Android 空指针异常-尝试从PHPMYADMIN服务器检索数据
我正在编写一个应用程序，其中我试图从服务器PHPMYADMIN获取以前的订单详细信息，并希望在ListView中显示这些订单详细信息，但每当我运行我的应用程序getting NullPointerException时，请检查我的代码，并告诉我缺少什么以及我在哪里出错 日志显示：Android 空指针异常-尝试从PHPMYADMIN服务器检索数据,android,android-listview,Android,Android Listview,我正在编写一个应用程序，其中我试图从服务器PHPMYADMIN获取以前的订单详细信息，并希望在ListView中显示这些订单详细信息，但每当我运行我的应用程序getting NullPointerException时，请检查我的代码，并告诉我缺少什么以及我在哪里出错 日志显示： 05-22 12:33:35.652: E/AndroidRuntime(786): Caused by: java.lang.NullPointerException 05-22 12:33:35.652: E/And
05-22 12:33:35.652: E/AndroidRuntime(786): Caused by: java.lang.NullPointerException
05-22 12:33:35.652: E/AndroidRuntime(786): at OrdersActivity.showInfo(OrdersActivity.java:121)
05-22 12:33:35.652: E/AndroidRuntime(786): at OrdersActivity.onCreate(OrdersActivity.java:75)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.Activity.performCreate(Activity.java:5104)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-22 12:33:35.652: E/AndroidRuntime(786): ... 11 more
public class OrdersActivity extends Activity {
TextView total, items ;
String strMemberID,resultServer,MemberID;
ListView list;
OrdersAdapter adapter;
ArrayList<HashMap<String, String>> itemsList;
/** Called when the activity is first created. */
@SuppressWarnings("deprecation")
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_orders);
// Permission StrictMode
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
showInfo();
itemsList = new ArrayList<HashMap<String, String>>();
list = (ListView) findViewById(R.id.listView1);
adapter = new OrdersAdapter(this, itemsList);
list.setAdapter(adapter);
if (isNetworkAvailable()) {
new MyAsyncTask().execute();
} else {
AlertDialog alertDialog = new AlertDialog.Builder(OrdersActivity.this).create();
alertDialog.setMessage("The Internet connection appears to be offline.");
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
});
alertDialog.show();
}
}
public void showInfo()
{
total = (TextView)findViewById(R.id.txtTotalAmount);
items = (TextView)findViewById(R.id.txtItemDetails);
String url = "http://172.16.0.4/res/order_fetch.php";
Intent intent= getIntent();
MemberID = intent.getStringExtra("MemberID");
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("sMemberID", MemberID));
resultServer = getHttpPost(url,params);
String strTotal = "";
String strItems = "";
JSONObject c;
try {
c = new JSONObject(resultServer);
strTotal = c.getString("TotalAmount");
strItems = c.getString("ItemDetails");
if(!strMemberID.equals(""))
{
total.setText(strTotal);
items.setText(strItems);
}
else
{
total.setText("-");
items.setText("-");
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public String getHttpPost(String url,List<NameValuePair> params) {
StringBuilder str = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
try {
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse response = client.execute(httpPost);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) { // Status OK
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String line;
while ((line = reader.readLine()) != null) {
str.append(line);
}
} else {
Log.e("Log", "Failed to download result..");
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return str.toString();
}
private boolean isNetworkAvailable() {
ConnectivityManager cm = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
NetworkInfo info = cm.getActiveNetworkInfo();
return (info != null);
}
class MyAsyncTask extends
AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {
private ProgressDialog progressDialog = new ProgressDialog(
OrdersActivity.this);
@Override
protected void onPreExecute() {
progressDialog.setMessage("Loading, Please wait.....");
progressDialog.show();
}
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
String... params) {
// TODO Auto-generated method stub
return null;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
list = (ListView) findViewById(R.id.listView1);
adapter = new OrdersAdapter(OrdersActivity.this, itemsList);
list.setAdapter(adapter);
this.progressDialog.dismiss();
list.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}
});
}
}
}
public class OrdersAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
