I’m getting this error when running.

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setNavigationMode(int)' on a null object reference

Primary Activity .java

    public class MainActivity <T extends Fragment> extends ActionBarActivity implements ListView.OnItemClickListener
    {  
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

ActionBar actionBar = getSupportActionBar();

actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
    actionBar.setDisplayShowTitleEnabled(false);

ActionBar.Tab tab;
    tab = actionBar.newTab()
            .setText("Categories")
            .setTabListener(new TabListener<CategoriesFragment>(
                    this, "Categories", CategoriesFragment.class));
    actionBar.addTab(tab);

tab = actionBar.newTab()
            .setText("Acceuil")
            .setTabListener(new TabListener<AcceuilFragment>(
                    this, "Acceuil", AcceuilFragment.class));
    actionBar.addTab(tab);
    tab = actionBar.newTab()
            .setText("Topics")
            .setTabListener(new TabListener<TopicsFragment>(
                    this, "Topics", TopicsFragment.class));
    actionBar.addTab(tab);

tab = actionBar.newTab()
            .setText("Tendances")
            .setTabListener(new TabListener<TendancesFragment>(
                    this, "Tendances", TendancesFragment.class));
    actionBar.addTab(tab);

setRef();

Set the custom toolbar
    if (toolbar != null)
    {
        toolbar.setTitle(R.string.app_name);
        setSupportActionBar(toolbar);
    }

drawerToggle = new ActionBarDrawerToggle(
            this,
            drawerLayout,
            toolbar,
            R.string.open,
            R.string.close
    )

{
        public void onDrawerClosed(View view)
        {
            Log.d("MainActivity", "OnDrawerClosed");
            super.onDrawerClosed(view);
            invalidateOptionsMenu();
        }

public void onDrawerOpened(View drawerView)
        {
            Log.d("MainActivity", "OnDrawerOpened");
            super.onDrawerOpened(drawerView);
            invalidateOptionsMenu();
        }
    };

drawerLayout.setDrawerListener(drawerToggle);

getSupportActionBar().setDisplayHomeAsUpEnabled(true);

 use this setting to improve performance if you know that changes
     in content do not change the layout size of the RecyclerView
    mRecyclerView.setHasFixedSize(true);

 use a linear layout manager
    mLayoutManager = new LinearLayoutManager(this);
    mRecyclerView.setLayoutManager(mLayoutManager);
    mRecyclerView.setItemAnimator(new DefaultItemAnimator());

 specify an adapter (see also next example)
    mAdapter = new MyAdapter(myDataset);
    mRecyclerView.setAdapter(mAdapter);

}

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

private void setRef()
{
     create reference to the xml views
    mRecyclerView = (android.support.v7.widget.RecyclerView) findViewById(R.id.my_recycler_view);
    fab = (Button) findViewById(R.id.addButton);
    drawerLayout = (android.support.v4.widget.DrawerLayout) findViewById(R.id.drawer_layout);
    drawerLayout.setStatusBarBackground(R.color.primarydark);

toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
    leftDrawerList = (ListView) findViewById(R.id.list_drawer);

View list_header = getLayoutInflater().inflate(R.layout.drawerlist_header, null);
    leftDrawerList.addHeaderView(list_header);
    navigationDrawerAdapter = new ArrayAdapter<String>(MainActivity.this, android. R.layout.simple_expandable_list_item_1, leftSliderData);
    leftDrawerList.setAdapter(navigationDrawerAdapter);
    leftDrawerList.setOnItemClickListener(this);
}

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id)
{
    Toast.makeText(getApplicationContext(), "Clicked on " + leftSliderData[position - 1], Toast.LENGTH_LONG).show();
}

public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
     Check if the fragment is already initialized
    if (mFragment == null) {
         If not, instantiate and add it to the activity
        mFragment = Fragment.instantiate(mActivity, mClass.getName());
        ft.add(android. R.id.content, mFragment, mTag);
    } else {
         If it exists, simply attach it in order to show it
        ft.attach(mFragment);
    }
}

public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
    if (mFragment != null) {
         Detach the fragment, because another one is being attached
        ft.detach(mFragment);
    }
}

public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
     User selected the already selected tab. Usually do nothing.
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context=". MainActivity">

