使用 SHARED PREFERENCES android studio 更改按钮的文本

Question

I'm making a simple app that has a button. When a pokemon is caught, I want the text to be "release" and when it's not, to be "catch.", When clicking the button. I want to change caught from true to false or vice-versa.

For now, i've done this (it doesn't work as I expected):

    public void toggleCatch(View view) {

        boolean caught;

        String name = nameTextView.getText().toString();

        SharedPreferences captured = getSharedPreferences("pokemon_name",Context.MODE_PRIVATE);

        if (captured.contains (name) ){
            catch_button.setText("Release");
            caught=true;
        }
        else{
            catch_button.setText("Catch!");
            caught=false;
        }

        if (caught) {
            getPreferences(Context.MODE_PRIVATE).edit().putString("pokemon_name", name).commit();
        } else {
            getPreferences(Context.MODE_PRIVATE).edit().remove(name).commit();
        }

    }

I would be very thankful if someone can help me!

I'm lost so I don't know if I'm on the correct path, my code is probably completely wrong.

Answer 1

SharedPreferences is a map of key-value pairs. So if you are trying to access the value you should check whether the key exists which in your case is pokemon_name .

if (captured.contains("pokemon_name")){
    ...
}

And when removing once again you should give the key, not the value.

...edit().remove("pokemon_name").commit();

---

Read SharedPreferences official documentation to understand better.

Answer 2

I guess here is what you want:

In your app, you have an EditText that allows users to input pokemon name. When users click on the toggle catch button,

• If the pokemon name is captured (the pokemon name has been saved in the SharePreferences ), then remove the pokemon name from the SharePreferences and set the text of the button to "Release".

• If the pokemon name is not captured (the pokemon name hasn't been saved in the SharePreferences ), then add the pokemon name to the SharePreferences and set the text of the button to "Catch.".

Solution

public void toggleCatch(View view) {
    String name = nameTextView.getText().toString().trim();
    SharedPreferences captured = getSharedPreferences("pokemon_name", Context.MODE_PRIVATE);
    boolean caught = captured.contains(name);
    if (caught) {
        captured.edit().remove(name).apply();
        catch_button.setText("Release");
    } else {
        captured.edit().putBoolean(name, true).apply();
        catch_button.setText("Catch!");
    }
}