String strName,strMemberID ;
public OrdersAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.listrow_orders, null);
TextView title = (TextView)vi.findViewById(R.id.txtTotalAmount);
TextView description = (TextView)vi.findViewById(R.id.txtItemDetails);
HashMap<String, String> item = new HashMap<String, String>();
item = data.get(position);
title.setText(item.get(strName));
description.setText(strMemberID);
return vi;
}
}
showinfo（）
错误行号121是：if（！strMemberID.equals（“”）
OrdersActivity.java:
05-22 12:33:35.652: E/AndroidRuntime(786): Caused by: java.lang.NullPointerException
05-22 12:33:35.652: E/AndroidRuntime(786): at OrdersActivity.showInfo(OrdersActivity.java:121)
05-22 12:33:35.652: E/AndroidRuntime(786): at OrdersActivity.onCreate(OrdersActivity.java:75)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.Activity.performCreate(Activity.java:5104)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-22 12:33:35.652: E/AndroidRuntime(786): ... 11 more
public class OrdersActivity extends Activity {
TextView total, items ;
String strMemberID,resultServer,MemberID;
ListView list;
OrdersAdapter adapter;
ArrayList<HashMap<String, String>> itemsList;
/** Called when the activity is first created. */
@SuppressWarnings("deprecation")
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_orders);
// Permission StrictMode
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
showInfo();
itemsList = new ArrayList<HashMap<String, String>>();
list = (ListView) findViewById(R.id.listView1);
adapter = new OrdersAdapter(this, itemsList);
list.setAdapter(adapter);
if (isNetworkAvailable()) {
new MyAsyncTask().execute();
} else {
AlertDialog alertDialog = new AlertDialog.Builder(OrdersActivity.this).create();
alertDialog.setMessage("The Internet connection appears to be offline.");
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
});
alertDialog.show();
}
}
public void showInfo()
{
total = (TextView)findViewById(R.id.txtTotalAmount);
items = (TextView)findViewById(R.id.txtItemDetails);
String url = "http://172.16.0.4/res/order_fetch.php";
Intent intent= getIntent();
MemberID = intent.getStringExtra("MemberID");
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("sMemberID", MemberID));
resultServer = getHttpPost(url,params);
String strTotal = "";
String strItems = "";
JSONObject c;
try {
c = new JSONObject(resultServer);
strTotal = c.getString("TotalAmount");
strItems = c.getString("ItemDetails");
if(!strMemberID.equals(""))
{
total.setText(strTotal);
items.setText(strItems);
}
else
{
total.setText("-");
items.setText("-");
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public String getHttpPost(String url,List<NameValuePair> params) {
StringBuilder str = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
try {
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse response = client.execute(httpPost);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) { // Status OK
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String line;
while ((line = reader.readLine()) != null) {
str.append(line);
}
} else {
Log.e("Log", "Failed to download result..");
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return str.toString();
}
private boolean isNetworkAvailable() {
ConnectivityManager cm = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
NetworkInfo info = cm.getActiveNetworkInfo();
return (info != null);
}
class MyAsyncTask extends
AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {
private ProgressDialog progressDialog = new ProgressDialog(
OrdersActivity.this);
@Override
protected void onPreExecute() {
progressDialog.setMessage("Loading, Please wait.....");
progressDialog.show();
}
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
String... params) {
// TODO Auto-generated method stub
return null;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
list = (ListView) findViewById(R.id.listView1);
adapter = new OrdersAdapter(OrdersActivity.this, itemsList);
list.setAdapter(adapter);
this.progressDialog.dismiss();
list.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}
});
}
}
}
