设置TypeFace NullpointerException

Question

我想在我的TypeFace中添加一个TextView。这是我的Java代码

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        TextView helptitle = (TextView)findViewById(R.id.title_help);
        Typeface typeface = Typeface.createFromAsset(getAssets(), "beyond_the_mountains.ttf");
        helptitle.setTypeface(typeface);
        setContentView(R.layout.activity_help);
}

但是当我运行这个应用程序时，我会发现一个日志猫错误。

Caused by: java.lang.NullPointerException
    at com.example.enxin.crystallise.Help.onCreate(Help.java:15)

有很多种NullPointerException，所以我不知道如何解决这个问题

Answer 1

问题是在设置内容视图之前调用findViewById()。

findViewById()隐式地调用getWindow()，当时它仍然是null。

在setContentView()初始化您的View之前调用

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_help);

    TextView helptitle = (TextView)findViewById(R.id.title_help);
    Typeface typeface = Typeface.createFromAsset(getAssets(), "beyond_the_mountains.ttf");
    helptitle.setTypeface(typeface);
}

Answer 2

 //You have mistaken the order
 setContentView(R.layout.activity_help);    
 TextView helptitle = (TextView)findViewById(R.id.title_help);
 Typeface typeface = Typeface.createFromAsset(getAssets(),    "beyond_the_mountains.ttf");
 helptitle.setTypeface(typeface);