android - 在 MyAdapter.getView 获取 Nullpointer，如何解决？

Question

我想在抽屉导航中添加图片，我把它放在 drawable 文件夹中，大小为 48*48，我的字符串数组字符串数组在 string.xml 中，

我遵循了教程，但最后我所做的更改导致我的应用程序崩溃，我无法弄清楚问题是什么以及如何解决？

这是异常(exception)

01-23 19:32:41.277: E/AndroidRuntime(16889): java.lang.NullPointerException
01-23 19:32:41.277: E/AndroidRuntime(16889):    at com.pKLabs.RgpvDigest.MyAdapter.getView(MainActivity.java:339)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.AbsListView.obtainView(AbsListView.java:2733)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.ListView.makeAndAddView(ListView.java:1811)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.ListView.fillDown(ListView.java:697)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.ListView.fillFromTop(ListView.java:763)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.ListView.layoutChildren(ListView.java:1641)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.AbsListView.onLayout(AbsListView.java:2546)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.View.layout(View.java:15664)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewGroup.layout(ViewGroup.java:4869)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.support.v4.widget.DrawerLayout.onLayout(DrawerLayout.java:914)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.View.layout(View.java:15664)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewGroup.layout(ViewGroup.java:4869)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.View.layout(View.java:15664)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewGroup.layout(ViewGroup.java:4869)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at com.android.internal.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:429)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.View.layout(View.java:15664)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewGroup.layout(ViewGroup.java:4869)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:453)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.widget.FrameLayout.onLayout(FrameLayout.java:388)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.View.layout(View.java:15664)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewGroup.layout(ViewGroup.java:4869)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2246)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1968)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1200)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6401)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:803)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.Choreographer.doCallbacks(Choreographer.java:603)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.Choreographer.doFrame(Choreographer.java:573)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:789)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.os.Handler.handleCallback(Handler.java:733)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.os.Handler.dispatchMessage(Handler.java:95)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.os.Looper.loop(Looper.java:157)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at android.app.ActivityThread.main(ActivityThread.java:5335)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at java.lang.reflect.Method.invokeNative(Native Method)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at java.lang.reflect.Method.invoke(Method.java:515)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
01-23 19:32:41.277: E/AndroidRuntime(16889):    at dalvik.system.NativeStart.main(Native Method)

主 Activity

 public class MainActivity extends ActionBarActivity implements
            OnItemClickListener {
        private DrawerLayout drawerLayout;
        private ListView listView;
        // private String[] navdra;
        private ActionBarDrawerToggle drawerListner;
        private MyAdapter myAdapter;
        Intent shareintent;

        @Override
        protected void onCreate(Bundle savedInstanceState) {

            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            // navdra = getResources().getStringArray(R.array.navdra);

            listView = (ListView) findViewById(R.id.drawerlist);
            myAdapter = new MyAdapter(this);
            // listView.setAdapter(new ArrayAdapter<String>(this,
            // android.R.layout.simple_expandable_list_item_1, navdra));
            listView.setAdapter(myAdapter);
            listView.setOnItemClickListener(this);
            drawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
            drawerListner = new ActionBarDrawerToggle(this, drawerLayout,
                    R.drawable.ic_drawer, R.string.dopen, R.string.dclose);
            /*
             * @Override public void onDrawerOpened(View drawerView) {
             * Toast.makeText(MainActivity.this, "Open", Toast.LENGTH_SHORT)
             * .show(); }
             * 
             * @Override public void onDrawerClosed(View drawerView) {
             * Toast.makeText(MainActivity.this, "Close", Toast.LENGTH_SHORT)
             * .show(); } }
             */

            drawerLayout.setDrawerListener(drawerListner);
            getSupportActionBar().setHomeButtonEnabled(true);
            getActionBar().setDisplayHomeAsUpEnabled(true);

            Button csv = (Button) findViewById(R.id.cs);
            csv.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {

