Question

我在Activity和edittext中有微调器。当我运行应用程序时，我收到了nullPointerException的警告。我没有在onCreate（）的编辑文本中检索SQLite数据。有人可以帮助我。这是我的代码。

public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.delete_entry);

        databaseHelper = new DatabaseHelper(this);
        databaseHelper.onOpen(db);

        spinner_searchByEmpName = (Spinner)findViewById(R.id.searchByEmpName);
        loadSerachBYProject() ;

        spinner_searchByEmpName.setOnItemSelectedListener(new OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> arg0, View arg1,
                    int arg2, long arg3) {
                // TODO Auto-generated method stub
                selectedEmployeeName = spinner_searchByEmpName.getSelectedItem().toString().trim();
                System.out.println("selectedProjectName " + selectedEmployeeName);

            }

            @Override
            public void onNothingSelected(AdapterView<?> arg0) {
                // TODO Auto-generated method stub

            }
        });


          etEmpName=(EditText)findViewById(R.id.Delete_editText_StaffEmployee_Name);
          etDepartment=(EditText)findViewById(R.id.Delete_editText_Department);
          etDesignation=(EditText)findViewById(R.id.Delete_editText_Designation);

        try {

            Cursor cursor = db.rawQuery("SELECT staff_employee_id, staff_emp_name, department, designation FROM employee_details WHERE staff_emp_name = ?",
                            new String[] { "" + selectedEmployeeName });

            etEmpName.setText(cursor.getString(cursor
                    .getColumnIndex("staff_emp_name")));

            etDepartment.setText(cursor.getString(cursor
                    .getColumnIndex("department")));

            etDesignation.setText(cursor.getString(cursor
                    .getColumnIndex("designation")));
        }

        catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }


    }


    private void loadSerachBYProject() 
    {
        DatabaseHelper databaseHelper = new DatabaseHelper(getApplicationContext());
        // Spinner Drop down elements
                List<String> projectsName = databaseHelper.getAllEmployeeName();

                // Creating adapter for spinner
                ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,android.R.layout.simple_spinner_item, projectsName);

                // Drop down layout style - list view with radio button
                dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

                // attaching data adapter to spinner
                spinner_searchByEmpName.setAdapter(dataAdapter);
    }


}

先谢谢。

这是我的日志猫错误信息

06-26 18:08:09.073: W/System.err(601): java.lang.NullPointerException
06-26 18:08:09.083: W/System.err(601):  at com.employee_review.Update_Entry.onCreate(Update_Entry.java:68)
06-26 18:08:09.083: W/System.err(601):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
06-26 18:08:09.083: W/System.err(601):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
06-26 18:08:09.083: W/System.err(601):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
06-26 18:08:09.092: W/System.err(601):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
06-26 18:08:09.092: W/System.err(601):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
06-26 18:08:09.103: W/System.err(601):  at android.os.Handler.dispatchMessage(Handler.java:99)
06-26 18:08:09.103: W/System.err(601):  at android.os.Looper.loop(Looper.java:123)
06-26 18:08:09.113: W/System.err(601):  at android.app.ActivityThread.main(ActivityThread.java:3683)
06-26 18:08:09.123: W/System.err(601):  at java.lang.reflect.Method.invokeNative(Native Method)
06-26 18:08:09.133: W/System.err(601):  at java.lang.reflect.Method.invoke(Method.java:507)
06-26 18:08:09.133: W/System.err(601):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-26 18:08:09.133: W/System.err(601):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-26 18:08:09.133: W/System.err(601):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

试试这个，我想

if(cursor!=null){
  etEmpName.setText(cursor.getString(cursor
            .getColumnIndex("staff_emp_name")));

    etDepartment.setText(cursor.getString(cursor
            .getColumnIndex("department")));

    etDesignation.setText(cursor.getString(cursor
            .getColumnIndex("designation")));  
}

Answer 2

db永远不会被初始化。它必须在onCreate（）中初始化，因为这是在Activity中运行的第一个方法。我明白这一点：

databaseHelper = new DatabaseHelper(this);
databaseHelper.onOpen(db);

我猜你真的应该这样：

databaseHelper = new DatabaseHelper(this);
db=databaseHelper.getReadableDatabase();

从Android中的Spinner选定项目中检索编辑文本中的SQLite数据

2 个答案: