NullPointerException with custom font from assets

问题

I'm trying to use custom font in my application, but i got that exception when when run the app:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setTypeface(android.graphics.Typeface)' on a null object reference

I have a working font and it's in the right path and that's my code:

private TextView tv;
private Typeface tf;

    tv = (TextView) findViewById(R.id.wlcText);
    tf = Typeface.createFromAsset(getAssets(), "en_font.ttf");
    tv.setTypeface(tf);

That's my XML:

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

<LinearLayout
    android:id="@+id/mainView"
    android:background="@color/semi_transparent_black"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:padding="@dimen/activity_vertical_margin">

    <TextView
        android:id="@+id/wlcText"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:textColor="@android:color/white"
        android:text="Test"
        android:textSize="25sp" />

</LinearLayout>

回答1:

tv is null. For whatever reason (e.g., failure to call setContentView()), you do not have a widget in the activity that can be found via R.id.wlcText.

来源：https://stackoverflow.com/questions/30549351/nullpointerexception-with-custom-font-from-assets