Android 在 onCreate 和 Activity onResume 中保存微调器状态

Question

我目前面临 2 个问题，微调器状态未保存，当我在 InformationActivity 上时微调器被重置。我在其他帖子上使用过这些信息，但似乎没有帮助。

目前我不能在InformationActivity 上的onBackPressed(); 中使用finish();，因为在我实现ZXing 库时它会回到ScannerView。当我在 HomeActivity 上时，如何保存 Spinner 状态并阻止程序崩溃 onBackPressed。

谢谢。

家庭活动：

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());
    }

}

信息活动：

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

在 sharedpreference 中保存 Spinner 位置：

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

从 sharedpreferences 中获取数据：

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);
}

也看看这个：

另一个要保存的示例：https://stackoverflow.com/a/29527936/8448886

SharedPreference 教程：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，获取该选定项目并存储该位置，然后当您首先返回活动加载微调器时，将该项目与数组项目进行比较并获取该项目的位置，然后将该位置设置为微调器我认为这样你就可以准确地选择该项目到微调器中。