安卓 java。lang空点异常
上面说第71行有错误，但我能猜出是什么错误，有什么灵魂愿意帮助我？谢谢
我的问题是，当我点击Main活动上的foodbutton时，系统崩溃。但是logcat显示了食物中的错误。java，这是另一个页面
这是代码
package com.yiqiexample.cabincrew;
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import 安卓.app.Activity;
import 安卓.app.ListActivity;
import 安卓.app.ProgressDialog;
import 安卓.content.Intent;
import 安卓.os.AsyncTask;
import 安卓.os.Bundle;
import 安卓.view.View;
import 安卓.view.View.OnClickListener;
import 安卓.widget.AdapterView;
import 安卓.widget.Button;
import 安卓.widget.CheckBox;
import 安卓.widget.EditText;
import 安卓.widget.ListAdapter;
import 安卓.widget.ListView;
import 安卓.widget.SimpleAdapter;
//import 安卓.widget.ImageView;
import 安卓.widget.TextView;
import 安卓.widget.Toast;
import 安卓.widget.AdapterView.OnItemClickListener;
public class Food extends ListActivity
implements OnClickListener {
// Progress Dialog
private ProgressDialog pDialog;
//testing on Emulator:
private static final String READ_COMMENTS_URL = "http://10.0.2.2/pbda2/foodordered.php";
// private CheckBox chkFood, chkDrinks, chkServices;
//private Button btnDisplay, chkClear, deliever, chkClearFood, fooddeliever, drinksdeliever, servicesdeliever, chkClearDrinks, chkClearServices;
//private TextView clearThis,orderdisplay, clearThisFood, foodorderdisplay, drinksorderdisplay, servicesorderdisplay, clearThisDrinks, clearThisServices;
private static final String TAG_SUCCESS = "success";
private static final String TAG_POSTS = "posts";
private static final String TAG_SEATNUMBER = "seatnumber";
private static final String TAG_FOODORDERED = "foodordered";
//it's important to note that the message is both in the parent branch of
//our JSON tree that displays a "Post Available" or a "No Post Available" message,
//and there is also a message for each individual post, listed under the "posts"
//category, that displays what the user typed as their message.
//An array of all of our comments
private JSONArray mComments = null;
//manages all of our comments in a list.
private ArrayList<HashMap<String, String>> mCommentList;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.food);
View v = findViewById(R.id.backmain);
//set event listener
v.setOnClickListener(this);
View z = findViewById(R.id.drinksbtn);
//set event listener
z.setOnClickListener(this);
View x = findViewById(R.id.servicebtn);
//set event listener
x.setOnClickListener(this);
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
//loading the comments via AsyncTask
new LoadComments().execute();
}
/**
* Retrieves recent post data from the server.
*/
public void updateJSONdata() {
// Instantiate the arraylist to contain all the JSON data.
// we are going to use a bunch of key-value pairs, referring
// to the json element name, and the content, for example,
// message it the tag, and "I'm awesome" as the content..
mCommentList = new ArrayList<HashMap<String, String>>();
// Bro, it's time to power up the J parser
JSONParser jParser = new JSONParser();
// Feed the beast our comments url, and it spits us
//back a JSON object. Boo-yeah Jerome.
JSONObject json = jParser.getJSONFromUrl(READ_COMMENTS_URL);
//when parsing JSON stuff, we should probably
//try to catch any exceptions:
try {
//I know I said we would check if "Posts were Avail." (success==1)
//before we tried to read the individual posts, but I lied...
//mComments will tell us how many "posts" or comments are
//available
mComments = json.getJSONArray(TAG_POSTS);
// looping through all posts according to the json object returned
for (int i = 0; i < mComments.length(); i++) {
JSONObject c = mComments.getJSONObject(i);
//gets the content of each tag
String seatnumber = c.getString(TAG_SEATNUMBER);
String foodordered = c.getString(TAG_FOODORDERED);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_SEATNUMBER, seatnumber);
map.put(TAG_FOODORDERED, foodordered);
// adding HashList to ArrayList
mCommentList.add(map);
//annndddd, our JSON data is up to date same with our array list
}
} catch (JSONException e) {
e.printStackTrace();
}
}
@Override
public void onClick(View arg0) {
if(arg0.getId() == R.id.backmain){
//define a new Intent for the second Activity
Intent intent = new Intent(this,MainActivity.class);
//start the second Activity
this.startActivity(intent);
}
if(arg0.getId() == R.id.drinksbtn){
//define a new Intent for the second Activity
Intent intent = new Intent(this,Drinks.class);
//start the second Activity
this.startActivity(intent);
}
if(arg0.getId() == R.id.servicebtn){
//define a new Intent for the second Activity
Intent intent = new Intent(this,Services.class);
//start the second Activity
this.startActivity(intent);
}
}
/**
* Inserts the parsed data into the listview.
*/
private void updateList() {
// For a ListActivity we need to set the List Adapter, and in order to do
//that, we need to create a ListAdapter. This SimpleAdapter,
//will utilize our updated Hashmapped ArrayList,
//use our single_post xml template for each item in our list,
//and place the appropriate info from the list to the
//correct GUI id. Order is important here.
ListAdapter adapter = new SimpleAdapter(this, mCommentList,
R.layout.single_post, new String[] { TAG_SEATNUMBER, TAG_FOODORDERED
//TAG_DRINKSORDERED, TAG_SERVICES
}, new int[] { R.id.seatnumber, R.id.orders
//R.id.drinkstv, R.id.servicestv,
});
// I shouldn't have to comment on this one:
setListAdapter(adapter);
// Optional: when the user clicks a list item we
//could do something. However, we will choose
//to do nothing...
ListView lv = getListView();
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// This method is triggered if an item is click within our
// list. For our example we won't be using this, but
// it is useful to know in real life applications.
}
});
}
public class LoadComments extends AsyncTask<Void, Void, Boolean> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(Food.this);
pDialog.setMessage("Loading orders...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected Boolean doInBackground(Void... arg0) {
//we will develop this method in version 2
updateJSONdata();
return null;
}
@Override
protected void onPostExecute(Boolean result) {
super.onPostExecute(result);
pDialog.dismiss();
//we will develop this method in version 2
updateList();
}
}
}
这是主页的编码
package com.yiqiexample.cabincrew;
import 安卓.os.Bundle;
import 安卓.app.Activity;
import 安卓.content.Intent;
import 安卓.view.Menu;
import 安卓.view.View;
import 安卓.view.View.OnClickListener;
public class MainActivity extends Activity
implements OnClickListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
View v = findViewById(R.id.foodbutton);
//set event listener
v.setOnClickListener(this);
View x= findViewById(R.id.drinks);
//set event listener
x.setOnClickListener(this);
View y = findViewById(R.id.services);
//set event listener
y.setOnClickListener(this);
}
@Override
public void onClick(View arg0) {
if(arg0.getId() == R.id.foodbutton){
//define a new Intent for the second Activity
Intent intent = new Intent(this,Food.class);
//start the second Activity
this.startActivity(intent);
}
if(arg0.getId() == R.id.drinks){
//define a new Intent for the second Activity
Intent intent = new Intent(this,Drinks.class);
//start the second Activity
this.startActivity(intent);
}
if(arg0.getId() == R.id.services){
//define a new Intent for the second Activity
Intent intent = new Intent(this,Services.class);
//start the second Activity
this.startActivity(intent);
}
}
@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;
}
}
食物。xml
<RelativeLayout xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
xmlns:tools="http://schemas.安卓.com/tools"
xmlns:安卓1="http://schemas.安卓.com/apk/res/安卓"
安卓1:id="@+id/bg2"
安卓:layout_width="match_parent"
安卓:layout_height="wrap_content"
安卓1:background="#E0FFFF" >
<Button
安卓1:id="@+id/backmain"
安卓1:layout_width="wrap_content"
安卓1:layout_height="wrap_content"
安卓1:layout_alignParentBottom="true"
安卓1:layout_alignParentRight="true"
安卓1:text="@string/backtomain" />
<Button
安卓1:id="@+id/servicesdelivered"
安卓1:layout_width="wrap_content"
安卓1:layout_height="wrap_content"
安卓1:layout_above="@+id/foodbtn"
安卓1:layout_alignLeft="@+id/backmain"
安卓1:text="@string/servicesdelivered"
安卓1:visibility="invisible" />
<Button
安卓:id="@+id/servicebtn"
安卓:layout_width="wrap_content"
安卓:layout_height="wrap_content"
安卓:layout_alignParentBottom="true"
安卓:layout_marginLeft="358dp"
安卓:layout_toRightOf="@+id/foodbutton"
安卓:text="SERVICES" />
<Button
安卓1:id="@+id/foodbtn"
安卓1:layout_width="wrap_content"
安卓1:layout_height="wrap_content"
安卓1:layout_alignParentBottom="true"
安卓1:layout_marginBottom="23dp"
安卓1:layout_marginRight="24dp"
安卓1:text="DRINKS ORDERS" />
<LinearLayout
安卓:id="@+id/top_layover"
安卓:layout_width="fill_parent"
安卓:layout_height="wrap_content"
安卓:layout_alignParentLeft="true"
安卓:layout_alignParentTop="true"
安卓:orientation="horizontal" >
<TextView
安卓1:layout_width="wrap_content"
安卓:layout_height="wrap_content"
安卓:layout_gravity="center"
安卓:gravity="center"
安卓:text="@string/foodtitle"
安卓:textAppearance="?安卓:attr/textAppearanceLarge" />
</LinearLayout>
<ListView
安卓:id="@安卓:id/list"
安卓:layout_width="fill_parent"
安卓:layout_height="wrap_content"
安卓:layout_below="@+id/top_layover"
安卓1:layout_alignBottom="@+id/servicesdelivered"
安卓:background="#fff"
安卓:divider="@安卓:color/transparent"
安卓:scrollbars="none" />
<LinearLayout
安卓:id="@+id/bottom_layover"
安卓:layout_width="fill_parent"
安卓:layout_height="wrap_content"
安卓:layout_alignParentBottom="true"
安卓:layout_alignParentLeft="true"
安卓:orientation="horizontal"
安卓:weightSum="2" >
<LinearLayout
安卓:layout_width="0dp"
安卓:layout_height="wrap_content"
安卓:layout_weight="1"
安卓:orientation="vertical" >
</LinearLayout>
<LinearLayout
安卓:layout_width="0dp"
安卓:layout_height="wrap_content"
安卓:layout_weight="1"
安卓:orientation="vertical" >
</LinearLayout>
</LinearLayout>
</RelativeLayout>
这是LOGCAT
11-03 04:23:36.974: W/dalvikvm(756): threadid=1: thread exiting with uncaught exception (group=0x41465700)
11-03 04:23:37.093: E/AndroidRuntime(756): FATAL EXCEPTION: main
11-03 04:23:37.093: E/AndroidRuntime(756): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.yiqiexample.cabincrew/com.yiqiexample.cabincrew.Food}: java.lang.NullPointerException
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.app.ActivityThread.access$600(ActivityThread.java:141)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.os.Handler.dispatchMessage(Handler.java:99)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.os.Looper.loop(Looper.java:137)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.app.ActivityThread.main(ActivityThread.java:5103)
11-03 04:23:37.093: E/AndroidRuntime(756): at java.lang.reflect.Method.invokeNative(Native Method)
11-03 04:23:37.093: E/AndroidRuntime(756): at java.lang.reflect.Method.invoke(Method.java:525)
11-03 04:23:37.093: E/AndroidRuntime(756): at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-03 04:23:37.093: E/AndroidRuntime(756): at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-03 04:23:37.093: E/AndroidRuntime(756): at dalvik.system.NativeStart.main(Native Method)
11-03 04:23:37.093: E/AndroidRuntime(756): Caused by: java.lang.NullPointerException
11-03 04:23:37.093: E/AndroidRuntime(756): at com.yiqiexample.cabincrew.Food.onCreate(Food.java:71)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.app.Activity.performCreate(Activity.java:5133)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-03 04:23:37.093: E/AndroidRuntime(756): at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
11-03 04:23:37.093: E/AndroidRuntime(756): ... 11 more
11-03 04:23:43.713: I/Process(756): Sending signal. PID: 756 SIG: 9
11-03 04:23:46.715: D/dalvikvm(895): GC_FOR_ALLOC freed 44K, 4% free 2600K/2708K, paused 57ms, total 60ms
11-03 04:23:46.753: I/dalvikvm-heap(895): Grow heap (frag case) to 4.941MB for 2457616-byte allocation
11-03 04:23:46.893: D/dalvikvm(895): GC_FOR_ALLOC freed 2K, 3% free 4998K/5112K, paused 130ms, total 130ms
11-03 04:23:47.793: D/gralloc_goldfish(895): Emulator without GPU emulation detected.
