Wie zu beheben NullPointerException in v4.DrawerLayout?
Ich versuche zur Umsetzung einer navigation Schublade, aber für einige Gründe, warum immer bin diesem null-Zeiger-Ausnahme.
Ich haben verbrachte eine Menge Zeit auf, aber vergeblich. Dies ist ein Teil von meinem code. Ich kann nicht verstehen, warum es ist wieder null-pointer-exception.
Brauche ich zum importieren einer Bibliothek oder so???
Vielen Dank im Voraus.
package com.motobeans.productions.aloha;
import android.app.FragmentManager;
import android.os.Bundle;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBarDrawerToggle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import java.util.Locale;
import android.app.Fragment;
import android.support.v7.widget.Toolbar;
import android.widget.ImageView;
import android.widget.ListView;
public class Activity_test extends ActionBarActivity {
private String[] mPlanetTitles;
private DrawerLayout mDrawerLayout;
private ListView mDrawerList;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mTitle;
private CharSequence mDrawerTitle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test);
Toolbar toolbar = (Toolbar) findViewById(R.id.tool_bar);
setSupportActionBar(toolbar);
mPlanetTitles = getResources().getStringArray(R.array.planets_array);
mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
mDrawerList = (ListView) findViewById(R.id.left_drawer);
mTitle = mDrawerTitle = getTitle();
//Set the adapter for the list view
mDrawerList.setAdapter(new ArrayAdapter<String>(this,
R.layout.drawer_list_item, mPlanetTitles));
//Set the list's click listener
mDrawerList.setOnItemClickListener(new DrawerItemClickListener());
mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, toolbar,
R.string.drawer_open, R.string.drawer_close) {
/** Called when a drawer has settled in a completely closed state. */
public void onDrawerClosed(View view) {
super.onDrawerClosed(view);
getActionBar().setTitle(mTitle);
invalidateOptionsMenu(); //creates call to onPrepareOptionsMenu()
}
/** Called when a drawer has settled in a completely open state. */
public void onDrawerOpened(View drawerView) {
super.onDrawerOpened(drawerView);
getActionBar().setTitle(mDrawerTitle);
invalidateOptionsMenu(); //creates call to onPrepareOptionsMenu()
}
};
//Set the drawer toggle as the DrawerListener
mDrawerLayout.setDrawerListener(mDrawerToggle);
}
@Override
public boolean onPrepareOptionsMenu(Menu menu) {
//If the nav drawer is open, hide action items related to the content view
boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
menu.findItem(R.id.action_websearch).setVisible(!drawerOpen);
return super.onPrepareOptionsMenu(menu);
}
Dies ist die logcat-Ausgabe
Process: com.motobeans.productions.aloha, PID: 1330
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.motobeans.productions.aloha/com.motobeans.productions.aloha.Activity_test}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.DrawerLayout.setDrawerListener(android.support.v4.widget.DrawerLayout$DrawerListener)' 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$MethodAndArgsCaller.run(ZygoteInit.java:903)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.widget.DrawerLayout.setDrawerListener(android.support.v4.widget.DrawerLayout$DrawerListener)' on a null object reference
at com.motobeans.productions.aloha.Activity_test.onCreate(Activity_test.java:74)
at android.app.Activity.performCreate(Activity.java:5990)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
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)
InformationsquelleAutor varunkr | 2015-07-19
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Wie es scheint, mDrawerLayout ist null, beim Aufruf
.setDrawerListener()
.Stellen Sie sicher, Sie verwenden die gleiche id für die navigation Schublade in
findViewById(R.id.drawer_layout)
und in der layout-Datei.InformationsquelleAutor GSala
Ähnlichen Problem berichtet wurde über google auf https://code.google.com/p/android/issues/detail?id=202478
Aber nach releas der Android Support Bibliothek, revision 23.2.1 (März 2016) wurde Dieses Problem behoben.
update-Support-Bibliothek zu
Android Support Library to 23.2.1
oder mehr aktualisierte version.InformationsquelleAutor Amit Vaghela
verwenden
getSupportActionBar()
stattgetActionBar()
InformationsquelleAutor Karthik Kompelli