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，并将所选项目放入邮件正文中.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，调试器不显示任何内容(我使用的是 Android Studio)但是当我单击将我带入此活动的按钮时，应用程序崩溃，Android Studio 的调试器向我显示 java.lang.NullPointerException 在行中:

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:

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

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

我该如何解决这个问题?

how can i fix this?

推荐答案

getSelectedItem() 如果您的微调器上没有选择任何内容并且调用 toString() ，则返回 null使您的应用程序崩溃.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();

并在您的 onClick 中执行:

and in your onClick do:

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

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