求大神指教，本人在初学安卓，遇到了这个：Unfortunately，xxx has stopped！网上大部分说的原因是活动没注册，我明明注册了啊到底是什么回事啊，求大神指教package wsg.myapplication; import android.app.Activity; import android.content.Intent; import android.os.Bundle; import android.view.View; import android.view.Window; import android.widget.Button; import android.widget.EditText; import java.util.Calendar; public class ThirdActivity extends Activity {     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         requestWindowFeature(Window.FEATURE_NO_TITLE);         setContentView(R.layout.third_layout);         Button bt3=(Button)findViewById(R.id.button3);         bt3.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 EditText editText=(EditText)findViewById(R.id.editText);                 EditText editText2=(EditText)findViewById(R.id.editText2);                 EditText editText3=(EditText)findViewById(R.id.editText3);                 int year,month,day;                 int year2,month2,day2;                 int i1,i2,i,week;                 year2=Integer.parseInt(editText.getText().toString());                 month2=Integer.parseInt(editText2.getText().toString());                 day2=Integer.parseInt(editText3.getText().toString()) ;                 i1=dayofyear(year2,month2,day2);                 Calendar c = Calendar.getInstance();                 year = c.get(Calendar.YEAR);                 month = c.get(Calendar.MONTH);                 day = c.get(Calendar.DAY_OF_MONTH);                 i2=dayofyear(year,month,day);                 i=i1-i2;                 week=i/7+1;                 Intent intent1=new Intent(ThirdActivity.this,FirstActivity.class);                 startActivity(intent1);             }         });     }    public int dayofyear(int year,int month,int day){         int dateSum = 0;         for(int i = 1; i < month; i++){             switch(i){                 case 1:                 case 3:                 case 5: case 7: case 8: case 10: case 12:dateSum += 31; break;                 case 4: case 6: case 9: case 11:dateSum += 30; break;                 case 2:                     if(((year % 4 == 0) &&(year % 100 != 0)) || (year % 400 == 0))                         dateSum += 29;                     else dateSum += 28;             }         }         return dateSum = (dateSum + day);     } }这段代码有问题吗？从第三个活动跳到第一个活动程序就崩了