Question

假设我的应用具有以下要求：

首先显示登录屏幕（如果在SQLite上未检测到登录会话）
如果登录成功，则显示QR码扫描屏幕（全屏）
如果扫描成功，则将结果存储在SQLite上并将其显示在“产品”屏幕上
如果您在“产品”屏幕中并按回去，则立即QR 出现代码扫描屏幕。依此类推。

这是我的代码（不相关的部分被省略了）。

LoginActivity.java

public class LoginActivity extends AppCompatActivity {

    private EditText edtUsername;
    private EditText edtPassword;
    private Button btnLogin;

    // store username & password in SQLite db
    // taken from https://www.androidhive.info/2012/08/android-session-management-using-shared-preferences/
    SessionManager session;

    // manage stored items in SQLite
    private DatabaseHelper db;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        spinner.setAdapter(adapter);

        db = new DatabaseHelper(this);

        session = new SessionManager(getApplicationContext());
        if (session.isLoggedIn()){
            IntentIntegrator scanIntegrator = new IntentIntegrator(LoginActivity.this);
            scanIntegrator.setOrientationLocked(false);
            scanIntegrator.initiateScan();
        }

        edtUsername = (EditText) findViewById(R.id.edtName);
        edtPassword = (EditText) findViewById(R.id.edtPassword);
        btnLogin = (Button) findViewById(R.id.btnLogin);
    }


    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        IntentResult scanningResult = IntentIntegrator.parseActivityResult(requestCode, resultCode, data);
        if (scanningResult != null){
            String scanContent = scanningResult.getContents();
            String[] data = parseContent(scanContent);

            db.insertItem(new Item(data[0], data[1], data[2]));

            Intent iii = new Intent(LoginActivity.this, ScanResultActivity.class);
            startActivity(iii);
        }
    }

}

ScanResultActivity.java

public class ScanResultActivity extends AppCompatActivity {

    private RecyclerView recView;
    private ItemAdapter mAdapter;
    private DatabaseHelper db;
    private List<Item> itemList;

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

        recView = (RecyclerView) findViewById(R.id.recycler_view);
        itemList = new ArrayList<>();

        db = new DatabaseHelper(this);
        itemList.addAll(db.getAllItems());

        mAdapter = new ItemAdapter(this, itemList);
        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
        recView.setLayoutManager(mLayoutManager);
        recView.setItemAnimator(new DefaultItemAnimator());
        recView.addItemDecoration(new MyDividerItemDecoration(this, LinearLayoutManager.VERTICAL, 16));
        recView.setAdapter(mAdapter);
    }
}

第1-3部分运行良好。唯一的问题是一旦您进入4，然后按返回按钮，您将跳至其“非登录状态”的登录活动，因此您必须重复登录过程。相反，我想要的是再次运行QR码扫描部分。该怎么做？

Answer 1

您可以隔离登录屏幕。除了两个活动，您还可以拥有三个：LoginActivity-> QRCodeScanActivity-> ScanResultActivity。

这样，如果用户按下“后退”按钮，他将返回到QRCodeScanActivity。

Answer 2

在onBackPressed();方法中，只需调用finesh()方法，您将回到QRCodeScanActivity

按下后退按钮时如何调用QR码扫描仪？

2 个答案: