java - NullPointerException - edittext.gettext()

Question

我想通过调用 getText().toString() 方法获取“EditText et”的值...但是我的应用程序因 NullPointerException 而崩溃。

可能是因为我在没有创建新 Activity 的情况下将布局“activity_add_question_popup.xml 作为 PopupWindow。不幸的是我是 Android Studio 的新手。谁能告诉我哪里出了问题？

日志:

java.lang.IllegalStateException: Could not execute method of the activity
        at android.view.View$1.onClick(View.java:4007)
        at android.view.View.performClick(View.java:4756)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at    com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
 Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at android.view.View$1.onClick(View.java:4002)
        at android.view.View.performClick(View.java:4756)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
 Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.text.Editable android.widget.EditText.getText()' on a null object reference
        at com.brandsplorer.neverever20.Settings.saveNewQuestion(Settings.java:203)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at android.view.View$1.onClick(View.java:4002)
        at android.view.View.performClick(View.java:4756)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

布局:

<LinearLayout
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceSmall"
        android:text="@string/game_title"
        android:id="@+id/addQuestion_title"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:textSize="20sp"
        android:layout_gravity="left|center_horizontal"
        android:layout_marginLeft="30sp" />

    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/et"
        android:layout_below="@+id/game_title_activity"
        android:layout_centerHorizontal="true"
        android:layout_gravity="center_horizontal|top"
        android:layout_alignTop="@+id/addQuestion_title"
        android:gravity="left|center_vertical"
        android:layout_marginTop="40sp"
        android:hint="Gib deine Frage ein..."
        android:ems="10" />

    <FrameLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:layout_marginTop="50sp">

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="110dp"
            android:layout_height="wrap_content"
            android:text="Speichern"
            android:id="@+id/addQuestionSaveBtn"
            android:layout_alignTop="@+id/newQuestionEdit"
            android:layout_alignParentBottom="true"
            android:layout_alignParentLeft="true"
            android:layout_alignParentStart="true"
            android:layout_gravity="bottom|right"
            android:onClick="saveNewQuestion" />

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="110sp"
            android:layout_height="wrap_content"
            android:text="Zurück"
            android:id="@+id/addQuestionBackBtn"
            android:layout_alignTop="@+id/newQuestionEdit"
            android:layout_alignParentRight="true"
            android:layout_alignParentEnd="true"
            android:layout_gravity="left|bottom"
            android:onClick="closePopup" />
    </FrameLayout>

  </LinearLayout>

</FrameLayout>

类:Settings.java

package com.brandsplorer.neverever20;

public class Settings extends ActionBarActivity {

Button settingsBack, addQuestion;
CheckBox chkBox_sex, chkBox_day, chkBox_job, chkBox_alcohol, chkBox_own;
TextView settingsTitle, category;

EditText editText;

LayoutInflater layoutInflater;
View popupView;
PopupWindow popupWindow;
//KEYS
public static final String MyPREFERENCES = "MyPrefs";
public static final String sex = "sexBox";
public static final String day = "dayBox";
public static final String alc = "alcBox";
public static final String job = "jobBox";
public static final String own = "ownBox";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_settings);

    settingsBack = (Button)findViewById(R.id.settingsBackBtn);
    addQuestion = (Button)findViewById(R.id.addQuestionBtn);

    chkBox_alcohol = (CheckBox)findViewById(R.id.alcBox);
    chkBox_day = (CheckBox)findViewById(R.id.dayBox);
    chkBox_sex = (CheckBox)findViewById(R.id.sexBox);
    chkBox_job = (CheckBox)findViewById(R.id.jobBox);
    chkBox_own = (CheckBox)findViewById(R.id.ownBox);

    settingsTitle = (TextView)findViewById(R.id.settings_title);
    category = (TextView)findViewById(R.id.kategorien);

    //initializing editText
    editText = (EditText)findViewById(R.id.et);

    loadSavedPreferences();
 }

 public void backToMain(View view){
    if(chkBox_job.isChecked()==false && chkBox_sex.isChecked()==false &&   chkBox_day.isChecked()==false && chkBox_alcohol.isChecked()==false && chkBox_own.isChecked()==false){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(false);
        builder.setMessage("Mindestens eine Kategorie muss ausgewählt sein");
        builder.setNegativeButton("OK",new DialogInterface.OnClickListener()     {
            @Override
            public void onClick(DialogInterface dialog, int which) {

                dialog.cancel();
            }
        });
        AlertDialog alert=builder.create();
        alert.show();
    }
    else {
        savePreferences();
        loadSavedPreferences();
        finish();
    }
}

/*
Here I am getting the Popup.
A button in my activity_settings.xml runs this method over an onClick   attribute.
 */
public void addQuestion(View view){
    layoutInflater =   (LayoutInflater)getBaseContext().getSystemService(LAYOUT_INFLATER_SERVICE);
    popupView = layoutInflater.inflate(R.layout.activity_add_question_popup, null);
    popupWindow = new PopupWindow(popupView, ActionBar.LayoutParams.WRAP_CONTENT, ActionBar.LayoutParams.WRAP_CONTENT);
    popupWindow.showAtLocation(addQuestion, Gravity.CENTER, 0, 0);

}
public void closePopup(View view){
    popupWindow.dismiss();
}


@Override
public void onBackPressed() {

    if(chkBox_job.isChecked()==false && chkBox_sex.isChecked()==false && chkBox_day.isChecked()==false && chkBox_alcohol.isChecked()==false && chkBox_own.isChecked()==false){
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setCancelable(false);
        builder.setMessage("Mindestens eine Kategorie muss ausgewählt sein");
        builder.setNegativeButton("OK",new DialogInterface.OnClickListener()     {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.cancel();
            }
        });
        AlertDialog alert=builder.create();
        alert.show();
    }
    else {
        savePreferences();
        loadSavedPreferences();
        finish();
    }

}

public void loadSavedPreferences(){
    SharedPreferences sharedPreferences = getSharedPreferences("CheckboxData", Context.MODE_PRIVATE);

    boolean checkedSex = sharedPreferences.getBoolean(sex, true);
    if(checkedSex){
        chkBox_sex.setChecked(true);
    }
    else{
        chkBox_sex.setChecked(false);
    }

    boolean checkedAlc = sharedPreferences.getBoolean(alc, true);
    if(checkedAlc){
        chkBox_alcohol.setChecked(true);
    }
    else{
        chkBox_alcohol.setChecked(false);
    }
    boolean checkedDay = sharedPreferences.getBoolean(day, true);
    if(checkedDay){
        chkBox_day.setChecked(true);
    }
    else{
        chkBox_day.setChecked(false);
    }
    boolean checkedJob = sharedPreferences.getBoolean(job, true);
    if(checkedJob){
        chkBox_job.setChecked(true);
    }
    else{
        chkBox_job.setChecked(false);
    }
    boolean checkedOwn = sharedPreferences.getBoolean(own, false);
    if(checkedOwn){
        chkBox_own.setChecked(true);
    }
    else{
        chkBox_own.setChecked(false);
    }


}

public void savePreferences(){
    SharedPreferences sharedPreferences = getSharedPreferences("CheckboxData", Context.MODE_PRIVATE);
    Editor editor = sharedPreferences.edit();
    editor.putBoolean(sex, chkBox_sex.isChecked());
    editor.putBoolean(alc, chkBox_alcohol.isChecked());
    editor.putBoolean(job, chkBox_job.isChecked());
    editor.putBoolean(day, chkBox_day.isChecked());
    editor.putBoolean(own, chkBox_own.isChecked());
    editor.commit();
}

public void saveNewQuestion(View view){
    //because of this editText.getText() I get an error.
    //editText is null for some reason...
    String question = editText.getText().toString();
    String file_name = "sentences_own";
    if(question.isEmpty()){
        Toast.makeText(getApplicationContext(), "Frage darf nicht leer sein!", Toast.LENGTH_LONG).show();
    }
    else {
        try {
            FileOutputStream fileOutputStream = openFileOutput(file_name, MODE_APPEND);
            fileOutputStream.write(question.getBytes());
            fileOutputStream.close();
            Toast.makeText(getApplicationContext(), "Frage gespeichert!", Toast.LENGTH_LONG).show();
        }
        catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }
}


}

Answer 1

您得到一个 NullPointerException，因为 EditText 不是在您调用它的 function 中定义的。将 editText = (EditText)findViewById(R.id.et); 移动到您的 saveNewQuestion 函数中。