<!-- Setting this one to true makes the status bar
    to have a non-transparent shitty background -->

<!--
     As the main content view, the view below consumes the entire
     space available using match_parent in both dimensions.
-->

<FrameLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="false">

<include layout="@layout/actionbarlayout"></include>

<include layout="@layout/content_view"></include>

<Button
        android:id="@+id/addButton"
        android:text="+"
        android:textSize="25sp"
        android:textColor="@android:color/white"
        android:textAlignment="center"
        android:layout_marginRight="15dp"
        android:layout_marginBottom="15dp"
        android:background="@drawable/circlebtn"
        android:layout_width="56dp"
        android:layout_height="56dp"
        android:stateListAnimator="@animator/anim"
        android:elevation="4dp"
        style="?android:buttonStyleSmall"
        android:layout_gravity="right|bottom" >
    </Button>

</FrameLayout>

<com.androprogrammer.test.materialapp1.ScrimInsetsFrameLayout
    android:id="@+id/container"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    android:elevation="8dp"
    android:layout_gravity="start"
    app:insetForeground="#4000">

<ListView
        android:id="@+id/list_drawer"
        android:layout_width="@dimen/drawer_width"
        android:layout_height="match_parent"
        android:choiceMode="singleChoice"
        android:background="@android:color/white"
        android:fitsSystemWindows="true">
    </ListView>

</com.androprogrammer.test.materialapp1.ScrimInsetsFrameLayout>
</android.support.v4.widget.DrawerLayout>

Value/styles.xml

<resources>

<!-- Base application theme. -->
<style name="AppTheme" parent="AppTheme.Base"/>

<style name="AppTheme.Base" parent="Theme.AppCompat.Light">
    <item name="colorPrimary">@color/primary</item>
    <item name="colorPrimaryDark">@color/primarydark</item>
    <item name="colorAccent">@color/primary</item>
    <item name="colorControlHighlight">@color/primary</item>
    <item name="android:windowNoTitle">true</item>
    <item name="windowActionBar">false</item>
    <item name="drawerArrowStyle">@style/DrawerArrowStyle</item>
    <item name="windowActionModeOverlay">true</item>

</style>

<style name="DrawerArrowStyle" parent="Widget.AppCompat.DrawerArrowToggle">
    <item name="spinBars">true</item>
    <item name="color">@android:color/white</item>
</style>
</resources>

v21/styles.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
<style name="AppTheme" parent="AppTheme.Base">
    <item name="android:windowDrawsSystemBarBackgrounds">true</item>
    <item name="android:statusBarColor">@android:color/transparent</item>
    <item name="android:windowContentTransitions">true</item>
    <item name="android:windowAllowEnterTransitionOverlap">true</item>
    <item name="android:windowAllowReturnTransitionOverlap">true</item>
    <item name="android:windowSharedElementEnterTransition">@android:transition/move</item>
    <item name="android:windowSharedElementExitTransition">@android:transition/move</item>

</style>
</resources>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.androprogrammer.test.materialapp1" >

<application
    android:allowBackup="true"
    android:icon="@drawable/ic_launcher"
    android:label="@string/app_name"
    android:theme="@style/AppTheme" >
    <activity
        android:name=". MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

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

</manifest>

Please help 🙂

Try changing the parent style

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">

and ActionBarActivity is deprecated, you should use AppCompatActivity

I’m trying to upload images from gallery and camera to the server. When I select an image from the gallery to upload to the server, it works fine. But when I select the image captured by the camera to upload to the server, it crashes and displays an error.

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.net.Uri.getScheme()' on a null object reference

在 OnActivityResult 處。

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

if (requestCode == PICK_IMAGE && resultCode == RESULT_OK
                && null != data) {
            Uri selectedImage = data.getData();
            String[] filePathColumn = { MediaStore.Images.Media.DATA };

Cursor cursor = getContentResolver().query(selectedImage,
                    filePathColumn, null, null, null);
            cursor.moveToFirst();

int columnIndex = cursor.getColumnIndex(filePathColumn[0]);
            String picturePath = cursor.getString(columnIndex);
            cursor.close();

decodeFile(picturePath);
            new ImageUploadTask().execute();
        }else {

Toast.makeText(getApplicationContext(), "User Canceled",
                    Toast.LENGTH_LONG).show();
        }
    }

