Question

在我的数据库中存储名称，注释和日期时间字段（YYYY-MM-DD HH：MM）。当我尝试使用select语句检索数据时，它不起作用并显示空指针异常，用于创建和插入数据库的代码是

            SQLiteDatabase database;
            String st = yeartopass+"-"+monthtopass+"-"+daytopass+" "+hourtopass+":"+minutetopass;
            database = getApplicationContext().openOrCreateDatabase(
                    "universalreminder", MODE_PRIVATE, null);

            database.execSQL("create table if not exists birthdaytable(nameofperson varchar(20),comment varchar(150),bdatetime varchar(20));");
            database.execSQL("insert into birthdaytable values('"+name+"','"+comment+"','"+st+"');");
            Toast.makeText(getApplicationContext(),st,Toast.LENGTH_LONG).show();

这是我尝试选择的代码

  public class CustomDialog extends Activity{
SQLiteDatabase database;
TextView text;
Calendar cal = Calendar.getInstance();
public void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);


    //              database.execSQL("select bdatetime from birthdaytable ");
            // Create custom dialog object
            final Dialog dialog = new Dialog(CustomDialog.this);
            // Include dialog.xml file
            dialog.setContentView(R.layout.dialogwindow);
            // Set dialog title
            dialog.setTitle("Custom Dialog");
            getname();
            // set values for custom dialog components - text, image and button
            text = (TextView) dialog.findViewById(R.id.textView1indialog);


            dialog.show();

            Button declineButton = (Button) dialog.findViewById(R.id.buttonindialog);
            // if decline button is clicked, close the custom dialog
            declineButton.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    // Close dialog
                    dialog.dismiss();
                }
            });



}
public void getname(){
    final String TAG = "CustomDialog";
    int year, month, day, hour, minute;
    year = cal.get(Calendar.YEAR);
    month = cal.get(Calendar.MONTH);
    day = cal.get(Calendar.DAY_OF_MONTH);
    hour = cal.get(Calendar.HOUR_OF_DAY);
    minute = cal.get(Calendar.MINUTE);
    String datetimecheck = year+"-"+month+"-"+day+" "+hour+":"+minute;
    try{
    database = getApplicationContext().openOrCreateDatabase(
            "universalreminder", MODE_PRIVATE, null);
    Toast.makeText(getApplicationContext(), datetimecheck+" ", Toast.LENGTH_LONG).show();
    Cursor cursor = database.rawQuery("select nameofperson from birthdaytable where bdatetime = '"+datetimecheck+"';",null);
            // where bdatetime = '" + datetimecheck+"'",null );
            //("birthdaytable", new String[] {"nameofperson"}, "bdatetime = '" + datetimecheck+"'", null, null, null, null);
    if(cursor.moveToNext()){
        text.setText(cursor.getString(0));

    }
    }catch(Exception e){
        Log.e(TAG, "", e);
        Toast.makeText(getApplicationContext(),e+ " ", Toast.LENGTH_LONG).show();

    }
}
     }

当我打印异常时，它说java.lang.NullPoninterException

我的日志cat条目是

    04-20 11:29:26.690: E/CustomDialog(1142): java.lang.NullPointerException
    04-20 11:29:26.690: E/CustomDialog(1142):   at com.universalremainder.CustomDialog.getname(CustomDialog.java:71)
    04-20 11:29:26.690: E/CustomDialog(1142):   at com.universalremainder.CustomDialog.onCreate(CustomDialog.java:34)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.app.Activity.performCreate(Activity.java:5243)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.app.ActivityThread.access$700(ActivityThread.java:135)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.os.Handler.dispatchMessage(Handler.java:102)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.os.Looper.loop(Looper.java:137)
    04-20 11:29:26.690: E/CustomDialog(1142):   at android.app.ActivityThread.main(ActivityThread.java:4998)
    04-20 11:29:26.690: E/CustomDialog(1142):   at java.lang.reflect.Method.invokeNative(Native Method)
    04-20 11:29:26.690: E/CustomDialog(1142):   at java.lang.reflect.Method.invoke(Method.java:515)
    04-20 11:29:26.690: E/CustomDialog(1142):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
    04-20 11:29:26.690: E/CustomDialog(1142):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
    04-20 11:29:26.690: E/CustomDialog(1142):   at dalvik.system.NativeStart.main(Native Method)

这是第71行的遗嘱

     text.setText(cursor.getString(0));

和第34行

     getname();

Answer 1

这是第71行的遗嘱
text.setText(cursor.getString(0));

text是null。

没有足够的上下文来帮助您准确地初始化它，但可能类似于

text = (TextView)dialog.findViewById(R.id.some_textview_id);

诀窍。

比较当前日期和时间并从数据库中检索数据

1 个答案: