android - 适配器的内容已更改但 ListView 未收到通知 - 使用 AsyncTask

Question

我正在使用 AsyncTask 来设置我的项目和东西，在 postExecute 中我调用一个同步方法来执行此操作

mAllResultsAdapter.setItems(mAllResultsItem);
mAllResultsAdapter.notifyDataSetChanged();
mListView.invalidate();
mListView.requestLayout();

大多数时候，如果我下载新数据并更新我的 ListView /适配器，它就可以正常工作，而且非常好。但有时它会以某种方式崩溃，任何人都可以帮助我解决这个问题。

这是我的崩溃日志。

  03-19 14:15:02.170: E/AndroidRuntime(23242): FATAL EXCEPTION: main
03-19 14:15:02.170: E/AndroidRuntime(23242): java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(2131034153, class android.widget.ListView) with Adapter(class com....tracebuzz.allresults.AllResultsAdapter)]
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.ListView.layoutChildren(ListView.java:1556)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.AbsListView.onLayout(AbsListView.java:1993)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.View.layout(View.java:9606)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.ViewGroup.layout(ViewGroup.java:3879)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.FrameLayout.onLayout(FrameLayout.java:400)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.View.layout(View.java:9606)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.ViewGroup.layout(ViewGroup.java:3879)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.RelativeLayout.onLayout(RelativeLayout.java:912)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.View.layout(View.java:9606)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.ViewGroup.layout(ViewGroup.java:3879)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.FrameLayout.onLayout(FrameLayout.java:400)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.View.layout(View.java:9606)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.ViewGroup.layout(ViewGroup.java:3879)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1542)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1403)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1314)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.View.layout(View.java:9606)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.ViewGroup.layout(ViewGroup.java:3879)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.widget.FrameLayout.onLayout(FrameLayout.java:400)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.View.layout(View.java:9606)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.ViewGroup.layout(ViewGroup.java:3879)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.ViewRoot.performTraversals(ViewRoot.java:1288)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.view.ViewRoot.handleMessage(ViewRoot.java:2066)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.os.Handler.dispatchMessage(Handler.java:99)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.os.Looper.loop(Looper.java:132)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at android.app.ActivityThread.main(ActivityThread.java:4126)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at java.lang.reflect.Method.invokeNative(Native Method)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at java.lang.reflect.Method.invoke(Method.java:491)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:844)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602)
03-19 14:15:02.170: E/AndroidRuntime(23242):    at dalvik.system.NativeStart.main(Native Method)

我应该用我的代码更新我的问题，所以在这里。

public class AllResultsActivity extends TBActivity{

public String   identifier,
                feedIdentifier,
                apiKey,
                tagID,
                titleName;

private ProcesReuest procesReuest;

public ArrayList<Integer> tempIDHolder = new ArrayList<Integer>();
public ArrayList<AllResultsItem> mAllResultsItem;
public AllResultsAdapter mAllResultsAdapter;
public ListView mListView;
private Context mContext;
private ViewFlipper mViewFlipper;
private TextView mTitleText;
private int itemsForLoad = 50;
private boolean firstRun = true;

private ProgressBar mLoadItemsIndicator;
private int visibleThreshold = 5;
private int mPage = 1;
private int previousTotal = 0;
private boolean loading = true;
private SharedPreferences mSettings;
private Editor mEdit;
private View footerView;
private int itemHolder;


@Override
public void onBackPressed() {
    super.onBackPressed();
    procesReuest.cancel(true);
    AllResultsActivity.this.finish();
}
@Override
public void onCreate(Bundle savedInstanceState) {
    this.requestWindowFeature(Window.FEATURE_NO_TITLE);
    this.setContentView(R.layout.all_results_view);
    super.onCreate(savedInstanceState);
    getExtras();
    mContext = this;
    itemsForLoad = 50;

    loadItems(apiKey);
    initListview();
}

private void initListview() {
    mAllResultsItem = new ArrayList<AllResultsItem>();
    mAllResultsAdapter = new AllResultsAdapter(this, mAllResultsItem);
    mListView.setAdapter(mAllResultsAdapter);
    mAllResultsAdapter.notifyDataSetChanged();
}

@Override
public void bindResources() {
    mLoadItemsIndicator = (ProgressBar)findViewById(R.id.all_results_view_more_items_indicator);
    mListView = (ListView)findViewById(R.id.all_results_listview);
    mViewFlipper = (ViewFlipper)findViewById(R.id.all_results_view_viewflipper);
    mTitleText   = (TextView) findViewById(R.id.all_results_view_title_text);
    mSettings   = getSharedPreferences(WBAConstants.TRACEBUZZ, MODE_PRIVATE);
    mEdit       =   mSettings.edit();   

}

@Override
public void bindListeners() {
    mListView.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> arg0, View view, int id, long arg3) {

        String url = (String) view.getTag(R.string.item_url);
        Intent intnt = new Intent(AllResultsActivity.this, WebviewWithControllsActivity.class); 
            if(url.contains("twitter")) {
                int     UQID    = (Integer)view.getTag(R.id.twitter_result_identifier);
                String table    = (String)view.getTag(R.string.twitter_table);

                intnt.putExtra("UQID", UQID);
                intnt.putExtra("apiKey", apiKey);
                intnt.putExtra("table", table);
            }
            View bar = (View)findViewById(R.id.all_results_title_bar);
            int barHeight = bar.getHeight();
            intnt.putExtra("barHeight", barHeight);
            intnt.putExtra("URL", url); 
            AllResultsActivity.this.startActivity(intnt);           
        }
    });

    mListView.setOnScrollListener(new OnScrollListener() {

        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
        }

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            Log.d("","totalItemCount = " + totalItemCount);
            if (loading) {
                if (totalItemCount > previousTotal) {
                    loading = false;
                    previousTotal = totalItemCount;
                    itemHolder = previousTotal;
                } 
            }
            if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
                    mLoadItemsIndicator.setVisibility(View.VISIBLE);
                    mListView.invalidate();

                    mPage++;
                    loadItems(apiKey);
                    loading = true;
            } else  {

            }
        }   
    });     
}   

private void loadItems(String passedApiKey) {   

    procesReuest = new ProcesReuest();
    procesReuest.execute(identifier, feedIdentifier, passedApiKey);
}

public void getExtras() {
    Bundle extras = getIntent().getExtras();

    feedIdentifier = null;
    tagID = null;
    apiKey = null;
    if(extras != null) {
        identifier      = extras.getString("identifier");
        feedIdentifier  = extras.getString("feedidentifier");
        apiKey          = extras.getString("apiKey");
        titleName       = extras.getString("tag_name");
        tagID           = extras.getString("tag_id");
        if((titleName != null) && (!titleName.equals("null"))) {
            mTitleText.setText(titleName);
        }
    }
}

public void displayDialog() {
    AlertDialog.Builder dialog = new AlertDialog.Builder(this);
    dialog.setTitle("Error");
    dialog.setMessage("Failed to contact server, check your Internet connection or try again later");
    dialog.setNegativeButton("back", new OnClickListener() {

        @Override
        public void onClick(DialogInterface dialog, int which) {
            AllResultsActivity.this.finish();
        }
    });
    dialog.show();
}


private synchronized void addSyncedItems() throws InterruptedException {

        if(firstRun){
            mAllResultsAdapter.setItems(mAllResultsItem);
            firstRun = false;
        }   
                mAllResultsAdapter.notifyDataSetChanged();

                mListView.invalidate();
                mLoadItemsIndicator.setVisibility(View.GONE);   

