我正在尝试使用此处的教程编写一个简单的登录页面。这是我的 Java 页面：
public class Main extends Activity implements OnClickListener{
EditText etUser, etPass;
Button bLogin;
//Create string variables that will have the input assigned to them
String username, password;
//Create a HTTPClient as the form container
HttpClient httpclient;
//Use HTTP POST method
HttpPost httppost;
//Create an array list for the input data to be sent
ArrayList<NameValuePair> nameValuePairs;
//Create a HTTP Response and HTTP Entity
HttpResponse response;
HttpEntity entity;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
initialise();
}
private void initialise() {
// TODO Auto-generated method stub
etUser = (EditText) findViewById(R.id.username);
etPass = (EditText) findViewById(R.id.password);
bLogin = (Button) findViewById(R.id.login_button);
//Now to set an onClickListener
bLogin.setOnClickListener(this);
}
@Override
public void onClick(View v) {
// This is where we will be working now
//Create new default HTTPClient
httpclient = new DefaultHttpClient();
//Create new HTTP POST with URL to php file as parameter
httppost = new HttpPost("http://10.0.2.2:8080/logine/work.php");
//Assign input text to strings
username = etUser.getText().toString();
password = etPass.getText().toString();
//place them in an array list
nameValuePairs.add(new BasicNameValuePair("username", username));
nameValuePairs.add(new BasicNameValuePair("password", password));
//Next block of code needs to be surrounded by try/catch block for it to work
try {
//Add array list to http post
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
//assign executed form container to response
response = httpclient.execute(httppost);
//check status code, need to check status code 200
if(response.getStatusLine().getStatusCode()== 200){
//assign response entity to http entity
entity = response.getEntity();
//check if entity is not null
if(entity != null){
//Create new input stream with received data assigned
InputStream instream = entity.getContent();
//Create new JSON Object. assign converted data as parameter.
JSONObject jsonResponse = new JSONObject(convertStreamToString(instream));
//assign json responses to local strings
String retUser = jsonResponse.getString("user");//mySQL table field
String retPass = jsonResponse.getString("pass");
}
}
} catch(Exception e){
e.printStackTrace();
}
}//END onClick()
private static String convertStreamToString(InputStream is) {
/*
* To convert the InputStream to String we use the BufferedReader.readLine()
* method. We iterate until the BufferedReader return null which means
* there's no more data to read. Each line will appended to a StringBuilder
* and returned as String.
*/
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
try {
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return sb.toString();
}//END convertStreamToString()
}
这是 Logcat Stacktrace
java.lang.NullPointerException
at com.Application.Main.onClick(Main.java:79)
at android.view.View.performClick(View.java:2485)
at android.view.View$PerformClick.run(View.java:9080)
at android.os.Handler.handleCallback(Handler.java:587)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:123)
at android.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
09-20 15:23:58.258: ERROR/InputDispatcher(60): channel '40725a60 com.Application/com.Application.Main (server)' ~ Consumer closed input channel or an error occurred. events=0x8
09-20 15:23:58.258: ERROR/InputDispatcher(60): channel '40725a60 com.Application/com.Application.Main (server)' ~ Channel is unrecoverably broken and will be disposed!
我在做什么错。当然我不太了解 java.BTW 我的 AVD 是 2.3.3