Le Tutoriel de Android SharedPreferences

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1- Qu'est ce que SharedPreferences?

Tout d'abord, pour clarifier ce qui est SharedPreferences, vous pouvez voir une situation:

Vous jouez à un jeu sur  Android, avant de jouer au jeu, vous choisissez les paramètres du jeu tels que la luminosité, les niveaux de volume et le niveau de difficulté. Après l'avoir terminé, vous pouvez désactiver le jeu et continuer à jouer le lendemain. SharedPreferences vous permet de sauvegarder tous les paramètres que vous avez définis précédemment et vous permet de redéfinir les paramètres qui peuvent être utilisés sans devoir être réinitialisés.
SharedPreferences enregistre les données brutes sous la forme des paires de valeurs-clés (key-value) aux fichiers de l'application. Vous pouvez également choisir un mode de stockage privé (PRIVATE) que d'autres applications ne peuvent pas accéder à ces fichiers, donc c'est sécurisé.

2- L'exemple avec SharedPreferences

Aperçu les images de l'interface de l'application:
Créez un nouveu projet nommé  AndroidSharedPreferences:
  • File > New > New Project > Empty Activity
    • Name: AndroidSharedPreferences
    • Package name: org.o7planning.androidsharedpreferences
    • Language: Java
If you are interested in the steps to design this application interface, see the appendix at the end of the article.
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="0dp"
        android:layout_height="37dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Game Settings"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="0dp"
        android:layout_height="24dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="22dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Sound:"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <SeekBar
        android:id="@+id/seekBar_sound"
        android:layout_width="0dp"
        android:layout_height="24dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="25dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView2" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="0dp"
        android:layout_height="22dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="19dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Bightness:"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/seekBar_sound" />

    <SeekBar
        android:id="@+id/seekBar_brightness"
        android:layout_width="0dp"
        android:layout_height="22dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="31dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView3" />

    <TextView
        android:id="@+id/textView4"
        android:layout_width="0dp"
        android:layout_height="27dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="29dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:text="Difficulty Level:"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/seekBar_brightness" />

    <RadioGroup
        android:id="@+id/radioGroup_diffLevel"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="37dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:orientation="horizontal"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView4">

        <RadioButton
            android:id="@+id/radioButton_easy"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Easy" />

        <RadioButton
            android:id="@+id/radioButton_medium"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Medium" />

        <RadioButton
            android:id="@+id/radioButton_hard"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Hard" />
    </RadioGroup>

    <Button
        android:id="@+id/button_save"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="33dp"
        android:text="Save"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/radioGroup_diffLevel" />

</androidx.constraintlayout.widget.ConstraintLayout>
MainActivity.java
package org.o7planning.androidsharedpreferences;

import androidx.appcompat.app.AppCompatActivity;
import android.content.Context;
import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.SeekBar;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {


    private SeekBar seekBarSound ;
    private SeekBar seekBarBrightness;

    private RadioGroup radioGroupDiffLevel;
    private RadioButton radioButtonEasy;
    private RadioButton radioButtonMedium;
    private RadioButton radioButtonHard;

    private Button buttonSave;

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

        this.seekBarBrightness= (SeekBar)this.findViewById(R.id.seekBar_brightness);
        this.seekBarSound= (SeekBar)this.findViewById(R.id.seekBar_sound);

        this.seekBarBrightness.setMax(100);
        this.seekBarSound.setMax(100);

        this.radioGroupDiffLevel= (RadioGroup) this.findViewById(R.id.radioGroup_diffLevel);
        this.radioButtonEasy=(RadioButton) this.findViewById(R.id.radioButton_easy);

        this.radioButtonMedium = (RadioButton)this.findViewById(R.id.radioButton_medium);
        this.radioButtonHard=(RadioButton) this.findViewById(R.id.radioButton_hard);

        this.buttonSave = (Button) this.findViewById(R.id.button_save);

        this.buttonSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                MainActivity.this.doSave(view);
            }
        });

        // Load saved game setting.
        this.loadGameSetting();
    }


    private void loadGameSetting()  {
        SharedPreferences sharedPreferences= this.getSharedPreferences("gameSetting", Context.MODE_PRIVATE);

        if(sharedPreferences!= null) {

            int brightness = sharedPreferences.getInt("brightness", 90);
            int sound = sharedPreferences.getInt("sound",95);
            int checkedRadioButtonId = sharedPreferences.getInt("checkedRadioButtonId", R.id.radioButton_medium);

            this.seekBarSound.setProgress(sound);
            this.seekBarBrightness.setProgress(brightness);
            this.radioGroupDiffLevel.check(checkedRadioButtonId);

        } else {
            this.radioGroupDiffLevel.check(R.id.radioButton_medium);
            Toast.makeText(this,"Use the default game setting",Toast.LENGTH_LONG).show();
        }

    }

    // Called when user click to Save button.
    public void doSave(View view)  {
        // The created file can only be accessed by the calling application
        // (or all applications sharing the same user ID).
        SharedPreferences sharedPreferences= this.getSharedPreferences("gameSetting", Context.MODE_PRIVATE);

        SharedPreferences.Editor editor = sharedPreferences.edit();

        editor.putInt("brightness", this.seekBarBrightness.getProgress());
        editor.putInt("sound", this.seekBarSound.getProgress());

        // Checked RadioButton ID.
        int checkedRadioButtonId = radioGroupDiffLevel.getCheckedRadioButtonId();

        editor.putInt("checkedRadioButtonId", checkedRadioButtonId);

        // Save.
        editor.apply();

        Toast.makeText(this,"Game Setting saved!",Toast.LENGTH_LONG).show();
    }
}
Après avoir sauvegardé, vous pouvez quitter l'application et la rouvrir, les paramètres que vous avez enregistrés seront automatiquement définis pour le jeu.

3- Appendix: Interface design

Add TextView(s), SeekBar(s) to the interface.
Add RadioGroup and RadioButton(s) to the interface.
Add a Button to the interface:
Set ID, Text for components on the interface:

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