这是我的RestAPI.java
/* JSON API for android appliation */
package com.ezchart.restfulapiclient;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
import java.text.SimpleDateFormat;
import java.util.Collection;
import java.util.Date;
import java.util.HashMap;
import java.util.Locale;
import java.util.Map;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.net.HttpURLConnection;
import java.net.URL;
import org.json.JSONObject;
import org.json.JSONArray;
public class RestAPI {
//url connection string to connect webservice
private final String urlString = "http://localhost:4475/Handler1.ashx";
private static String convertStreamToUTF8String(InputStream stream)
throws IOException {
String result = "";
//build a new string
StringBuilder sb = new StringBuilder();
try {
InputStreamReader reader = new InputStreamReader(stream, "UTF-8");
char[] buffer = new char[4096];
int readedChars = 0;
while (readedChars != -1) {
readedChars = reader.read(buffer);
if (readedChars > 0)
sb.append(buffer, 0, readedChars);
}
result = sb.toString();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
return result;
}
private String load(String contents) throws IOException {
//new urlString for connection
URL url = new URL(urlString);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setConnectTimeout(60000);
conn.setDoOutput(true);
conn.setDoInput(true);
OutputStreamWriter w = new OutputStreamWriter(conn.getOutputStream());
w.write(contents);
w.flush();
InputStream istream = conn.getInputStream();
String result = convertStreamToUTF8String(istream);
return result;
}
private Object mapObject(Object o) {
Object finalValue = null;
if (o.getClass() == String.class) {
finalValue = o;
} else if (Number.class.isInstance(o)) {
finalValue = String.valueOf(o);
} else if (Date.class.isInstance(o)) {
//create date format
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yyyy hh:mm:ss",
new Locale("en", "USA"));
finalValue = sdf.format((Date) o);
} else if (Collection.class.isInstance(o)) {
Collection<?> col = (Collection<?>) o;
JSONArray jarray = new JSONArray();
for (Object item : col) {
jarray.put(mapObject(item));
}
finalValue = jarray;
} else {
Map<String, Object> map = new HashMap<String, Object>();
Method[] methods = o.getClass().getMethods();
for (Method method : methods) {
if (method.getDeclaringClass() == o.getClass()
&& method.getModifiers() == Modifier.PUBLIC
&& method.getName().startsWith("get")) {
String key = method.getName().substring(3);
try {
Object obj = method.invoke(o, null);
Object value = mapObject(obj);
map.put(key, value);
finalValue = new JSONObject(map);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
return finalValue;
}
//Creating new account
public JSONObject CreateNewAccount(String firstName, String lastName,
String userName, String password) throws Exception {
JSONObject result = null;
JSONObject o = new JSONObject();
JSONObject p = new JSONObject();
o.put("interface", "RestAPI");
o.put("method", "CreateNewAccount");
//add-in for new user details
p.put("firstName", mapObject(firstName));
p.put("lastName", mapObject(lastName));
p.put("userName", mapObject(userName));
p.put("password", mapObject(password));
o.put("parameters", p);
String s = o.toString();
String r = load(s);
result = new JSONObject(r);
return result;
}
//getting the user details
public JSONObject GetUserDetails(String userName) throws Exception {
JSONObject result = null;
JSONObject o = new JSONObject();
JSONObject p = new JSONObject();
o.put("interface", "RestAPI");
o.put("method", "GetUserDetails");
p.put("userName", mapObject(userName));
o.put("parameters", p);
String s = o.toString();
String r = load(s);
result = new JSONObject(r);
return result;
}
//using username and pw for authentucation
public JSONObject UserAuthentication(String userName, String passsword)
throws Exception {
JSONObject result = null;
JSONObject o = new JSONObject();
JSONObject p = new JSONObject();
o.put("interface", "RestAPI");
//UserAuthentication method using json object
o.put("method", "UserAuthentication");
p.put("userName", mapObject(userName));
p.put("passsword", mapObject(passsword));
o.put("parameters", p);
String s = o.toString();
String r = load(s);
result = new JSONObject(r);
return result;
}
//get the Dept. information
public JSONObject GetDepartmentDetails() throws Exception {
JSONObject result = null;
JSONObject o = new JSONObject();
JSONObject p = new JSONObject();
o.put("interface", "RestAPI");
o.put("method", "GetDepartmentDetails");
o.put("parameters", p);
String s = o.toString();
String r = load(s);
result = new JSONObject(r);
return result;
}}
我的主要活动
package com.ezchart.restfulapiclient;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.MenuItem;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends Activity{
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//Display three main feature on the screen
String listItem []={"Login","Create User Account","Department Details"};
ListView lvMain=(ListView)findViewById(R.id.lv_main);
lvMain.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, listItem));
lvMain.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
long arg3) {
if(arg2==0)
{
Intent i=new Intent(MainActivity.this,LoginActivity.class);
startActivity(i);
}
else if(arg2==1)
{
Intent i=new Intent(MainActivity.this,CreateUserActivity.class);
startActivity(i);
}
else if(arg2==2)
{
Intent i=new Intent(MainActivity.this,DeptActivity.class);
startActivity(i);
}
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
