" TEXT NOT NULL, "+KEY_ER_RATE+" REAL, "+ KEY_ER_RATE_DB + " REAL)");
db.execSQL("CREATE TABLE " + TABLE_ASURANSI_RATE + " ("+ KEY_AS_ID + " INTEGER PRIMARY KEY, "+ KEY_AS_ZO + " INTEGER, " + KEY_AS_TENOR+ " INTEGER," + KEY_AS_TLO + " REAL,"+ KEY_AS_COMPREHENSIVE + " REAL," + KEY_AS_COMBINE+ " REAL)");
// Inserts pre-defined departments
db.setTransactionSuccessful();
} finally {
db.endTransaction();
}
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS " + TABLE_EFFECTIVE_RATE);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_ASURANSI_RATE);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_ER_LINKER);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_AS_LINKER);
db.execSQL("DROP TABLE IF EXISTS " + TABLE_AS_L_ZONA);
onCreate(db);
}
public int updateEntryEffectiveRate(EntryEffectiveRate er) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(KEY_ER_ID, er.getERId());
values.put(KEY_ER_TENOR, er.getERTenor());
values.put(KEY_ER_RATE, er.getERrate());
values.put(KEY_ER_RATE_DB, er.getERrateDB());
// updating row
return db.update(TABLE_EFFECTIVE_RATE, values, KEY_ER_ID + " = ?",
new String[] { String.valueOf(er.getERId()) });
}
//
public void deleteEntryEffectiveRate(long er_id) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_EFFECTIVE_RATE, KEY_ER_ID + " = ?",
new String[] { String.valueOf(er_id) });
}
public void saveEntryEffectiveRate(int id, int tenor,String ko,String co, double rate,
double ratedb) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues valuesER = new ContentValues();
valuesER.put(KEY_ER_ID, id);
valuesER.put(KEY_ER_TENOR, tenor);
valuesER.put(KEY_ER_KO, ko);
valuesER.put(KEY_ER_CO, co);
valuesER.put(KEY_ER_RATE, rate);
valuesER.put(KEY_ER_RATE_DB, ratedb);
db.insert(TABLE_EFFECTIVE_RATE, null, valuesER);
}
public void saveEntryAsuransiRate(int ASid,int ASzo,int AStenor,double tlo,double comp,double comb) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues valuesAS = new ContentValues();
valuesAS.put(KEY_AS_ID, ASid);
valuesAS.put(KEY_AS_ZO, ASzo);
valuesAS.put(KEY_AS_TENOR, AStenor);
valuesAS.put(KEY_AS_TLO, tlo);
valuesAS.put(KEY_AS_COMPREHENSIVE, comp);
valuesAS.put(KEY_AS_COMBINE, comb);
db.insert(TABLE_ASURANSI_RATE, null, valuesAS);
}
public void saveKondisi(String K,String C) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues valuesK = new ContentValues();
valuesK.put(KEY_ER_L_K,K );
valuesK.put(KEY_ER_L_C, C);
db.insert(TABLE_ER_LINKER, null, valuesK);
}
public void saveTipeAsuransi(String ty) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues valuesTA = new ContentValues();
valuesTA.put(KEY_AS_L_Ty, ty);
db.insert(TABLE_AS_LINKER, null, valuesTA);
}
public void saveZona(String za,String ze) {
SQLiteDatabase db = this.getWritableDatabase();
ContentValues valuesZO = new ContentValues();
valuesZO.put(KEY_AS_L_Z_ZONA, za);
valuesZO.put(KEY_AS_L_Z_ZONE, ze);
db.insert(TABLE_AS_L_ZONA, null, valuesZO);
}
//
public void deleteEntryAsuransiRate(long as_id) {
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_ASURANSI_RATE, KEY_AS_ID + " = ?",
new String[] { String.valueOf(as_id) });
}
我在mainclass中声明数据库，它将使用DatabaseMaster2 db;数据库master进行解析和存储是扩展sqliteopenhelper的数据库类的名称
我将日志放入以确保解析成功完成。它是。 有关将数据存储到数据库的任何建议吗？
答案 0 :(得分：3)
首先用getwritable（）打开你的数据库....然后试试这段代码
JSONObject json_give_field_1 = jsonArray_items.getJSONObject(0);
for (int i = 0; i < jsonArray_items.length(); i++) {
JSONObject fields_value;
try {
cv.put("databasefield", fields_value.getString(field));
db.insert(database_table, null, cv);
} catch (JSONException e) {
e.printStackTrace();
}
}
之后，必须通过db.close（）关闭数据库; 希望它对你有用
答案 1 :(得分：1)
不使用Json Parser，而是尝试将Gson库从Json转换为String，反之亦然。有关详细示例，请参阅此answer。
创建一个包含所需信息的类，然后使用Gson将其序列化。