11-03 04:31:41.842: I/Choreographer(895): Skipped 125 frames! The application may be doing too much work on its main thread.
11-03 04:31:42.284: I/Choreographer(895): Skipped 62 frames! The application may be doing too much work on its main thread.
11-03 04:31:42.913: I/Choreographer(895): Skipped 71 frames! The application may be doing too much work on its main thread.
11-03 04:32:15.008: D/dalvikvm(895): GC_FOR_ALLOC freed 143K, 4% free 5688K/5892K, paused 138ms, total 186ms
11-03 04:32:16.063: I/Choreographer(895): Skipped 91 frames! The application may be doing too much work on its main thread.
11-03 04:32:16.603: I/Choreographer(895): Skipped 58 frames! The application may be doing too much work on its main thread.
11-03 04:32:42.023: I/Choreographer(895): Skipped 46 frames! The application may be doing too much work on its main thread.
11-03 04:32:44.223: I/Choreographer(895): Skipped 30 frames! The application may be doing too much work on its main thread.
11-03 04:32:45.053: I/Choreographer(895): Skipped 122 frames! The application may be doing too much work on its main thread.
11-03 04:32:45.513: I/Choreographer(895): Skipped 68 frames! The application may be doing too much work on its main thread.
11-03 04:32:46.555: I/Choreographer(895): Skipped 135 frames! The application may be doing too much work on its main thread.
11-03 04:32:49.742: D/dalvikvm(895): GC_FOR_ALLOC freed 152K, 4% free 6327K/6544K, paused 350ms, total 378ms
11-03 04:32:50.245: D/dalvikvm(895): GC_FOR_ALLOC freed 59K, 4% free 7253K/7540K, paused 187ms, total 190ms
11-03 04:32:50.349: I/Choreographer(895): Skipped 192 frames! The application may be doing too much work on its main thread.
11-03 04:32:54.232: I/Choreographer(895): Skipped 35 frames! The application may be doing too much work on its main thread.
11-03 04:32:54.702: I/Choreographer(895): Skipped 73 frames! The application may be doing too much work on its main thread.
11-03 04:32:55.134: I/Choreographer(895): Skipped 71 frames! The application may be doing too much work on its main thread.
11-03 04:32:55.968: I/Choreographer(895): Skipped 112 frames! The application may be doing too much work on its main thread.
11-03 04:32:59.177: D/dalvikvm(895): GC_FOR_ALLOC freed 1715K, 21% free 6795K/8580K, paused 279ms, total 332ms
11-03 04:32:59.322: I/Choreographer(895): Skipped 134 frames! The application may be doing too much work on its main thread.
11-03 04:33:03.003: I/Choreographer(895): Skipped 53 frames! The application may be doing too much work on its main thread.
11-03 04:33:04.183: I/Choreographer(895): Skipped 35 frames! The application may be doing too much work on its main thread.
11-03 04:33:04.643: I/Choreographer(895): Skipped 35 frames! The application may be doing too much work on its main thread.
11-03 04:33:08.103: I/Choreographer(895): Skipped 43 frames! The application may be doing too much work on its main thread.
11-03 04:34:58.453: D/AndroidRuntime(951): Shutting down VM
11-03 04:34:58.453: W/dalvikvm(951): threadid=1: thread exiting with uncaught exception (group=0x41465700)
11-03 04:34:58.464: E/AndroidRuntime(951): FATAL EXCEPTION: main
11-03 04:34:58.464: E/AndroidRuntime(951): java.lang.RuntimeException: Unable to instantiate application 安卓.app.Application: java.lang.IllegalStateException: Unable to get package info for com.yiqiexample.cabincrew; is package not installed?
