Android在onCreate中保存微调器状态，并在onResume中保存活动

Question

I am currently facing 2 problems, the spinner state is not saving and when I am on the InformationActivity the spinner is reset. I have used the information on other posts but it doesnt seem to help.

At the moment I cant use finish(); in my onBackPressed(); on InformationActivity because it goes back to the ScannerView as I am Implementing the ZXing library. How could I save the Spinner state and also stop the program from crashing onBackPressed when I am on HomeActivity .

Thanks.

HomeActivity:

public class HomeActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener{

    private FirebaseAuth firebaseAuth;
    private Button buttonLogout;
    private ZXingScannerView scannerView;
    private final int permission_code = 1;

    String [] selectedProfile;

    Spinner spinner;
    ArrayAdapter<CharSequence> adapter;

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

        firebaseAuth = FirebaseAuth.getInstance();
        if(firebaseAuth.getCurrentUser() == null){
            finish();
            startActivity(new Intent(this, MainActivity.class));
        }
        FirebaseUser user = firebaseAuth.getCurrentUser();

        if (savedInstanceState != null) {
            spinner.setSelection(savedInstanceState.getInt("yourSpinner", 0));
            // do this for each of your text views
        }
        else {
            //android spinner to select profile
            spinner = (Spinner) findViewById(R.id.spinnerProfiles);
            adapter = ArrayAdapter.createFromResource(this, R.array.restrictions, android.R.layout.simple_spinner_item);
            adapter.setDropDownViewResource(android.R.layout.simple_list_item_1);
            spinner.setAdapter(adapter);
            spinner.setOnItemSelectedListener(this);
        }

    }


    //opens camera when button is pressed
    public void scanBarcode(View view) {
        //check if user given app camera permissions
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, permission_code);

        }
        //opens camera
        scannerView = new ZXingScannerView(this);
        scannerView.setResultHandler(new ZXingScannerResultHandler());
        //stops camera and scannerview
        setContentView(scannerView);
        scannerView.startCamera();

    }

    //selects an item from the spinner and passes it to InformationActivity
    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        String item = parent.getItemAtPosition(position).toString();
        Toast.makeText(getBaseContext(), item + " Selected", Toast.LENGTH_SHORT).show();
        switch (position){
            case 0:
                selectedProfile = getResources().getStringArray(R.array.Wheat);
                break;
            case 1:
                selectedProfile = getResources().getStringArray(R.array.Crustaceans);
                break;
            case 2:
                selectedProfile = getResources().getStringArray(R.array.Eggs);
                break;

        }
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {

    }


    //stops camera and outputs barcode result to a Toast
    class ZXingScannerResultHandler implements ZXingScannerView.ResultHandler {
        @Override
        public void handleResult(Result result) {
            String resultBarcode = result.getText();
            Intent intent = new Intent(getApplicationContext(), InformationActivity.class);
            intent.putExtra("BarcodeString", resultBarcode.toString());
            intent.putExtra("ProfileArray", selectedProfile);
            startActivity(intent);
            scannerView.stopCamera();
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == permission_code) {
            if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                Toast.makeText(this, "Permission Granted", Toast.LENGTH_LONG).show();
            } else {
                Toast.makeText(this, "Permission Denied", Toast.LENGTH_LONG).show();
            }

        }
        //go back to home after permissions accepted
        Intent intent = new Intent(getApplicationContext(), HomeActivity.class);
        startActivity(intent);
        scannerView.stopCamera();
    }


    //goes back to homepage when back button is pressed
    @Override
    public void onBackPressed() {
        setContentView(R.layout.activity_home);
        scannerView.stopCamera();
    }

    //stops the camera on pause
    @Override
    public void onPause(){
        super.onPause();
        scannerView.stopCamera();
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putInt("yourSpinner", spinner.getSelectedItemPosition());
    }

}

InformationActivity:

public class InformationActivity extends AppCompatActivity {

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

        TextView barcodeView = (TextView) findViewById(R.id.tvBarcode);
        barcodeView.setText(getIntent().getExtras().getString("BarcodeString"));

        TextView profileView = (TextView) findViewById(R.id.tvProfile);
        String[] selectedProfile = getIntent().getStringArrayExtra("ProfileArray");
        profileView.setText(selectedProfile[0]);


    }


    @Override
    public void onBackPressed() {
        Intent intent = new Intent(getApplicationContext(), HomeActivity.class);
        startActivity(intent);
    }
}

Answer 1

To Save Spinner posotion in sharedpreference :

int userChoice = spinner.getSelectedItemPosition();
SharedPreferences sharedPref = getSharedPreferences("FileName",0);
SharedPreferences.Editor prefEditor = sharedPref.edit();
prefEditor.putInt("userChoiceSpinner",usersChoice);
prefEditor.commit();

Get Data from sharedpreferences :

SharedPreferences sharedPref = getSharedPreferences("FileName",MODE_PRIVATE);
int spinnerValue = sharedPref.getInt("userChoiceSpinner",-1);
if(spinnerValue != -1) {
  // set the selected value of the spinner 
  spinner.setSelection(spinnerValue);
}

Also look into this :

One Another Example to save : https://stackoverflow.com/a/29527936/8448886

SharedPreference Tutorial : https://www.journaldev.com/9412/android-shared-preferences-example-tutorial

Answer 2

当您当时从微调器中选择任何项目时，请获取该选定的项目并存储该位置，然后当您首先回到活动加载微调器时，将该项目与数组项目进行比较并获得该项目的位置，然后将该位置设置为微调器这样，您就可以精确选择旋转器中的该项目。