Question

我正在尝试修改向导中建议的菜单抽屉。在创建抽屉菜单时。它生成以下文件： MainActivity2.java

布局：

1-activity_main2

2-app_bar_main2

3-content_main2

4- nav_header_main2

activity_main2布局如下：

  <?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_main2"
    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_main2"
    app:menu="@menu/activity_main2_drawer" />

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

Nav_Header_main2如下：

     <?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">

<ImageView android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/nav_header_vertical_spacing"
    android:src="@mipmap/hadir_ic"
    android:id="@+id/imageView" />

<TextView android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:paddingTop="@dimen/nav_header_vertical_spacing"
    android:text="Android Studio"
    android:id="@+id/USERNAME"
    android:textAppearance="@style/TextAppearance.AppCompat.Body1"
    />


 </LinearLayout>

My Main2Activiy如下：

   public class Main2Activity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {


private String USERNAME ;
private TextView UserName ;

private Intent intent  ;
Bundle bundle = new Bundle();


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    //UserName = (TextView) findViewById(R.id.USERNAME) ;
    setSupportActionBar(toolbar);
    intent = getIntent();

    USERNAME = intent.getStringExtra("USERNAME");
    //UserName.setText(USERNAME);


    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);
}

@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main2, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    /*if (id == R.id.action_settings) {
        return true;
    }
   */
           return super.onOptionsItemSelected(item);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    int id = item.getItemId();

    if (id == R.id.nav_camara) {
        // Handle the camera action
    } else if (id == R.id.nav_gallery) {

    } else if (id == R.id.nav_slideshow) {

    } else if (id == R.id.nav_manage) {

    } else if (id == R.id.nav_share) {

    } else if (id == R.id.nav_send) {

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}
 }

我想访问此活动的nav_header_main2布局中的USERNAME ViewText。

错误：

     11-28 18:26:23.367 28297-28323/hadirfinalversion.amjad.hadirfinal  W/EGL_emulation: eglSurfaceAttrib not implemented
     11-28 18:26:23.367 28297-28323/hadirfinalversion.amjad.hadirfinal W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xad74cd80, error=EGL_SUCCESS
     11-28 18:26:23.988 28297-28323/hadirfinalversion.amjad.hadirfinal E/Surface: getSlotFromBufferLocked: unknown buffer: 0xabe943e0
     11-28 18:26:24.185 28297-28297/hadirfinalversion.amjad.hadirfinal D/AndroidRuntime: Shutting down VM
     11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime: FATAL EXCEPTION: main
     11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime: Process: hadirfinalversion.amjad.hadirfinal, PID: 28297
     11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime: java.lang.RuntimeException: Unable to start activity ComponentInfo{hadirfinalversion.amjad.hadirfinal/hadirfinalversion.amjad.hadirfinal.Main2Activity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread.-wrap11(ActivityThread.java)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:102)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:148)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5417)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Native Method)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at hadirfinalversion.amjad.hadirfinal.Main2Activity.onCreate(Main2Activity.java:51)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.Activity.performCreate(Activity.java:6237)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread.-wrap11(ActivityThread.java) 
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:102) 
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:148) 
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at android.app.ActivityThread.main(ActivityThread.java:5417) 
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Native Method) 
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
      11-28 18:26:24.186 28297-28297/hadirfinalversion.amjad.hadirfinal E/AndroidRuntime:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

Answer 1

您可以像TextView

中的任何其他观点一样访问MainActivity2.java中的特定main_activity2

TextView userName = (TextView) findViewById(R.id.USERNAME);

然后将其设置为您想要的任何内容，如

userName.setText(R.string.app_name);

自main_activity2 design.widget.NavigationView headerLayout设置为

以来

app:headerLayout="@layout/nav_header_main2"

TextView

并且您的USERNAME nav_header_main2位于MainActivity2布局中，您可以从TextView访问该ID。希望它有所帮助：）

编辑：

好的，我可以在您的代码和我的代码之间发现的唯一区别是我在初始化DrawerLayout和NavigationView后初始化了super.onCreate(savedInstanceState); setContentView(R.layout.activity_main2); Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); //UserName = (TextView) findViewById(R.id.USERNAME) ; REMOVE setSupportActionBar(toolbar); intent = getIntent(); USERNAME = intent.getStringExtra("USERNAME"); //UserName.setText(USERNAME); REMOVE 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); UserName = (TextView) findViewById(R.id.USERNAME) ; // add here UserName.setText(USERNAME); // add here

<table style="width:100%">
    <tr>
        <td class="test1" style=""><div style="background-color:#63BE7B;">227.96</div></td>
        <td class="test2" style=""><div style="background-color:#F8696B;">227.96</div></td>
        <td class="test" style=""><div style="color:blue;">227.96</div></td>
        <td class="test1" style="">227.96</td>
        <td class="test1" style="color:white;"><div style="background-color:#F8696B;">227.96</div></td>
    </tr>
</table>
<button type="button" id="size">Change font size</button>

从Java类访问MenuDrawerNavigator标头

1 个答案: