我有MainActivite。我嘗試將文本設置爲TextView tvUserName。 直到今天一切正常,但現在我無法通過findViewById訪問此變量。此變量的值爲null。無法訪問TextView
也許這是一個錯誤的代碼,它會在系統庫更新後停止正常工作。
我沒有做任何特別的事情,不明白該怎麼做。
Caused by: java.lang.NullPointerException
當我嘗試將文本設置爲這個變量
private static TextView tvUserName;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
currentLocale = getResources().getConfiguration().locale;
LocaleHelper.onCreate(this, currentLocale + "");
setContentView(R.layout.activity_main);
context = this;
fragmentManager = getSupportFragmentManager();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(MainActivity.this);
navigationView.setEnabled(false);
DrawerLayout mDrawer = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawer.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED);
tvUserName = (TextView) findViewById(R.id.navUserName);
//?????
}
--------- activity_main.xml中--------------- ---
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="horizontal"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools" android:id="@+id/drawer_layout"
android:layout_width="match_parent" android:layout_height="match_parent"
android:fitsSystemWindows="true" tools:openDrawer="start">
<include layout="@layout/app_bar_main" android:layout_width="match_parent"
android:layout_height="match_parent" />
<android.support.design.widget.NavigationView android:id="@+id/nav_view"
android:layout_width="wrap_content" android:layout_height="match_parent"
android:layout_gravity="start" android:fitsSystemWindows="true"
app:headerLayout="@layout/nav_header_main" app:menu="@menu/activity_main_drawer"/>
</android.support.v4.widget.DrawerLayout>
</LinearLayout>
------- nav_header_main -----------------
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="wrap_content"
android:paddingLeft="16dp"
android:background="@drawable/side_nav_bar"
android:theme="@style/ThemeOverlay.AppCompat.Dark" android:orientation="vertical"
android:gravity="bottom">
<TextView android:layout_width="match_parent" android:layout_height="wrap_content"
android:paddingTop="@dimen/nav_header_vertical_spacing" android:text="Phone4Pay"
android:textAppearance="@style/TextAppearance.AppCompat.Body1" />
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingTop="2dp"
android:paddingBottom="15dp" >
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
android:id="@+id/navUserName"/>
</LinearLayout>
</LinearLayout>
您使用的是什麼IDE?您嘗試清潔該項目? –
AndroidStudio 1.4,該怎麼做? – koa73