Question

我在textview中设置文本时遇到空指针异常。 textview位于仪表板活动的导航视图中。

在主要活动中，我试图设置这样的文字：

public class Dashboard extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener {
protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_dashboard);
        TextView StudentNameView = (TextView) navigationView.findViewById(R.id.studentName);
        StudentNameView.setText("Test");
}
}

这是我的信息中心活动的xml

<?xml version="1.0" encoding="utf-8"?>
<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_dashboard" 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_dashboard"
        app:menu="@menu/activity_dashboard_drawer" />

</android.support.v4.widget.DrawerLayout>

我的导航标题菜单是

<?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="@dimen/nav_header_height"
    android:background="@drawable/side_nav_bar"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    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=""
        android:textAppearance="@style/TextAppearance.AppCompat.Body1"
       android:id="@+id/studentName"
        />

    <TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="" android:id="@+id/studentEmail" />

</LinearLayout>

Answer 1

更重要的是使用lib版本v7：23.1.1 使用compile＆＃39; com.android.support：appcompat-v7：23.1.1＆＃39;

在你的代码中写下以下行

import java.util.Arrays;
public class RangeTest {
public static void main(String[] args) {
    int[] a = new int[] {0,1,2,3,4,5,6,7,8,9};
    int[] b = Arrays.copyOfRange(a, Integer.MIN_VALUE, 10);
    // If we'll use Integer.MIN_VALUE+100 instead Integer.MIN_VALUE,
    // OutOfMemoryError will be thrown
    for (int k = 0; k < b.length; k++)
        System.out.print(b[k] + " ");
   }
}

Answer 2

将R.layout。NAME_OF_LAYOUT替换为TextView为

的布局名称

查看navView = LayoutInflater.from（this）.inflate（R.layout.NAME_OF_LAYOUT，null）;

public class Dashboard extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_dashboard);

    View navView = LayoutInflater.from(this).inflate(R.layout.NAME_OF_LAYOUT, null); //navigation header menu layout
    TextView StudentNameView = (TextView)   navView.findViewById(R.id.studentName);
    StudentNameView.setText("Test");

   }
}

编辑：

public class Dashboard extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_dashboard);

    View navView = LayoutInflater.from(this).inflate(R.layout.NAME_OF_LAYOUT, null); //navigation header menu layout
    TextView StudentNameView = (TextView)   navView.findViewById(R.id.studentName);
    StudentNameView.setText("Test");

    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);

    navigationView.addHeaderView(navView);

   }
}

Answer 3

@using (Ajax.BeginForm("Foo1", "FooController", new AjaxOptions { OnSuccess = "HandlePostback" }))
{
    <input type="hidden" name="pageId" id="pageId" />
    <input type="submit" value="Save" id="btnsubmit" />
}


    [HttpPost]
    public ActionResult Foo1(int pageId)
    {
        return View();
    }

Answer 4

在获得NavigationView参考之前，您是否已获取View和TextView的引用？（像这样的东西）

android.support.design.widget.NavigationView navigationView= (NavigationView) findViewById (R.id.nav_view);

View view = navigationView.getHeaderView(0);

Answer 5

做我写的，也许它会帮助你的朋友

NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
    View v = navigationView.getHeaderView(0);
    txt_nama = (TextView) v.findViewById(R.id.tv_nama);
    txt_nama.setText("Halo, " + nama);

如何在NavigationView中的textView中设置文本

5 个答案: