onbackpressed方法错误

Question

我正在使用身份验证进入页面，在通过身份验证后，只有用户才能进入页面。我为onbackpressed()编写了一段代码，但它不起作用。这里的DatabaseDemo和Login是两个类。当我按back按钮时，显示的是带有用户名和密码的登录类。

DatabaseDemo.java

public class DatabaseDemo extends TabActivity {
    DatabaseHelper dbHelper;
    GridView grid;
    TextView txtTest;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        SetupTabs();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu)
    {
        menu.add(1, 1, 1, "Add Employee");
        return true;
    }
    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId())
        {
        //Add employee
        case 1:
            Intent addIntent=new Intent(this,AddEmployee.class);
            startActivity(addIntent);
            break;
        }
        super.onOptionsItemSelected(item);
        return false;
    }
    void SetupTabs()
    {
        TabHost host=getTabHost();
        TabHost.TabSpec spec=host.newTabSpec("tag1");
        Intent in1=new Intent(this, AddEmployee.class);
        spec.setIndicator("Add Employee");
        spec.setContent(in1);

        TabHost.TabSpec spec2=host.newTabSpec("tag2");
        Intent in2=new Intent(this, GridList.class);

        spec2.setIndicator("Employees");
        spec2.setContent(in2);

        host.addTab(spec);
        host.addTab(spec2);
    }
    @Override
    public void onBackPressed() 
    {
        Intent i = new Intent(DatabaseDemo.this, Login.class);
        startActivity(i);
    }
}

我有更多的课程，对于其他意图来说，它工作得很好。

Login.java

public class Login extends Activity implements OnClickListener{
    Button btn;
    EditText et1, et2;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);

        btn = (Button)findViewById(R.id.btnlogin);
        btn.setOnClickListener(this);
        et1 = (EditText)findViewById(R.id.Leditename);
        et2 = (EditText)findViewById(R.id.Leditpw);

    }
    @Override
    public void onBackPressed() 
    {
        super.onBackPressed();
        finish();
    }
    @Override
    public void onClick(View v) {
        String ename = et1.getText().toString().trim();
        System.out.println("ename is..." +ename);
        String epw = et2.getText().toString().trim();
        System.out.println("Password is..." +epw);

        if(ename.equals("srikanth") && epw.equals("12345")){
            Toast.makeText(getApplicationContext(), "valid login..!", Toast.LENGTH_LONG).show();
            Intent in = new Intent(getApplicationContext(), DatabaseDemo.class);
            startActivity(in);      
        }
        else
        {
            Toast.makeText(getApplicationContext(), "Invalid authentication..!", Toast.LENGTH_LONG).show();
            Intent intent = new Intent(getApplicationContext(), Login.class);
            startActivity(intent);
        }
    }

Logcat未显示任何错误。

02-14 17:45:33.595: I/ActivityManager(59): Starting activity: Intent { cmp=com.android.databaseex/.DatabaseDemo }
02-14 17:45:34.835: I/ActivityManager(59): Displayed activity com.android.databaseex/.DatabaseDemo: 1141 ms (total 1141 ms)
02-14 17:45:50.145: I/System.out(613): ename is...srikanth
02-14 17:45:50.145: I/System.out(613): Password is...12345
02-14 17:45:50.175: I/ActivityManager(59): Starting activity: Intent { cmp=com.android.databaseex/.DatabaseDemo }
02-14 17:45:51.055: I/ActivityManager(59): Displayed activity com.android.databaseex/.DatabaseDemo: 819 ms (total 819 ms)

Answer 1

您需要跳过super.onBackPressed();行：

@Override
    public void onBackPressed() 
    {
        Intent i = new Intent(DatabaseDemo.this, Login.class);
        startActivity(i);
    }

Answer 2

使用onkeydown()代替onBackpressed方法

public boolean onKeyDown(int keyCode, KeyEvent event) {
        // TODO Auto-generated method stub

        if(keyCode == KeyEvent.KEYCODE_BACK){

            Intent i = new Intent(DatabaseDemo.this, Login.class);
        startActivity(i);
        }
        return super.onKeyDown(keyCode, event);
    }

Answer 3

@Override
public void onBackPressed() 
{
    Intent i = new Intent(DatabaseDemo.this, Login.class);
    startActivity(i);
}

这是完美的工作，请先检查您的androidmanifest文件，是否有活动登录条目？如果有，则没有任何问题，否则使活动登录到清单文件中