I get an error on this line of onActivityResult

 Cursor cursor = getContentResolver().query(selectedImage,
                        filePathColumn, null, null, null);
                cursor.moveToFirst();

The method I use to turn on the camera when I click the button.

  loadimage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {

AlertDialog.Builder builder = new AlertDialog.Builder(Add_Info.this);
                builder.setMessage("Select Image From")
                        .setCancelable(true)
                        .setPositiveButton("Camera", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {

Intent intent = new Intent(android.provider.MediaStore.ACTION_IMAGE_CAPTURE);
                                startActivityForResult(intent, CAMERA_REQUEST);
                                mImageCaptureUri = Uri.fromFile(new File(Environment
                                        .getExternalStorageDirectory(), "tmp_avatar_"
                                        + String.valueOf(System.currentTimeMillis())
                                        + ".jpg"));
                            }
                        })
                        .setNegativeButton("Gallery", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                Intent i = new Intent(
                                        Intent.ACTION_PICK,
                                        android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);

startActivityForResult(i, RESULT_LOAD_IMAGE);

}
                        });
                AlertDialog alert = builder.create();
                alert.show();

}
        });

Help me with this. I don’t know how to get this error after I use already in my previous project.

Thanks in advance

I had the same issue with the Camera api and the onActivityResult intent, and I ended up finding that it depends on your android device version, in Android M (Marshmallow – 6.0–6.0. 1) The onActivityResult intent looks like this:

requestCode : 230 resultCode : -1 intent :Intent{dat=file:///storage/emulated/0/Pictures/Rahnama/IMG_20160508_121332_1519065    564.jpg typ=image/jpeg } RESULT_OK : -1

For Android versions lower than Marshmallow:

requestCode : 230 resultCode : -1 intent : Intent { dat=content://media/external/images/media/309 (has extras) } RESULT_OK : -1

I think you have to check android version onActivityResult and android version Marshmallow to get direct files from paths in Uri and Intent:

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (Build.VERSION.SDK_INT == Build.VERSION_CODES. M){
            final Uri data = intent.getData();
            final File file = new File(data.getPath());
             now you can upload your image file
    }else{
            in android version lower than M your method must work
    }

Hope it works for you.

I’m trying to get data about movies from a movie database. Then use the gridview in my layout and I want to display it on my device. I do this by using the ArrayAdapter. I just want to display the name of the movie in the grid.
But I keep getting “java.lang.NullPointerException: Try calling the virtual method ‘java.lang.’ on an empty object reference. String java.lang.Object.toString()'” error.
My code is as follows:

public class MainActivityFragment extends Fragment {
    ArrayAdapter<String> mMovieAdapter;

public MainActivityFragment() {
    }

@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        mMovieAdapter = new ArrayAdapter<String>(getActivity(), R.layout.item_movies, R.id.image_view_movie, new ArrayList<String>());
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        GridView listView = (GridView) rootView.findViewById(R.id.gridview_movies);
        listView.setAdapter(mMovieAdapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                Intent intent = new Intent(getActivity(), DetailActivity.class);
                String forecast = mMovieAdapter.getItem(i);
                intent.putExtra(Intent.EXTRA_TEXT, forecast);
                startActivity(intent);
                /*
                 * Context context = getActivity(); String forecast =
                 * mForecastAdapter.getItem(i); int duration =
                 * Toast.LENGTH_SHORT; Toast.makeText(context, forecast,
                 * duration).show();
                 */
            }
        });
        return rootView;
    }

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }

@Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
         Inflate the menu; this adds items to the action bar if it is present.
        inflater.inflate(R.menu.moviefragment, menu);
    }

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

 TO update weather when activity starts
    @Override
    public void onStart() {
        super.onStart();
        updateMovie();
    }

private void updateMovie() {
        FetchMovieTask movieTask = new FetchMovieTask();
        movieTask.execute();
    }

class FetchMovieTask extends AsyncTask<Void, Void, String[]> {
        private final String LOG_TAG = FetchMovieTask.class.getSimpleName();

@Override
        protected String[] doInBackground(Void... params) {
            /* if(params.length == 0) { return null; } */
             These two need to be declared outside the try/catch
             so that they can be closed in the finally block.
            HttpURLConnection urlConnection = null;
            BufferedReader reader = null;

