防止edittext为空

Question

我有以下代码,我想用它来确保我的edittext不会为空.因此,如果第一个绘制的0(零)被移除,它必须在焦点改变时恢复为0,这是到目前为止的应用程序:

package your.test.two;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

public class TesttwoActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        EditText edtxt = (EditText)findViewById(R.id.editText1);
        // if I don't add the following the app crashes (obviously):
        edtxt.setText("0");
        edtxt.setOnFocusChangeListener(new View.OnFocusChangeListener() {

            public void onFocusChange(View v, boolean hasFocus) {
                // TODO Auto-generated method stub
                update();   
            }
        });
    }

    public void update() {
        EditText edittxt = (EditText)findViewById(R.id.editText1);
        Integer i = Integer.parseInt(edittxt.getText().toString());
        // If i is an empty value, app crashes so if I erase the zero
        //on the phone and change focus, the app crashes
    }
}

我在update()方法中尝试了以下内容:

String str = edittxt.getText().toString();
if (str == "") {
    edittxt.setText("0");
}

但它不起作用.如何允许edittext永远不会是emty,在空时恢复为零,但在值存在时则不会.我已经确定edittext只能允许数值.

Answer 1

if(str.equals("")){
    edittxt.setText("0");
}

WarrenFaith是对的.请参阅此文章以了解有关此问题的更多信息:Java String.equals与==