public class OrdersAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
String strName,strMemberID ;
public OrdersAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.listrow_orders, null);
TextView title = (TextView)vi.findViewById(R.id.txtTotalAmount);
TextView description = (TextView)vi.findViewById(R.id.txtItemDetails);
HashMap<String, String> item = new HashMap<String, String>();
item = data.get(position);
title.setText(item.get(strName));
description.setText(strMemberID);
return vi;
}
}
公共类OrdersActivity扩展活动{
TextView总计，个项目；
字符串strMemberID、resultServer、MemberID；
列表视图列表；
OrdersAdapter适配器；
ArrayList项目列表；
/**在首次创建活动时调用*/
@抑制警告（“弃用”）
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
//TODO自动生成的方法存根
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_orders）；
//权限限制模式
如果（android.os.Build.VERSION.SDK_INT>9）{
StrictMode.ThreadPolicy policy=新建StrictMode.ThreadPolicy.Builder（）.permitAll（）.build（）；
StrictMode.setThreadPolicy（策略）；
}
showInfo（）；
itemsList=新的ArrayList（）；
列表=（ListView）findViewById（R.id.listView1）；
适配器=新的OrdersAdapter（此，itemsList）；
list.setAdapter（适配器）；
if（isNetworkAvailable（））{
新建MyAsyncTask（）.execute（）；
}否则{
AlertDialog AlertDialog=新建AlertDialog.Builder（OrdersActivity.this）.create（）；
alertDialog.setMessage（“Internet连接似乎处于脱机状态”）；
alertDialog.setButton（“确定”，新的DialogInterface.OnClickListener（）{
public void onClick（DialogInterface dialog，int which）{
}
});
alertDialog.show（）；
}
}
public void showInfo（）
{
总计=（TextView）findViewById（R.id.txtTotalAmount）；
items=（TextView）findViewById（R.id.txtItemDetails）；
字符串url=”http://172.16.0.4/res/order_fetch.php";
Intent=getIntent（）；
MemberID=intent.getStringExtra（“MemberID”）；
List params=new ArrayList（）；
添加（新的BasicNameValuePair（“sMemberID”，MemberID））；
resultServer=getHttpPost（url，参数）；
字符串strTotal=“”；
字符串strItems=“”；
JSONObject c；
试一试{
c=新的JSONObject（resultServer）；
strTotal=c.getString（“TotalAmount”）；
strItems=c.getString（“ItemDetails”）；
如果（！strMemberID.equals（“”）
{
总计.setText（strTotal）；
items.setText（strItems）；
}
其他的
{
总计。setText（“-”）；
项目。setText（“-”）；
}
}捕获（JSONException e）{
//TODO自动生成的捕捉块
e、 printStackTrace（）；
}
}
公共字符串getHttpPost（字符串url，列表参数）{
StringBuilder str=新的StringBuilder（）；
HttpClient=new DefaultHttpClient（）；
HttpPost HttpPost=新的HttpPost（url）；
试一试{
setEntity（新的UrlEncodedFormEntity（参数））；
HttpResponse response=client.execute（httpPost）；
StatusLine StatusLine=response.getStatusLine（）；
int statusCode=statusLine.getStatusCode（）；
如果（statusCode==200）{//状态正常
HttpEntity=response.getEntity（）；
InputStream内容=entity.getContent（）；
BufferedReader=新的BufferedReader（新的InputStreamReader（内容））；
弦线；
而（（line=reader.readLine（））！=null）{
str.append（行）；
}
}否则{
Log.e（“日志”，“下载结果失败…”）；
}
}捕获（客户端协议例外e）{
e、 printStackTrace（）；
}捕获（IOE异常）{
e、 printStackTrace（）；
}
return str.toString（）；
}
专用布尔值isNetworkAvailable（）{
ConnectivityManager cm=（ConnectivityManager）getSystemService（CONNECTIVITY_服务）；
NetworkInfo=cm.getActiveNetworkInfo（）；
返回（信息！=null）；
}
类MyAsyncTask扩展
异步任务{
private ProgressDialog ProgressDialog=新建ProgressDialog(
OrdersActivity.this）；
@凌驾
受保护的void onPreExecute（）{
setMessage（“正在加载，请稍候…”）；
progressDialog.show（）；
}
@凌驾
受保护的ArrayList doInBackground(
字符串…参数）{
//TODO自动生成的方法存根
返回null；
}
@凌驾
受保护的void onPostExecute（ArrayList结果）{
列表=（ListView）findViewById（R.id.listView1）；
adapter=newordersadapter（OrdersActivity.this，itemsList）；
list.setAdapter（适配器）；
此.progressDialog.discouse（）文件；
list.setOnItemClickListener（新的OnItemClickListener（）{
public void onItemClick（AdapterView父级、视图、，
内部位置，长id）{
}
});
}
}
}
OrdersAdapter.java:
05-22 12:33:35.652: E/AndroidRuntime(786): Caused by: java.lang.NullPointerException
05-22 12:33:35.652: E/AndroidRuntime(786): at OrdersActivity.showInfo(OrdersActivity.java:121)
05-22 12:33:35.652: E/AndroidRuntime(786): at OrdersActivity.onCreate(OrdersActivity.java:75)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.Activity.performCreate(Activity.java:5104)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
05-22 12:33:35.652: E/AndroidRuntime(786): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
05-22 12:33:35.652: E/AndroidRuntime(786): ... 11 more
public class OrdersActivity extends Activity {
TextView total, items ;