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.app.LoadedApk.makeApplication(LoadedApk.java:509)
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.app.ActivityThread.handleBindApplication(ActivityThread.java:4417)
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.app.ActivityThread.access$1300(ActivityThread.java:141)
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.os.Handler.dispatchMessage(Handler.java:99)
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.os.Looper.loop(Looper.java:137)
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.app.ActivityThread.main(ActivityThread.java:5103)
11-03 04:34:58.464: E/AndroidRuntime(951): at java.lang.reflect.Method.invokeNative(Native Method)
11-03 04:34:58.464: E/AndroidRuntime(951): at java.lang.reflect.Method.invoke(Method.java:525)
11-03 04:34:58.464: E/AndroidRuntime(951): at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-03 04:34:58.464: E/AndroidRuntime(951): at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-03 04:34:58.464: E/AndroidRuntime(951): at dalvik.system.NativeStart.main(Native Method)
11-03 04:34:58.464: E/AndroidRuntime(951): Caused by: java.lang.IllegalStateException: Unable to get package info for com.yiqiexample.cabincrew; is package not installed?
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.app.LoadedApk.initializeJavaContextClassLoader(LoadedApk.java:369)
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.app.LoadedApk.getClassLoader(LoadedApk.java:322)
11-03 04:34:58.464: E/AndroidRuntime(951): at 安卓.app.LoadedApk.makeApplication(LoadedApk.java:501)
11-03 04:34:58.464: E/AndroidRuntime(951): ... 11 more
11-03 04:35:10.544: D/dalvikvm(994): GC_FOR_ALLOC freed 55K, 5% free 2600K/2720K, paused 30ms, total 33ms
11-03 04:35:10.562: I/dalvikvm-heap(994): Grow heap (frag case) to 4.940MB for 2457616-byte allocation
11-03 04:35:10.673: D/dalvikvm(994): GC_FOR_ALLOC freed 2K, 3% free 4998K/5124K, paused 110ms, total 110ms
11-03 04:35:11.213: D/gralloc_goldfish(994): Emulator without GPU emulation detected.
11-03 04:40:44.032: D/AndroidRuntime(994): Shutting down VM
11-03 04:40:44.042: W/dalvikvm(994): threadid=1: thread exiting with uncaught exception (group=0x41465700)
11-03 04:40:44.112: E/AndroidRuntime(994): FATAL EXCEPTION: main
11-03 04:40:44.112: E/AndroidRuntime(994): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.yiqiexample.cabincrew/com.yiqiexample.cabincrew.Food}: java.lang.NullPointerException
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.app.ActivityThread.access$600(ActivityThread.java:141)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.os.Handler.dispatchMessage(Handler.java:99)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.os.Looper.loop(Looper.java:137)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.app.ActivityThread.main(ActivityThread.java:5103)
11-03 04:40:44.112: E/AndroidRuntime(994): at java.lang.reflect.Method.invokeNative(Native Method)
11-03 04:40:44.112: E/AndroidRuntime(994): at java.lang.reflect.Method.invoke(Method.java:525)
11-03 04:40:44.112: E/AndroidRuntime(994): at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-03 04:40:44.112: E/AndroidRuntime(994): at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-03 04:40:44.112: E/AndroidRuntime(994): at dalvik.system.NativeStart.main(Native Method)
11-03 04:40:44.112: E/AndroidRuntime(994): Caused by: java.lang.NullPointerException
11-03 04:40:44.112: E/AndroidRuntime(994): at com.yiqiexample.cabincrew.Food.onCreate(Food.java:71)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.app.Activity.performCreate(Activity.java:5133)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-03 04:40:44.112: E/AndroidRuntime(994): at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
11-03 04:40:44.112: E/AndroidRuntime(994): ... 11 more
如果您需要更多的编码来发现错误，请告诉我！：）
# 1 楼答案
假设第71行就是这个。-
此行必须将
z设置为空仔细检查
food布局是否包含id为drinksbtn且没有拼写错误的视图请注意，xml中没有
drinksbtn，也没有foodbutton