Question

我正在编写Android应用程序，但在使用异步任务时它失败了，我有一个异步任务，并且错误进入它的doInBackground（）方法其他一切看起来不错，但doInBackground（）方法无法正常工作。在doInBackground（）方法中，我已经编写了用于从数据库中获取记录的代码，而在调试时我发现记录是在数组列表中获取的，但是它们并没有进行geeting onPostExecute（String result）请帮帮我......

private class LoadMoreAsync extends AsyncTask<Context, Void, String> {
    private String strAddress;

    public LoadMoreAsync(Context mContext,String strAddress) {
        /*this.strCardNo = strCardNo;
        this.strFirstName = strFirstName;
        this.strMiddleName = strMiddleName;*/
        this.strAddress = strAddress;
        /*this.strCardNo = strCardNo;*/
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        ToastUtils.showToast(mContext, "Loading More...");
    }

    @Override
    protected String doInBackground(Context... arg0) {
        mVoterArray = new ArrayList<AddressInfo>();
        mVoterArray = extDbUtil.getAddresslist(strAddress , limit += 20);
        if (mVoterArray.isEmpty() || mVoterArray == null)
            return null;
        else
            return "";
    }

    @Override
    protected void onPostExecute(String result) {
        super.onPostExecute(result);
         IOUtils.stopLoading();
        if (result == null) {
            ToastUtils.showToast(mContext, "No Record Found!!");
        } else {
            int position = mListView.getLastVisiblePosition();
            mListAdapter = new ListAdapterNew2(mContext,
                    android.R.layout.simple_list_item_1, mVoterArray);
            mListView.setAdapter(mListAdapter);
            mListView.setSelectionFromTop(position, 0);
            mListAdapter.notifyDataSetChanged();
        }
    }
}

extDbUtil.getAddresslist的代码（strAddress，limit + = 20）;方法是

public ArrayList<AddressInfo> getAddresslist(String strAddress,int limit) {
    open();
    ArrayList<AddressInfo> mAddressArray = new ArrayList<AddressInfo>();
    String mQuery = "SELECT Address1,TotalMale,TotalFemale,TotalVoters, SrNo  FROM "
            + TABLE_ADDRESS;
    String Where = "";
    if (!strAddress.equals("NA")) {
        Where = " WHERE EAddress1 Like '%" + strAddress + "%'";

    }
    Log.i("SearchQuery", mQuery + Where + " LIMIT " + limit);
    Cursor mCursor = mDatabase.rawQuery(mQuery + Where + " LIMIT " + limit,
            null);

    if (mCursor != null) {
        if (mCursor.moveToFirst()) {                
            do {
                AddressInfo mAddress = new AddressInfo();
                mAddress.setSrNO(mCursor.getString(mCursor
                        .getColumnIndex("SrNo")));
                mAddress.setAddress(mCursor.getString(mCursor
                        .getColumnIndex("Address1")));
                mAddress.setTotalMale(mCursor.getString(mCursor
                        .getColumnIndex("TotalMale")));
                mAddress.setTotalFemal(mCursor.getString(mCursor
                        .getColumnIndex("TotalFemale")));
                mAddress.setTotalVoter(mCursor.getString(mCursor
                        .getColumnIndex("TotalVoters")));                   

