问在Android中插入数据时在片段中使用Sqlite数据库助手出错
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Stack Overflow用户

提问于 2016-01-24 23:38:12

回答 1查看 1.4K关注 0票数 -1

我绝对是Android的初学者。现在我在片段中使用Sqlite数据库时遇到错误。我的代码出了什么问题？

我的数据库助手类：

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "todo.db";
    private static final String TABLE_NAME = "task";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_DESCRIPTION = "description";
    private static final String COLUMN_DATE ="date";
    private static final String COLUMN_DONE = "done";
    private static final String CREATE_TABLE = "CREATE TABLE "+TABLE_NAME+" ("+COLUMN_ID+" INTEGER PRIMARY KEY AUTOINCREMENT,"+COLUMN_DESCRIPTION+" TEXT,"+
    COLUMN_DATE+" DATE,"+COLUMN_DONE+" BOOLEAN)";
    SQLiteDatabase db;

    public DatabaseHelper(Context context)
    {
        super(context,DATABASE_NAME,null,DATABASE_VERSION);
    }


    @Override
    public void onCreate(SQLiteDatabase db)
    {
        this.db = db;
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String query = "DROP TABLE IF EXISTS "+TABLE_NAME;
        db.execSQL(query);
        this.onCreate(db);
    }

    public  void insertTask(Task task)
    {
        db = getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_DESCRIPTION,task.getDescription());
        values.put(COLUMN_DATE,task.getDate().toString());
        values.put(COLUMN_DONE,Boolean.FALSE.toString());
        db.insert(TABLE_NAME, null, values);
        db.close();
    }
}

这是我的片段类：

public class CreateTaskFragment extends Fragment{
    private DatabaseHelper dbHelper = new DatabaseHelper(getActivity());
    private Button saveBtn;
    private EditText tfDescription,tfDate;
    private int yy,mm,dd;
    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {


        View view = inflater.inflate(R.layout.create_task,container,false);

        tfDescription = (EditText)view.findViewById(R.id.tf_task_description);
        tfDate = (EditText)view.findViewById(R.id.tf_task_date);
        tfDate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                setPickerDate(v);
            }
        });

        saveBtn = (Button)view.findViewById(R.id.btn_save_task);
        saveBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                saveTask();
            }
        });

        return view;
    }

    public void setPickerDate(View v)
    {
        final Calendar calendar = Calendar.getInstance();
        int yy = calendar.get(Calendar.YEAR);
        int mm = calendar.get(Calendar.MONTH);
        int dd = calendar.get(Calendar.DAY_OF_MONTH);
        DatePickerDialog datePicker = new DatePickerDialog(getActivity(), new DatePickerDialog.OnDateSetListener() {
            @Override
            public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
                String date = String.valueOf(monthOfYear+1)+"/"+String.valueOf(dayOfMonth)+"/"+String.valueOf(year);
                tfDate.setText(date);
            }
        }, yy, mm, dd);
        datePicker.show();
    }

    public void saveTask()
    {
        String description = tfDescription.getText().toString();
        String date = tfDate.getText().toString();

        if(description.isEmpty())
        {
            Toast.makeText(getActivity().getBaseContext(),"Description is required",Toast.LENGTH_SHORT).show();
        }
        else if(date.isEmpty())
        {
            Toast.makeText(getActivity().getBaseContext(),"Date is required",Toast.LENGTH_SHORT).show();
        }
        else if(description.length()<getResources().getInteger(R.integer.min_description_length))
        {
            String minChar = String.valueOf(getResources().getInteger(R.integer.min_description_length));
            Toast.makeText(getActivity().getBaseContext(),"Description should be minium "+minChar+" characters",Toast.LENGTH_SHORT).show();
        }
        else{
            //check date
            SimpleDateFormat format = new SimpleDateFormat("MM/dd/yyyy");
            boolean parseOk = false;
            Date taskDate = new Date();
            try{
                taskDate = format.parse(date);
                Task task = new Task();
                task.setDescription(description);
                task.setDate(taskDate);
                dbHelper.insertTask(task);
                parseOk = true;
            }
            catch(ParseException e)
            {
                parseOk = false;
            }

            if(parseOk)
            {
                //insert task to database
                Toast.makeText(getActivity().getBaseContext(),"Task saved",Toast.LENGTH_SHORT).show();
            }
            else{
                Toast.makeText(getActivity().getBaseContext(),"Invalid date format",Toast.LENGTH_SHORT).show();
            }
        }
    }
}

当我点击保存按钮时。这是抛出错误。

这是我单击保存按钮后的logcat：

   01-24 15:49:30.007 575-575/? V/InputMethodService: onEvaluateInputViewShown: config.hardKeyboardHidden = 1
01-24 15:49:30.011 575-597/? E/BinaryDictionaryGetter: Could not find a dictionary pack
01-24 15:49:30.011 575-597/? E/ActivityThread: Failed to find provider info for com.android.inputmethod.latin.dictionarypack
01-24 15:49:31.167 1765-1765/? D/AndroidRuntime: Shutting down VM
01-24 15:49:31.167 1765-1765/? W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0xa6206908)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime: FATAL EXCEPTION: main
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime: java.lang.NullPointerException
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:224)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at com.waiyanhein.todo.todo.DatabaseHelper.insertTask(DatabaseHelper.java:46)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at com.waiyanhein.todo.todo.CreateTaskFragment.saveTask(CreateTaskFragment.java:100)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at com.waiyanhein.todo.todo.CreateTaskFragment$2.onClick(CreateTaskFragment.java:49)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at android.view.View.performClick(View.java:4204)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at android.view.View$PerformClick.run(View.java:17355)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at android.os.Handler.handleCallback(Handler.java:725)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:92)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:137)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5041)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at java.lang.reflect.Method.invokeNative(Native Method)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Method.java:511)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
01-24 15:49:31.167 1765-1765/? E/AndroidRuntime:     at dalvik.system.NativeStart.main(Native Method)
01-24 15:49:31.167 415-426/? W/ActivityManager:   Force finishing activity com.waiyanhein.todo.todo/.MainActivity
01-24 15:49:31.231 415-426/? D/dalvikvm: GC_FOR_ALLOC freed 1480K, 53% free 6135K/12844K, paused 5ms, total 6ms
01-24 15:49:31.239 415-418/? D/dalvikvm: GC_CONCURRENT freed 46K, 47% free 6925K/12844K, paused 2ms+1ms, total 10ms
01-24 15:49:31.251 415-431/? D/dalvikvm: GC_FOR_ALLOC freed 107K, 45% free 7160K/12844K, paused 7ms, total 7ms
01-24 15:49:31.263 415-418/? D/dalvikvm: GC_CONCURRENT freed 1K, 36% free 8260K/12844K, paused 1ms+0ms, total 10ms
01-24 15:49:31.263 415-431/? D/dalvikvm: WAIT_FOR_CONCURRENT_GC blocked 3ms
01-24 15:49:31.267 415-431/? I/dalvikvm-heap: Grow heap (frag case) to 10.614MB for 2536932-byte allocation
01-24 15:49:31.279 415-423/? D/dalvikvm: GC_FOR_ALLOC freed <1K, 30% free 10737K/15324K, paused 13ms, total 13ms
01-24 15:49:31.743 415-428/? W/ActivityManager: Activity pause timeout for ActivityRecord{5325c494 u0 com.waiyanhein.todo.todo/.MainActivity}
01-24 15:49:31.747 415-470/? I/qtaguid: Failed write_ctrl(s 1 10023) res=-1 errno=1
01-24 15:49:31.747 415-470/? W/NetworkManagementSocketTagger: setKernelCountSet(10023, 1) failed with errno -1
01-24 15:49:31.791 598-598/? W/EGL_genymotion: eglSurfaceAttrib not implemented
01-24 15:49:32.359 415-470/? I/qtaguid: Failed write_ctrl(s 0 10062) res=-1 errno=1
01-24 15:49:32.359 415-470/? W/NetworkManagementSocketTagger: setKernelCountSet(10062, 0) failed with errno -1
01-24 15:49:42.307 415-428/? W/ActivityManager: Activity destroy timeout for ActivityRecord{5325c494 u0 com.waiyanhein.todo.todo/.MainActivity}

android

sqlite

android-fragments

android-sqlite

回答 1

Stack Overflow用户

回答已采纳

发布于 2016-01-24 23:47:10

您得到的错误是您的片段的第101行上的空指针异常。从你的帖子中很难看出第101行代表什么，但我假设它是具有以下内容的行：

dbHelper.insertTask(task);

您在类的顶部将dbHelper声明为成员变量，但从未实例化它。相反，您只需调用：

new DatabaseHelper(getActivity());

而不会将其附加到dbHelper。将该行更改为：

dbHelper = new DatabaseHelper(getActivity());

它将有望修复您的错误。

票数 1

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/34977675

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