Android应用程序在启动时因空指针异常而崩溃

时间:2015-05-02 06:12:16

标签: java android nullpointerexception

我是android和java的新手我尝试在教程中创建一个导航抽屉屏幕:

http://www.androidhive.info/2013/11/android-sliding-menu-using-navigation-drawer/

但我得到例外:

--------- beginning of crash
05-02 11:23:49.153    2738-2738/kanix.highrise.com.highrise E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: kanix.highrise.com.highrise, PID: 2738
    java.lang.RuntimeException: Unable to start activity ComponentInfo{kanix.highrise.com.highrise/kanix.highrise.com.highrise.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
            at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
            at android.app.Activity.performCreate(Activity.java:5937)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-02 11:23:49.390    2738-2751/kanix.highrise.com.highrise I/art﹕ Background partial concurrent mark sweep GC freed 360(66KB) AllocSpace objects, 0(0B) LOS objects, 52% free, 465KB/977KB, paused 1.273ms total 220.874ms
05-02 11:26:01.559    2791-2791/kanix.highrise.com.highrise D/AndroidRuntime﹕ Shutting down VM
05-02 11:26:01.715    2791-2791/kanix.highrise.com.highrise E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: kanix.highrise.com.highrise, PID: 2791
    java.lang.RuntimeException: Unable to start activity ComponentInfo{kanix.highrise.com.highrise/kanix.highrise.com.highrise.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
            at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
            at android.app.Activity.performCreate(Activity.java:5937)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-02 11:26:01.772    2791-2803/kanix.highrise.com.highrise I/art﹕ Background partial concurrent mark sweep GC freed 345(52KB) AllocSpace objects, 0(0B) LOS objects, 51% free, 479KB/991KB, paused 43.642ms total 205.582ms
05-02 11:27:33.452    2835-2835/kanix.highrise.com.highrise I/art﹕ Not late-enabling -Xcheck:jni (already on)
05-02 11:27:33.581    2835-2835/kanix.highrise.com.highrise D/AndroidRuntime﹕ Shutting down VM
05-02 11:27:33.581    2835-2835/kanix.highrise.com.highrise E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: kanix.highrise.com.highrise, PID: 2835
    java.lang.RuntimeException: Unable to start activity ComponentInfo{kanix.highrise.com.highrise/kanix.highrise.com.highrise.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
            at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
            at android.app.Activity.performCreate(Activity.java:5937)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
05-02 11:29:36.573    2917-2917/kanix.highrise.com.highrise D/AndroidRuntime﹕ Shutting down VM
05-02 11:29:36.573    2917-2917/kanix.highrise.com.highrise E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: kanix.highrise.com.highrise, PID: 2917
    java.lang.RuntimeException: Unable to start activity ComponentInfo{kanix.highrise.com.highrise/kanix.highrise.com.highrise.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
            at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)
            at android.app.Activity.performCreate(Activity.java:5937)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5221)
            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:899)
           

at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

我复制了代码并且我的代码中有一些活动完美运行但是现在我尝试将导航抽屉活动添加到我的应用程序但它在启动时崩溃了。我的清单文件是这样的:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="kanix.highrise.com.highrise" >

    <application
        android:allowBackup="true"
        android:icon="@mipmap/icon"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".StartActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.VIEW" />
                <action android:name="com.example.intentdemo.LAUNCH" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
            android:name=".LoginActivity"
            android:icon="@mipmap/ic_launcher"
            android:label="loginactivity" >
            <intent-filter>
                <action android:name="android.intent.action.VIEW" />
                <action android:name="com.example.intentdemo.LAUNCH" />

                <category android:name="android.intent.category.DEFAULT" />

                <data android:scheme="http" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Dashboard"
            android:label="@string/title_activity_dashboard" >
            <intent-filter>
                <action android:name="android.intent.action.VIEW" />
                <action android:name="com.example.intentdemo.LAUNCH" />

                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>
        </activity>
        <activity
            android:name=".MainActivity"
            android:label="@string/title_activity_main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>


        </activity>
    </application>

</manifest>

我的主要活动java类是这样的:

package kanix.highrise.com.highrise;



import java.util.ArrayList;

import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.content.res.Configuration;
import android.content.res.TypedArray;
import android.os.Bundle;
import android.support.v4.app.ActionBarDrawerToggle;
import android.support.v4.widget.DrawerLayout;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;

import kanix.highrise.com.highrise.adapter.NavDrawerListAdapter;
import kanix.highrise.com.highrise.model.NavDrawerItem;

public class MainActivity extends Activity {
    private DrawerLayout mDrawerLayout;
    private ListView mDrawerList;
    private ActionBarDrawerToggle mDrawerToggle;

    // nav drawer title
    private CharSequence mDrawerTitle;

    // used to store app title
    private CharSequence mTitle;

    // slide menu items
    private String[] navMenuTitles;
    private TypedArray navMenuIcons;

    private ArrayList<NavDrawerItem> navDrawerItems;
    private NavDrawerListAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mTitle = mDrawerTitle = getTitle();

