Question

我正在创建一个AlertDialog，我可以在SQLite数据库中输入一个新值。如果我在onCreate（）方法中单独调用Insert方法，则该方法有效，但是当我尝试在setPositiveButton onClick侦听器中调用该方法时，它不起作用，它会给我一个java.lang.NullPointerException错误。我试图将值保存到变量并将其传递给方法，它仍然给我相同的错误，我尝试分配值。有谁知道我做错了什么，谢谢。

public void onAddItemClick(View view){
    // get the add_item view
    LayoutInflater layoutInflater = LayoutInflater.from(context);
    View addView = layoutInflater.inflate(R.layout.add_item, null);

    AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(context);

    // Set add_item to alertdialog builder
    alertDialogBuilder.setView(addView);

    final EditText insertValue = (EditText)findViewById(R.id.txtInsert);

    // Set Dialog Message
    alertDialogBuilder.setCancelable(false).setPositiveButton("Add to Database",
            new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int id) {
                    // Will Create a new course and insert into the database
                    insertNewCourse(insertValue.getText().toString());
                }
            })
            .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialogInterface, int id) {
                    dialogInterface.cancel();
                }
            });

    // Create alert dialog
    AlertDialog alertDialog = alertDialogBuilder.create();

    // show it now
    alertDialog.show();
}

这是logcat消息

java.lang.NullPointerException at com.example.gradetracker.app.MainActivity$2.onClick(MainActivity.java:77) at com.android.internal.app.AlertController$ButtonHandler.handleMessage(AlertController.java:166) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:136) at android.app.ActivityThread.main(ActivityThread.java:5017) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:515) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595) at dalvik.system.NativeStart.main(Native Method)

Answer 1

转换为.toString()之前检查null

    if(insertValue.getText() != null) {
        insertNewCourse(insertValue.getText().toString());
    }

尝试将EditText转换为字符串时出现java.lang.NullPointerException

1 个答案: