在下面的代码中,我在第 9/10 行使用 findViewById() 得到 NullPointerException.
在我的主类中,我只是从这个类中实例化了一个对象,以使用 .getFrom()
In the following code i get a NullPointerException on lines 9/10 with findViewById().
In my main class I just instantiated an object from this class, to use .getFrom()
public class UserInteraction extends Activity {
EditText etFrom;
int from;
EditText etTill;
int till;
public UserInteraction(){
etFrom = (EditText)findViewById(R.id.et_from);
etTill = (EditText)findViewById(R.id.et_till);
}
public int getFrom() {
String s = etFrom.getText().toString();
int i = Integer.parseInt(s);
return i;
}
public int getTill() {
String s = etTill.getText().toString();
int i = Integer.parseInt(s);
return i;
}
是不是我的主类中设置了 contentView ..?可能是什么原因?
Is it that the contentView is set in my main class ..? What could be the cause ?
setContentView
方法应该在调用 findViewById
之前以适当的布局调用之前.它通常在 onCreate(Bundle savedInstance)
方法中调用.
The setContentView
method should be called with appropriate layout before calling findViewById
. It is usually called in onCreate(Bundle savedInstance)
method.
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