            } while (mCursor.moveToNext());
            }


    }
    mCursor.close();
    CleanUp();
    return mAddressArray;
}

即将发生错误

    01-03 22:59:05.310: D/memalloc(15369): ion: Mapped buffer base:0x51d44000 size:4096 offset:0 fd:87
01-03 22:59:05.310: I/SearchQuery(15369): SELECT Address1,TotalMale,TotalFemale,TotalVoters, SrNo  FROM Addresses WHERE EAddress1 Like '%R%' LIMIT 20
01-03 22:59:05.330: W/dalvikvm(15369): threadid=16: thread exiting with uncaught exception (group=0x41a09600)
01-03 22:59:05.340: D/memalloc(15369): ion: Mapped buffer base:0x555da000 size:196608 offset:0 fd:84
01-03 22:59:05.340: D/memalloc(15369): ion: Mapped buffer base:0x51d4b000 size:4096 offset:0 fd:90
01-03 22:59:05.340: E/AndroidRuntime(15369): FATAL EXCEPTION: AsyncTask #3
01-03 22:59:05.340: E/AndroidRuntime(15369): java.lang.RuntimeException: An error occured while executing doInBackground()
01-03 22:59:05.340: E/AndroidRuntime(15369):    at android.os.AsyncTask$3.done(AsyncTask.java:299)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at java.lang.Thread.run(Thread.java:864)
01-03 22:59:05.340: E/AndroidRuntime(15369): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
01-03 22:59:05.340: E/AndroidRuntime(15369):    at android.os.Handler.<init>(Handler.java:121)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at android.widget.Toast$TN.<init>(Toast.java:322)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at android.widget.Toast.<init>(Toast.java:91)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at android.widget.Toast.makeText(Toast.java:238)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at com.phoenix.rajtantra.SearchByAdd$List_Async.doInBackground(SearchByAdd.java:284)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at com.phoenix.rajtantra.SearchByAdd$List_Async.doInBackground(SearchByAdd.java:1)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at android.os.AsyncTask$2.call(AsyncTask.java:287)
01-03 22:59:05.340: E/AndroidRuntime(15369):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
01-03 22:59:05.340: E/AndroidRuntime(15369):    ... 5 more
01-03 22:59:05.540: D/memalloc(15369): ion: Mapped buffer base:0x5570a000 size:1536000 offset:0 fd:92
01-03 22:59:05.540: D/memalloc(15369): ion: Mapped buffer base:0x53c33000 size:4096 offset:0 fd:94

Answer 1

如果您阅读堆栈跟踪，它会告诉您根本原因：

Caused by: java.lang.RuntimeException: Can't create handler inside thread 
that has not called Looper.prepare()

有another answer here on SO详细介绍了这个问题。

Answer 2

您检查的方式，如果有任何数据是错误的。而不是使用另一个String，检查ArrayList本身。在这里做出改变

private class LoadMoreAsync extends AsyncTask<Context, Void, Void>

在这里：

@Override
protected String doInBackground(Context... arg0) {
    // This just gets data from DB on background Thread
    mVoterArray = new ArrayList<AddressInfo>();
    mVoterArray = extDbUtil.getAddresslist(strAddress , limit += 20);

    return null;
}

@Override
protected void onPostExecute(Void v) {
    super.onPostExecute();

    // If the mVoterArray isnt null and if it isnt empty, then there is some data in there.
    if (mVoterArray != null && !mVoterArray.isEmpty()) {
        int position =  mListView.getLastVisiblePosition();
        mListAdapter = new ListAdapterNew2(mContext,
                android.R.layout.simple_list_item_1, mVoterArray);
        mListView.setAdapter(mListAdapter);
        mListView.setSelectionFromTop(position, 0);
        mListAdapter.notifyDataSetChanged();
    } else {
        ToastUtils.showToast(mContext, "No Record Found!!");
    }
}

<强> EDIT1：

在你的getAdressList（）方法中，你正在创建一个AddressInfo对象。但是你永远不会把它添加到你的ArrayList中。这就是为什么你总是得到没有数据的Toast。

do {
   AddressInfo mAddress = new AddressInfo();
   mAddress.setSrNO(mCursor.getString(mCursor
           .getColumnIndex("SrNo")));
   mAddress.setAddress(mCursor.getString(mCursor
            .getColumnIndex("Address1")));
   mAddress.setTotalMale(mCursor.getString(mCursor
            .getColumnIndex("TotalMale")));
   mAddress.setTotalFemal(mCursor.getString(mCursor
            .getColumnIndex("TotalFemale")));
   mAddress.setTotalVoter(mCursor.getString(mCursor
            .getColumnIndex("TotalVoters")));    

   // Add AddressInfo obejct ot ArrayList!
   mAddressArray.add(mAddress);

} while (mCursor.moveToNext());

android FATAL EXCEPTION：AsyncTask＃2

2 个答案: