我是开发Android应用程序的新手。我已经阅读了很多关于我问的问题的相关帖子，但帖子中的提示或解决方案并没有解决我的问题。 （寻找一周的解决方案，真的需要帮助才能继续我的项目）非常感谢...
错误行号121
Image LinK
update.java：
package pounkumarpurushothaman.ghssvmm;
import android.app.Activity;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.Spinner;
import android.widget.Toast;
import org.apache.http.HttpEntity;
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.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
public class update extends ActionBarActivity {
public static final String KEY_121 ="http://ghssvmm.site40.net/update.php";
static Activity thisActivity = null;
InputStream is = null;
// LinearLayout yy=(LinearLayout)findViewById(R.id.uy);
// LinearLayout pp=(LinearLayout)findViewById(R.id.up);
//LinearLayout cc=(LinearLayout)findViewById(R.id.uc);
//LinearLayout ca=(LinearLayout)findViewById(R.id.uca);
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_update);
getServerData();
}
@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_update, 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();
//noinspection SimplifiableIfStatement
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
private void getServerData() {
thisActivity=this;
EditText f = (EditText) findViewById(R.id.ufst);
EditText l = (EditText) findViewById(R.id.ulst);
Spinner bld=(Spinner)findViewById(R.id.ubld);
Spinner stat=(Spinner)findViewById(R.id.ustatus);
Spinner bth=(Spinner)findViewById(R.id.ubat);
EditText dob = (EditText) findViewById(R.id.udob);
EditText phn1 = (EditText) findViewById(R.id.uphn);
EditText phn2 = (EditText) findViewById(R.id.uphn2);
EditText padd = (EditText) findViewById(R.id.upadd);
EditText radd = (EditText) findViewById(R.id.uradd);
EditText vill = (EditText) findViewById(R.id.uvill);
Spinner sec=(Spinner)findViewById(R.id.usec);
Spinner deg=(Spinner)findViewById(R.id.udeg);
EditText dept = (EditText) findViewById(R.id.udept);
EditText clg = (EditText) findViewById(R.id.uclg);
EditText yop = (EditText) findViewById(R.id.uyop);
EditText pos = (EditText) findViewById(R.id.upos);
EditText cmp = (EditText) findViewById(R.id.ucom);
EditText cadd = (EditText) findViewById(R.id.ucaddr);
String result = "";
//the year data to send
final ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("email","abc@gmail.com"));
Thread thread = new Thread(new Runnable(){
@Override
public void run() {
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(KEY_121);
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
} catch (Exception e) {
Toast.makeText(thisActivity, "Error in http connection " + e.toString(),Toast.LENGTH_LONG).show();
}
}
});
thread.start();
//convert response to string
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line+"n");
}
is.close();
result=sb.toString();
}catch(Exception e){
Toast.makeText(this, "Error converting result "+e.toString(),Toast.LENGTH_LONG).show();
}
//parse json data
try{
JSONArray jArray = new JSONArray(result);
for(int i=0;i<jArray.length();i++){
JSONObject json_data = jArray.getJSONObject(i);
f.setText(json_data.getString("fname"));
l.setText(json_data.getString("lname"));
dob.setText(json_data.getString("dob"));
switch(json_data.getString("blood")){
case "O Positive":
bld.setSelection(1);
break;
case "O Negative":
bld.setSelection(2);
break;
case "A Positive":
bld.setSelection(3);
break;
case "A Negative":
bld.setSelection(4);
break;
case "B Positive":
bld.setSelection(5);
break;
case "B Negative":
bld.setSelection(6);
break;
case "AB Positive":
bld.setSelection(7);
break;
case "AB Negative":
bld.setSelection(8);
break;
}
switch(json_data.getString("section")) {
case "A":
sec.setSelection(1);
break;
case "B":
sec.setSelection(2);
break;
case "C":
sec.setSelection(3);
break;
}
phn1.setText(json_data.getString("phn"));
phn2.setText(json_data.getString("phn2"));
padd.setText(json_data.getString("add"));
radd.setText(json_data.getString("add2"));
switch(json_data.getString("status")) {
case "Student":
stat.setSelection(1);
/* cc.setVisibility(View.INVISIBLE);
yy.setVisibility(View.INVISIBLE);
pp.setVisibility(View.INVISIBLE);
ca.setVisibility(View.INVISIBLE);*/
break;
case "Employee":
stat.setSelection(2);
/*cc.setVisibility(View.VISIBLE);
yy.setVisibility(View.VISIBLE);
pp.setVisibility(View.VISIBLE);
ca.setVisibility(View.VISIBLE);*/
break;
case "Un Employee":
stat.setSelection(3);
/* cc.setVisibility(View.INVISIBLE);
yy.setVisibility(View.VISIBLE);
pp.setVisibility(View.INVISIBLE);
ca.setVisibility(View.INVISIBLE);*/
break;
}
switch(json_data.getString("degree")) {
case "B.E":
deg.setSelection(1);
break;
case "Arts and Science":
deg.setSelection(2);
break;
case "Medical":
deg.setSelection(3);
break;
}
dept.setText(json_data.getString("dept"));
clg.setText(json_data.getString("clg"));
yop.setText(json_data.getString("yop"));
pos.setText(json_data.getString("pos"));
cmp.setText(json_data.getString("com"));
cadd.setText(json_data.getString("caddr"));
vill.setText(json_data.getString("vill"));
//Get an output to the screen
}
}catch(JSONException e) {
Toast.makeText(this, "Error parsing data " + e.toString(), Toast.LENGTH_LONG).show();
}
}
}
**
Logcat： **
04-06 14:11:39.580 25919-25919/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: pounkumarpurushothaman.ghssvmm, PID: 25919
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{pounkumarpurushothaman.ghssvmm/pounkumarpurushothaman.ghssvmm.update}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2225)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access$800(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.Window.findViewById(int)' on a null object reference
at android.app.Activity.findViewById(Activity.java:2081)
at pounkumarpurushothaman.ghssvmm.update.<init>(update.java:34)
at java.lang.reflect.Constructor.newInstance(Native Method)
at java.lang.Class.newInstance(Class.java:1572)
at android.app.Instrumentation.newActivity(Instrumentation.java:1088)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2388)
at android.app.ActivityThread.access$800(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1292)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityThread.main(ActivityThread.java:5312)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:901)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:696)
答案 0 :(得分：0)
以下是执行POST请求后如何获得响应。
HttpResponse response = httpClient.execute(httpPost);
String op = EntityUtils.toString(response.getEntity(), "UTF-8");
Log.d("Response:", op);