                    Intent intent = new Intent(v.getContext(), Semester.class);
                    startActivityForResult(intent, 0);
                }
            });

            Button cal = (Button) findViewById(R.id.cal);
            cal.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {

                    Intent intent = new Intent(v.getContext(), Calculator.class);
                    startActivityForResult(intent, 0);
                }
            });

            Button iq = (Button) findViewById(R.id.interviewquestion);

            iq.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {

                    Intent intent = new Intent(v.getContext(),
                            InterviewQuestion.class);
                    startActivityForResult(intent, 0);
                }
            });

            Button cg = (Button) findViewById(R.id.program);
            cg.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    Intent intent = new Intent(v.getContext(), Programs.class);
                    startActivityForResult(intent, 0);
                }
            });

            Button abt = (Button) findViewById(R.id.about);
            abt.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    Toast.makeText(getApplicationContext(), "PKlabs!!!",
                            Toast.LENGTH_SHORT).show();
                    // Intent intent = new Intent
                    // (v.getContext(),InterviewQuestion.class);
                    // startActivityForResult(intent,0);
                }
            });

        }

        @Override
        public void onConfigurationChanged(Configuration newConfig) {
            // TODO Auto-generated method stub
            super.onConfigurationChanged(newConfig);
            drawerListner.onConfigurationChanged(newConfig);
        }

        @Override
        protected void onPostCreate(Bundle savedInstanceState) {
            // TODO Auto-generated method stub
            super.onPostCreate(savedInstanceState);
            drawerListner.syncState();
        }

        @Override
        public boolean onCreateOptionsMenu(Menu menu) {

            MenuItem item = menu.add("share"); // your desired title here
            item.setIcon(R.drawable.share_icon); // your desired icon here
            item.setShowAsAction(MenuItem.SHOW_AS_ACTION_ALWAYS);

            item.setOnMenuItemClickListener(new OnMenuItemClickListener() {

                @Override
                public boolean onMenuItemClick(MenuItem item) {
                    shareintent = new Intent(android.content.Intent.ACTION_SEND);
                    shareintent.setType("text/plain");
                    String shareBody = "Here is the share content body";
                    shareintent.putExtra(android.content.Intent.EXTRA_SUBJECT,
                            "Subject Here");
                    shareintent.putExtra(Intent.EXTRA_TEXT, "Hi there");
                    startActivity(Intent.createChooser(shareintent, "Share via"));
                    return true;
                }
            });

            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            int id = item.getItemId();
            if (id == R.id.action_settings) {
                return true;
            }

            if (drawerListner.onOptionsItemSelected(item)) {
                return true;
            }

            return super.onOptionsItemSelected(item);
        }

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

            if (position == 0) {

                Uri uri = Uri
                        .parse("https://2ce74af0d8de8783b91cdd315eeba0340a4b9277.googledrive.com/host/0B2sDUzNeIK0KODB0ZDRMVjFPaFE/Jobs.html");
                Intent intent = new Intent(Intent.ACTION_VIEW, uri);
                startActivity(intent);

            } else if (position == 1) {
                Intent intent = new Intent(this, Careerguid.class);
                startActivityForResult(intent, 0);
            } else if (position == 2) {
                Toast.makeText(this, "Coming Soon!!!", Toast.LENGTH_LONG).show();
            }

            // }
            else if (position == 3) {
                Uri uri = Uri.parse("http://www.google.com");
                Intent intent = new Intent(Intent.ACTION_VIEW, uri);
                startActivity(intent);
            }

            else if (position == 4) {
                Intent intent = new Intent(Intent.ACTION_SEND);
                intent.setType("plain/text");
                final PackageManager pm = getPackageManager();
                final List<ResolveInfo> matches = pm.queryIntentActivities(intent,
                        0);
                ResolveInfo best = null;
                for (final ResolveInfo info : matches)
                    if (info.activityInfo.packageName.endsWith(".gm")
                            || info.activityInfo.name.toLowerCase().contains(
                                    "gmail"))
                        best = info;
                if (best != null)
                    intent.setClassName(best.activityInfo.packageName,
                            best.activityInfo.name);
                intent.putExtra(Intent.EXTRA_EMAIL,
                        new String[] { "laboratorypk@gmail.com" });
                intent.putExtra(Intent.EXTRA_SUBJECT, "Query/Feedback");
                intent.putExtra(Intent.EXTRA_TEXT, "");
                startActivity(Intent.createChooser(intent, ""));
            }
            if (position == 5) {
                Intent intent = new Intent(Intent.ACTION_SEND);
                intent.setType("plain/text");
                final PackageManager pm = getPackageManager();
                final List<ResolveInfo> matches = pm.queryIntentActivities(intent,
                        0);
                ResolveInfo best = null;
                for (final ResolveInfo info : matches)
                    if (info.activityInfo.packageName.endsWith(".gm")
                            || info.activityInfo.name.toLowerCase().contains(
                                    "gmail"))
                        best = info;
                if (best != null)
                    intent.setClassName(best.activityInfo.packageName,
                            best.activityInfo.name);
                intent.putExtra(Intent.EXTRA_EMAIL,
                        new String[] { "laboratorypk@gmail.com" });
                intent.putExtra(Intent.EXTRA_SUBJECT, "PC Games");
                intent.putExtra(Intent.EXTRA_TEXT,
                        "Hey! I need PC Games pls share the List.");
                startActivity(Intent.createChooser(intent, ""));
            }

            drawerLayout.closeDrawers();
            selectItem(position);
        }

        public void selectItem(int position) {
            // TODO Auto-generated method stub
            listView.setItemChecked(position, true);

        }

        public void setTitle(String title) {
            getSupportActionBar().setTitle(title);
        }

        private Toast toast;
        private long lastBackPressTime = 0;

        @Override
        public void onBackPressed() {
            if (this.lastBackPressTime < System.currentTimeMillis() - 4000) {
                toast = Toast.makeText(this, "Press back again to exit",
                        Toast.LENGTH_LONG);
                toast.show();
                this.lastBackPressTime = System.currentTimeMillis();
                drawerLayout.closeDrawers();
            } else {
                if (toast != null) {
                    toast.cancel();
                }
                super.onBackPressed();
            }
        }

    }

    class MyAdapter extends BaseAdapter {
        private Context context;
        String[] navlist;
        int[] images = { R.drawable.job, R.drawable.career, R.drawable.project,
                R.drawable.facebook, R.drawable.mail, R.drawable.games };

        public MyAdapter(Context context) {
            this.context = context;
            navlist = context.getResources().getStringArray(R.array.navdra);
        }

        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return navlist.length;
        }

        @Override
        public Object getItem(int position) {
            // TODO Auto-generated method stub
            return navlist[position];
        }

        @Override
        public long getItemId(int position) {
            // TODO Auto-generated method stub
            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);
                inflater.inflate(R.layout.customrow, parent, false);
            }

            else {
                row = convertView;
            }
            TextView titleTextView = (TextView) row.findViewById(R.id.textView11);
            ImageView titleImageView = (ImageView) row
                    .findViewById(R.id.imageView1);
            titleTextView.setText(navlist[position]);
            titleImageView.setImageResource(images[position]);

            return row;
        }

    }

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

        <ImageView
            android:id="@+id/imageView1"
            android:layout_width="wrap_content"
            android:layout_weight="1"
            android:layout_height="wrap_content"
           />




        <TextView
            android:layout_margin="8dp"
            android:id="@+id/textView11"
            android:layout_width="wrap_content"
            android:layout_weight="1"
            android:layout_height="wrap_content"
            android:gravity="center"
            />

    </LinearLayout>

Answer 1

row为null，将inflate的返回值赋给row变量。

row = inflater.inflate(R.layout.customrow, parent, false);