使用共享首选项保存一个数组列表并将其显示在列表视图中

Question

I have two activities. I want to get edittext data from Note.java and put it in listview from MainActivity.java. But I couldn't do it in list format.

Note.java

  public class Note extends FragmentActivity implements


EditText editText,editText2;


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



    editText = (EditText)findViewById(R.id.editText);



SharedPreferences sharedPref = getSharedPreferences("note", Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = sharedPref.edit();

        editor.putString("myKey", editText.getText().toString());
        editor.commit();
  }

MainActivity.java

public class MainActivity extends AppCompatActivity{

ListView listView;
List list;

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

    listView = (ListView) findViewById(R.id.listView);

  SharedPreferences sharedPref = getSharedPreferences("note", Context.MODE_PRIVATE);
    String baslik = sharedPref.getString("myKey",null);

    list = new ArrayList<String>();

    ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this,
            android.R.layout.simple_list_item_1,list);
    list.add(baslik);
    listView.setAdapter(arrayAdapter);
    arrayAdapter.notifyDataSetChanged();

}

Answer 1

SharedPreferences can store only primitive data types.you can not store References types in SharedPreferences .for this case I use Gson library.

Step 1 : Convert list to String

Gson g = new Gson();
String str  = g.toJson(list);

Step 2 : Store String in SharedPreferences

for getting data from SharedPreferences you must deserialize your String like this:

Gson g = new Gson();
Type type = new TypeToken<ArrayList<YourClass>>(){}.getType();
List<YourClass> clazz = g.fromJson(yourString,type);

Answer 2

Suppose you want to save and load List by Sharedprefernces:

public static final String NEWS = "news";
 private SharedPreferences mPreferences;

public void saveNews(List<ResponseNews> news) {
    mPreferences.edit().putString(NEWS, new Gson().toJson(news)).commit();
}

public List<ResponseNews> loadNews() {
    return new Gson().fromJson(mPreferences.getString(NEWS, ""), new TypeToken<List<ResponseNews>>() {
    }.getType());
}