}

/** Subclass for processing the ResultReqesut for the specified type **/

private class ProcesReuest extends AsyncTask<String, Void, Exception>{
    Downloader downloader = new Downloader();
    JSONObject result = null;
    List<NameValuePair> postParams;
    boolean timeOut;
    @Override
    protected Exception doInBackground(String... params) {
        Log.d("","doInBackground " + apiKey);

        try {
            postParams = new ArrayList<NameValuePair>(2);       
            postParams.add(new BasicNameValuePair("api_key",apiKey));
            postParams.add(new BasicNameValuePair("num","100"));
            postParams.add(new BasicNameValuePair("feed_id", feedIdentifier));
            postParams.add(new BasicNameValuePair("page", Integer.toString(mPage)));
            postParams.add(new BasicNameValuePair("order", "time DESC"));
            postParams.add(new BasicNameValuePair("tag_id", tagID));
            postParams.add(new BasicNameValuePair("format", "json"));
            Log.d("","postParams = " + postParams);
            downloadJSON(postParams);
            proccesJSON();
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;
    }

    @Override
    protected void onPostExecute(Exception exception) {
        Log.d("","onPostExecute");
            try {
                addSyncedItems();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        try {
                if(!result.getJSONObject("results").getString("result_count").equals("0")){
                    mViewFlipper.setDisplayedChild(2);
                } else {
                    Log.d("","View 3");
                    mViewFlipper.setDisplayedChild(2);
                }
            } catch (Exception e) {
                // TODO: handle exception
            }
    }

    private void proccesJSON() throws JSONException, IOException {
        String UIDHolderString = mSettings.getString(WBAConstants.UIDHOLDER, "empty");
        JSONArray arrayHolder = null;

        if(UIDHolderString.equals("empty")){
            arrayHolder = new JSONArray();
        } else {
            arrayHolder = new JSONArray(UIDHolderString);       
        }

    if(result != null){
        JSONObject feedResults = result.getJSONObject("results").getJSONObject("result");
        Log.d("","" + feedResults);
        String uniqueItemID = null;
        Iterator<String> feedResultIter = feedResults.keys();

        while (feedResultIter.hasNext()) {
            uniqueItemID = (String) feedResultIter.next();  
            Log.d("","" + uniqueItemID);

            if(!uniqueItemID.equals("metaresult")) {
            AllResultsItem item = new AllResultsItem();


            if(UIDHolderString.contains(uniqueItemID)) {
                item.setNewFeed(0);
            } else {
                item.setNewFeed(1);
                arrayHolder.put(uniqueItemID);
            }

            JSONObject resultItem = feedResults.getJSONObject(uniqueItemID);        
                String typeFeed = resultItem.getString("type");
                if(!typeFeed.contains("twitter") && typeFeed != null){      
                    if(resultItem.has("tags") && resultItem.getString("tags")!= null) {
                        JSONObject tags = resultItem.getJSONObject("tags");     

                        Iterator<String> tagIter = tags.keys();
                        ArrayList<String> tagHolder = new ArrayList<String>();
                        while (tagIter.hasNext()) {
                            String tagID = (String) tagIter.next();
                            String tagName = tags.getString(tagID);
                            tagHolder.add(tagName);         
                        }                   
                        item.setTagNames(tagHolder.toString());
                    }
                    item.setType(typeFeed);
                    if((resultItem.has("title")) && (!resultItem.isNull("title")) && (!resultItem.getString("title").equals("null") )) {
                        item.setResultTitle(resultItem.getString("title"));
                    } 
                    if(resultItem.has("unique_id")) {
                        item.setResultIdentifier(Integer.parseInt(resultItem.getString("unique_id")));
                    }
                    if(resultItem.has("src_link") && (resultItem.getString("src_link") != null)) {
                        item.setMessageURL(resultItem.getString("src_link"));
                    }
                    if(resultItem.has("date_time")) {
                        item.setDate( resultItem.getString("date_time"));
                    }
                    if(resultItem.has("description")) {
                        item.setMessage(resultItem.getString("description"));
                    }

