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그래,이 문제에 대한 해결책을 찾고 있었는데 발견 한 모든 해결책이 작동하지 않습니다. 내 navigationView에서 Sign In 버튼의 텍스트를 변경하려고합니다. 로그인 여부에 따라 Sign In/Sign In을 선택하고 버튼을 누르면 로그인 또는 로그 아웃하도록합니다. 어떤 이유로 내 응용 프로그램이 null 객체 참조 (아래 로그 중 일부)에 치명적인 예외로 인해 충돌합니다. 내가 도대체 뭘 잘못하고있는 겁니까?navigationView setText null 객체 참조에 치명적인 예외가 발생했습니다.
"signInOutText();"가 생성되었습니다. 그래서 나는 다른 장소에 그것을 배치하려고 할 수 있습니다, 그것은 현재 onResume에 있지만 나는 onCreate에서 시도하고 원래 onResume에서 모두했다. 잘만되면 나는 단순한 무엇인가를 간과하고있다. 나는 내 코드 중 일부를 MainActivity.java 아래에서 자른 것이므로 너무 길지 않았지만 모든 것을보아야하는지 알고 싶습니다.
MainActivity.java
public class MainActivity extends AppCompatActivity {
//Defining Variables
private Toolbar toolbar;
private NavigationView navigationView;
private DrawerLayout drawerLayout;
String category;
MenuItem mPreviousMenuItem;
private ProgressDialog mProgressDialog;
String providerId,uid,name,email;
Uri photoUrl;
private static final String TAG = "MainActivity";
// set name of your preferences list
private static String MY_PREFERENCES = "Settings";
String userNameLoad, emailLoad, profileLoad;
TextView usernameTextView, emailTextView, signInTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Initializing Toolbar and setting it as the actionbar
toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
//Initializing NavigationView
navigationView = (NavigationView) findViewById(R.id.navigation_view);
//Setting Navigation View Item Selected Listener to handle the item click of the navigation menu
navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
// This method will trigger on item Click of navigation menu
@Override
public boolean onNavigationItemSelected(MenuItem menuItem) {
menuItem.setCheckable(true);
menuItem.setChecked(true);
if (mPreviousMenuItem != null) {
mPreviousMenuItem.setChecked(false);
}
mPreviousMenuItem = menuItem;
//Closing drawer on item click
drawerLayout.closeDrawers();
//Check to see which item was being clicked and perform appropriate action
switch (menuItem.getItemId()){
//Replacing the main content with fragments
case R.id.home:
//code for button
break;
case R.id.cat1:
//code for button
break;
case R.id.signIn:
signInOut();
break;
default:
break;
}
return true;
}
});
// Initializing Drawer Layout and ActionBarToggle
drawerLayout = (DrawerLayout) findViewById(R.id.drawer);
ActionBarDrawerToggle actionBarDrawerToggle = new ActionBarDrawerToggle(this,drawerLayout,toolbar,R.string.openDrawer, R.string.closeDrawer){
@Override
public void onDrawerClosed(View drawerView) {
// Code here will be triggered once the drawer closes as we dont want anything to happen so we leave this blank
super.onDrawerClosed(drawerView);
}
@Override
public void onDrawerOpened(View drawerView) {
// Code here will be triggered once the drawer open as we don't want anything to happen so we leave this blank
super.onDrawerOpened(drawerView);
}
};
//Setting the actionbarToggle to drawer layout
drawerLayout.setDrawerListener(actionBarDrawerToggle);
//calling sync state is necessary or else your hamburger icon wont show up
actionBarDrawerToggle.syncState();
}
private void signInOutText() {
//Initializing NavigationView
navigationView = (NavigationView) findViewById(R.id.navigation_view);
//Get header xml from navigationView
View header = navigationView.getHeaderView(0);
//Check if user logged in, change sign in sign out button to correct text
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
if (user != null) {
signInTextView = (TextView) header.findViewById(R.id.signIn);
signInTextView.setText(R.string.sign_out);
} else {
signInTextView = (TextView) header.findViewById(R.id.signIn);
signInTextView.setText(R.string.sign_in);
}
}
private void signInOut(){
//TODO add Code .... if logged in logout
Intent intent = new Intent(MainActivity.this, ChooserActivity.class);
startActivity(intent);
finish();
}
public void setActionBarTitle(String title) {
if(getSupportActionBar() != null){
getSupportActionBar().setTitle(title);
}
}
@Override
public void onResume() {
super.onResume();
// Set title
setActionBarTitle(getString(R.string.app_name));
signInOutText();
}
}
로그인
Unable to resume activity {com.test.app/com.test.app.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void
android.widget.TextView.setText(int)' on a null object reference
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4156)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4250)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3361)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(int)' on a null object reference
at com.test.app.MainActivity.signInOutText(MainActivity.java:203)
at com.test.app.MainActivity.onResume(MainActivity.java:307)
at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1286)
at android.app.Activity.performResume(Activity.java:6987)
at android.app.ActivityThread.performResumeActivity(ActivityThread.java:4145)
at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:4250)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3361)
at android.app.ActivityThread.access$1100(ActivityThread.java:222)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1795)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:158)
at android.app.ActivityThread.main(ActivityThread.java:7229)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)
activity_main.xml
01,233 도움을메뉴/drawer.xml는
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
<group android:id="@+id/drawer_group"
android:checkable="true">
<item
android:id="@+id/home"
android:checked="false"
android:icon="@drawable/ic_home_black_24dp"
android:title="@string/home_string" />
</group>
<group android:id="@+id/group_cat"
android:checkable="true">
<item
android:id="@+id/menuCategories"
android:title="@string/categories_string"
android:layout_gravity="bottom">
<menu>
<item
android:id="@+id/cat1"
android:checked="false"
android:icon="@drawable/ic_inbox_black"
android:title="@string/cat1_string" />
</menu>
</item>
</group>
<group android:id="@+id/group_signInOut"
android:checkable="true">
<item
android:id="@+id/signIn"
android:checked="false"
android:icon="@drawable/ic_power_settings_new_black_24dp"
android:title="@string/sign_in" />
</group>
</menu>
감사합니다!