Question

我想知道为什么我的SharedPreference方法不能保存我的数据这是我的代码

保存功能（每次执行我的程序后都会调用此函数）：

public void save(double tamt) {
    SharedPreferences saveamount = getSharedPreferences("TotalAmount" , MODE_PRIVATE);
    SharedPreferences.Editor editor = saveamount.edit();
    editor.clear();
    editor.putString("LastAmount",String.valueOf(tamt));
    editor.apply();
}

我在onCreate()方法中调用了阅读方法：

public void loadAmt() {
    SharedPreferences loadamount = getSharedPreferences("TotalAmount" ,0);
    String amt = loadamount.getString("TotalAmount","");
    if (amt.matches("")){
        return;
    }
    else {
        total = Double.parseDouble(loadamount.getString("TotalAmount" ,"0"));
        et.setText(String.valueOf(total));
    }
}

是否因为保存或阅读方法？
每次退出程序并重新打开后，数据都不会显示。

Answer 1

因为你保存

editor.putString("LastAmount",String.valueOf(tamt));

但你检索

String amt = loadamount.getString("TotalAmount","0");

它们是不同的键你必须检索

String amt = loadamount.getString("LastAmount","");

而且：

total = Double.parseDouble(loadamount.getString("TotalAmount" ,"0"));
et.setText(String.valueOf(total));}

应改为

// USELESS, you already have the string in amt
//total = Double.parseDouble(loadamount.getString("TotalAmount" ,"0"));
et.setText(String.valueOf(amt));}

Answer 2

您的错误是TotalAmount是您的文件名，并且您正在尝试获取一个字符串TotalAmount，该字符串不存在，因为您使用密钥{{1}保存了您的值}。所以只需修改加载方法

LastAmount

Answer 3

在 loadAmt（）方法中，您的密钥不适合获取偏好设置信息，请执行以下操作：

 public void loadAmt()
{
    SharedPreferences loadamount = getSharedPreferences("TotalAmount" ,0);
    String amt = loadamount.getString("LastAmount",""); //change here to LastAmount
    if (amt.matches("")){
        return;
    }
    else {
    total = Double.parseDouble(loadamount.getString("LastAmount" ,"0")); //change here to LastAmount
    et.setText(String.valueOf(total));}

  }

Answer 4

以下是您的代码：

public void save(double tamt) {
            SharedPreferences saveamount = getSharedPreferences("TotalAmount" , Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = saveamount.edit();
            editor.clear();
            editor.putString("LastAmount",String.valueOf(tamt));
            editor.commit();}

我在OnCreate函数中使用了阅读功能

 public void loadAmt()
{
    SharedPreferences loadamount = getSharedPreferences("TotalAmount" ,Context.MODE_PRIVATE);
    String amt = loadamount.getString("LastAmount","");
    if (amt.matches("")){
        return;
    }else {
    total = Double.parseDouble(loadamount.getString("LastAmount" ,"0"));
    et.setText(String.valueOf(total));}

  }

共享首选项不会保存我的数据

4 个答案: