[英]NullPointerException SQLiteAssetHelper
I am trying to get a list of information from my database and display that into a custom listview. 我试图从我的数据库中获取信息列表,并将其显示到自定义列表视图中。 I already have my DatabaseHelper, Fragment, and Adapter setup. 我已经有了DatabaseHelper,Fragment和Adapter设置。 Here are the errors I am receiving: 以下是我收到的错误:
04-29 13:36:52.539: E/AndroidRuntime(8135): FATAL EXCEPTION: main
04-29 13:36:52.539: E/AndroidRuntime(8135): java.lang.NullPointerException
04-29 13:36:52.539: E/AndroidRuntime(8135): at com.readystatesoftware.sqliteasset.SQLiteAssetHelper.<init>(SQLiteAssetHelper.java:110)
04-29 13:36:52.539: E/AndroidRuntime(8135): at com.readystatesoftware.sqliteasset.SQLiteAssetHelper.<init>(SQLiteAssetHelper.java:130)
04-29 13:36:52.539: E/AndroidRuntime(8135): at com.rcd.mypr.Workouts.WorkoutsDatabaseHelper.<init>(WorkoutsDatabaseHelper.java:35)
04-29 13:36:52.539: E/AndroidRuntime(8135): at com.rcd.mypr.Workouts.WorkoutsFragment.onCreateView(WorkoutsFragment.java:36)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:828)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1032)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.app.BackStackRecord.run(BackStackRecord.java:622)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1382)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.app.FragmentManagerImpl$1.run(FragmentManager.java:426)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.os.Handler.handleCallback(Handler.java:605)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.os.Handler.dispatchMessage(Handler.java:92)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.os.Looper.loop(Looper.java:137)
04-29 13:36:52.539: E/AndroidRuntime(8135): at android.app.ActivityThread.main(ActivityThread.java:4424)
04-29 13:36:52.539: E/AndroidRuntime(8135): at java.lang.reflect.Method.invokeNative(Native Method)
04-29 13:36:52.539: E/AndroidRuntime(8135): at java.lang.reflect.Method.invoke(Method.java:511)
04-29 13:36:52.539: E/AndroidRuntime(8135): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
04-29 13:36:52.539: E/AndroidRuntime(8135): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
04-29 13:36:52.539: E/AndroidRuntime(8135): at dalvik.system.NativeStart.main(Native Method)
Here is my WorkoutsDatabaseHelper.java 这是我的WorkoutsDatabaseHelper.java
package com.rcd.mypr.Workouts;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import com.readystatesoftware.sqliteasset.SQLiteAssetHelper;
public class WorkoutsDatabaseHelper extends SQLiteAssetHelper {
// All Static variables
// Database Version
private static final int DATABASE_VERSION = 1;
// Database Name
private static final String DATABASE_NAME = "workoutsDatabase.sqlite";
private static final String WORKOUTS_TABLE = "workouts";
// Workouts Table Columns names
private static final String KEY_ID = "_id";
private static final String KEY_WORKOUT_NAME = "workout_name";
private static final String KEY_HERO_LAST_NAME = "hero_last_name";
private static final String KEY_HERO_FIRST_NAME = "hero_first_name";
private static final String KEY_HERO_MIDDLE_NAME = "hero_middle_name";
private static final String KEY_HERO_DESCRIPTION = "hero_description";
private static final String KEY_DATE_ADDED = "date_added";
private static final String KEY_WORKOUT = "workout";
private static final String KEY_MEASUREMENT = "measurement";
private static final String KEY_PHOTO = "photo";
public WorkoutsDatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
public Cursor getWorkoutNames() {
SQLiteDatabase db = getReadableDatabase();
Cursor cursor = db.query(WORKOUTS_TABLE, new String[] {"_id", "workout_name"}, null, null, null,
null, KEY_WORKOUT_NAME + " ASC");
return cursor;
}
}
And Lastly, here is my WorkoutsFragment.java 最后,这是我的WorkoutsFragment.java
package com.rcd.mypr.Workouts;
import android.app.Fragment;
import android.content.Context;
import android.database.Cursor;
import android.os.Bundle;
import android.support.v4.widget.SimpleCursorAdapter;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import com.rcd.mypr.R;
public class WorkoutsFragment extends Fragment {
WorkoutsDatabaseHelper db;
SimpleCursorAdapter adapter;
ListView listContent;
private int position;
Cursor cursor;
private Context mContext;
WorkoutsAdapter workoutsAdapter;
public WorkoutsFragment(){}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
db = new WorkoutsDatabaseHelper(mContext);
mContext = getActivity();
View rootView = inflater.inflate(R.layout.activity_workouts, container, false);
listContent = (ListView) rootView.findViewById(android.R.id.list);
// Create the Adapter
workoutsAdapter = new WorkoutsAdapter(mContext, cursor);
// Set the adapter to ListView
listContent.setAdapter(workoutsAdapter);
return rootView;
}
private void initViews(){
//Typeface tf = Typeface.createFromAsset(mContext.getAssets(),"Roboto-Light.ttf");
}
private void addItemsToList(){
Cursor cursor = db.getWorkoutNames();
Log.d("history.java", "finished Cursor cursor = db.getAllLogs();");
String[] from = {"_id", "workouts_name"};
int[] to = {R.id.tv_id, R.id.tv_label};
adapter = new SimpleCursorAdapter(mContext, R.layout.single_item, cursor, from, to, 0);
listContent.setAdapter(adapter);
}
public void onResume(){
super.onResume();
workoutsAdapter = new WorkoutsAdapter(mContext, cursor);
listContent.setAdapter(workoutsAdapter);
}
}
If there is anything else you need to see please let me know. 如果您还需要查看其他内容,请告知我们。
The error is in the onCreateView()
-method of your Fragment
. 错误发生在Fragment
的onCreateView()
方法中。 You initialize your WorkoutsDatabaseHelper
with a null
Context
. 使用null
Context
初始化WorkoutsDatabaseHelper
。
db = new WorkoutsDatabaseHelper(mContext);
mContext = getActivity();
Switch these two lines and try again... 切换这两行,然后再试一次......
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