当我使用spinner下拉列表或setOnItemSelectedListener时出现错误：
nav_login.xml：
strinarray：
主要活动：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Firebase.setAndroidContext(this);
Firebase rootRef = new Firebase("https://intense-heat-4844.firebaseio.com/property");
navigationView = (NavigationView) findViewById(R.id.nav_view);
View mLoginButton = navigationView.inflateHeaderView(R.layout.nav_header);
mLoginButton.findViewById(R.id.Login);
if (!myBooleanVariable) {
mLoginButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//Calling activity LoginRegister
Intent intent = new Intent(getApplication(),LoginRegister.class);
startActivity(intent);
}
});
}
Intent intent = getIntent();
if (null != intent) {
myBooleanVariable = intent.getBooleanExtra("my_boolean_key",myBooleanVariable);
if (myBooleanVariable) {
navigationView.getHeaderView(0).setVisibility(View.GONE);
navigationView = (NavigationView) findViewById(R.id.nav_view);
View mUserLoggedIn = navigationView.inflateHeaderView(R.layout.nav_header_login);
final Spinner spinner;
spinner = (Spinner) findViewById(R.id.spinner);
spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView例外：
03-01 13:17:47.039 8587-8587/com.example.syedsaadali.myapplication I/System.out﹕ User ID: 4310e794-0b9b-4fad-afd0-e3f73c5f7412,Provider: password
03-01 13:17:47.074 8587-8587/com.example.syedsaadali.myapplication D/AndroidRuntime﹕ Shutting down VM
03-01 13:17:47.074 8587-8587/com.example.syedsaadali.myapplication E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.syedsaadali.myapplication,PID: 8587
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.syedsaadali.myapplication/com.example.syedsaadali.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setOnItemSelectedListener(android.widget.AdapterView$OnItemSelectedListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
at android.app.ActivityThread.access$800(ActivityThread.java:151)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5254)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setOnItemSelectedListener(android.widget.AdapterView$OnItemSelectedListener)' on a null object reference
at com.example.syedsaadali.myapplication.MainActivity.onCreate(MainActivity.java:72)
最佳答案
