如何保存广播组的状态？

Question

我希望用户选中他选中的同一个单选按钮之前在应用程序关闭之前检查过。

这是我的源代码

package com.example.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TextView;
import android.widget.Toast;

import com.example.myapplication.R;

public class MainActivity extends AppCompatActivity {

    RadioGroup radioGroup;
    RadioButton radioButton;
    TextView textView;

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

        radioGroup = findViewById(R.id.radioGroup);
        textView = findViewById(R.id.text_view_selected);

        Button buttonApply = findViewById(R.id.button_apply);
        buttonApply.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int radioId = radioGroup.getCheckedRadioButtonId();

                radioButton = findViewById(radioId);

                textView.setText("Your choice: " + radioButton.getText());
            }
        });
    }

    public void checkButton(View v) {
        int radioId = radioGroup.getCheckedRadioButtonId();

        radioButton = findViewById(radioId);

        Toast.makeText(this, "Selected Radio Button: " + radioButton.getText(),
                Toast.LENGTH_SHORT).show();

    }
}

我希望保存单选按钮状态以备下次应用时使用用过。

Answer 1

你应该看看 sharedPreferences : https://developer.android.com/training/data-storage/shared-preferences

保存您的数据：

SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("myRadio", radioButton.getText());
editor.commit();

检索数据：

SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
String defaultValue = "";
String radioButtonText = sharedPref.getString("myRadio", defaultValue);

现在，您可以这样做：

public class MainActivity extends AppCompatActivity {

   RadioGroup radioGroup;
   RadioButton radioButton;
   TextView textView;
   // Declare SharedPreferences as attributes
   private SharedPreferences sharedPref;
   private SharedPreferences.Editor editor;

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

        radioGroup = findViewById(R.id.radioGroup);
        textView = findViewById(R.id.text_view_selected);
        // Retrieve SharedPreferences 
        sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
        editor = sharedPref.edit();

        Button buttonApply = findViewById(R.id.button_apply);
        buttonApply.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int radioId = radioGroup.getCheckedRadioButtonId();

                radioButton = findViewById(radioId);

                textView.setText("Your choice: " + radioButton.getText());
            }
        });
    }

   @Override
   protected void onResume() {
       int radioIdChecked = -1;
       radioIdChecked = sharedPref.getInt("myRadioChecked", radioIdChecked);
       if (radioIdChecked == -1) {
           // ERROR, don't check anything
           Log.d("TAG", "error: don't check anything");
       }
       else {
           RadioButton radioButton = radioGroup.findViewById(radioIdChecked);
           if (radioButton != null) {
               radioButton.setChecked(true);
           }
       }
    }

   @Override
   protected void onPause() {
        editor.putInt("myRadioChecked", radioGroup.getCheckedRadioButtonId());
        editor.commit();
   }

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