导航抽屉中的空指针异常

Question

我目前正在学习如何使用标题旁边的图标创建导航抽屉。 https://www.youtube.com/watch?v=rs4LW3GxOgE

我按照代码进行操作。在他之前的教程中，我正确运行，但当我来到这里时，将图标放在导航中。当我运行我的程序时，我得到了NullpointerException。我的错误的原因是什么？请帮帮我。这是我的代码。

MainActivity.java

public class MainActivity extends ActionBarActivity implements AdapterView.OnItemClickListener {

    private ListView listView;
    private DrawerLayout drawerLayout;
    private ActionBarDrawerToggle drawerListener;
    private MyAdapter myAdapter;

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

        drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
        listView = (ListView) findViewById(R.id.drawerList);
        myAdapter = new MyAdapter(this);
        listView.setAdapter(myAdapter);
        listView.setOnItemClickListener(this);
        drawerListener = new ActionBarDrawerToggle(this, drawerLayout, R.string.navigation_drawer_open, R.string.navigation_drawer_close){
            @Override
            public void onDrawerOpened(View drawerView) {
                Toast.makeText(MainActivity.this, "Drawer Opened", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onDrawerClosed(View drawerView) {
                Toast.makeText(MainActivity.this, "Drawer Closed", Toast.LENGTH_SHORT).show();
            }
        };
        drawerLayout.setDrawerListener(drawerListener);
        getSupportActionBar().setHomeButtonEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if(drawerListener.onOptionsItemSelected(item)){
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

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

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

    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        selectItem(position);
    }

    private void selectItem(int position) {
        listView.setItemChecked(position, true);
    }
    public void setTitle(String title){
        getSupportActionBar().setTitle(title);
    }
}
class MyAdapter extends BaseAdapter {
    private Context context;
    String [] list;
    int[] images = {R.drawable.subok, R.drawable.suboks, R.drawable.subokss};
    public MyAdapter(Context context){
        this.context = context;
        list= context.getResources().getStringArray(R.array.title);
    }
    @Override
    public int getCount() {
        return list.length;
    }

    @Override
    public Object getItem(int position) {
        return list[position];
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View row = null;
        if(convertView == null){
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            row = inflater.inflate(R.layout.custom_row, parent, false);
        }else{
            row = convertView;
        }
        TextView textView = (TextView) row.findViewById(R.id.t1);
        ImageView imageView = (ImageView) row.findViewById(R.id.m1);
        textView.setText(list[position]);
        imageView.setImageResource(images[position]);
        return null;
    }
}

activity_main.xml中

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

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

    <ListView
        android:background="#ff8800"
        android:divider="@null"
        android:id="@+id/drawerList"
        android:layout_width="240dp"
        android:layout_height="match_parent">
    </ListView>
</android.support.v4.widget.DrawerLayout>

custom_row.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/m1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>

    <TextView
        android:layout_margin="8dp"
        android:id="@+id/t1"
        android:layout_width="match_parent"
        android:gravity="center"
        android:layout_height="wrap_content"
        android:text="Large Text"
        android:textAppearance="?android:attr/textAppearanceLarge"/>

</LinearLayout>

的strings.xml

<string-array name="title">
    <item>Driver Details</item>
    <item>List of Drivers</item>
    <item>Maps and Route</item>
</string-array>

这是错误。

08-31 19:14:41.571  24525-24525/com.example.group.taxisafe E/AndroidRuntime﹕ FATAL EXCEPTION: main
    java.lang.NullPointerException
            at android.widget.AbsListView.obtainView(AbsListView.java:2161)
            at android.widget.ListView.makeAndAddView(ListView.java:1831)
            at android.widget.ListView.fillDown(ListView.java:674)
            at android.widget.ListView.fillFromTop(ListView.java:735)
            at android.widget.ListView.layoutChildren(ListView.java:1652)
            at android.widget.AbsListView.onLayout(AbsListView.java:1994)
            at android.view.View.layout(View.java:14008)
            at android.view.ViewGroup.layout(ViewGroup.java:4373)
            at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:907)
            at android.view.View.layout(View.java:14008)
            at android.view.ViewGroup.layout(ViewGroup.java:4373)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
            at android.view.View.layout(View.java:14008)
            at android.view.ViewGroup.layout(ViewGroup.java:4373)
            at android.support.v7.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:493)
            at android.view.View.layout(View.java:14008)
            at android.view.ViewGroup.layout(ViewGroup.java:4373)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
            at android.view.View.layout(View.java:14008)
            at android.view.ViewGroup.layout(ViewGroup.java:4373)
            at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1663)
            at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1521)
            at android.widget.LinearLayout.onLayout(LinearLayout.java:1434)
            at android.view.View.layout(View.java:14008)
            at android.view.ViewGroup.layout(ViewGroup.java:4373)
            at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
            at android.view.View.layout(View.java:14008)
            at android.view.ViewGroup.layout(ViewGroup.java:4373)
            at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1892)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1711)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:989)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4351)
            at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
            at android.view.Choreographer.doCallbacks(Choreographer.java:562)
            at android.view.Choreographer.doFrame(Choreographer.java:532)
            at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
            at android.os.Handler.handleCallback(Handler.java:725)
            at android.os.Handler.dispatchMessage(Handler.java:92)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:5041)
            at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
        at dalvik.system.NativeStart.main(Native Method)