Seems like there are many questions that are similar to mine but the answers posted there dosen't seem to work for me. My program is supposed to simply just open up a new page that allows webview. But when i try to open this page, errors show without many hints on where the problem lies.
好像有很多问题和我的相似，但是我的答案似乎对我不起作用。我的程序应该只是打开一个允许webview的新页面。但是，当我试图打开这个页面时，错误显示了问题所在，却没有给出任何提示。
public class DetailedEventActivity extends Activity {
TextView name;
TextView desc;
TextView link;
String pid;
String myName;
String myDesc;
String myLink;
Button eLink;
// Progress Dialog
private ProgressDialog pDialog;
// JSON parser class
JSONParser jsonParser = new JSONParser();
// single profile url
private static final String url_event_detials = "http://10.0.2.2:8888/week_6/get_all_event.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_EVENT = "event";
private static final String TAG_PID = "eventID";
private static final String TAG_NAME = "eventName";
private static final String TAG_DESC = "eventDescription";
private static final String TAG_LINK = "link";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.detail_event);
// getting profile details from intent
Intent i = getIntent();
// getting profile id (pid) from intent
pid = i.getStringExtra(TAG_PID);
myName = i.getStringExtra(TAG_NAME);
myDesc = i.getStringExtra(TAG_DESC);
myLink = i.getStringExtra(TAG_LINK);
name = (TextView) findViewById(R.id.inputName);
desc = (TextView) findViewById(R.id.inputDesc);
//link = (TextView) findViewById(R.id.inputLink);
name.setText(myName);
desc.setText(myDesc);
link.setText(myLink);
eLink = (Button) findViewById(R.id.eventLink);
eLink.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
WebView webview = new WebView(DetailedEventActivity.this);
setContentView(webview);
WebSettings webSettings = webview.getSettings();
webSettings.setJavaScriptEnabled(true);
webview.loadUrl(myLink);
}
});
// Getting complete profile details in background thread
}
And the codes leads up to this other class.
代码指向另一个类。
public class ViewEventActivity extends ListActivity {
String pid;
String name;
String desc;
String link;
// Progress Dialog
private ProgressDialog pDialog;
// Creating JSON Parser object
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> eventList;
// url to get all profile list
private static String url_all_event = "http://10.0.2.2:8888/week_6/get_all_event.php";
// JSON Node names
private static final String TAG_SUCCESS = "success";
private static final String TAG_EVENT = "event";
private static final String TAG_PID = "eventID";
private static final String TAG_NAME = "eventName";
private static final String TAG_DESC = "eventDescription";
private static final String TAG_LINK = "link";
// profiles JSONArray
JSONArray event = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.all_event);
// Hashmap for ListView
eventList = new ArrayList<HashMap<String, String>>();
// Loading profiles in Background Thread
new LoadAllEvent().execute();
// Get listview
ListView lv = getListView();
// on seleting single event
// launching Edit event Screen
lv.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
// String pid = ((TextView) view.findViewById(R.id.pid)).getText().toString();
//Roy
String myPid = eventList.get(position).get(TAG_PID);
String myName = eventList.get(position).get(TAG_NAME);
String myDesc = eventList.get(position).get(TAG_DESC);
String myLink = eventList.get(position).get(TAG_LINK);
// Starting new intent
Intent in = new Intent(getApplicationContext(),DetailedEventActivity.class);
// sending pid to next activity
in.putExtra(TAG_PID, myPid);
Log.d("Put Extra ", "id = "+ myPid);
in.putExtra(TAG_NAME, myName);
Log.d("Put Extra ", "name = "+ myName);
in.putExtra(TAG_DESC, myDesc);
Log.d("Put Extra ", "desc = "+ myDesc);
in.putExtra(TAG_LINK, myLink);
Log.d("Put Extra ", "link = "+ myLink);
// starting new activity and expecting some response back
startActivityForResult(in, 100);
}
});
}
// Response from Edit profile Activity
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
// if result code 100
if (resultCode == 100) {
// if result code 100 is received
// means user edited/deleted profile
// reload this screen again
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
/**
* Background Async Task to Load all profile by making HTTP Request
* */
class LoadAllEvent extends AsyncTask<String, String, String> {
/**
* Before starting background thread Show Progress Dialog
* */
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(ViewEventActivity.this);
pDialog.setMessage("Loading event. Please wait...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
/**
* getting All profiles from url
* */
protected String doInBackground(String... args) {
// Building Parameters
List<NameValuePair> params = new ArrayList<NameValuePair>();
// getting JSON string from URL
JSONObject json = jParser.makeHttpRequest(url_all_event, "GET", params);
// Check your log cat for JSON reponse
Log.d("All Event ", json.toString());
try {
// Checking for SUCCESS TAG
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
// profiles found
// Getting Array of profiles
event = json.getJSONArray(TAG_EVENT);
// looping through All profiles
for (int i = 0; i < event.length(); i++) {
JSONObject c = event.getJSONObject(i);
Log.d("View Json ", "i = "+i);
// Storing each json item in variable
String id = c.getString(TAG_PID);
Log.d("View Json ", "id = "+ id);
String name = c.getString(TAG_NAME);
Log.d("View Json ", "name = "+ name);
String desc = c.getString(TAG_DESC);
Log.d("View Json ", "desc = "+ desc);
String link = c.getString(TAG_LINK);
Log.d("View Json ", "link = "+ link);
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_PID, id);
map.put(TAG_NAME, name);
map.put(TAG_DESC, desc);
map.put(TAG_LINK, link);
// adding HashList to ArrayList
eventList.add(map);
}
} else {
// no profiles found
// Launch Add New profile Activity
Intent i = new Intent(getApplicationContext(),
MainScreenActivity.class);
//Main Page Aagin
pDialog = new ProgressDialog(ViewEventActivity.this);
pDialog.setMessage("Redirecting to main page");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
// Closing all previous activities
i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(i);
}
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
/**
* After completing background task Dismiss the progress dialog
* **/
protected void onPostExecute(String file_url) {
// dismiss the dialog after getting all profiles
pDialog.dismiss();
// updating UI from Background Thread
runOnUiThread(new Runnable() {
public void run() {
/**
* Updating parsed JSON data into ListView
* */
ListAdapter adapter = new SimpleAdapter(
ViewEventActivity.this, eventList,
R.layout.list_event, new String[] { TAG_PID,
TAG_NAME},
new int[] { R.id.pid, R.id.name });
// updating listview
setListAdapter(adapter);
}
});
}
}
}
And the error i keep getting on the LogCat is:
我在LogCat上的错误是:
11-17 11:21:55.819: E/AndroidRuntime(1391): FATAL EXCEPTION: main
11-17 11:21:55.819: E/AndroidRuntime(1391): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.test/com.example.test.DetailedEventActivity}: java.lang.NullPointerException
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.app.ActivityThread.access$600(ActivityThread.java:141)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.os.Handler.dispatchMessage(Handler.java:99)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.os.Looper.loop(Looper.java:137)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-17 11:21:55.819: E/AndroidRuntime(1391): at java.lang.reflect.Method.invokeNative(Native Method)
11-17 11:21:55.819: E/AndroidRuntime(1391): at java.lang.reflect.Method.invoke(Method.java:525)
11-17 11:21:55.819: E/AndroidRuntime(1391): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-17 11:21:55.819: E/AndroidRuntime(1391): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-17 11:21:55.819: E/AndroidRuntime(1391): at dalvik.system.NativeStart.main(Native Method)
11-17 11:21:55.819: E/AndroidRuntime(1391): Caused by: java.lang.NullPointerException
11-17 11:21:55.819: E/AndroidRuntime(1391): at com.example.test.DetailedEventActivity.onCreate(DetailedEventActivity.java:77)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.app.Activity.performCreate(Activity.java:5133)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
11-17 11:21:55.819: E/AndroidRuntime(1391): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2175)
11-17 11:21:55.819: E/AndroidRuntime(1391): ... 11 more
I am aware that this question might seem trivial but i just started learning java last month, so guidiance and help is much appreciated. Thanks!
我知道这个问题可能看起来微不足道，但我上个月才开始学习java，所以非常感谢您的指导和帮助。谢谢!
2 个解决方案
#1
0
your textview link causes null pointer exception,
你的textview链接导致空指针异常，
link.setText(myLink); // <-- null here
so change
所以改变
//link = (TextView) findViewById(R.id.inputLink);
to
来
link = (TextView) findViewById(R.id.inputLink);
#2
1
You are accessing the link object without a proper initialization:
没有适当的初始化，您正在访问链接对象:
//link = (TextView) findViewById(R.id.inputLink);
link.setText(myLink);
#1
0
your textview link causes null pointer exception,
你的textview链接导致空指针异常，
link.setText(myLink); // <-- null here
so change
所以改变
//link = (TextView) findViewById(R.id.inputLink);
to
来
link = (TextView) findViewById(R.id.inputLink);
#2
1
You are accessing the link object without a proper initialization:
没有适当的初始化，您正在访问链接对象:
//link = (TextView) findViewById(R.id.inputLink);
link.setText(myLink);