不同类别/方法之间的意图

Question

I want to send 2 different values to the InformationActivity.
Firstly: I want to send the barcode number, and a list (which works correctly). But for some reason the list that i send (wheat or crus or eggs depending on what i press) doesnt appear in the InformationActivity.
I think that the problem is because it is in 2 different classes.

How I could change the code so that it sends both the barcode string and one of the lists into the next activity?

PS. I tried declaring intent as a global variable and that crashes the app PSS. at the moment I am just testing it by printing i item in that array.

Main:

public class HomeActivity extends AppCompatActivity{

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

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();

    //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(new AdapterView.OnItemSelectedListener() {
        @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();
            Intent intent = new Intent(getApplicationContext(), InformationActivity.class);
            switch (position){
                case 0:
                    String[] wheat = getResources().getStringArray(R.array.Wheat);
                    intent.putExtra("Profile", wheat);
                    break;
                case 1:
                    String[] crus = getResources().getStringArray(R.array.Crustaceans);
                    intent.putExtra("Profile", crus);
                    break;
                case 2:
                    String[] eggs = getResources().getStringArray(R.array.Eggs);
                    intent.putExtra("Profile", eggs);
                    break;
            }
        }

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

}


//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();

}

//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("barcode", resultBarcode.toString());
        startActivity(intent);
        scannerView.stopCamera();
    }
}

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("barcode"));

    TextView profileView = (TextView) findViewById(R.id.tvProfile);
    String[] Profile = getIntent().getStringArrayExtra("Profile");
    profileView.setText(Profile[1]);


}


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

Answer 1

Your onItemSelected() method is adding a String[] to an Intent object, but then just throwing that Intent away.

 @Override public void onItemSelected(AdapterView<?> parent, View view, int position, long id) { ... Intent intent = new Intent(getApplicationContext(), InformationActivity.class); switch (position){ case 0: String[] wheat = getResources().getStringArray(R.array.Wheat); intent.putExtra("Profile", wheat); break; case 1: String[] crus = getResources().getStringArray(R.array.Crustaceans); intent.putExtra("Profile", crus); break; case 2: String[] eggs = getResources().getStringArray(R.array.Eggs); intent.putExtra("Profile", eggs); break; } } 

Later on, you start the activity with a different Intent :

 @Override public void handleResult(Result result) { String resultBarcode = result.getText(); Intent intent = new Intent(getApplicationContext(), InformationActivity.class); intent.putExtra("barcode", resultBarcode.toString()); startActivity(intent); scannerView.stopCamera(); } 

It's important to understand that these two intents are not shared somehow; the first one is completely separate from the second, and as soon as onItemSelected() finishes executing, the intent is thrown away.

What you should do is change your onItemSelected() method so that it stores information about the selection somehow (maybe update a variable in your activity), and then change your handleResult() method to read that saved information and add the array to the intent. Maybe something like this:

String[] selectedArray;

@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    ...
    switch (position){
        case 0:
            selectedArray = getResources().getStringArray(R.array.Wheat);
            break;
        case 1:
            selectedArray = getResources().getStringArray(R.array.Crustaceans);
            break;
        case 2:
            selectedArray = getResources().getStringArray(R.array.Eggs);
            break;
    }
}

@Override
public void handleResult(Result result) {
    String resultBarcode = result.getText();
    Intent intent = new Intent(getApplicationContext(), InformationActivity.class);
    intent.putExtra("barcode", resultBarcode.toString());
    intent.putExtra("Profile", selectedArray);
    startActivity(intent);
    scannerView.stopCamera();
}

Answer 2

我认为您应该使用startActivityForResult（）更好地管理活动之间的信息交换，并构建一个更可靠的应用程序。

Answer 3

You need to call scanBarcode() function to fire the intent and launch InformationActivity using the perfect solution provided by Ben:

String[] selectedArray;
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
    ...
    switch (position){
        case 0:
            selectedArray = getResources().getStringArray(R.array.name);
            break;
        case 1:
            selectedArray = getResources().getStringArray(R.array.name);
            break;
    }
}

Also simply call finish(); function in onBackPressed() of InformationActivity to navigate to Mainactivity :

    @Override
public void onBackPressed() {
    super.finish(); // or use super.onBackPressed(); 
}

Happy Coding :)