在SharedPreferences中增加并保存增量

Question

I have a simple scenario but can't seem to wrap my head around it.

I want to save a incremented value as a int to SharedPreferences every time a user tap on a item, let me show what I have:

int counter = 0;

mBtn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        counter++;
        SharedPreferences shareOpenClose = getSharedPreferences("Counter", Context.MODE_PRIVATE);
        SharedPreferences.Editor editorOpenClose = shareOpenClose.edit();
        editorOpenClose.putInt("count", counter);
        editorOpenClose.apply();

        SharedPreferences getCount = getSharedPreferences("Counter", Context.MODE_PRIVATE);
        int getCountAmmount = getCount.getInt("count", 0);

        if (getCountAmmount>3){
        Toast.makeText(c, "success!", Toast.LENGTH_SHORT).show();
        }

    }
});

So, when I close the activity and open it again the counter will be reset to zero and the first save to SharedPreferences back to 0. If I keep the activity open and test this it work and I get the toast as expected.

Can someone please point out what I'm doing wrong?

Answer 1

Because you never set the counter back when the activity loads. try this:

int counter = 0;


onCreate(...){
    SharedPreferences countPref = getSharedPreferences("Counter", Context.MODE_PRIVATE);
    counter = countPref.getInt("count", 0);
}

mBtn.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {
        counter++;
        SharedPreferences countPref = getSharedPreferences("Counter", Context.MODE_PRIVATE);
        SharedPreferences.Editor editorOpenClose = countPref.edit();
        editorOpenClose.putInt("count", counter);
        editorOpenClose.apply();


        if (counter>3){
        Toast.makeText(c, "success!", Toast.LENGTH_SHORT).show();
        }

    }
});

Answer 2

Make the following changes in your code

@Override
protected void onCreate(Bundle savedInstanceState) {
    SharedPreferences shareOpenClose = getSharedPreferences("Counter", Context.MODE_PRIVATE);
    final SharedPreferences.Editor editorOpenClose = shareOpenClose.edit();
    final int[] counter = {0};
    mBtn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            counter[0]++;

            editorOpenClose.putInt("count", counter[0]);
            editorOpenClose.apply();

            SharedPreferences getCount = getSharedPreferences("Counter", Context.MODE_PRIVATE);
            int getCountAmmount = getCount.getInt("count", 0);

            if (getCountAmmount>3){
                Toast.makeText(c, "success!", Toast.LENGTH_SHORT).show();
            }

        }
    });
}

I hope this will help you, Happy Coding