Android Data Storage: Organizing Information in Key-Value Pairs

Greetings! I am currently developing an application and facing an issue that requires assistance.

log cat of the error:java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
                                                                               at cqdevelopers.incrediblediet.Fragment3.getAddressKeyValueFile(Fragment3.java:90)
                                                                               at cqdevelopers.incrediblediet.Fragment3.onCreateView(Fragment3.java:25)



<!-- begin snippet: js hide: false -->

<!-- language: lang-js -->

    05-16 02:25:21.711 6498-6498/cqdevelopers.incrediblediet E/AndroidRuntime: FATAL EXCEPTION: main
                                                                               Process: cqdevelopers.incrediblediet, PID: 6498
                                                                               java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference
                                                                                   at cqdevelopers.incrediblediet.Fragment3.getAddressKeyValueFile(Fragment3.java:90)
                                                                                   at cqdevelopers.incrediblediet.Fragment3.onCreateView(Fragment3.java:25)
                                                                                   at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974)
                                                                                   at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067)
                                                                                   at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252)
                                                                                   at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742)
                                                                                   at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617)
                                                                                   at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:570)
                                                                                   at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
                                                                                   at android.support.v4.view.ViewPager.populate(ViewPager.java:1177)
                                                                                   at android.support.v4.view.ViewPager.populate(ViewPager.java:1025)
                                                                                   at android.support.v4.view.ViewPager$3.run(ViewPager.java:254)
                                                                                   at android.support.v4.view.ViewPager.completeScroll(ViewPager.java:1920)
                                                                                   at android.support.v4.view.ViewPager.onInterceptTouchEvent(ViewPager.java:2050)
                                                                                   at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2108)
                                                                                   at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2553)
                                                                                   at android.view.Grou...

Fragment3.java:

public class Fragment3 extends Fragment {
    private EditText editText;
    private TextView textView;
    private Button button;

    @Override
    public View onCreateView(LayoutInflater inflater,
                             @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View v = inflater.inflate(R.layout.fragment3_layout, container, false);

        getAddressKeyValueFile();
        editText = (EditText) v.findViewById(R.id.tvadress);
        textView = (TextView) v.findViewById(R.id.textView);
        button = (Button) v.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String address = null;

                address = editText.getText().toString();
                textView.setText(address);

                setAddressKeyValueFile(address);

            }
        });


        return v;
    }


    private void getAddressKeyValue() {
        SharedPreferences sharedPreferences = this.getActivity().getSharedPreferences("r", Context.MODE_PRIVATE);

        String key = getString(R.string.address);
        String existingAddress = sharedPreferences.getString(key, null);

        if (existingAddress != null) {

            TextView textView = (TextView) getActivity().findViewById(R.id.textView);
            textView.setText(existingAddress);

        }


    }

    private void setAddressKeyValue(String address)
    {
        SharedPreferences sharedPreferences = this.getActivity().getSharedPreferences("d" ,Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();

        String key = getString(R.string.address);
        editor.putString(key,address);

        editor.commit();


    }

    private void getAddressKeyValueFile()
    {
        Context context = getContext().getApplicationContext();

        String fileName = getString(R.string.filename);
        SharedPreferences sharedPreferences = context.getSharedPreferences(fileName,Context.MODE_PRIVATE);

        String key = getString(R.string.address);
        String existingAddress = sharedPreferences.getString(key,null);

        if(existingAddress != null)
        {
            TextView textView = (TextView) getActivity().findViewById(R.id.textView);
            textView.setText(existingAddress);
        }

    }


    private void setAddressKeyValueFile(String address)
    {
        Context context = getContext().getApplicationContext();
        String fileName = getString(R.string.filename);
        SharedPreferences sharedPreferences = context.getSharedPreferences(fileName,Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPreferences.edit();

        String key = getString(R.string.address);
        editor.putString(key, address);

        editor.commit();
    }
}

And fragment3.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="cqdevelopers.incrediblediet.MainActivity$PlaceholderFragment">


    <EditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/tvadress"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="register"
        android:id="@+id/textView2"
        android:layout_marginTop="23dp"
        android:layout_below="@+id/button"
        android:layout_centerHorizontal="true" />

    <Button
        style="?android:attr/buttonStyleSmall"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="New Button"
        android:id="@+id/button"
        android:layout_below="@+id/tvadress"
        android:layout_centerHorizontal="true" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:id="@+id/textView"
        android:layout_marginTop="29dp"
        android:layout_below="@+id/textView2"
        android:layout_centerHorizontal="true" />

</RelativeLayout>

If you could take a look at the exception and guide me where I might have made an error, your valuable assistance would be greatly appreciated. Thank you in advance.

javascriptjavaandroidsharedpreferencestextview

Answer №1

rearrange the getAddressKeyValueFile method

//getAddressKeyValueFile();
editText = (EditText) v.findViewById(R.id.tvadress);
textView = (TextView) v.findViewById(R.id.textView);
getAddressKeyValueFile();

remove the following line:

TextView textView = (TextView) getActivity().findViewById(R.id.textView);

from inside the getAddressKeyValueFile() function

Answer №2

It appears that this particular code snippet 

textView = (TextView) v.findViewById(R.id.textView);
is attempting to retrieve the TextView with the identifier textView from the layout of the activity rather than the fragment.

A suggested modification would be:

if(textView!=null){
    textView.setText(existingAddress);
}

This adjustment should be made in both the getAddressKeyValueFile() and getAddressKeyValue() methods.

Furthermore, within the onCreateView(...) method, ensure that getAddressKeyValueFile(); is only called once the textView object has been properly initialized.

Answer №3

Update the getAddressValueFile function to modify how the strings are retrieved.

private void getAddressKeyValueFile()
    {
        Context context = getContext().getApplicationContext();

        String fileName = getResources.getString(R.string.filename);
        SharedPreferences sharedPreferences = context.getSharedPreferences(fileName,Context.MODE_PRIVATE);

        String key = getResources.getString(R.string.address);
        String existingAddress = sharedPreferences.getString(key,null);

        if(existingAddress != null)
        {
            TextView textView = (TextView) getActivity().findViewById(R.id.textView);
            textView.setText(existingAddress);
        }

    }

Rather than using 

getString(R.string.filename)

use 

getResources.getString(R.string.filename)

Additionally, apply similar changes to the setAddressKeyValue method.

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