共享首选项仅适用于首次应用重启。 在重新启动应用程序第二次卡视图标题不保留

Question

I have created an app which adds cards and a title is set on each card after taking a name input from user. In order to retain the cards and the title during app restart I am using sharedpreferences and saving the individual card titles in an array. The issue is after first app restart the card titles are retained but on further app restart the card titles are not retained. Although the number of cards are still retained.

    public class MainActivity extends AppCompatActivity { 

        private CardView cardview;
        private CardView cardview2;
        private LinearLayout.LayoutParams layoutparams1;
        private LinearLayout layout;
        public SharedPreferences mSettings;
        int mCount;
        int i=0,j=0;
        public TextView tv1;
        public TextView tv4;
        public TextView tv3;
        String name;
        String names[] = new String[10];
        String key[] = {"A","B","C","D","F","G","H"};

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            mCount=0;

            Button b1 = findViewById(R.id.button);
            layout=findViewById(R.id.view);
            tv1 = findViewById(R.id.textView);

            b1.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    names[mCount] = tv1.getText().toString().trim();
                    mCount++;
                    saveName();
                }
            });
        }

       private void saveName()    //Cardview-1 function to 
        {
            cardview = new CardView(getApplicationContext());
            layoutparams1 = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
            layoutparams1.setMargins(18, 30, 18, 0);
            cardview.setLayoutParams(layoutparams1);
            cardview.setCardBackgroundColor(Color.WHITE);
            cardview.setMinimumHeight(400);

            tv3 = new TextView(getApplicationContext());
            tv3.setText(tv1.getText().toString().trim());

            cardview.setRadius(30);
            cardview.addView(tv3);
            layout.addView(cardview);
        }

        private void saveName2()  //Cardview 2 function
        {
            cardview2 = new CardView(getApplicationContext());
            layoutparams1 = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
            layoutparams1.setMargins(18, 30, 18, 0);
            cardview2.setLayoutParams(layoutparams1);
            cardview2.setCardBackgroundColor(Color.WHITE);
            cardview2.setMinimumHeight(400);
            tv4 = new TextView(getApplicationContext());

            mSettings = getSharedPreferences("APP_PREFERENCES", Context.MODE_PRIVATE);
            name = mSettings.getString(key[j],"");
            tv4.setText(name);
            j++;

            cardview2.setRadius(30);
            cardview2.addView(tv4);
            layout.addView(cardview2);
        }

        @Override
        public void onPause() {
            super.onPause();
            mSettings = getSharedPreferences("APP_PREFERENCES", Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = mSettings.edit();
            editor.putInt("COUNT_CARDS", mCount);
            for(int i=0; i<mCount; i++)
            editor.putString(key[i],names[i]);
            editor.commit();
        }

        @Override
        public void onResume() {
            super.onResume();
            mSettings = getSharedPreferences("APP_PREFERENCES", Context.MODE_PRIVATE);
            if(mSettings.contains("COUNT_CARDS"))
            {
                mCount = mSettings.getInt("COUNT_CARDS", 0);
                for (int i=0; i<mCount; i++)
                    saveName2();
            }
        }
    }

XML File

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:id="@+id/layout"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Save"
        android:id="@+id/button"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="50dp" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/view"
        android:orientation="vertical"
        android:layout_marginTop="200dp"
        android:background="@color/cardview_dark_background">

    </LinearLayout>

    <EditText
        android:id="@+id/textView"
        android:layout_width="match_parent"
        android:layout_height="40dp" />

</RelativeLayout>

Answer 1

There is no need to store every card in onPause() method. We will only write new card in sharedPref as prev cards are already presen in sharedPref. So when you are trying to save the prev cards in the loop, there is a problem.( writing blank value).

public class MainActivity extends AppCompatActivity {

    private CardView cardview;
    private CardView cardview2;
    private LinearLayout.LayoutParams layoutparams1;
    private LinearLayout layout;
    public SharedPreferences mSettings;
    int mCount;
    int i=0,j=0;
    public TextView tv1;
    public TextView tv4;
    public TextView tv3;
    String name;
    String names[] = new String[10];
    String key[] = {"A","B","C","D","F","G","H"};

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mCount=0;

        Button b1 = findViewById(R.id.button);
        layout=findViewById(R.id.view);
        tv1 = findViewById(R.id.textView);

        b1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                names[mCount] = tv1.getText().toString().trim();
                mCount++;
                saveName();
            }
        });
    }

    private void saveName()    //Cardview-1 function to
    {
        cardview = new CardView(getApplicationContext());
        layoutparams1 = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
        layoutparams1.setMargins(18, 30, 18, 0);
        cardview.setLayoutParams(layoutparams1);
        cardview.setCardBackgroundColor(Color.WHITE);
        cardview.setMinimumHeight(400);

        tv3 = new TextView(getApplicationContext());
        tv3.setText(tv1.getText().toString().trim());

        cardview.setRadius(30);
        cardview.addView(tv3);
        layout.addView(cardview);

        saveInPref();
    }

    private void saveInPref() {
        mSettings = getSharedPreferences("APP_PREFERENCES", Context.MODE_PRIVATE);
        SharedPreferences.Editor editor = mSettings.edit();
        editor.putInt("COUNT_CARDS", mCount);
        editor.putString(key[mCount-1],names[mCount-1]);
        editor.apply();
    }

    private void saveName2()  //Cardview 2 function
    {
        cardview2 = new CardView(getApplicationContext());
        layoutparams1 = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
        layoutparams1.setMargins(18, 30, 18, 0);
        cardview2.setLayoutParams(layoutparams1);
        cardview2.setCardBackgroundColor(Color.WHITE);
        cardview2.setMinimumHeight(400);
        tv4 = new TextView(getApplicationContext());

        mSettings = getSharedPreferences("APP_PREFERENCES", Context.MODE_PRIVATE);
        name = mSettings.getString(key[j],"");
        tv4.setText(name);
        j++;

        cardview2.setRadius(30);
        cardview2.addView(tv4);
        layout.addView(cardview2);
    }


    @Override
    public void onResume() {
        super.onResume();
        mSettings = getSharedPreferences("APP_PREFERENCES", Context.MODE_PRIVATE);
        if(mSettings.contains("COUNT_CARDS"))
        {
            mCount = mSettings.getInt("COUNT_CARDS", 0);
            for (int i=0; i<mCount; i++)
                saveName2();
        }
    }
}

So when you click on the SAVE button then only you can save card in SharedPref. This will save in unnecessary write operation on sharedPref.