android Rest请求在onprogress方法上崩溃
我正试图在屏幕上显示一个正在进行的响应，但我的应用程序正在崩溃，我是android新手，但我知道，在我实施onprogress方法之前，我会进行一步操作，因为它首先得到了服务器的响应，然后我更新了显示，但当我运行时，在应用程序上看不到来自服务器的响应。任何帮助都将不胜感激 崩溃时的logCat输出：android Rest请求在onprogress方法上崩溃,android,rest,asynchronous,Android,Rest,Asynchronous,我正试图在屏幕上显示一个正在进行的响应，但我的应用程序正在崩溃，我是android新手，但我知道，在我实施onprogress方法之前，我会进行一步操作，因为它首先得到了服务器的响应，然后我更新了显示，但当我运行时，在应用程序上看不到来自服务器的响应。任何帮助都将不胜感激 崩溃时的logCat输出： 12-20 13:01:30.636: D/dalvikvm(597): GC_CONCURRENT freed 189K, 4% free 10154K/10503K, paused 19ms+2
12-20 13:01:30.636: D/dalvikvm(597): GC_CONCURRENT freed 189K, 4% free 10154K/10503K, paused 19ms+21ms
12-20 13:01:31.806: D/dalvikvm(597): GC_CONCURRENT freed 391K, 6% free 10278K/10823K, paused 27ms+20ms
12-20 13:01:31.876: D/dalvikvm(597): GC_FOR_ALLOC freed 370K, 6% free 10235K/10887K, paused 39ms
12-20 13:01:31.926: D/dalvikvm(597): GC_FOR_ALLOC freed 351K, 6% free 10242K/10887K, paused 41ms
12-20 13:01:31.976: D/dalvikvm(597): GC_FOR_ALLOC freed 319K, 6% free 10245K/10887K, paused 40ms
12-20 13:01:32.036: D/dalvikvm(597): GC_FOR_ALLOC freed 322K, 6% free 10243K/10887K, paused 45ms
12-20 13:01:32.156: D/AndroidRuntime(597): Shutting down VM
12-20 13:01:32.156: W/dalvikvm(597): threadid=1: thread exiting with uncaught exception (group=0x409951f8)
12-20 13:01:32.176: E/AndroidRuntime(597): FATAL EXCEPTION: main
12-20 13:01:32.176: E/AndroidRuntime(597): java.lang.NullPointerException
12-20 13:01:32.176: E/AndroidRuntime(597): at android.app.Activity.findViewById(Activity.java:1794)
12-20 13:01:32.176: E/AndroidRuntime(597): at edu.byu.hummedia.ReadWebpageAsyncTask$DownloadWebPageTask.onProgressUpdate(ReadWebpageAsyncTask.java:147)
12-20 13:01:32.176: E/AndroidRuntime(597): at edu.byu.hummedia.ReadWebpageAsyncTask$DownloadWebPageTask.onProgressUpdate(ReadWebpageAsyncTask.java:1)
12-20 13:01:32.176: E/AndroidRuntime(597): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:618)
12-20 13:01:32.176: E/AndroidRuntime(597): at android.os.Handler.dispatchMessage(Handler.java:99)
12-20 13:01:32.176: E/AndroidRuntime(597): at android.os.Looper.loop(Looper.java:137)
12-20 13:01:32.176: E/AndroidRuntime(597): at android.app.ActivityThread.main(ActivityThread.java:4340)
12-20 13:01:32.176: E/AndroidRuntime(597): at java.lang.reflect.Method.invokeNative(Native Method)
12-20 13:01:32.176: E/AndroidRuntime(597): at java.lang.reflect.Method.invoke(Method.java:511)
12-20 13:01:32.176: E/AndroidRuntime(597): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-20 13:01:32.176: E/AndroidRuntime(597): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-20 13:01:32.176: E/AndroidRuntime(597): at dalvik.system.NativeStart.main(Native Method)
12-20 13:06:01.806: I/Process(597): Sending signal. PID: 597 SIG: 9
package edu.byu.hummedia;
import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.Activity;
import android.app.FragmentTransaction;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
public class Hummedia extends Activity implements ActionBar.TabListener {
/** Called when the activity is first created. */
ListView myListView = null;
public ArrayAdapter<String> adapter;
Button basicSubmitButton;
Button advancedSubmitButton;
EditText myBasicEditText;
EditText myAdvancedEditText;
EditText title;
EditText language;
EditText category;
EditText keyword;
ActionBar bar;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
bar = getActionBar();
bar.addTab(bar.newTab().setText("Basic\nSearch").setTabListener(this));
bar.addTab(bar.newTab().setText("Advanced\nSearch").setTabListener(this));
bar.addTab(bar.newTab().setText("Results").setTabListener(this));
//bar.addTab(bar.newTab().setText("Exit").setTabListener(this));
bar.setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM | ActionBar.DISPLAY_USE_LOGO);
bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
bar.setDisplayShowHomeEnabled(true);
// remove the activity title to make space for tabs
bar.setDisplayShowTitleEnabled(false);
bar.setDisplayUseLogoEnabled(false);
}
public void onTabReselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
if (tab.getText().equals("Basic\nSearch"))
{
Toast.makeText(this, "Searching for: " + "basic" + "...", Toast.LENGTH_SHORT).show();
}
if (tab.getText().equals("Advanced\nSearch"))
{
Toast.makeText(this, "Searching for: " + "Advanced" + "...", Toast.LENGTH_SHORT).show();
}
if (tab.getText().equals("Results"))
{
Toast.makeText(this, "Searching for: " + "Results" + "...", Toast.LENGTH_SHORT).show();
}
}
public void onTabSelected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
if (tab.getText().equals("Basic\nSearch"))
{
setContentView(R.layout.basic);
basicSubmitButton = (Button)findViewById(R.id.myBasicSubmitbutton);
myBasicEditText = (EditText)findViewById(R.id.myBasicEditText);
}
if (tab.getText().equals("Advanced\nSearch"))
{
setContentView(R.layout.advanced);
advancedSubmitButton = (Button)findViewById(R.id.myAdvancedSubmitbutton);
title = (EditText)findViewById(R.id.title);
language = (EditText)findViewById(R.id.language);
category = (EditText)findViewById(R.id.category);
keyword = (EditText)findViewById(R.id.keyword);
//Toast.makeText(this, "Searching for: " + "Advanced" + "...", Toast.LENGTH_SHORT).show();
}
if (tab.getText().equals("Results"))
{
setContentView(R.layout.results);
//Toast.makeText(this, "Searching for: " + "Results" + "...", Toast.LENGTH_SHORT).show();
}
}
public void basicSubmitButton(View view) {
String query = myBasicEditText.getText().toString();
bar.setSelectedNavigationItem(2);
ReadWebpageAsyncTask basicSubmission = new ReadWebpageAsyncTask();
basicSubmission.query(query);
myListView = (ListView) findViewById (R.id.lv);
myListView.setTextFilterEnabled(true);
myListView.clearChoices();
adapter = new ArrayAdapter<String>(Hummedia.this,
android.R.layout.simple_list_item_1,
basicSubmission.mediaList);
myListView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
public void advancedSubmitButton(View view) {
String mytitle = title.getText().toString();
String mylanguage = language.getText().toString();
String mycategory = category.getText().toString();
String mykeyword = keyword.getText().toString();
String query="";
if (mytitle.isEmpty() != true)
{
query+="title="+mytitle;
}
if (mylanguage.isEmpty() != true)
{
query+="language="+mylanguage;
}
if (mycategory.isEmpty() != true)
{
query+="subject="+mycategory;
}
if (mykeyword.isEmpty() != true)
{
query+="keyword="+mykeyword;
}
//Toast.makeText(this, "I was called...", Toast.LENGTH_SHORT).show();
bar.setSelectedNavigationItem(2);
ReadWebpageAsyncTask advancedSubmission = new ReadWebpageAsyncTask();
advancedSubmission.advquery(query);
//bar.setSelectedNavigationItem(2);
myListView = (ListView) findViewById (R.id.lv);
myListView.setTextFilterEnabled(true);
myListView.clearChoices();
adapter = new ArrayAdapter<String>(Hummedia.this,
android.R.layout.simple_list_item_1,
advancedSubmission.mediaList);
myListView.setAdapter(adapter);
adapter.notifyDataSetChanged();
}
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
// TODO Auto-generated method stub
}
}
package edu.byu.hummedia;
import java.io.BufferedReader;
import android.widget.Toast;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONArray;
import android.view.View;
import android.widget.ProgressBar;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.SystemClock;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.Toast;
public class ReadWebpageAsyncTask extends ListActivity {
ProgressBar progressBar;
private TextView textView;
public ListView myListView = null;
List<String> mediaList = new ArrayList();
public ArrayAdapter<String> adapter;
String[] newArray;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
progressBar = (ProgressBar)findViewById(R.id.progressbar);
progressBar.setProgress(0);
super.onCreate(savedInstanceState);
//setContentView(R.layout.main);
String[] values = new String[] { "Android", "iPhone", "WindowsMobile",
"Blackberry", "WebOS", "Ubuntu", "Windows7", "Max OS X",
"Linux", "OS/2" };
newArray = new String[mediaList.size()];mediaList.toArray(newArray);
adapter = new ArrayAdapter<String>(this,
android.R.layout.simple_list_item_1, newArray);
setListAdapter(adapter);
readWebpage(myListView);
}
@Override
protected void onListItemClick(ListView l, View v, int position, long id) {
String item = (String) getListAdapter().getItem(position);
Toast.makeText(this, item + " selected", Toast.LENGTH_LONG);
}
private class DownloadWebPageTask extends AsyncTask<String, Integer, String> {
int myProgress;
@Override
protected String doInBackground(String... urls) {
String response = "";
String responseBuilder;
String responseString = "";
JSONArray jsonArray;
JSONObject jObject = new JSONObject();
for (String url : urls) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse execute = client.execute(httpGet);
InputStream content = execute.getEntity().getContent();
BufferedReader buffer = new BufferedReader(
new InputStreamReader(content));
String s = "";
while ((s = buffer.readLine()) != null) {
response += s;
}
} catch (Exception e) {
e.printStackTrace();
}
}
try {
jsonArray = new org.json.JSONArray(response);
jObject = jsonArray.toJSONObject(jsonArray);
for (int i=0;i<jObject.length();i++)
{
responseBuilder="\n";
responseBuilder+= "\n title: "+((JSONObject) jsonArray.getJSONObject(i).get("videoinfo")).get("title");
responseBuilder+= "\n subject: "+ ((JSONObject) jsonArray.getJSONObject(i).get("videoinfo")).get("subject");
responseBuilder+= "\n language: "+ ((JSONObject) jsonArray.getJSONObject(i).get("videoinfo")).get("language");
mediaList.add(responseBuilder);
responseString += responseBuilder;
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
while(myProgress<100){
myProgress++;
publishProgress(myProgress);
SystemClock.sleep(100);
}
return responseString;
}
@Override
protected void onPreExecute() {
// TODO Auto-generated method stub
// Toast.makeText(ReadWebpageAsyncTask.this,
// "onPreExecute", Toast.LENGTH_LONG).show();
myProgress = 0;
}
protected void onProgressUpdate(Integer... values) {
// TODO Auto-generated method stub
if (progressBar == null)
progressBar = (ProgressBar)findViewById(R.id.progressbar);
progressBar.setProgress(values[0]);
}
protected void onPostExecute(Void result) {
// TODO Auto-generated method stub
// Toast.makeText(ReadWebpageAsyncTask.this,
// "onPostExecute", Toast.LENGTH_LONG).show();
}
}
public void readWebpage(View view) {
DownloadWebPageTask task = new DownloadWebPageTask();
task.execute(new String[] { "http://hummedia.byu.edu/mediainfo/search/?title=Harry" });
}
public void query(String query) {
DownloadWebPageTask task = new DownloadWebPageTask();
task.execute(new String[] { "http://hummedia.byu.edu/mediainfo/search/?keyword="+query});
}
public void advquery(String query) {
DownloadWebPageTask task = new DownloadWebPageTask();
task.execute(new String[] { "http://hummedia.byu.edu/mediainfo/search/?"+query});
}
}
您发布的日志会准确地告诉您代码中的哪一行导致了问题。看起来您没有正确测试对progressbar控件的引用是否成功。将代码更改为：
protected void onProgressUpdate(Integer... values)
{
// TODO Auto-generated method stub
progressBar = (ProgressBar)findViewById(R.id.progressbar);
if (progressBar != null)
{
progressBar.setProgress(values[0]);
}
else
{
// check your resources because something doesn't match
}
}