將clickListeners放置在我的代碼中的位置？

Question

該應用程序具有初始消息屏幕，它在第一次運行時顯示，其中從用戶使用datepicker獲取日期，然後從下次直接轉到main.xml。這是我在的onCreate試圖 邏輯（）

if(<date set>) 
{ 
    <open main.xml> 
    <listeners> 
} 
else 
{ 
    <get date from user> 
    <set flag> 
    setContentView(R.layout.initial_msg); 
    <make changes in main.xml according to date> 
} 

的問題是它執行它獲得的日期，但聽衆不加載在第一時間，我認爲這是因爲根本沒有被執行的代碼。當我把偵聽器放在if塊之外時，我得到一個空指針異常。但是，當我關閉應用程序，並再次啓動它的作品，因爲這個時候打開if（）阻止其他（）。

public class pgactivity extends Activity 
{ 
    /** Called when the activity is first created. */ 
    SharedPreferences prefs; 
    Calendar c=Calendar.getInstance(); 
    Calendar tempDate; 
    TextView tv1,tv2; 
    Menu theMenu; 
    LayoutInflater li; 
    int week; 

DatePickerDialog.OnDateSetListener d=new DatePickerDialog.OnDateSetListener() 
{ 
    //@override 
    public void onDateSet(DatePicker view, int year, int monthOfYear,int dayOfMonth) 
    { 
     c.set(Calendar.DATE,dayOfMonth); 
     c.set(Calendar.MONTH,monthOfYear); 
     c.set(Calendar.YEAR,year); 
     if(checkValidity()) 
     { 
      SharedPreferences.Editor editor=prefs.edit(); 
      //set the flag that indicates concieved_date has been added 
      editor.putBoolean("concieved_date", true); 

      int datepref; 
      datepref=c.get(Calendar.DATE); 
      datepref=datepref*1000000; 
      datepref+=c.get(Calendar.MONTH)*10000; 
      datepref+=c.get(Calendar.YEAR); 
      editor.putInt("date",datepref); 
      editor.commit(); 
      setContentView(R.layout.main); 
      setData(); 
     } 
    } 
}; 
/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); 
    //check if concieved date is set from the prefs file "app_data" 
    //if yes open application page else open initial message screen to set the date 
    prefs=getApplicationContext().getSharedPreferences("app_data",Context.MODE_APPEND); 

    if(prefs.getBoolean("concieved_date", false)) 
    { 

     setContentView(R.layout.main); 
     setData(); 

     //Listener for the temp button 'false' 
     //It resets the flag used to indicate if date is set or not. used for testing purpose 
     Button btn1=(Button)findViewById(R.id.setfalse); 
     btn1.setOnClickListener(new View.OnClickListener() 
     {    
      public void onClick(View v) 
      { 
       SharedPreferences.Editor editor=prefs.edit(); 
       editor.putBoolean("concieved_date", false); 
       editor.commit(); 

       TextView tv3=(TextView)findViewById(R.id.test); 
       tv3.setText("entered listener"); 
      } 
    }); 

     //Listener for the weekly_tip text view 
     //when clicked open the layout giving the full description 
     TextView tv2=(TextView)findViewById(R.id.weekly_tip); 
     tv2.setOnClickListener(new View.OnClickListener() 
     { 
      @Override 
      public void onClick(View v) 
      { 
       Intent j=new Intent(pgactivity.this,weekly.class); 
       Bundle b=new Bundle(); 
       b.putInt("cur_week",week); 
       j.putExtras(b); 
       startActivity(j); 
      } 
     }); 

     //Listener for open_remainders button to switch to Remainders page 
     Button btn2=(Button)findViewById(R.id.open_remainders); 
     btn2.setOnClickListener(new View.OnClickListener() 
     { 
      @Override 
      public void onClick(View v) 
      { 
       Intent i=new Intent(pgactivity.this,RemaindersPage.class); 
       startActivity(i); 
      } 
     }); 
    } 
    else 
    { 
     setContentView(R.layout.initial_msg); 

     //click listener for textview 2 
     TextView tv1=(TextView)findViewById(R.id.init_msg); 
     tv1.setOnClickListener(new View.OnClickListener() 
     { 
      public void onClick(View v) 
      { 
       SharedPreferences.Editor editor=prefs.edit(); 
       editor.putBoolean("concieved_date", true); 
       editor.commit(); 

       new DatePickerDialog(pgactivity.this,d, 
         c.get(Calendar.YEAR), 
         c.get(Calendar.MONTH), 
         c.get(Calendar.DAY_OF_MONTH)).show(); 
      } 
     }); 
    } 

} 

void setData() 
{ 
    Long sec,tempSec; 
    int date,day,month,year; 
    date=prefs.getInt("date", 10101010); 
    day=date/1000000; 
    date=date%1000000; 
    month=date/10000; 
    date=date%10000; 
    year=date; 
    c.set(year, month, day); 
    tempDate=c; 

    //insert value to concieved_date textfield 
    tv1=(TextView)findViewById(R.id.concieved_date); 
    tv1.setText(android.text.format.DateFormat.format("dd MMM yyyy", tempDate)); 

    //insert value to delivery_date 
    tv1=(TextView)findViewById(R.id.delivery_date); 
    tempDate.add(Calendar.DATE, 280); 
    tv1.setText(android.text.format.DateFormat.format("dd MMM yyyy", tempDate)); 

    //insert value to days_to_delivery 
    tv1=(TextView)findViewById(R.id.days_to_delivery); 
    c=Calendar.getInstance(); //c has current date 
    sec=tempDate.getTimeInMillis()-c.getTimeInMillis(); //find diff in millisecs 
    sec=sec/86400000; 
    tv1.setText(sec.toString()); 

    //insert value for days_into_pregnancy 
    tv1=(TextView)findViewById(R.id.days_into_pregnancy); 
    tempSec=280-sec; 
    tv1.setText(tempSec.toString()); 

    //insert value for current_week 
    tv1=(TextView)findViewById(R.id.current_week); 
    tempSec=tempSec/7; 
    week=tempSec.intValue(); 
    tv1.setText(tempSec.toString()); 
} 

//user method to check the date validity : check if date entered is a reasonable value 
boolean checkValidity() 
{ 
    Long duration; 
    tempDate=Calendar.getInstance(); //get today's date in c 

    //check if user date is on or before today's date 
    if(tempDate.before(c)) 
    { 
     AlertDialog.Builder ad=new AlertDialog.Builder(this); 
     ad.setMessage("Specified date should be on or before today's date"); 
     ad.setNeutralButton("OK",new DialogInterface.OnClickListener() 
       { 
        public void onClick(DialogInterface arg0,int arg1){} 
       } 
     ); 
     ad.show(); 
     return false; 
    } 
    //check if diff between user date and todays date is more than 280 days 
    duration=tempDate.getTimeInMillis()-c.getTimeInMillis(); 
    duration/=86400000; 
    if(duration>280) 
    { 
     AlertDialog.Builder ad=new AlertDialog.Builder(this); 
     ad.setMessage("Specified date can be atmost 280 days before today's date"); 
     ad.setNeutralButton("OK",new DialogInterface.OnClickListener() 
       { 
        public void onClick(DialogInterface arg0,int arg1){} 
       } 
     ).show(); 
     return false; 
    } 
    return true;  
} 

}

Answer 1

如果你需要你的聽衆在else - 塊，也可以在if - 阻塞之前把這個代碼。

如果執行if或else時佈局更改，則可以使用onClick-attribute in your XML-Layout定義。您可以使用SharedPreferences來保存您的數據。