我在抽屉里工作，我想在标题中获取一些信息，例如google示例中的图标，名称和标题
我得到的错误是：
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.xbxvxe.rndfy, PID: 4467
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xbxvxe.rndfy/com.xbxvxe.rndfy.activity.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.support.design.widget.NavigationView.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.support.design.widget.NavigationView.findViewById(int)' on a null object reference
at com.xbxvxe.rndfy.activity.MainActivity.onCreate(MainActivity.java:88)
at android.app.Activity.performCreate(Activity.java:7009)
at android.app.Activity.performCreate(Activity.java:7000)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6494)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
我进入这一行：
header = (PercentRelativeLayout) navigationView.findViewById(R.id.navigation_drawer_account_section);
我的主要课程是：
// @BindView(R.id.navigation_drawer_header)
NavigationView navigationView;
PercentRelativeLayout header;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init(savedInstanceState);
//display data of user
txtFullName = (TextView) findViewById(R.id.fullname);
// SqLite database handler
db = new SQLiteHandler(getApplicationContext());
// session manager
session = new SessionManager(getApplicationContext());
if (!session.isLoggedIn()) {
logoutUser();
}
// Fetching user details from SQLite
HashMap<String, String> user = db.getUserDetails();
String nom = user.get("nom");
String prenom = user.get("prenom");
// Navigation header
navigationView = (NavigationView) this.findViewById(R.id.navigation_drawer_header);
header = (PercentRelativeLayout) navigationView.findViewById(R.id.navigation_drawer_account_section);
// Displaying the user details on the screen
TextView txtFullName = (TextView) header.findViewById(R.id.fullname);
txtFullName.setText(nom + " " + prenom);
}
我的主要布局：
<?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"
android:id="@+id/main_activity_DrawerLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true">
<!-- The main content view -->
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<include layout="@layout/toolbar" />
<FrameLayout
android:id="@+id/main_activity_content_frame"
android:layout_width="match_parent"
android:layout_height="match_parent" />
</LinearLayout>
<android.support.design.widget.NavigationView
android:id="@+id/activity_main_navigation_view"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:layout_gravity="start"
android:maxWidth="@dimen/navigation_drawer_max_width"
app:elevation="@dimen/elevation_nav_drawer"
app:headerLayout="@layout/navigation_drawer_header"
app:menu="@menu/navigation_drawer_body" />
</android.support.v4.widget.DrawerLayout>
我的标题布局是这样的：
<?xml version="1.0" encoding="utf-8"?>
<android.support.percent.PercentRelativeLayout 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/navigation_drawer_header"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:context="com.xbxvxe.rndfy.activity.MainActivity">
<FrameLayout
android:id="@+id/navigation_drawer_header_clickable"
android:clickable="true"
android:foreground="@drawable/nav_drawer_header_foreground"
app:layout_aspectRatio="178%"
app:layout_widthPercent="100%">
<ImageView
android:id="@+id/navigation_drawer_user_account_picture_cover"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scaleType="centerCrop"
android:src="@drawable/image_nav_drawer_account_background"
tools:ignore="ContentDescription" />
</FrameLayout>
<LinearLayout
android:id="@+id/navigation_drawer_account_section"
android:paddingBottom="@dimen/spacing_8"
android:paddingStart="@dimen/vertical_keyline_first"
android:paddingEnd="@dimen/vertical_keyline_first"
android:paddingLeft="@dimen/vertical_keyline_first"
android:paddingRight="@dimen/vertical_keyline_first"
android:gravity="bottom"
android:orientation="vertical"
app:layout_aspectRatio="178%"
app:layout_widthPercent="100%">
<ImageView
android:id="@+id/navigation_drawer_user_account_picture_profile"
android:layout_width="@dimen/nav_drawer_profile_image_size"
android:layout_height="@dimen/nav_drawer_profile_image_size"
app:srcCompat="@drawable/ic_account_circle_white_64dp"
tools:ignore="ContentDescription" />
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="@dimen/spacing_56"
android:gravity="center_vertical"
android:orientation="vertical">
<TextView
android:id="@+id/fullname"
android:layout_width="215dp"
android:layout_height="32dp"
android:text="@string/fullname"
android:textSize="13dp" />
<TextView
android:id="@+id/email"
android:layout_width="215dp"
android:layout_height="32dp"
android:text="@string/email"
android:textSize="13dp" />
</LinearLayout>
</LinearLayout>
</android.support.percent.PercentRelativeLayout>
答案 0 :(得分：0)
您定义您的
NavigationView，其ID为activity_main_navigation_view，而不是navigation_drawer_header 因此您需要正确投射ID。
更改
navigationView = (NavigationView) this.findViewById(R.id.activity_main_navigation_view);
代替：
navigationView = (NavigationView) this.findViewById(R.id.navigation_drawer_header);
然后，获取导航标题：
View header = navigationView.inflateHeaderView(R.layout.your_navigation_header);
答案 1 :(得分：0)
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
navigationView.setItemIconTintList(null);
View headerLayout = navigationView.getHeaderView(0);
final TextView user_name = (TextView) headerLayout.findViewById(R.id.user_name);
答案 2 :(得分：0)
更正此问题之后：-
navigationView = (NavigationView) this.findViewById(R.id.activity_main_navigation_view);
删除行：-
header = (PercentRelativeLayout) navigationView.findViewById(R.id.navigation_drawer_account_section);
并添加以下代码：-
View header = navigationView.getHeaderView(0);
// Displaying the user details on the screen
TextView txtFullName = (TextView) header.findViewById(R.id.fullname);
txtFullName.setText(nom + " " + prenom);