Android Null Pointer的问题

Question

我在主activity里面设置了有三个tab的切换卡，在第三个tab里面是个ListView，单击ListView会弹出时间选择对话框
public void onSetWarn(){
LayoutInflater factoryInflater = LayoutInflater.from(MainActivity.this);
final View dialogView = factoryInflater.inflate(R.layout.dialog, null);
AlertDialog dialog = new AlertDialog.Builder(MainActivity.this).setTitle("设置")
.setView(dialogView)
.setPositiveButton("确定", new DialogInterface.OnClickListener() {

public void onClick(DialogInterface dialog, int which) {
Toast.makeText(getApplicationContext(), "设置成功！", Toast.LENGTH_SHORT).show();
}
})
.setNegativeButton("取消", new DialogInterface.OnClickListener() {

public void onClick(DialogInterface dialog, int which) {

}
}).create();
/*
timePicker = (TimePicker) this.findViewById(R.id.TimePicker1);
timePicker.setIs24HourView(true);
*/
dialog.show();
}我到底该把timePicker = (TimePicker) this.findViewById(R.id.TimePicker1);
timePicker.setIs24HourView(true);
这段代码放在哪呢？ 我试了好几个地方都是NULL pointer错误

Answer 1

dialog.xml文件如下：<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >
    <TextView 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="提醒时间"
        />
    <TimePicker 
        android:id="@+id/TimePicker1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
      <TextView 
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="提醒方式"
        />
      <LinearLayout 
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          >
      <CheckBox 
          android:id="@+id/checkBox1"
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:text="铃声"
          />
      <CheckBox 
          android:id="@+id/checkBox2"
          android:layout_width="fill_parent"
          android:layout_height="wrap_content"
          android:text="震动"
          />
      </LinearLayout>
</LinearLayout>

Answer 2

timePicker = (TimePicker) this.findViewById(R.id.TimePicker1);
this换成dialogView，