Question

I’m trying to create a list of keys from a SharedPreferences object. Since the user can add new pairs key-value, I need to do it dynamically.

Here is the onCreate function of my activity:

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        LayoutInflater inflater = this.getLayoutInflater();
        LinearLayout layout = (LinearLayout)inflater.inflate(R.layout.activity_show_saved, null);

        this.add_here = (LinearLayout)layout.findViewById(R.id.saved_list);

        // Loading shared preferences
        SharedPreferences sp = this.getSharedPreferences("saved_sequences", MODE_PRIVATE);
        Map<String, ?> kv = sp.getAll();

        int i = 0;
        // Iterating through shared preferences
        for(Map.Entry<String, ?> entry : kv.entrySet()) {
            Toast.makeText(this, entry.getKey(), Toast.LENGTH_SHORT).show();
            TextView to_add = new TextView(this);
            to_add.setText(entry.getKey());
            to_add.setId(i++);
            this.add_here.addView(to_add, LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
        }

        this.setContentView(layout);
    }

Where this.add_here is a class variable declared as private LinearLayout. And here is the xml file which is being inflated:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    xmlns:ads="http://schemas.android.com/apk/lib/com.google.ads"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="@color/background"
    tools:context=".ShowSaved" >

    <com.google.ads.AdView 
        android:id="@+id/adViewTop"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        ads:adUnitId="*****************"
        ads:adSize="SMART_BANNER"
        ads:testDevices="TEST_EMULATOR"
        ads:loadAdOnCreate="true" />

    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent" >

        <LinearLayout
            android:id="@+id/saved_list"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

        </LinearLayout>

    </ScrollView>


</LinearLayout>

Unfortunately I get a blank screen. The problem is in adding the TextViews, since the Toast inside the while correctly shows saved keys as it’s expected to do.

Answer 1

As someone have already stated in the comments, that was not the right way of doing it. Here is the result achieved using a ListView. Have a look.

public class ShowSaved extends Activity implements OnItemClickListener {

    // Layout
    private ListView add_here;
    private TextView empty_view;

    // String Array
    private ArrayList<String> string = new ArrayList<String>();

    // SharedPreferences object and editor
    private SharedPreferences sp;

    // Array adapter for ListView add_here
    private ArrayAdapter<String> saved;

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

        this.setContentView(R.layout.activity_show_saved);

        this.add_here = (ListView)findViewById(R.id.saved_list);
        this.empty_view = (TextView)findViewById(R.id.empty_text);

        // Loading shared preferences and editor
        this.sp = this.getSharedPreferences("saved_sequences", MODE_PRIVATE);

        // Creating the Adapter with all strings in an array
        this.saved = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, android.R.id.text1, string);
        this.saved.setNotifyOnChange(true);

        // Retrieving all pairs in SharedPreferences sp
        Map<String, ?> kv = sp.getAll();

        // Iterating through shared preferences
        for(Map.Entry<String, ?> entry : kv.entrySet()) {       
            saved.add(entry.getKey());
        }

        // Setting Adapter to ListView and empty View
        this.add_here.setEmptyView(empty_view);
        this.add_here.setAdapter(this.saved);

        // Setting Listener for ListView add_here
        this.add_here.setOnItemClickListener(this);
    }

Note: this code won’t compile on its own since it lacks the onItemClick function required for the OnItemClickListener interface.