使用共享首选项时，Android应用程序崩溃

Question

I'm making a simple android app that saves a user name and an email address using shared preferences. But the problem is that whenever I declare the shared preferences, the app crashes. When I delete the shared preferences code, the app runs fine.

Can somebody see the problem?

Here is my code:

public class PreferencesActivity extends Activity implements OnClickListener {
private TextView textUserName;
private TextView textEmail;
private String userName;
private String email;
public static final String MyPREFERENCES = "MyPrefs" ;

SharedPreferences sharedPref;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    sharedPref = this.getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);
    setContentView(R.layout.activity_preferences);

    textUserName = (TextView)findViewById(R.id.txtUserName);
    userName = textUserName.getText().toString();
    textEmail = (TextView)findViewById(R.id.txtEmail2);
    email = textEmail.getText().toString();

    Button saveButton = (Button)findViewById(R.id.btnSave);
    saveButton.setOnClickListener(this);
}

@Override
public void onClick(View v) {

    Editor editor = sharedPref.edit();

    if(v.getId() == R.id.btnSave) {
        editor.putString(userName, email);
        editor.commit();
    }
}
}

EDIT

Logcat:

10-30 20:41:25.246: E/AndroidRuntime(2797): java.lang.RuntimeException: Unable to start  activity   ComponentInfo{com.example.lab4ex1preferencesactivity/com.example.lab4ex1preferencesactivity.Prefe rencesActivity}: java.lang.ClassCastException: android.widget.EditText cannot be cast to android.widget.Button

Answer 1

You are getting this:

java.lang.ClassCastException: android.widget.EditText cannot be cast to android.widget.Button

So basically it's saying your casting an EditText to a Button . It would be in the following line:

Button saveButton = (Button)findViewById(R.id.btnSave);

So unless you're using the wrong ID and btnSave actually refers to an EditText field, it's a glitch. Most likely it's a glitch in Eclipse. Here's how to usually fix (it's common):

Go to the tabs at the top and select Project > Clean... and clean your project.

Answer 2

The error message says: "You cast the TextBox to Button". Are you gave the correct names for widgets? Check it!