        // load slide menu items
        navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items);

        // nav drawer icons from resources
        navMenuIcons = getResources()
                .obtainTypedArray(R.array.nav_drawer_icons);

        mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        mDrawerList = (ListView) findViewById(R.id.list_slidermenu);

        navDrawerItems = new ArrayList<NavDrawerItem>();

        // adding nav drawer items to array
        // Home
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1)));
        // Find People
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1)));
        // Photos
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1)));
        // Communities, Will add a counter here
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1), true, "22"));
        // Pages
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1)));
        // What's hot, We  will add a counter here
        navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1), true, "50+"));


        // Recycle the typed array
        navMenuIcons.recycle();

        mDrawerList.setOnItemClickListener(new SlideMenuClickListener());

        // setting the nav drawer list adapter
        adapter = new NavDrawerListAdapter(getApplicationContext(),
                navDrawerItems);
        mDrawerList.setAdapter(adapter);

        // enabling action bar app icon and behaving it as toggle button
        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);

        mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout,
                R.drawable.ic_drawer, //nav menu toggle icon
                R.string.app_name, // nav drawer open - description for accessibility
                R.string.app_name // nav drawer close - description for accessibility
        ) {
            public void onDrawerClosed(View view) {
                getActionBar().setTitle(mTitle);
                // calling onPrepareOptionsMenu() to show action bar icons
                invalidateOptionsMenu();
            }

            public void onDrawerOpened(View drawerView) {
                getActionBar().setTitle(mDrawerTitle);
                // calling onPrepareOptionsMenu() to hide action bar icons
                invalidateOptionsMenu();
            }
        };
        mDrawerLayout.setDrawerListener(mDrawerToggle);

        if (savedInstanceState == null) {
            // on first time display view for first nav item
            displayView(0);
        }
    }

    /**
     * Slide menu item click listener
     * */
    private class SlideMenuClickListener implements
            ListView.OnItemClickListener {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position,
                long id) {
            // display view for selected nav drawer item
            displayView(position);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // toggle nav drawer on selecting action bar app icon/title
        if (mDrawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        // Handle action bar actions click
        switch (item.getItemId()) {
        case R.id.action_settings:
            return true;
        default:
            return super.onOptionsItemSelected(item);
        }
    }

    /* *
     * Called when invalidateOptionsMenu() is triggered
     */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        // if nav drawer is opened, hide the action items
        boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList);
        menu.findItem(R.id.action_settings).setVisible(!drawerOpen);
        return super.onPrepareOptionsMenu(menu);
    }

    /**
     * Diplaying fragment view for selected nav drawer list item
     * */
    private void displayView(int position) {
        // update the main content by replacing fragments
        Fragment fragment = null;
        switch (position) {
        case 0:
            fragment = new HomeFragment();
            break;
        case 1:
            fragment = new FindPeopleFragment();
            break;
        case 2:
            fragment = new PhotosFragment();
            break;
        case 3:
            fragment = new CommunityFragment();
            break;
        case 4:
            fragment = new PagesFragment();
            break;
        case 5:
            fragment = new WhatsHotFragment();
            break;

        default:
            break;
        }

        if (fragment != null) {
            FragmentManager fragmentManager = getFragmentManager();
            fragmentManager.beginTransaction()
                    .replace(R.id.frame_container, fragment).commit();

            // update selected item and title, then close the drawer
            mDrawerList.setItemChecked(position, true);
            mDrawerList.setSelection(position);
            setTitle(navMenuTitles[position]);
            mDrawerLayout.closeDrawer(mDrawerList);
        } else {
            // error in creating fragment
            Log.e("MainActivity", "Error in creating fragment");
        }
    }

    @Override
    public void setTitle(CharSequence title) {
        mTitle = title;
        getActionBar().setTitle(mTitle);
    }

    /**
     * When using the ActionBarDrawerToggle, you must call it during
     * onPostCreate() and onConfigurationChanged()...
     */

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        // Sync the toggle state after onRestoreInstanceState has occurred.
        mDrawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        // Pass any configuration change to the drawer toggls
        mDrawerToggle.onConfigurationChanged(newConfig);
    }

}

3 个答案:

答案 0 :(得分:2)

您可能需要为活动使用操作栏主题。查看first part of this document。您可以在应用程序和活动部分中的清单中为活动指定主题。例如:

        android:theme="@style/Theme.AppCompat.Light"

答案 1 :(得分:1)

应用程序崩溃的主要原因是您正在使用支持操作栏切换操作栏。

尝试将Activity转换为ActionBarActivity并使用SupportActionBar代替操作栏。另外,请不要忘记在AppCompact中使用style.xml主题。

答案 2 :(得分:-1)

您的代码在Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference at kanix.highrise.com.highrise.MainActivity.onCreate(MainActivity.java:88)

上有错误

检查此link以修复错误。