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首先我新建了一个类Title类

public class Title extends Activity {

private TextView tx;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.title)

@Override

public void setTitle(CharSequence title)

((TextView) findViewById(R.id.text_title)).setText(title);

}

}

主要的问题来了,我在MainActivity中

(1)//这样写不会报错闪退

public class Third extends Title{ //让其继承Title类

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main_activity)

setTitle("新标题");

}

(2)//但是下面的写法却出现问题了

public class Third extends Activity{ //让其继承Activity类

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main_activity)

Title title=new Title(); //Title类实例化

title.setTitle("新标题"); //调用方法

}

//错误信息

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.owen.android.myapplication/com.owen.android.myapplication.Third}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference

//得到空指针的错误信息

该怎么解决！！！在线等！！！