                } else if(resultItem.getString("type").contains("twitter")){

                    Icon icon = new Icon();                                     
                    if((resultItem.has("title")) && (!resultItem.isNull("title")) && (!resultItem.getString("title").equals("null"))) {
                        item.setUserTwitter(resultItem.getString("title"));
                    } 
                    if(resultItem.has("unique_id")) {
                        item.setIdentifier(Integer.parseInt(resultItem.getString("unique_id")));
                    }
                    if(resultItem.has("src_link") && (resultItem.getString("src_link") != null)) {
                        item.setMessageURL(resultItem.getString("src_link"));

                    }
                    if(resultItem.has("date_time")) {                           

                        item.setDate(resultItem.getString("date_time"));
                    }
                    if(resultItem.has("description")) {
                        item.setMessageText(resultItem.getString("description"));

                    }
                    if(resultItem.has("image_link")) {
                        if(!resultItem.has("null")){
                            icon.setImageURL(resultItem.getString("image_link"));
                    }                   
                }       
                    if(resultItem.has("table")) {
                    item.setTable(resultItem.getString("table"));
                    }       

                        item.setType(typeFeed);
                        item.addIconsObject(icon);
                        if(resultItem.has("tags") && resultItem.getString("tags")!= null) {
                            JSONObject tags = resultItem.getJSONObject("tags");

                            Iterator<String> tagIter = tags.keys();
                            ArrayList<String> tagHolder = new ArrayList<String>();
                            while (tagIter.hasNext()) {
                                String tagID = (String) tagIter.next();
                                String tagName = tags.getString(tagID);

                                tagHolder.add(tagName);

                            }
                            item.setTagNames(tagHolder.toString());
                        }
                }
                mAllResultsItem.add(item);
            }
        }
        mEdit.putString(WBAConstants.UIDHOLDER, arrayHolder.toString());
        mEdit.commit();
        }
    }

    public boolean downloadJSON(List<NameValuePair>postParams) {
        try {
            result = downloader.getJSONFromURL("http://www.example.com/webservice/get_feed_results.php", true, postParams);
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return true;
    }
}
}

Syncronized 方法的原因只是为了尝试让适配器和 ListView 同时更新。

Answer 1

根据代码 fragment ，有一些标记为@Override的方法(bindResources()和bindListeners()等)既没有继承自官方API，也没有在AllResultsActivity中显式调用。假设这些已正确实现并涉及父类(super class)或其他地方。我在您的代码中看到的问题是:

@Override
public void onCreate(Bundle savedInstanceState) {
  ... ...

  loadItems(apiKey); // <-- method start AsyncTask, and finially involve mAllResultsAdapter.notifyDataSetChanged();
  initListview(); // <-- method that bind Adapter to ListView. i.e. mListView.setAdapter(mAllResultsAdapter);
}

问题是当 AysncTask 执行并调用 onPostExecute() 时(调用 mAllResultsAdapter.notifyDataSetChanged(); 时)，适配器尚未绑定(bind)到 ListView。只需调用 initListview();在 loadItems(apiKey) 之前；应该使 java.lang.IllegalStateException: 消失。

更新:
我深入查看了您的代码，问题是绑定(bind)到适配器的 ArrayList 在后台线程中发生了更改:

// proccesJSON() is called in AsyncTask.doInBackground()
private void proccesJSON() throws JSONException, IOException {
  ... ...

  mAllResultsItem.add(item); // <-- mAllResultsItem is bound to mAllResultsAdapter

  ... ...
}

您的适配器实际上是从后台线程修改的，与异常建议的完全一样。解决方案是将它移动到 UI 线程或简单地用 runOnUiThread() 包装它:

... ...

runOnUiThread(new Runnable() {
  public void run() {
    mAllResultsItem.add(item);
    mAllResultsAdapter.notifyDataSetChanged();
  }
}); // end of runOnUiThread

... ...

希望这对您有所帮助。