How to add an icon showing that that item has already been read, being saved the preferences using Sharedpreferences?

Question

This is a part of the app’s home menu:

Home Screen

The image below represents the initial screen of the application, which has the buttons "how to use" and "Introduction to dynamics", for the user to choose which task will do.

Screen "How to use"

Clicking on the ImagemButton (above the text "How to Use") the user goes to a new Layout in which there is a button back to main screen so that you can move forward to the next steps of the tutorial, as below:

Doubt

After the user has entered layout of the "how to use", have read and completed by clicking the button back to main screen wanted an icon to appear on ImagemButton to notify that he has already completed that task. So, when the user enters the application again, he can know which one he has already done and continue where he left off. As represented below:

What Android features/methods should I use so I can add an icon showing that that item has already been read?

Answer 1

As you mentioned, for relatively small collection of key values to save cases, use the Apis Sharedpreferences. An object SharedPreferences indicates a file that contains key value pairs and provides simple methods to read and write.

Each Sharedpreferences file is managed by the work structure and can be private or shared.

First can define a string static to give the name of your configuration and declare the image that will appear with the click of the button:

public static final String PREFS_NAME = "Preferences";
private ImageView img;

Then we create a method to add the image when the button is clicked and a preference is saved, this way:

private void onOff() {
    SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
    settings.edit().putBoolean("online", true).apply();

    boolean online = settings.getBoolean("online", false);
    if (online) {
        img.setImageResource(R.drawable.confirmacao);
    } else {
        img.setImageResource(R.drawable.fundo);
    }
}

To rescue the recorded value just you check this way, on the screen the image is on:

img = (ImageView) findViewById(R.id.img);

SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
Boolean online = settings.getBoolean("online", false);

if (online)
    img.setImageResource(R.drawable.confirmacao);
else
    img.setImageResource(R.drawable.fundo);

To the end, you must put this method onOff(); on the button you wish.

Therefore, you will do that above check every time you enter your application. Remembering that it is a quick way of doing and can be optimized. This is just a basic example for you to have more sense.

Remarks:

1 - "img" is the image id that has no background defined in the layout and is where the confirmation image is inserted.

2 - "confrimacao" is the name of the image file that represents the visualized notification.

3 - "background" is the name of an image file with nothing (transparent) saved in . png

4 - Perhaps the method onOff(); can be triggered on any button of my app due I use only one Activity throughout the app.

5 - There is a video on the page of the article "Far beyond Sqlite" (proposed below) that can help a lot.

There are other persistence techniques as an alternative, simple and agile, which allow the persistence of small amounts of data. They are:

• PreferenceActivity;

• Internal Storage;

• Armazenamento em Cache;

• External Storage.

See some articles:

• Data persistence on Android
• Far beyond the Sqlite
• Storage Options
• Persistence in Database