Question

我一直在寻找SO以及Google搜索，并决定扩展BaseActivity的活动是在我的项目中集成导航抽屉的最佳方式。每当我启动我的应用程序时，它会立即崩溃。下面我已经包含了我的BaseActivity代码，问题在于这一行：

    drawerLayout.setDrawerListener(drawerToggle);

导致NullPointerException

public class BaseActivity extends Activity
{
    public DrawerLayout drawerLayout;
    public ListView drawerList;
    public String[] layers;
    private ActionBarDrawerToggle drawerToggle;
    Intent twitch = new Intent(this, TwitchActivity.class);
    Intent community = new Intent(this, CommunityActivity.class);
    Intent esports = new Intent(this, ESportsActivity.class);
    Intent home = new Intent(this, MainActivity.class);

    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.id.drawer_layout);
        drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        final ActionBar actionBar = getActionBar();

        drawerToggle = new ActionBarDrawerToggle((Activity) this, drawerLayout, R.drawable.ic_launcher, 0, 0)
        {
            public void onDrawerClosed(View view)
            {
                actionBar.setTitle(R.string.app_name);
            }

            public void onDrawerOpened(View drawerView)
            {
                actionBar.setTitle(R.string.menu);
            }
        };
        drawerLayout.setDrawerListener(drawerToggle);

        actionBar.setDisplayHomeAsUpEnabled(true);
        actionBar.setHomeButtonEnabled(true);


        layers = getResources().getStringArray(R.array.layers);
        drawerList = (ListView) findViewById(R.id.left_drawer);
        drawerList.setAdapter(new ArrayAdapter<String>(this, R.layout.drawer_list_item, android.R.id.text1,
                layers));


        drawerList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> arg0, View arg1, int pos, long arg3) {
                String selected = arg0.getItemAtPosition(pos).toString();
                if(selected.equals("Twitch"))
                    startActivity(twitch);
                if(selected.equals("Community"))
                    startActivity(community);
                if(selected.equals("ESports"))
                    startActivity(esports);
                if(selected.equals("Home"))
                    startActivity(home);
            }
        });
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {

        if (drawerToggle.onOptionsItemSelected(item)) {
            return true;
        }
        return super.onOptionsItemSelected(item);

    }

    @Override
    protected void onPostCreate(Bundle savedInstanceState) {
        super.onPostCreate(savedInstanceState);
        drawerToggle.syncState();
    }

    @Override
    public void onConfigurationChanged(Configuration newConfig) {
        super.onConfigurationChanged(newConfig);
        drawerToggle.onConfigurationChanged(newConfig);
    }
}

我的主要活动

public class MainActivity extends BaseActivity {

private Spinner spinner;
public static String region;
public static String name;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    //.........

我的drawer_layout.xml

<?xml version="1.0" encoding="utf-8"?>

<android.support.v4.widget.DrawerLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/content_frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <!-- Nav Drawer -->
    <ListView android:id="@+id/left_drawer"
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:choiceMode="singleChoice"
        android:divider="@android:color/transparent"
        android:dividerHeight="0dp"
        android:background="#111111"/>
</android.support.v4.widget.DrawerLayout>

完全错误：

04-10 20:17:25.409    4548-4548/edu.appdesign.leaguestats E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: edu.appdesign.leaguestats, PID: 4548
    java.lang.RuntimeException: Unable to start activity ComponentInfo{edu.appdesign.leaguestats/edu.appdesign.leaguestats.MainActivity}: android.content.res.Resources$NotFoundException: Resource ID #0x7f08003d type #0x12 is not valid
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java)
            at android.app.ActivityThread.access$800(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java)
            at android.os.Handler.dispatchMessage(Handler.java)
            at android.os.Looper.loop(Looper.java)
            at android.app.ActivityThread.main(ActivityThread.java)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: android.content.res.Resources$NotFoundException: Resource ID #0x7f08003d type #0x12 is not valid
            at android.content.res.Resources.loadXmlResourceParser(Resources.java)
            at android.content.res.Resources.getLayout(Resources.java)
            at android.view.LayoutInflater.inflate(LayoutInflater.java)
            at android.view.LayoutInflater.inflate(LayoutInflater.java)
            at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java)
            at android.app.Activity.setContentView(Activity.java)
            at edu.appdesign.leaguestats.BaseActivity.onCreate(BaseActivity.java:34)
            at edu.appdesign.leaguestats.MainActivity.onCreate(MainActivity.java:42)
            at android.app.Activity.performCreate(Activity.java)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java)
            at android.app.ActivityThread.access$800(ActivityThread.java)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java)
            at android.os.Handler.dispatchMessage(Handler.java)
            at android.os.Looper.loop(Looper.java)
            at android.app.ActivityThread.main(ActivityThread.java)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

您的onCreate()必须在调用findViewById()之前调用setContentView()设置布局，才能从该布局中获取视图。并确保传递给setContentView()正确的布局资源（它应该是'R.layout.xxxxx'，其中'xxxxx'是XML布局文件的名称，没有'.xml'扩展名）。

扩展BaseActivity导航抽屉的问题

1 个答案: