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Android的CursorLoader和LoaderManager错误

本文介绍了Android的CursorLoader和LoaderManager错误的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我想实现对10的分钟API

一个CursorLoader和LoaderManager

不过，我不断收到关于AsyncTaskLoader.class的63号线（在异常发生的AsyncTaskLoader.class的源$ C ​​$ C的IllegalArgument异常如下，并在此<一个href=\"http://grep$c$c.com/file/repo1.maven.org/maven2/com.google.android/support-v4/r7/android/support/v4/content/AsyncTaskLoader.java#AsyncTaskLoader.LoadTask.onPostExecute%28java.lang.Object%29\"相对=nofollow> 链接 。

  / *运行在UI线程* /
@覆盖
保护无效onPostExecute（D数据）{
    如果（调试）Log.v（TAG，这+onPostExecute）;
    尝试{
        AsyncTaskLoader.this.dispatchOnLoadComplete（此，数据）;
    } {最后
        done.countDown（）;
    }
}

下面是在错误的堆栈：

  AsyncTaskLoader $ LoadTask.onPostExecute（对象）行：63
AsyncTaskLoader $ LoadTask（ModernAsyncTask）.finish（对象）线：461
ModernAsyncTask.access $ 500（ModernAsyncTask，对象）行：47
ModernAsyncTask $ InternalHandler.handleMessage（消息）线：474
ModernAsyncTask $ InternalHandler（处理器）.dispatchMessage（消息）行：99
Looper.loop（）行：137
ActivityThread.main（字符串[]）行：4424
Method.invokeNative（对象，对象[]，上课，下课[]，类，整型，布尔）行：不可用[本机方法]
Method.invoke（对象，对象...）线：511
ZygoteInit $ MethodAndArgsCaller.run（）行：784
ZygoteInit.main（字符串[]）线：551
NativeStart.main（字符串[]）行：不可用[本机方法]

我测试了我的内容提供商，我验证了查询方法返回从我SQLite数据库的有效光标。下面是我的活动源$ C ​​$ C，我想实现的CursorLoader和LoaderManager：

 进口android.database.Cursor;
进口android.os.Bundle;
进口android.support.v4.app.FragmentActivity;
进口android.support.v4.app.LoaderManager;
进口android.support.v4.content.CursorLoader;
进口android.support.v4.content.Loader;
进口android.support.v4.widget.SimpleCursorAdapter;
进口android.widget.ListView;公共类Screen1_MainData扩展FragmentActivity实现LoaderManager.LoaderCallbacks＆LT;＆光标GT; {    SimpleCursorAdapter适配器;
    LV的ListView;    @覆盖
    保护无效的onCreate（捆绑savedInstanceState）{
        super.onCreate（savedInstanceState）;
        的setContentView（R.layout.screen1_maindata）;
        initLoader（）;
    }    无效initLoader（）{
        的String [] = uiBindFrom {Useful_Info_TableMetaData.USEFUL_INFO_COLUMN_NAME};
        INT [] = uiBindTo {R.id.name};
        LV =（ListView控件）findViewById（R.id.screen1_MainListView）;
        getSupportLoaderManager（）initLoader（0，null，则此）。        适配器=新SimpleCursorAdapter（这一点，R.layout.row，空，uiBindFrom，
                uiBindTo，0）;
        lv.setAdapter（适配器）;
    }@覆盖
公共装载机＆LT;＆光标GT; onCreateLoader（INT为arg0，ARG1捆绑）{    的String [] =投影{Useful_Info_TableMetaData.USEFUL_INFO_COLUMN_NAME};    返回新CursorLoader（
            对此，//活动场景
            Useful_Info_TableMetaData.CONTENT_URI，投影，NULL，NULL，
            空值）;
}    @覆盖
    公共无效onLoadFinished（装载机＆LT;＆光标GT;装载机，游标数据）{
        adapter.swapCursor（数据）;
    }    @覆盖
    公共无效onLoaderReset（装载机＆LT;＆光标GT;装载机）{
        adapter.swapCursor（NULL）;
    }
}

有谁看到这里的东西，我做错了？

感谢。

该应用程序似乎使它到

  @覆盖
公共无效onLoadFinished（装载机＆LT;＆光标GT;装载机，游标数据）{
    adapter.swapCursor（数据）;
}

，然后抛出异常那里。

下面是logcat的：

  08-03 23：33：20.736：E / AndroidRuntime（17256）：致命异常：主要
08-03 23：33：20.736：E / AndroidRuntime（17256）：java.lang.IllegalArgumentException异常：列'_id'不存在
08-03 23：33：20.736：E / AndroidRuntime（17256）：在android.database.AbstractCursor.getColumnIndexOrThrow（AbstractCursor.java:267）
08-03 23：33：20.736：E / AndroidRuntime（17256）：在android.database.CursorWrapper.getColumnIndexOrThrow（CursorWrapper.java:78）
08-03 23：33：20.736：E / AndroidRuntime（17256）：在android.support.v4.widget.CursorAdapter.swapCursor（CursorAdapter.java:344）
08-03 23：33：20.736：E / AndroidRuntime（17256）：在android.support.v4.widget.SimpleCursorAdapter.swapCursor（SimpleCursorAdapter.java:326）


解决方案

尝试移动 initLoader 您的来电后， lv.setAdapter 。这将确保 onLoadFinished （因而 adapter.swapCursor（数据））将被调用的之后的 SimpleCursorAdapter 已与相关联的ListView 。

此外，请确保您的数据库中有一个名为列 _id 为您的主键，为的CursorAdapter 荣获' ŧ否则工作。 _id 需要返回从 CursorLoader 的结果的一部分。否则会抛出异常。

I am trying to implement a CursorLoader and LoaderManager on a min API of 10.

However, I keep getting an IllegalArgument Exception on Line 63 of AsyncTaskLoader.class (The source Code of the AsyncTaskLoader.class where the exception is happening is Below and at this link.

/* Runs on the UI thread */
@Override
protected void onPostExecute(D data) {
    if (DEBUG) Log.v(TAG, this + " onPostExecute");
    try {
        AsyncTaskLoader.this.dispatchOnLoadComplete(this, data);
    } finally {
        done.countDown();
    }
}

Below is the stack upon the error:

AsyncTaskLoader$LoadTask.onPostExecute(Object) line: 63 
AsyncTaskLoader$LoadTask(ModernAsyncTask).finish(Object) line: 461  
ModernAsyncTask.access$500(ModernAsyncTask, Object) line: 47    
ModernAsyncTask$InternalHandler.handleMessage(Message) line: 474    
ModernAsyncTask$InternalHandler(Handler).dispatchMessage(Message) line: 99  
Looper.loop() line: 137 
ActivityThread.main(String[]) line: 4424    
Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]  
Method.invoke(Object, Object...) line: 511  
ZygoteInit$MethodAndArgsCaller.run() line: 784  
ZygoteInit.main(String[]) line: 551 
NativeStart.main(String[]) line: not available [native method]

I tested my content provider and I validated that the query method returns a valid cursor from my Sqlite Database. Below is the source code of my activity that I am trying to implement the CursorLoader and LoaderManager:

import android.database.Cursor;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.LoaderManager;
import android.support.v4.content.CursorLoader;
import android.support.v4.content.Loader;
import android.support.v4.widget.SimpleCursorAdapter;
import android.widget.ListView;

public class Screen1_MainData extends FragmentActivity implements LoaderManager.LoaderCallbacks<Cursor> {

    SimpleCursorAdapter adapter;
    ListView lv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.screen1_maindata);
        initLoader();
    }

    void initLoader() {
        String[] uiBindFrom = { Useful_Info_TableMetaData.USEFUL_INFO_COLUMN_NAME };
        int[] uiBindTo = { R.id.name };
        lv = (ListView) findViewById(R.id.screen1_MainListView);
        getSupportLoaderManager().initLoader(0, null, this);

        adapter = new SimpleCursorAdapter(this, R.layout.row, null, uiBindFrom,
                uiBindTo, 0);
        lv.setAdapter(adapter);    
    }

@Override
public Loader<Cursor> onCreateLoader(int arg0, Bundle arg1) {

    String[] projection = { Useful_Info_TableMetaData.USEFUL_INFO_COLUMN_NAME };

    return new CursorLoader(
            this, // The Activity context
            Useful_Info_TableMetaData.CONTENT_URI, projection, null, null,
            null);
}

    @Override
    public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
        adapter.swapCursor(data);
    }

    @Override
    public void onLoaderReset(Loader<Cursor> loader) {
        adapter.swapCursor(null);
    }
}

Does anyone see something here that I am doing wrong?

Thanks.

The app seems to make it to 

@Override
public void onLoadFinished(Loader<Cursor> loader, Cursor data) {
    adapter.swapCursor(data);
}

and then it throws the exception there.

Below is the logcat:

08-03 23:33:20.736: E/AndroidRuntime(17256): FATAL EXCEPTION: main 
08-03 23:33:20.736: E/AndroidRuntime(17256): java.lang.IllegalArgumentException: column '_id' does not exist 
08-03 23:33:20.736: E/AndroidRuntime(17256): at android.database.AbstractCursor.getColumnIndexOrThrow(AbstractCursor.java:267) 
08-03 23:33:20.736: E/AndroidRuntime(17256): at android.database.CursorWrapper.getColumnIndexOrThrow(CursorWrapper.java:78) 
08-03 23:33:20.736: E/AndroidRuntime(17256): at android.support.v4.widget.CursorAdapter.swapCursor(CursorAdapter.java:344) 
08-03 23:33:20.736: E/AndroidRuntime(17256): at android.support.v4.widget.SimpleCursorAdapter.swapCursor(SimpleCursorAdapter.java:326)
解决方案

Try moving initLoader after your call to lv.setAdapter. This will ensure that onLoadFinished (and thus adapter.swapCursor(data)) will be called after the SimpleCursorAdapter has been associated with the ListView .

Also, make sure your database has a column named _id for your primary key, as the CursorAdapter won't work otherwise. _id needs to be returned as a part of the results from the CursorLoader's. Otherwise an exception will be thrown.

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09-22 12:22
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