String strMemberID,resultServer,MemberID;
ListView list;
OrdersAdapter adapter;
ArrayList<HashMap<String, String>> itemsList;
/** Called when the activity is first created. */
@SuppressWarnings("deprecation")
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_orders);
// Permission StrictMode
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
showInfo();
itemsList = new ArrayList<HashMap<String, String>>();
list = (ListView) findViewById(R.id.listView1);
adapter = new OrdersAdapter(this, itemsList);
list.setAdapter(adapter);
if (isNetworkAvailable()) {
new MyAsyncTask().execute();
} else {
AlertDialog alertDialog = new AlertDialog.Builder(OrdersActivity.this).create();
alertDialog.setMessage("The Internet connection appears to be offline.");
alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
}
});
alertDialog.show();
}
}
public void showInfo()
{
total = (TextView)findViewById(R.id.txtTotalAmount);
items = (TextView)findViewById(R.id.txtItemDetails);
String url = "http://172.16.0.4/res/order_fetch.php";
Intent intent= getIntent();
MemberID = intent.getStringExtra("MemberID");
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("sMemberID", MemberID));
resultServer = getHttpPost(url,params);
String strTotal = "";
String strItems = "";
JSONObject c;
try {
c = new JSONObject(resultServer);
strTotal = c.getString("TotalAmount");
strItems = c.getString("ItemDetails");
if(!strMemberID.equals(""))
{
total.setText(strTotal);
items.setText(strItems);
}
else
{
total.setText("-");
items.setText("-");
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public String getHttpPost(String url,List<NameValuePair> params) {
StringBuilder str = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
try {
httpPost.setEntity(new UrlEncodedFormEntity(params));
HttpResponse response = client.execute(httpPost);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) { // Status OK
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String line;
while ((line = reader.readLine()) != null) {
str.append(line);
}
} else {
Log.e("Log", "Failed to download result..");
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return str.toString();
}
private boolean isNetworkAvailable() {
ConnectivityManager cm = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE);
NetworkInfo info = cm.getActiveNetworkInfo();
return (info != null);
}
class MyAsyncTask extends
AsyncTask<String, Integer, ArrayList<HashMap<String, String>>> {
private ProgressDialog progressDialog = new ProgressDialog(
OrdersActivity.this);
@Override
protected void onPreExecute() {
progressDialog.setMessage("Loading, Please wait.....");
progressDialog.show();
}
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
String... params) {
// TODO Auto-generated method stub
return null;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
list = (ListView) findViewById(R.id.listView1);
adapter = new OrdersAdapter(OrdersActivity.this, itemsList);
list.setAdapter(adapter);
this.progressDialog.dismiss();
list.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
}
});
}
}
}
public class OrdersAdapter extends BaseAdapter {
private Activity activity;
private ArrayList<HashMap<String, String>> data;
private static LayoutInflater inflater=null;
String strName,strMemberID ;
public OrdersAdapter(Activity a, ArrayList<HashMap<String, String>> d) {
activity = a;
data=d;
inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
public int getCount() {
return data.size();
}
public Object getItem(int position) {
return position;
}
public long getItemId(int position) {
return position;
}
public View getView(int position, View convertView, ViewGroup parent) {
View vi=convertView;
if(convertView==null)
vi = inflater.inflate(R.layout.listrow_orders, null);
TextView title = (TextView)vi.findViewById(R.id.txtTotalAmount);
TextView description = (TextView)vi.findViewById(R.id.txtItemDetails);
HashMap<String, String> item = new HashMap<String, String>();
item = data.get(position);
title.setText(item.get(strName));
description.setText(strMemberID);
return vi;
}
}
公共类OrdersAdapter扩展BaseAdapter{
私人活动；
私有数组列表数据；
专用静态充气机=空；
字符串strName，strMemberID；
公共秩序适配器（A）