Android Manifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.ezchart.restfulapiclient"
android:versionCode="1"
android:versionName="1.0" >
<uses-permission android:name="android.permission.INTERNET" />
<uses-sdk
android:minSdkVersion="8"
android:targetSdkVersion="21" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
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=".LoginActivity"
android:label="@string/title_activity_login"
android:parentActivityName=".MainActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.ezchart.restfulapiclient.MainActivity" />
</activity>
<activity
android:name=".UserDetailsActivity"
android:label="@string/title_activity_user_details"
android:parentActivityName=".MainActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.ezchart.restfulapiclient.MainActivity" />
</activity>
<activity
android:name=".CreateUserActivity"
android:label="@string/title_activity_create_user"
android:parentActivityName=".MainActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.ezchart.restfulapiclient.MainActivity" />
</activity>
<activity
android:name=".DeptActivity"
android:label="@string/title_activity_dept"
android:parentActivityName=".MainActivity" >
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.ezchart.restfulapiclient.MainActivity" />
</activity>
</application>
</manifest>
activity_main.xml中
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<ListView
android:id="@+id/lv_main"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true" >
</ListView>
</RelativeLayout>
DeptActivity.java
package com.ezchart.restfulapiclient;
import java.util.ArrayList;
import org.json.JSONObject;
import android.annotation.TargetApi;
import android.app.Activity;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.app.NavUtils;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.Toast;
public class DeptActivity extends Activity {
ArrayAdapter<String> adapter;
ListView listv;
Context context;
ArrayList<String> data;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dept);
// Show the Up button in the action bar.
setupActionBar();
data = new ArrayList<String>();
listv = (ListView) findViewById(R.id.lv_dept);
context = this;
adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, data);
listv.setAdapter(adapter);
Toast.makeText(this,"Loading Please Wait..",Toast.LENGTH_SHORT).show();
new AsyncLoadDeptDetails().execute();
}
protected class AsyncLoadDeptDetails extends
AsyncTask<Void, JSONObject, ArrayList<DeptTable>> {
ArrayList<DeptTable> deptTable = null;
@Override
protected ArrayList<DeptTable> doInBackground(Void... params) {
// TODO Auto-generated method stub
RestAPI api = new RestAPI();
try {
JSONObject jsonObj = api.GetDepartmentDetails();
JSONParser parser = new JSONParser();
deptTable = parser.parseDepartment(jsonObj);
} catch (Exception e) {
// TODO Auto-generated catch block
Log.d("AsyncLoadDeptDetails", e.getMessage());
}
return deptTable;
}
@Override
protected void onPostExecute(ArrayList<DeptTable> result) {
// TODO Auto-generated method stub
for (int i = 0; i < result.size(); i++) {
data.add(result.get(i).getNo() + " " + result.get(i).getName());
}
adapter.notifyDataSetChanged();
Toast.makeText(context,"Loading Completed",Toast.LENGTH_SHORT).show();
}
}
/**
* Set up the {@link android.app.ActionBar}, if the API is available.
*/
@TargetApi(Build.VERSION_CODES.HONEYCOMB)
private void setupActionBar() {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
getActionBar().setDisplayHomeAsUpEnabled(true);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.dept, 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();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
我的logcat
12-31 01:36:14.463: E/AndroidRuntime(2465): FATAL EXCEPTION: main
12-31 01:36:14.463: E/AndroidRuntime(2465): Process: com.ezchart.restfulapiclient, PID: 2465
12-31 01:36:14.463: E/AndroidRuntime(2465): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.ezchart.restfulapiclient/com.ezchart.restfulapiclient.DeptActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.app.ActivityThread.-wrap11(ActivityThread.java)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.os.Handler.dispatchMessage(Handler.java:102)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.os.Looper.loop(Looper.java:148)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.app.ActivityThread.main(ActivityThread.java:5417)
12-31 01:36:14.463: E/AndroidRuntime(2465): at java.lang.reflect.Method.invoke(Native Method)
12-31 01:36:14.463: E/AndroidRuntime(2465): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
12-31 01:36:14.463: E/AndroidRuntime(2465): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
12-31 01:36:14.463: E/AndroidRuntime(2465): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.ActionBar.setDisplayHomeAsUpEnabled(boolean)' on a null object reference
12-31 01:36:14.463: E/AndroidRuntime(2465): at com.ezchart.restfulapiclient.DeptActivity.setupActionBar(DeptActivity.java:95)
12-31 01:36:14.463: E/AndroidRuntime(2465): at com.ezchart.restfulapiclient.DeptActivity.onCreate(DeptActivity.java:35)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.app.Activity.performCreate(Activity.java:6237)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
12-31 01:36:14.463: E/AndroidRuntime(2465): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
12-31 01:36:14.463: E/AndroidRuntime(2465): ... 9 more
当我运行应用程序时，我发现上面的错误。 我认为这是因为urlString问题但不太确定。 请帮我看看并给出一些建议。 谢谢。