Android共享首选项崩溃

Question

package com.software.roux.diabcalc;

import android.content.Intent;
import android.content.SharedPreferences;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.PrintWriter;

import static com.software.roux.diabcalc.R.id.bolus;

public class Settings extends AppCompatActivity {

    SharedPreferences mPrefs = getSharedPreferences("label", 0);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_settings);
        setTitle("Insulin Calculator by Ben Roux");

        String bolusString = mPrefs.getString("bolus", "0");
        String corrString = mPrefs.getString("correction", "0");
        String lowString = mPrefs.getString("low", "0");
        String highString = mPrefs.getString("high", "0");

        EditText b1 = (EditText)findViewById(R.id.bolus);
        b1.setText(bolusString);

        EditText b2 = (EditText)findViewById(R.id.correction);
        b2.setText(corrString);

        EditText b3 = (EditText)findViewById(R.id.targetlow);
        b3.setText(lowString);

        EditText b4 = (EditText)findViewById(R.id.targethigh);
        b4.setText(highString);
    }

    public void switchclick(View a) {
        if (a.getId() == R.id.backbutton) {
            Intent myIntent = new Intent(Settings.this, MainActivity.class);
            Settings.this.startActivity(myIntent);
        }
    }

    public void setclick(View b) {
        if (b.getId() == R.id.setter) {

            EditText b1 = (EditText)findViewById(R.id.bolus);
            String bolussave = ""+b1;
            SharedPreferences.Editor mEditor1 = mPrefs.edit();
            mEditor1.putString("bolus", bolussave).commit();

            EditText b2 = (EditText)findViewById(R.id.correction);
            String corrsave = ""+b2;
            SharedPreferences.Editor mEditor2 = mPrefs.edit();
            mEditor2.putString("correction", corrsave).commit();


            EditText b3 = (EditText)findViewById(R.id.targetlow);
            String lowsave = ""+b3;
            SharedPreferences.Editor mEditor3 = mPrefs.edit();
            mEditor3.putString("low", lowsave).commit();


            EditText b4 = (EditText)findViewById(R.id.targethigh);
            String highsave = ""+b4;
            SharedPreferences.Editor mEditor4 = mPrefs.edit();
            mEditor4.putString("high", highsave).commit();


        }
    }
}

更新崩溃日志：

Answer 1

稍后只需初始化sharedpreferencesmprefs。在oncreate方法中。

上下文仅在oncreate方法之后初始化。所以，这必须奏效：

SharedPreferences mPrefs;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_settings);
        setTitle("Insulin Calculator by Ben Roux");
 mPrefs= getSharedPreferences("label", 0);

另一个问题是，在当前代码中，您只是将edittext变量的地址保存在内存中。要检索文本,请使用以下命令：