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我想在您创建新的抽屉导航 Activity 时以编程方式更改下拉图像和文本。我试过这个:(假设 currentUser.firstName 不为空。
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
TextView message = (TextView) navigationView.findViewById(R.id.welcomeTextview);
message.setText("Hello " + currentUser.firstName.toString());
ImageView profilePicbtn = (ImageView)navigationView.findViewById(R.id.imageViewProfile);
profilePicbtn.setBackgroundResource(R.drawable.nat_profile);
我执行了“navigationView.findviewById()”，因为 imageView 和 TextView 在 nav_header_dashboard.xml 中。当我运行它时，它会崩溃，如果我删除它运行的 TextView 和 ImageView 声明。我只想更改顶部的图片并在单击下拉菜单时提供问候消息。还假设图像“nat_profile”存在。
这些是我的文件:
仪表盘.java
import android.graphics.Color;
import android.graphics.PorterDuff;
import android.os.Bundle;
import android.support.design.widget.TabLayout;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import java.util.*;
import android.content.Intent;
import android.widget.ImageView;
import android.widget.TextView;
public class Dashboard extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dashboard);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
drawer.setDrawerListener(toggle);
toggle.syncState();
NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
//testing lazaro
//TextView message = (TextView) navigationView.findViewById(R.id.welcomeTextview);
//message.setText("Hello " + currentUser.firstName.toString());
ImageView profilePicbtn = (ImageView)navigationView.findViewById(R.id.imageViewProfile);
profilePicbtn.setBackgroundResource(R.drawable.nat_profile);
activity_dashboard.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>
nav_header_dashboard.xml:
<?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"
android:layout_width="match_parent"
android:layout_height="@dimen/nav_header_height"
android:background="@drawable/side_nav_bar"
android:gravity="bottom"
android:orientation="vertical"
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">
<ImageView
android:id="@+id/imageViewProfile"
android:layout_width="90dp"
android:layout_height="90dp"
android:paddingTop="@dimen/nav_header_vertical_spacing"
app:srcCompat="@drawable/nat_profile" />
<TextView
android:id="@+id/welcomeTextview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:paddingTop="@dimen/nav_header_vertical_spacing"
android:textAppearance="@style/TextAppearance.AppCompat.Body1" />
</LinearLayout>
这是我在 values 文件夹中的 strings.xml:
<resources>
<string name="app_name">Life Management</string>
<string name="title_activity_login">Sign in</string>
<!-- Strings related to login -->
<string name="prompt_email">Email</string>
<string name="prompt_password">Password (optional)</string>
<string name="action_sign_in">Sign in or register</string>
<string name="action_sign_in_short">Sign in</string>
<string name="error_invalid_email">This email address is invalid</string>
<string name="error_invalid_password">This password is too short</string>
<string name="error_incorrect_password">This password is incorrect</string>
<string name="error_field_required">This field is required</string>
<string name="permission_rationale">"Contacts permissions are needed for providing email
completions."
</string>
<string name="title_activity_dashboard">DashboardActivity</string>
<string name="navigation_drawer_open">Open navigation drawer</string>
<string name="navigation_drawer_close">Close navigation drawer</string>
<string name="action_settings">Settings</string>
<string name="action_signout">Sign Out</string>
<string name="action_joy">JOY</string>
<string name="action_passion">PASSION</string>
<string name="action_givingback">GIVING BACK</string>
<string name="section_format">Hello World from section: %1$d</string>
<string name="title_activity_previous_cycle">Life Management</string>
<string name="title_home">Home</string>
<string name="title_dashboard">Dashboard</string>
<string name="title_notifications">Notifications</string>
</resources>
崩溃报告:
11-05 10:37:32.621 2890-2890/com.example.seniorprojectfall.test E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.seniorprojectfall.test, PID: 2890
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.seniorprojectfall.test/com.example.seniorprojectfall.test.Dashboard}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
at **com.example.seniorprojectfall.test.Dashboard.onCreate(Dashboard.java:354)**
at android.app.Activity.performCreate(Activity.java:6975)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6541)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Dashboard.java:354) 是一行:message.setText("Hello "+ currentUser.firstName.toString());