我使用了一些示例代码并尝试使用用户名和密码为 android 应用程序构建登录屏幕。但是，我收到以下错误"XYZ cannot be resolved or is not a field"。
在我的程序中，文件XYZ's中的 :tv和btn_ok字段，以及文件loginerror.java中的 , 。btn_sign_intxt_usernametxt_passwordloginactivity.java
这是我的代码loginerror.java...
public class LoginError extends Activity {
Button button;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
System.gc();
setContentView(R.layout.LoginError);
TextView textview = (TextView) findViewById(R.id.tv);
String loginMessage = getIntent().getStringExtra("LoginMessage");
textview.setText(loginMessage);
button = (Button) findViewById(R.id.btn_ok);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
finish();
}
});
}
}>
这是我的代码loginactivity.java...
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.xml.sax.InputSource;
import org.xml.sax.XMLReader;
public class LoginActivity extends Activity {
/** Called when the activity is first created. */
private static final String TAG = "Login";
Button signin;
String loginmessage = null;
Thread t;
private SharedPreferences mPreferences;
ProgressDialog dialog;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mPreferences = getSharedPreferences("CurrentUser", MODE_PRIVATE);
if (!checkLoginInfo()) {
signin = (Button) findViewById(R.id.btn_sign_in);
signin.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
showDialog(0);
t=new Thread() {
public void run() {
tryLogin();
}
};
t.start();
}
});
}
else {
/*Directly opens the Welcome page, if the username and password is already available
in the SharedPreferences*/
Intent intent=new Intent(getApplicationContext(),Welcome.class);
startActivity(intent);
finish();
}
}
protected Dialog onCreateDialog(int id) {
switch (id) {
case 0: {
dialog = new ProgressDialog(this);
dialog.setMessage("Speek is loading");
dialog.setIndeterminate(true);
dialog.setCancelable(true);
return dialog;
}
}
return null;
}
private Handler handler = new Handler() {
public void handleMessage(Message msg) {
String loginmsg=(String)msg.obj;
if(loginmsg.equals("SUCCESS")) {
removeDialog(0);
Intent intent=new Intent(getApplicationContext(),Welcome.class);
startActivity(intent);
finish();
}
}
};
public void tryLogin() {
Log.v(TAG, "Trying to Login");
EditText etxt_user = (EditText) findViewById(R.id.txt_username);
EditText etxt_pass = (EditText) findViewById(R.id.txt_password);
String username = etxt_user.getText().toString();
String password = etxt_pass.getText().toString();
DefaultHttpClient client = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://www.speek.com");
List nvps = new ArrayList();
nvps.add(new BasicNameValuePair("username", username));
nvps.add(new BasicNameValuePair("password", password));
try {
UrlEncodedFormEntity p_entity = new UrlEncodedFormEntity(nvps,
HTTP.UTF_8);
httppost.setEntity(p_entity);
HttpResponse response = client.execute(httppost);
Log.v(TAG, response.getStatusLine().toString());
HttpEntity responseEntity = response.getEntity();
Log.v(TAG, "Set response to responseEntity");
SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = spf.newSAXParser();
XMLReader xr = sp.getXMLReader();
LoginHandler myLoginHandler = new LoginHandler();
xr.setContentHandler(myLoginHandler);
xr.parse(retrieveInputStream(responseEntity));
ParsedLoginDataSet parsedLoginDataSet = myLoginHandler.getParsedLoginData();
if (parsedLoginDataSet.getExtractedString().equals("SUCCESS")) {
// Store the username and password in SharedPreferences after the successful login
SharedPreferences.Editor editor=mPreferences.edit();
editor.putString("UserName", username);
editor.putString("PassWord", password);
editor.commit();
Message myMessage=new Message();
myMessage.obj="SUCCESS";
handler.sendMessage(myMessage);
} else if(parsedLoginDataSet.getExtractedString().equals("ERROR")) {
Intent intent = new Intent(getApplicationContext(), LoginError.class);
intent.putExtra("LoginMessage", parsedLoginDataSet.getMessage());
startActivity(intent);
removeDialog(0);
}
} catch (Exception e)
{
Intent intent = new Intent(getApplicationContext(), LoginError.class);
intent.putExtra("LoginMessage", "Unable to login");
startActivity(intent);
removeDialog(0);
}
}
private InputSource retrieveInputStream(HttpEntity httpEntity) {
InputSource insrc = null;
try {
insrc = new InputSource(httpEntity.getContent());
} catch (Exception e) {
}
return insrc;
}
//Checking whether the username and password has stored already or not
private final boolean checkLoginInfo() {
boolean username_set = mPreferences.contains("UserName");
boolean password_set = mPreferences.contains("PassWord");
if ( username_set || password_set ) {
return true;
}
return false;
}
}
这是我的main.xml...
<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android" >
<Button
android:id="@+id/btn_sign_in"
android:layout_width="100dp"
android:layout_height="wrap_content"
android:text="Sign In"
android:layout_x="103dp"
android:layout_y="197dp"/>
<EditText
android:id="@+id/txt_username"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:hint="Username"
android:singleLine="true"
android:textSize="18sp"
android:layout_x="40dp"
android:layout_y="32dp" />
<EditText
android:id="@+id/txt_password"
android:layout_width="250dp"
android:layout_height="wrap_content"
android:hint="Password"
android:singleLine="true"
android:textSize="18sp"
android:password="true"
android:layout_x="40dp"
android:layout_y="86dp" />
</AbsoluteLayout>
这是我的loginerror.xml档案...
<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent"
xmlns:android="http://schemas.android.com/apk/res/android" >
<TextView
android:id="@+id/tv"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:gravity="center_vertical|center_horizontal"/>
<Button android:id="@+id/btn_ok" android:layout_width="80dp"
android:layout_height="wrap_content" android:text="OK"
android:layout_x="83dp" android:layout_y="60dp" />
</AbsoluteLayout>
错误发生在这些行...
1. TextView textview = (TextView) findViewById(R.id.tv);
2. button = (Button) findViewById(R.id.btn_ok);
3. signin = (Button) findViewById(R.id.btn_sign_in);
4. EditText etxt_user = (EditText) findViewById(R.id.txt_username);
EditText etxt_pass = (EditText) findViewById(R.id.txt_password);
我必须在主程序中添加任何东西来解决这个问题吗？问题是什么意思？