 Will contain the raw JSON response as a string.
            String movieJsonStr = null;

try {
                 Construct the URL for the OpenWeatherMap query
                 Possible parameters are avaiable at OWM's forecast API page,
                 at
                 http://openweathermap.org/API#forecast
                final String BASE_URL = "http://api.themoviedb.org/3/discover/movie?";
                final String QUERY_PARAM = "sort_by";
                final String KEY_PARAM = "&api_key";
                 Using UriBuilder
                Uri builtUri = Uri.parse(BASE_URL).buildUpon().appendQueryParameter(QUERY_PARAM, "popularity.desc").appendQueryParameter(KEY_PARAM, "c20129fdf73b5df3ab44548ad7f73586"). build();
                URL url = new URL(builtUri.toString());
                 Printing the url in the log
                 Log.v(LOG_TAG, "Built URI " + builtUri.toString());

 Create the request to OpenWeatherMap, and open the connection
                urlConnection = (HttpURLConnection) url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();

 Read the input stream into a String
                InputStream inputStream = urlConnection.getInputStream();
                StringBuffer buffer = new StringBuffer();
                if (inputStream == null) {
                     Nothing to do.
                    return null;
                }
                reader = new BufferedReader(new InputStreamReader(inputStream));

String line;
                while ((line = reader.readLine()) != null) {
                     Since it's JSON, adding a newline isn't necessary (it
                     won't affect parsing)
                     But it does make debugging a *lot* easier if you print
                     out the completed
                     buffer for debugging.
                    buffer.append(line + "\n");
                }

if (buffer.length() == 0) {
                     Stream was empty. No point in parsing.
                    return null;
                }
                movieJsonStr = buffer.toString();

} catch (IOException e) {
                Log.e(LOG_TAG, "Error ", e);
                 If the code didn't successfully get the weather data, there's
                 no point in attemping
                 to parse it.
                return null;
            } finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (final IOException e) {
                        Log.e(LOG_TAG, "Error closing stream", e);
                    }
                }
            }
            try {
                return getMovieDataFromJson(movieJsonStr);
            } catch (JSONException j) {
                Log.e(LOG_TAG, "JSON Error", j);
            }
            return null;
        }

private String[] getMovieDataFromJson(String forecastJsonStr) throws JSONException {
            String title;
            JSONObject movieJson = new JSONObject(forecastJsonStr);
            JSONArray movieArray = movieJson.getJSONArray("results");

String[] resultStrs = new String[100];
            for (int i = 0; i < movieArray.length(); i++) {
                 Get the JSON object representing the day
                JSONObject movie = movieArray.getJSONObject(i);

title = movie.getString("original_title");
                resultStrs[i] = title;
                Log.v(LOG_TAG, resultStrs[i]);
            }

/*
             * for (String s : resultStrs) { Log.v(LOG_TAG, "Forecast entry: " +
             * s); }
             */
            return resultStrs;
        }

@Override
        protected void onPostExecute(String[] strings) {
            super.onPostExecute(strings);
            mMovieAdapter.clear();
            mMovieAdapter.addAll(strings);
        }
    }
}

My error log is:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.Object.toString()' on a null object reference
        at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
        at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
        at android.widget.AbsListView.obtainView(AbsListView.java:2344)
        at android.widget.GridView.makeAndAddView(GridView.java:1433)
        at android.widget.GridView.makeRow(GridView.java:361)
        at android.widget.GridView.fillDown(GridView.java:302)
        at android.widget.GridView.fillGap(GridView.java:262)
        at android.widget.AbsListView.trackMotionScroll(AbsListView.java:4968)
        at android.widget.AbsListView$FlingRunnable.run(AbsListView.java:4512)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
        at android.view.Choreographer.doCallbacks(Choreographer.java:580)
        at android.view.Choreographer.doFrame(Choreographer.java:549)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5312)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)

I suspect this is a bug that Blackbelt also mentioned in the review

String[] resultStrs = new String[100];

It should be

String[] resultStrs = new String[movieArray.length()];

Because you now say to the GridView that you have always 100 movies, but when there are fewer than 100 movies, you will provide an empty element to the GridView