我正在测试一个应用程序，它从解析中将数据检索到 ListView 中，但是当我运行该应用程序时，它崩溃并显示“不幸的是应用程序已停止”。不知道为什么？ 这是我的代码
主要activity.java
public class MainActivity extends Activity
{
ListView listview;
List<ParseObject> ob;
ProgressDialog mProgressDialog;
FinalAdapter adapter;
private List<CodeList> codelist = null;
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.beg_layout);
new RemoteDataTask().execute();
}
private class RemoteDataTask extends AsyncTask<Void, Void, Void>
{
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(MainActivity.this);
// Set progressdialog title
mProgressDialog.setTitle("Testing");
// Set progressdialog message
mProgressDialog.setMessage("Loading. Please wait this may take few moments ....");
mProgressDialog.setIndeterminate(true);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params)
{
codelist = new ArrayList<CodeList>();
try{
ParseQuery<ParseObject> query = new ParseQuery<ParseObject>(
"BeginnerActivity");
query.orderByAscending("_created_at");
ob = query.find();
for(ParseObject begactivity : ob){
ParseFile listimg = (ParseFile) begactivity.get("alphabetimg");
ParseFile levelimg = (ParseFile) begactivity.get("levelimg");
ParseFile apiimg = (ParseFile) begactivity.get("apiimg");
ParseFile descimgone = (ParseFile) begactivity.get("descimgone");
ParseFile descimgtwo = (ParseFile) begactivity.get("descimgtwo");
CodeList map = new CodeList();
map.setListHeading((String) begactivity.get("listheading"));
map.setSingleItemHeading((String) begactivity.get("heading"));
map.setDescription((String) begactivity.get("subheading"));
map.setApiText((String) begactivity.get("apitext"));
map.setFinalCodeText((String) begactivity.get("codetext"));
map.setAlphabetimg(listimg.getUrl());
map.setLevelImg(levelimg.getUrl());
map.setApiImg(apiimg.getUrl());
map.setPreviewImgOne(descimgone.getUrl());
map.setPreviewImgTwo(descimgtwo.getUrl());
codelist.add(map);
}
}catch(ParseException e){
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
// Locate the listview in listview_main.xml
listview = (ListView) findViewById(R.id.beg_layoutListView);
// Pass the results into ListViewAdapter.java
adapter = new FinalAdapter(MainActivity.this,
codelist);
// Binds the Adapter to the ListView
listview.setAdapter(adapter);
// Close the progressdialog
mProgressDialog.dismiss();
}
}
}
codelist.java
public class CodeList
{
private String alphabetimg;
private String listHeading;
private String levelImg;
private String singleItemHeading;
private String description;
private String apiImg;
private String apiText;
private String previewImgOne;
private String previewImgTwo;
private String finalCodeText;
public void setAlphabetimg(String alphabetimg)
{
this.alphabetimg = alphabetimg;
}
public String getAlphabetimg()
{
return alphabetimg;
}
public void setListHeading(String listHeading)
{
this.listHeading = listHeading;
}
public String getListHeading()
{
return listHeading;
}
public void setLevelImg(String levelImg)
{
this.levelImg = levelImg;
}
public String getLevelImg()
{
return levelImg;
}
public void setSingleItemHeading(String singleItemHeading)
{
this.singleItemHeading = singleItemHeading;
}
public String getSingleItemHeading()
{
return singleItemHeading;
}
public void setDescription(String description)
{
this.description = description;
}
public String getDescription()
{
return description;
}
public void setApiImg(String apiImg)
{
this.apiImg = apiImg;
}
public String getApiImg()
{
return apiImg;
}
public void setApiText(String apiText)
{
this.apiText = apiText;
}
public String getApiText()
{
return apiText;
}
public void setPreviewImgOne(String previewImgOne)
{
this.previewImgOne = previewImgOne;
}
public String getPreviewImgOne()
{
return previewImgOne;
}
public void setPreviewImgTwo(String previewImgTwo)
{
this.previewImgTwo = previewImgTwo;
}
public String getPreviewImgTwo()
{
return previewImgTwo;
}
public void setFinalCodeText(String finalCodeText)
{
this.finalCodeText = finalCodeText;
}
public String getFinalCodeText()
{
return finalCodeText;
}
}
解析application.java
public class ParseApplication extends Application {
@Override
public void onCreate() {
super.onCreate();
// Add your initialization code here
Parse.initialize(this, "4rOrqK23m0nVq187Of3rhDe0TK1R7FObdBWhfX10", "afKA4B9ohvk3M9pZNv9qK2ypbrdOpXi0FPnrXOu6");
ParseUser.enableAutomaticUser();
ParseACL defaultACL = new ParseACL();
// If you would like all objects to be private by default, remove this line.
defaultACL.setPublicReadAccess(true);
ParseACL.setDefaultACL(defaultACL, true);
}
}
最终的 adapter.java
public class FinalAdapter extends BaseAdapter
{
Context context;
LayoutInflater inflater;
ImageLoader imageLoader;
private List<CodeList> codeList = null;
private ArrayList<CodeList> arraylist;
public FinalAdapter(Context context,
List<CodeList> codeList) {
this.context = context;
this.codeList = codeList;
inflater = LayoutInflater.from(context);
this.arraylist = new ArrayList<CodeList>();
this.arraylist.addAll(codeList);
imageLoader = new ImageLoader(context);
}
public class ViewHolder{
TextView listHeading;
ImageView alphabetList;
}
@Override
public int getCount()
{
return codeList.size();
}
@Override
public Object getItem(int position)
{
return codeList.get(position);
}
@Override
public long getItemId(int position)
{
return position;
}
@Override
public View getView(final int position, View view, ViewGroup parent)
{
final ViewHolder holder;
if(view == null){
holder = new ViewHolder();
view = inflater.inflate(R.layout.beg_list_item,null);
holder.listHeading = (TextView) view.findViewById(R.id.beg_list_itemTextView);
holder.alphabetList = (ImageView) view.findViewById(R.id.beg_list_itemImageView);
view.setTag(holder);
}else{
holder = (ViewHolder) view.getTag();
}
holder.listHeading.setText(codeList.get(position).getListHeading());
imageLoader.DisplayImage(codeList.get(position).getAlphabetimg(),
holder.alphabetList);
view.setOnClickListener(new OnClickListener(){
@Override
public void onClick(View arg0){
Intent intent = new Intent(context, SingleItemView.class);
intent.putExtra("listheading",
(codeList.get(position).getListHeading()));
intent.putExtra("alphabetimg",
(codeList.get(position).getAlphabetimg()));
// Start SingleItemView Class
context.startActivity(intent);
}
});
return view;
}
}
singleitemview.java
public class SingleItemView extends Activity.
{
String heading;
String subHeading;
String levelImg;
String apiImg;
String apiText;
String descImgOne;
String descImgTwo;
String codeText;
ImageLoader imgloader = new ImageLoader(this);
@Override
protected void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.singleitemview);
Intent i = getIntent();
heading= i.getStringExtra("heading");
subHeading = i.getStringExtra("subheading");
levelImg = i.getStringExtra("levelimg");
apiImg = i.getStringExtra("apiimg");
apiText = i.getStringExtra("apitext");
descImgOne = i.getStringExtra("descimgone");
descImgTwo = i.getStringExtra("descimgtwo");
codeText = i.getStringExtra("codetext");
TextView headingtxt = (TextView)findViewById(R.id.singleitemheading);
TextView subheadingtxt = (TextView)findViewById(R.id.singleitemsubheading);
TextView apitxt = (TextView)findViewById(R.id.singleitemviewapitext);
TextView codetxt = (TextView) findViewById(R.id.singleitemviewcodetext);
ImageView level =(ImageView) findViewById(R.id.levelimg);
ImageView api =(ImageView) findViewById(R.id.singleitemviewapiimg);
ImageView descone =(ImageView) findViewById(R.id.descriptionimgone);
ImageView desctwo =(ImageView) findViewById(R.id.descriptionimgtwo);
headingtxt.setText(heading);
subheadingtxt.setText(subHeading);
apitxt.setText(apiText);
codetxt.setText(codeText);
imgloader.DisplayImage(levelImg, level);
imgloader.DisplayImage(apiImg, api);
imgloader.DisplayImage(descImgOne, descone);
imgloader.DisplayImage(descImgTwo, desctwo);
}
}
android list .xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.mycompany.myapp" >
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<application
android:name="ParseApplication"
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=".SingleItemView">
</activity>
</application>
</manifest>
日志
11-20 12:04:38.716 14897 14937 E AndroidRuntime FATAL EXCEPTION: AsyncTask #1 11-20 12:04:38.716 14897 14937 E AndroidRuntime Process: com.mycompany.myapp, PID: 14897 11-20 12:04:38.716 14897 14937 E AndroidRuntime java.lang.RuntimeException: An error occured while executing doInBackground() 11-20 12:04:38.716 14897 14937 E AndroidRuntime at android.os.AsyncTask$3.done(AsyncTask.java:304) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at java.util.concurrent.FutureTask.setException(FutureTask.java:222) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at java.util.concurrent.FutureTask.run(FutureTask.java:242) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at java.lang.Thread.run(Thread.java:818) 11-20 12:04:38.716 14897 14937 E AndroidRuntime Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.parse.ParseFile.getUrl()' on a null object reference 11-20 12:04:38.716 14897 14937 E AndroidRuntime at com.mycompany.myapp.MainActivity$RemoteDataTask.doInBackground(MainActivity.java:73) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at com.mycompany.myapp.MainActivity$RemoteDataTask.doInBackground(MainActivity.java) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at android.os.AsyncTask$2.call(AsyncTask.java:292) 11-20 12:04:38.716 14897 14937 E AndroidRuntime at java.util.concurrent.FutureTask.run(FutureTask.java:237) 11-20 12:04:38.716 14897 14937 E AndroidRuntime ... 4 more 11-20 12:04:51.596 15592 15592 D AndroidRuntime >>>>>> START com.android.internal.os.RuntimeInit uid 0 <<<<<< 11-20 12:04:51.612 15592 15592 D AndroidRuntime CheckJNI is OFF 11-20 12:04:51.958 15592 15592 D AndroidRuntime Calling main entry com.android.commands.am.Am 11-20 12:04:51.976 15592 15592 D AndroidRuntime Shutting down VM
最佳答案
你应该听你的调试器:D
这是你的错误。
...AndroidRuntime Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.parse.ParseFile.getUrl()' on a null object reference
所以其中一行:
map.setAlphabetimg(listimg.getUrl());
map.setLevelImg(levelimg.getUrl());
map.setApiImg(apiimg.getUrl());
map.setPreviewImgOne(descimgone.getUrl());
map.setPreviewImgTwo(descimgtwo.getUrl());
发送错误，因为调用 getUrl() 的对象为空。使用您的调试器来检查哪个是相关的或尝试/捕获 NullPointerException。
关于android - 不幸的是应用程序已停止，doinbackground() 出错，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33820826/