Я пытаюсь использовать AlertDialog в своем приложении, но для этого требуется ввод данных. Поэтому мне пришлось создать интерфейс и переопределить метод onAttach() в моем пользовательском классе DialogFragment. Как только я правильно настроил все как в классе Dialog, так и в MainActivity, я попытался запустить свое приложение, и оно дало мне исключение во время выполнения, ссылающееся, среди прочего, на нулевой указатель. Я не уверен, почему это так, и мне нужна помощь, пожалуйста, помогите. Ниже вы увидите переопределение моего метода интерфейса, место, где вызывается мой метод .show(), код моего класса DialogFragment и, наконец, мой журнал ошибок.
public class MainActivity extends FragmentActivity implements CDia_exp.NDListener
{
//Integers and Strings for performing calculations
int a;
int b;
static int deci_cnt;
int cnt;
int temp;
Double exp_x;
Double exp;
Double [] num_trk;
String [] op_trk;
String num_hold;
String op_hold;
String del_hold;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//....Lots of other code here.......
//Exp_x Button
opSet[6].setOnClickListener(new View.OnClickListener()
{
public void onClick(View v)
{
if(num_hold != "")
{
cDia_exp.show(getSupportFragmentManager(), "exp_x");
del_hold = tViews[0].getText().toString();
for(int x = num_hold.length() - 1; x >= 0; x--)
{
del_hold = del_hold.substring(0, del_hold.length() - 1);
}
num_hold = exp.toString();
tViews[0].setText(del_hold + num_hold);
return;
}
else
{
return;
}
}
});
}
//Objects and Overrides for calling foreign functions
CTrim cTrim = new CTrim();
CDia cDia = new CDia();
CDia_exp cDia_exp = new CDia_exp();
EditText exp_inp = (EditText) findViewById(R.id.exp_inp);
@Override
public void onDPClick(DialogFragment dialog)
{
exp = Double.parseDouble(num_hold);
exp_x = Double.parseDouble(exp_inp.getText().toString());
for(double x = exp_x; x > 0; x--)
{
exp *= exp;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
Мой пользовательский класс DialogFragment
package com.example.musicalc;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v4.app.DialogFragment;
import android.view.LayoutInflater;
public class CDia_exp extends DialogFragment
{
public interface NDListener
{
public void onDPClick(DialogFragment dialog);
}
NDListener expListener;
@Override
public void onAttach(Activity activity)
{
super.onAttach(activity);
try
{
expListener = (NDListener) activity;
}
catch(ClassCastException e)
{
throw new ClassCastException(activity.toString() + "does not implement NDListener");
}
}
@Override
public Dialog onCreateDialog(Bundle savedInstanceState)
{
AlertDialog.Builder aDia = new AlertDialog.Builder(getActivity());
LayoutInflater inflater = getActivity().getLayoutInflater();
aDia.setView(inflater.inflate(R.layout.calc_dia, null)).setPositiveButton(R.string.diaOk_b, new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int id)
{
expListener.onDPClick(CDia_exp.this);
}
}).setNegativeButton(R.string.cancel_b, new DialogInterface.OnClickListener()
{
@Override
public void onClick(DialogInterface dialog, int id)
{
getDialog().cancel();
}
});
return aDia.create();
}
}
А теперь журнал ошибок
07-20 14:23:43.599: E/Trace(24173): error opening trace file: No such file or directory (2)
07-20 14:23:43.622: D/AndroidRuntime(24173): Shutting down VM
07-20 14:23:43.622: W/dalvikvm(24173): threadid=1: thread exiting with uncaught exception (group=0x4137d2a0)
07-20 14:23:43.653: E/AndroidRuntime(24173): FATAL EXCEPTION: main
07-20 14:23:43.653: E/AndroidRuntime(24173): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.musicalc/com.example.musicalc.MainActivity}: java.lang.NullPointerException
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2060)
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2174)
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.app.ActivityThread.access$700(ActivityThread.java:141)
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1267)
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.os.Handler.dispatchMessage(Handler.java:99)
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.os.Looper.loop(Looper.java:137)
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.app.ActivityThread.main(ActivityThread.java:5059)
07-20 14:23:43.653: E/AndroidRuntime(24173): at java.lang.reflect.Method.invokeNative(Native Method)
07-20 14:23:43.653: E/AndroidRuntime(24173): at java.lang.reflect.Method.invoke(Method.java:511)
07-20 14:23:43.653: E/AndroidRuntime(24173): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
07-20 14:23:43.653: E/AndroidRuntime(24173): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:555)
07-20 14:23:43.653: E/AndroidRuntime(24173): at dalvik.system.NativeStart.main(Native Method)
07-20 14:23:43.653: E/AndroidRuntime(24173): Caused by: java.lang.NullPointerException
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.app.Activity.findViewById(Activity.java:1851)
07-20 14:23:43.653: E/AndroidRuntime(24173): at com.example.musicalc.MainActivity.<init>(MainActivity.java:43)
07-20 14:23:43.653: E/AndroidRuntime(24173): at java.lang.Class.newInstanceImpl(Native Method)
07-20 14:23:43.653: E/AndroidRuntime(24173): at java.lang.Class.newInstance(Class.java:1319)
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
07-20 14:23:43.653: E/AndroidRuntime(24173): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2051)
07-20 14:23:43.653: E/AndroidRuntime(24173): ... 11 more
07-20 14:25:56.817: E/Trace(24308): error opening trace file: No such file or directory (2)
07-20 14:25:56.934: D/AndroidRuntime(24308): Shutting down VM
07-20 14:25:56.934: W/dalvikvm(24308): threadid=1: thread exiting with uncaught exception (group=0x4137d2a0)
07-20 14:25:57.013: E/AndroidRuntime(24308): FATAL EXCEPTION: main
07-20 14:25:57.013: E/AndroidRuntime(24308): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.musicalc/com.example.musicalc.MainActivity}: java.lang.NullPointerException
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2060)
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2174)
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.app.ActivityThread.access$700(ActivityThread.java:141)
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1267)
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.os.Handler.dispatchMessage(Handler.java:99)
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.os.Looper.loop(Looper.java:137)
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.app.ActivityThread.main(ActivityThread.java:5059)
07-20 14:25:57.013: E/AndroidRuntime(24308): at java.lang.reflect.Method.invokeNative(Native Method)
07-20 14:25:57.013: E/AndroidRuntime(24308): at java.lang.reflect.Method.invoke(Method.java:511)
07-20 14:25:57.013: E/AndroidRuntime(24308): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:792)
07-20 14:25:57.013: E/AndroidRuntime(24308): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:555)
07-20 14:25:57.013: E/AndroidRuntime(24308): at dalvik.system.NativeStart.main(Native Method)
07-20 14:25:57.013: E/AndroidRuntime(24308): Caused by: java.lang.NullPointerException
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.app.Activity.findViewById(Activity.java:1851)
07-20 14:25:57.013: E/AndroidRuntime(24308): at com.example.musicalc.MainActivity.<init>(MainActivity.java:803)
07-20 14:25:57.013: E/AndroidRuntime(24308): at java.lang.Class.newInstanceImpl(Native Method)
07-20 14:25:57.013: E/AndroidRuntime(24308): at java.lang.Class.newInstance(Class.java:1319)
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.app.Instrumentation.newActivity(Instrumentation.java:1053)
07-20 14:25:57.013: E/AndroidRuntime(24308): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2051)
07-20 14:25:57.013: E/AndroidRuntime(24308): ... 11 more