问题
i have the following exception when i running the following application
Activity:
package com.google.android.SmartStudentmCompanion;
import java.io.BufferedReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
public class Login extends Activity{
public static String ip_address="192.168.1.101";
EditText username;
EditText password;
Button login;
Button exit;
Toast toast;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.loginscreen);
System.out.println("onCreate()...");
username = (EditText) findViewById(R.id.username);
password = (EditText) findViewById(R.id.password);
this.login = (Button)findViewById(R.id.loginButton);
this.login.setOnClickListener(new View.OnClickListener() {
String usrnm;
String pwd;
@Override
public void onClick(View v) {
usrnm = username.getText().toString();
pwd = password.getText().toString();
System.out.println("onClick()...");
int length = 0;
try {
System.out.println("hello");
String page = executeHttpPost(usrnm,pwd);
System.out.println(page);
length = page.length();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if (length == 0){
Toast.makeText(getApplicationContext(),
"Invalid username and/or password",
Toast.LENGTH_SHORT).show();
}
else {
/*Toast.makeText(getApplicationContext(),
"Valid username and password",
Toast.LENGTH_SHORT).show();*/
Intent myIntent = new Intent(v.getContext(), VideoViewer.class);
startActivityForResult(myIntent, 0);
}
}
});
this.exit = (Button)findViewById(R.id.exitButton);
this.exit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
finish();
}
});
}
public String executeHttpPost(String username, String password) throws Exception {
BufferedReader in = null;
try {
ApplicationEx app = (ApplicationEx)this.getApplication();
HttpClient client = app.getHttpClient();
HttpPost request = new HttpPost("http://"+ip_address+"/smartstudentmcompanion/check.php");
List<NameValuePair> postParameters = new ArrayList<NameValuePair>();
postParameters.add(new BasicNameValuePair("un", username));
postParameters.add(new BasicNameValuePair("pwd", password));
UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(postParameters);
request.setEntity(formEntity);
HttpResponse response = client.execute(request);
/*in = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
StringBuffer sb = new StringBuffer("");
String line = "";
String NL = System.getProperty("line.separator");
while ((line = in.readLine()) != null) {
sb.append(line + NL);
}
in.close();*/
String page = EntityUtils.toString(response.getEntity());
System.out.println("page: " + page);
return page;
} finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
Application:
package com.google.android.SmartStudentmCompanion;
import org.apache.http.HttpVersion;
import org.apache.http.client.HttpClient;
import org.apache.http.conn.ClientConnectionManager;
import org.apache.http.conn.scheme.PlainSocketFactory;
import org.apache.http.conn.scheme.Scheme;
import org.apache.http.conn.scheme.SchemeRegistry;
import org.apache.http.conn.ssl.SSLSocketFactory;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;
import org.apache.http.params.BasicHttpParams;
import org.apache.http.params.HttpParams;
import org.apache.http.params.HttpProtocolParams;
import org.apache.http.protocol.HTTP;
import android.app.Application;
import android.util.Log;
public class ApplicationEx extends Application {
private static final String TAG = "ApplicationEx";
private HttpClient httpClient;
@Override
public void onCreate(){
super.onCreate();
httpClient = createHttpClient();
}
@Override
public void onLowMemory() {
super.onLowMemory();
shutdownHttpClient();
}
@Override
public void onTerminate() {
super.onTerminate();
shutdownHttpClient();
}
private HttpClient createHttpClient(){
Log.d(TAG,"createHttpClient()...");
HttpParams params = new BasicHttpParams();
HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1);
HttpProtocolParams.setContentCharset(params, HTTP.DEFAULT_CONTENT_CHARSET);
HttpProtocolParams.setUseExpectContinue(params, true);
SchemeRegistry schReg = new SchemeRegistry();
schReg.register(new Scheme("http",
PlainSocketFactory.getSocketFactory(), 80));
schReg.register(new Scheme("https",
SSLSocketFactory.getSocketFactory(), 443));
ClientConnectionManager conMgr = new ThreadSafeClientConnManager(params,schReg);
return new DefaultHttpClient(conMgr, params);
}
public HttpClient getHttpClient() {
return httpClient;
}
private void shutdownHttpClient() {
if(httpClient!=null && httpClient.getConnectionManager()!=null) {
httpClient.getConnectionManager().shutdown();
}
}
}
manifest:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.google.android.SmartStudentmCompanion"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".Login"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name=".VideoViewer"></activity>
</application>
<uses-permission
android:name="android.permission.INTERNET" />
<uses-sdk android:minSdkVersion="8" />
</manifest>
回答1:
In your manifest change
<application android:icon="@drawable/icon" android:label="@string/app_name">
to
<application android:icon="@drawable/icon" android:label="@string/app_name"
android:name=".ApplicationEx">
Since you have not stated the android:name for the <applicaton> the OS looks for the default Application class. In order to point it to your Application subclass you should use android:name attribute.
来源：https://stackoverflow.com/questions/4317676/android-classcastexception-at-android-app-application