我想我可以在登录后绕过登录 Activity ，但如何检索用户名并将其传递给下一个 Activity 。我得到用户名的值为 NULL
这是登录 Activity
public class LoginActivity extends AppCompatActivity {
/*
* Database helper field
*/
private DatabaseHelper databaseHelper;
/*
Edittext username and password
*/
private EditText uName, pwd;
/*
Button login and signup
*/
private Button loginButton, signupButton;
private String username, password;
/**
* Create activity when register button and log in button clicked
* @param savedInstanceState saved instance state
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
Toolbar toolbar = (Toolbar)findViewById(R.id.login_toolbar);
toolbar.setTitle("LOGIN");
databaseHelper = new DatabaseHelper(this);
uName = (EditText)findViewById(R.id.uNameToLogin_editText);
pwd = (EditText)findViewById(R.id.pwdToLogin_editText);
SharedPreferences sharedPreferences = getSharedPreferences
(getString(R.string.SHARED_PREFS), MODE_PRIVATE);
boolean isLoggedIn = sharedPreferences.getBoolean(getString(R.string.LOGGEDIN), false);
if (isLoggedIn){
Intent newIntent = new Intent(LoginActivity.this, FinderActivity.class);
newIntent.putExtra("Username", username);
startActivity(newIntent);
finish();
}
/*
* Sign up button clicked takes user to registration form
*/
signupButton = (Button)findViewById(R.id.signupButton);
signupButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(LoginActivity.this, RegisterActivity.class);
startActivity(intent);
}
});
/*
*Log in activity
*/
loginButton = (Button)findViewById(R.id.loginButton);
loginButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
username = uName.getText().toString();
password = pwd.getText().toString();
//log in successfull using correct username and password
String pass = databaseHelper.searchPassword(username);
if (pass.equals(password)){
SharedPreferences sharedPreferences = getSharedPreferences
(getString(R.string.SHARED_PREFS), MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putBoolean(getString(R.string.LOGGEDIN), true);
editor.commit();
Toast.makeText(LoginActivity.this, "Welcome! " + username,
Toast.LENGTH_LONG).show();
//change to new search intent
Intent newIntent = new Intent(LoginActivity.this, FinderActivity.class);
newIntent.putExtra("Username", username);
startActivity(newIntent);
finish();
} else {
//error shows if inccorrect password or username
Toast.makeText(LoginActivity.this, "Username or Password Incorrect!, Try Again",
Toast.LENGTH_LONG).show();
}
}
});
}
}
这是我的 NextActivity，它包含菜单栏中的注销操作
public class FinderActivity extends AppCompatActivity {
private static final String TAG = "FinderActivity";
private String address = "";
public List<LocationInfo> locationList;
public ListView mListView;
public ArrayAdapter<LocationInfo> locationAdapter;
private int numberOfLocation;
public LocationAddress locationAddress;
public String api_url, uName;
public double lat, lng;
SharedPreferences mSharePreferences;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_finder);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
Intent intent = getIntent();
uName = intent.getStringExtra("Username");
String welcomeString = "Welcome, " + uName;
getSupportActionBar().setTitle(welcomeString);
Log.i(TAG, "On create called");
View b = findViewById(R.id.customButton);
b.setVisibility(View.GONE);
/*
retrieve search button actions
*/
Button searchButton = (Button) findViewById(R.id.search_button);
searchButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//pass address to location class
EditText search = (EditText) findViewById(R.id.search_EditText);
address = search.getText().toString();
LocationAddress.setAddress(address);
if (locationList != null) {
locationList.clear();
}
if (address.equals("")) {
Toast.makeText(FinderActivity.this, "PLease enter your address!",
Toast.LENGTH_LONG).show();
} else {
/*
* manging connection from the application to networking service
* before attempting to fetch url, make sure there is a network connection
*/
ConnectivityManager connectivityManager = (ConnectivityManager)
getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networtInfo = connectivityManager.getActiveNetworkInfo();
if (networtInfo != null && networtInfo.isConnected()) {
GetAddressTask task = new GetAddressTask();
task.execute();
View b = findViewById(R.id.customButton);
b.setVisibility(View.GONE);
Log.i(TAG, "connected");
} else {
Log.i(TAG, "not connected");
}
/*
Retrieve data to listview
*/
showListView();
/*
itemClick listener for each item in the list view
*/
mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent intent = new Intent(FinderActivity.this, ParkingLocation.class);
api_url = locationList.get(position).getUrl_api();
intent.putExtra("key_api_url", api_url);
intent.putExtra("username", uName);
startActivity(intent);
}
});
}
}
});
/*
Custom search button actions if and only if search button gives null results
*/
Button customSearch = (Button) findViewById(R.id.customButton);
customSearch.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (address.equals("")) {
Toast.makeText(FinderActivity.this, "PLease enter your address!",
Toast.LENGTH_LONG).show();
} else if (LocationAddress.getNumOfLocations() > 0) {
Toast.makeText(FinderActivity.this, "This action is only available if no parking locations found!!",
Toast.LENGTH_LONG).show();
} else { //open custom search activity
Intent newIntent = new Intent(FinderActivity.this, CustomSearchActivity.class);
Bundle b = new Bundle();
b.putDouble("key_lat", lat);
b.putDouble("key_lng", lng);
b.putString("username", uName);
newIntent.putExtras(b);
startActivity(newIntent);
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.menu_main, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
switch (id) {
//log out action
case R.id.action_logout:
mSharePreferences = getSharedPreferences(getString
(R.string.SHARED_PREFS), MODE_PRIVATE);
SharedPreferences.Editor editor = mSharePreferences.edit();
editor.putBoolean(getString(R.string.LOGGEDIN), false);
editor.commit();
Intent backIntent = new Intent(FinderActivity.this, LoginActivity.class);
startActivity(backIntent);
return true;
//show my saved places view
case R.id.action_show:
Intent intent = new Intent(FinderActivity.this, MyDestination.class);
intent.putExtra("username", uName);
startActivity(intent);
return true;
}
//show list of destination once this button clicked
return super.onOptionsItemSelected(item);
}
最佳答案
如果你想通过 Intent 传递数据，你应该在 FinderActivity.java 的 onCreate 上设置它
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.layout);
if (getIntent() != null) {
final Bundle extras = getIntent().getExtras();
if (extras != null) {
userName = extras.getString("Username");
}
}
}
如果你想在 SharedPreferences 上保存，你必须在 LoginActivity 上保存并在 FinderActivity.java 上保存 解释如何的链接 -> How to use SharedPreferences in Android to store, fetch and edit values
关于android - 使用 SharedPreferences 从 Edittext 中检索用户名以进行下一个 Activity ，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/34072492/