我在Android應用程序中有導航活動。我使用Android Studio的默認模板創建導航抽屜。 以下是在Nav_headder_main.xml導航活動中的Android錯誤
<?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:id="@+id/Name"
android:textAppearance="@style/TextAppearance.AppCompat.Body1"
/>
<TextView android:layout_width="wrap_content" android:layout_height="wrap_content"
android:id="@+id/mailId" />
</LinearLayout>
我想設置從動態的Java文件TextView的價值的代碼。下面是Java代碼:
package example.android.webdroid.loginapplication;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.FragmentTransaction;
import android.view.View;
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 android.widget.TextView;
import example.android.webdroid.loginapplication.Util.User;
import example.android.webdroid.loginapplication.Util.UserDataStore;
import example.android.webdroid.loginapplication.fragments.UpdateProfile;
public class Home extends AppCompatActivity
implements NavigationView.OnNavigationItemSelectedListener {
TextView tvUserName,tvMailId;
UserDataStore userData;
String auth="no";
Toolbar toolbar;
NavigationView navigationView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
// Intent i=getIntent();
/*if(i!=null) {
auth = i.getExtras().getString("auth");
}*/
//To set up MainFragment - Uncomment this
/*MainFragment fragment =new MainFragment();
FragmentTransaction fragTran=getSupportFragmentManager().beginTransaction();
fragTran.replace(R.id.displayPage,fragment);
fragTran.commit();*/
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
fab.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
.setAction("Action", null).show();
}
});
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) findViewById(R.id.nav_view);
navigationView.setNavigationItemSelectedListener(this);
tvUserName=(TextView)navigationView.findViewById(R.id.Name);
tvMailId=(TextView)navigationView.findViewById(R.id.mailId);
userData=new UserDataStore(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.home, 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.
switch (item.getItemId()){
case R.id.nav_contact:
Intent intent = new Intent(Intent.ACTION_DIAL);
intent.setData(Uri.parse("tel:000000"));
startActivity(intent);
break;
case R.id.nav_updateProfile:
UpdateProfile fragment =new UpdateProfile();
FragmentTransaction fragTran=getSupportFragmentManager().beginTransaction();
fragTran.replace(R.id.displayPage, fragment);
fragTran.commit();
break;
case R.id.nav_logout:
userData.ClearUserData();
userData.setUserLoggedIn(false);
startActivity(new Intent(this,Login.class));
break;
default:
break;
}
DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
drawer.closeDrawer(GravityCompat.START);
return true;
}
@Override
protected void onStart() {
super.onStart();
if(authentiateUser()){
displayUserDetails();
}
else {
startActivity(new Intent(this, Login.class));
}
}
public void displayUserDetails(){
User user=userData.getLoggedInUserData();
if(user==null){
System.out.println("LoginAppln_Nag User null=========");
}
else {
System.out.println("LoginAppln_Nag User not null=========" + user.mailId + user.customerId);
tvUserName.setText("Welcome " + user.mailId);
tvMailId.setText(user.name);
}
}
public boolean authentiateUser(){
return userData.getUserLoggedIn();
}
}
以下是代碼activity_home.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_home" 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="false"
app:headerLayout="@layout/nav_header_home" app:menu="@menu/activity_home_drawer" />
</android.support.v4.widget.DrawerLayout>
我得到的NullPointerException異常而TextView的字段設置值。
java.lang.RuntimeException: Unable to start activity ComponentInfo{example.android.webdroid.loginapplication/example.android.webdroid.loginapplication.Home}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
12-29 21:25:48.640 24076-24076/example.android.webdroid.loginapplication E/AndroidRuntime: at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2390
)
我想設置的名稱在導航抽屜的叫頭部分。導航抽屜中的文本視圖僅在拉出時纔可見。我是新來的Android編程和我不知道,有沒有什麼不同的方式來設置文本視圖導航抽屜
'user.name'爲空。在日誌中檢查 – piotrek1543
在你使用的日誌中:'user.customerId'和'user.mailId',但你沒有檢查這個客戶的名字;-) – piotrek1543