Question

我是Java / Android编程的新手，我正在使用AlertDialog，我希望存储两个字符串并增加一个计数器，然后将其存储在SharedPreferences中。

AlertDialog

    public boolean createEvent(MenuItem item){
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    // Get the layout inflater
    LayoutInflater inflater = this.getLayoutInflater();

    // Inflate and set the layout for the dialog
    // Pass null as the parent view because its going in the dialog layout
    builder.setView(inflater.inflate(R.layout.create_new, null))
            .setTitle("Add A Custom Event")
            // Add action buttons
            .setPositiveButton("Create", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int id) {
                    EditText dateBoxBox = (EditText)findViewById(R.id.dateBox); //error thrown here
                    EditText nameBoxBox = (EditText)findViewById(R.id.nameBox);
                    String nameString = nameBoxBox.getText().toString();
                    String dateString = dateBoxBox.getText().toString();
                    eventAdd(nameString, dateString);
                }
            })
            .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int id) {
                    //do nothing
                }
            })
            .show();
    return true;

}

create_new.xml

<EditText
    android:id="@+id/nameBox"
    android:inputType="textPersonName"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="16dp"
    android:layout_marginLeft="4dp"
    android:layout_marginRight="4dp"
    android:layout_marginBottom="4dp"
    android:hint="Name" />
<EditText
    android:id="@+id/dateBox"
    android:inputType="date"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="4dp"
    android:layout_marginLeft="4dp"
    android:layout_marginRight="4dp"
    android:layout_marginBottom="16dp"
    android:hint="Date"/>

这是我在尝试将这些东西提交给SharedPreferences时调用的函数

eventAdd（）

public void eventAdd(String sName, String sDate) {
    SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
    SharedPreferences.Editor editor = settings.edit();
    int iEventCounter = settings.getInt("eventCounter", 0);
    editor.putInt("eventCounter", iEventCounter+1);
    editor.putString("event1Name", sName);
    editor.putString("event1Date", sDate);

    // Commit the edits!
    editor.commit();
    TextView testTextView = (TextView)findViewById(R.id.section_label);
    testTextView.setText(sName);
}

我可以看到logcat中出现错误的位置，但无法弄清楚它为什么会这样做。

logcat的

FATAL EXCEPTION: main
java.lang.NullPointerException
        at com.cistoran.electriccountdown.MainActivity$2.onClick(MainActivity.java:124)
        at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:5270)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:525)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:974)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:790)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

final View view = inflater.inflate(R.layout.create_new, null)
builder.setView(view);
//and add other settings you've done builder.set...

更改

EditText dateBoxBox = (EditText)findViewById(R.id.dateBox);
EditText nameBoxBox = (EditText)findViewById(R.id.nameBox);

要

EditText dateBoxBox = (EditText)view.findViewById(R.id.dateBox);
EditText nameBoxBox = (EditText)view.findViewById(R.id.nameBox);

java.lang.NullPointerException On Button Click

1 个答案: