SharedPreferences覆盖值

Question

我正在制作一个应用程序，其中我使用旋转器、EditText和按钮当用户填充文本并单击按钮时，文本将显示在旋转器中，我的问题是我做了所有的工作，但当我将数据添加到旋转器中时，它会覆盖上一个数据，上一个数据不会显示出来

public class MainActivity extends Activity {
    Spinner spinner1;
    Button add;
    EditText subject;
    ArrayAdapter btArrayAdapter;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        spinner1 = (Spinner) findViewById(R.id.spinner);
        ArrayAdapter dataAdapter = new ArrayAdapter(MainActivity.this,android.R.layout.simple_spinner_item, list);
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner1.setAdapter(btArrayAdapter);
        add = (Button) findViewById(R.id.button);
        subject = (EditText) findViewById(R.id.editText);
        spinner1.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> adapter, View v,
                                       int position, long id) {
                String item = adapter.getItemAtPosition(position).toString();

                // Showing selected spinner item
                Toast.makeText(getApplicationContext(),
                        "Selected Subject : " + item, Toast.LENGTH_LONG).show();
            }

            @Override
            public void onNothingSelected(AdapterView<?> arg0) {


            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        SharedPreferences sharedPref =getSharedPreferences("Info", Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = sharedPref.edit();
        editor.putString("Spinner_name",subject.getText().toString());
        editor.commit();
    }

    public void btnClick(View view)
    {
        String content;
        content = subject.getText().toString();
        btArrayAdapter.add(content);
         btArrayAdapter = new ArrayAdapter(MainActivity.this,android.R.layout.simple_spinner_item);
        btArrayAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

    }
}

Answer 1

您可以通过保留单个ArrayAdapter并在单击按钮时更新它来实现该功能。此外，正如Code-Apprentice所说，您可以在preferenceondestory中以set 的形式保存数据。

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Set;

public class MainActivity extends Activity {

    /* Views */
    Spinner spinner;
    Button add;
    EditText subject;

    /* Adapter */
    ArrayAdapter<String> dataAdapter;
    ArrayList<String> list = new ArrayList<String>();

    /* Preference */
    SharedPreferences sharedPref;

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

        /* initializing views */
        spinner = (Spinner) findViewById(R.id.spinner);
        add = (Button) findViewById(R.id.button);
        subject = (EditText) findViewById(R.id.editText);

        /* Get spinner data from preference */
        sharedPref = getSharedPreferences("Info", Context.MODE_PRIVATE);
        Set<String> savedStringSet = sharedPref.getStringSet("SpinnerData", null);
        if (savedStringSet != null) {
            list = new ArrayList<>(savedStringSet);
        }

        /* Setting up spinner */
        dataAdapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_item,
                list.toArray(new String[list.size()]));
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(dataAdapter);
        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {

            @Override
            public void onItemSelected(AdapterView<?> adapter, View v,
                                       int position, long id) {
                String item = adapter.getItemAtPosition(position).toString();

                // Showing selected spinner item
                Toast.makeText(getApplicationContext(),
                        "Selected Subject : " + item, Toast.LENGTH_LONG).show();
            }

            @Override
            public void onNothingSelected(AdapterView<?> arg0) {


            }
        });
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        /* save list in shared preference */
        SharedPreferences.Editor editor = sharedPref.edit();
        editor.putStringSet("SpinnerData", new HashSet<String>(list));
        editor.apply();
    }

    public void btnClick(View view) {
        String content = subject.getText().toString();      // get user entered text.

        /* update spinner */
        list.add(content);          // add to data list..
        dataAdapter = new ArrayAdapter<String>(MainActivity.this, android.R.layout.simple_spinner_item, list);
        dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

        /* set updated spinner */
        spinner.setAdapter(dataAdapter);
    }
}

注意：如果您不想在“”按钮单击时保存空字符串，您可能需要在btnclick方法中对编辑文本值进行一些验证。