在特定行上写入属性文件

Question

Please let me know if this question has been asked before.

The Goal

In my android application when a user launches the App it loads the Login.class first. This class checks to see if a local file (in the included file path of the App) called app_prefs.prop exists (which it does) and then it checks the following fields structured like so:

username=
user_hash=
saved_email=
email_hash=

Those fields are blank by default just like so. I am reading them using the following code:

public static String getConfigValue(Context context, String name) {
    Resources resources = context.getResources();
    String TAG = "Retrieve";
    try {
        InputStream rawResource = resources.openRawResource(R.raw.app_prefs);
        Properties properties = new Properties();
        properties.load(rawResource);
        return properties.getProperty(name);
    } catch (Resources.NotFoundException e) {
        Log.e(TAG, "Unable to find the config file: " + e.getMessage());
    } catch (IOException e) {
        Log.e(TAG, "Failed to open config file.");
    }
    return null;
}

If they return empty values, which by default they will, then the login screen is showed. If they do not, the login is attempted by default and if successful it will continue to the App, if not, login is shown again of course.

The Issue

When they sign in, I want to write the data into those fields. Currently its being sent to and from the server using JSON and works awesome. I am able to extract this data as well to a string variable which I am then passing to my save to config file after logging the user in but before continuing to the next App screen. This is where the problem lies, I have enabled the permission

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

I have also passed all the values to it, but they are not being written to the lines I want them too. Here is the code I am using to write the file with:

private void commitUserInfotoFile(Context context, String username, String passhash, String rmemail, String rmemailhash) {
    Resources resources = context.getResources();
    String TAG = "Store";
    try {
        InputStream rawResource = resources.openRawResource(R.raw.app_prefs);
        Properties properties = new Properties();
        properties.load(rawResource);
        //tried using setProperty as well as put but neither works
        properties.setProperty("username", username);
        properties.put("username", username);
        properties.setProperty("user_hash", passhash);
        properties.setProperty("saved_email", rmemail);
        properties.setProperty("email_hash", rmemailhash);
        Log.e(TAG, "Wrote the values to the stored file");
    } catch (Resources.NotFoundException e) {
        Log.e(TAG, "Unable to find the config file: " + e.getMessage());
    } catch (IOException e) {
        Log.e(TAG, "IO Exception loading file.");
    }
}

Yet its not storing those values to the file even tho I get the message Wrote the values to the stored file in my console. I am a little confused as to the writing of properties using this method so any help would be appreciated. Thanks

Answer 1

You never store the result of your edits back into the resource. setProperty() just updates some internal key-value pair in the Properties object, it does not update it's source. You need to call Properties.store(OutputStream, String) when you are done with your edits. See here:

https://developer.android.com/reference/java/util/Properties.html#store(java.io.OutputStream, java.lang.String)