Android:微调器上的getSelectedItem问题 [英] Android: problems with getSelectedItem on a spinner

问题描述

我有一个Spinner，并将选定的项目放在邮件正文中. 这是我的代码:

I have a Spinner, and put the selected item in the body of a mail. this is my code:

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

    Spinner spinnerTaglia = (Spinner) findViewById(R.id.spinnerTaglia);

// Create an ArrayAdapter using the string array and a default spinner layout ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,     R.array.Taglie, android.R.layout.simple_spinner_item);

// Specify the layout to use when the list of choices appears adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinnerTaglia.setPrompt("Seleziona la taglia!");

// Apply the adapter to the spinner
    spinnerTaglia.setAdapter(new NothingSelectedSpinnerAdapter(
            adapter,
            R.layout.contact_spinner_row_nothing_selected,
            // R.layout.contact_spinner_nothing_selected_dropdown, // Optional
            this));

    final String taglia = spinnerTaglia.getSelectedItem().toString();


    Button btnCompilaOrdine = (Button) findViewById(R.id.btnCompilaOrdine);
    btnCompilaOrdine.setOnClickListener(new View.OnClickListener(){

        public void onClick(View arg0) {

    Intent i = new Intent(Intent.ACTION_SEND);
    i.setType("message/rfc822");
    i.putExtra(Intent.EXTRA_EMAIL  , new String[]{"[e-mail]"});
    i.putExtra(Intent.EXTRA_SUBJECT, "MAIL OBJECT");
    i.putExtra(Intent.EXTRA_TEXT   , "Taglia: "+taglia);
    try {
        startActivity(Intent.createChooser(i, "Send mail..."));
    } catch (android.content.ActivityNotFoundException ex) {
        Toast.makeText(Modulo.this, "There are no email clients installed.", Toast.LENGTH_SHORT).show();
    }

    }
    });
}

应用程序在模拟器中正确启动，调试器什么也没有显示(我正在使用Android Studio)，但是当我单击该按钮后，该应用程序崩溃了，Android Studio的调试器显示了在该行中:

The application start correctly in the emulator and the debugger show me nothing (I'm using Android Studio) but when i click on the button that take me in this activity the application crash and the Android Studio's Debugger show me a java.lang.NullPointerException in the row:

最终字符串标签= spinnerTaglia.getSelectedItem().toString();

final String taglia = spinnerTaglia.getSelectedItem().toString();

我该如何解决?

推荐答案

getSelectedItem()如果在微调器上没有选择任何内容，并且调用toString()使应用程序崩溃，则返回null.摆脱

getSelectedItem() returns null if there is nothing selected on your spinner and calling toString() is making your application crash. Get rid of

final String taglia = spinnerTaglia.getSelectedItem().toString();

，然后在您的onClick中完成

and in your onClick do:

if (spinnerTaglia.getSelectedItem() == null) {
      return;
}
String taglia = spinnerTaglia.getSelectedItem().toString();
// the other code

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