NullPointerException异常初始化的变量？ [英] NullPointerException on initialized variable?

问题描述

我有TextView的[？]有问题，我TextView的初始化我bcuz想要让它滚动，但我心中已经有误差

I have a problem with TextView [?], i initialized textview bcuz i wanna make it scrollable but i'v got error

    public void onCreate(Bundle savedInstanceState)
{
     super.onCreate(savedInstanceState);
     dc = new DigitalClock(this);
     textViewMesssage = new TextView(this);
     dc = (DigitalClock) findViewById(R.id.digitalClock1);
     textViewMesssage = (TextView) findViewById(R.id.textV);
     textViewMesssage.setMovementMethod(new ScrollingMovementMethod());
     setContentView(R.layout.main);
     addListenerOnButton();

}
public void addListenerOnButton() {
    buttonTest = (Button) findViewById(R.id.button_id);
    buttonTest.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View arg0) {
                                  Calendar c = Calendar.getInstance();
                                  SimpleDateFormat sdf = new SimpleDateFormat("dd:MMMM:yyyy HH:mm:ss a");
                                  String strDate = sdf.format(c.getTime());
        }

    });
}

main.xml中

main.xml

<TextView  
    android:id="@+id/textV"
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:text="MainActivity"
    android:layout_gravity="left"
    android:scrollbars = "vertical"
    />
<Button
    android:id="@+id/button_id"  
    android:layout_width="100dp" 
    android:layout_height="wrap_content" 
    android:text="Hello"
    android:layout_gravity="right"

    />

和误差

20：36：04.407 18740 XXX.X错误AndroidRuntime产生的原因：显示java.lang.NullPointerException
20：36：04.407 18740 XXX.X错误AndroidRuntime在XXX.X.MainActivity.onCreate（MainActivity.java:40）
40线是 textViewMesssage.setMovementMethod（新ScrollingMovementMethod（））;

20:36:04.407 18740 XXX.X ERROR AndroidRuntime Caused by: java.lang.NullPointerException 20:36:04.407 18740 XXX.X ERROR AndroidRuntime at XXX.X.MainActivity.onCreate(MainActivity.java:40) 40 line is textViewMesssage.setMovementMethod(new ScrollingMovementMethod());

我全光照API LVL 8：D抱歉，但我已经老了HTC进行调试

I'm usin API lvl 8 :D sorry but i have old HTC for debugging

推荐答案

的setContentView（R.layout.main）; 您尝试获得来自任何意见之前，必须调用布局XML。

setContentView(R.layout.main); must be called before you try getting any views from the layout XML.

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