Question

我尝试使用AsyncTasks插入我的数据库。我打电话的时候：

    new insert(tableName).execute(val).get;

它按预期工作，但它会阻止UI线程。

我宁愿打电话

    new insert(tableName).execute(val);

但是当我这样做时，doInBackground抛出一个SQL错误，而我传入的ContentValues是空的。这是我的AsyncTask：

            private class insert extends AsyncTask<ContentValues, Object, Long>{

        String inTable;
        long id = -1;
        insert(TableNames table){
            inTable = table.getSQL(); //This simple gets the String value TableName
        }
        @Override
        protected void onPostExecute(Long result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
                Log.i(tag, "PostExecute: "+ inTable + " " + String.valueOf(id));    
        }

        @Override
        protected Long doInBackground(ContentValues... values) {
            try {
                id = getWritableDatabase().insert(inTable, null, values[0]);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return id;
        }

    }

在这种情况下，我并不关心他的回报价值。插入物是火，忘了它。

Log Cat：

Error inserting 
 android.database.sqlite.SQLiteException: near "null": syntax error (code 1): , while compiling: INSERT INTO TrackingLog(null) VALUES (NULL)
    at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
    at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
    at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
    at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
    at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
    at android.database.sqlite.SQLiteStatement.<init>(SQLiteStatement.java:31)
    at android.database.sqlite.SQLiteDatabase.insertWithOnConflict(SQLiteDatabase.java:1467)
    at android.database.sqlite.SQLiteDatabase.insert(SQLiteDatabase.java:1339)
    at com.westat.nopus.util.data.DataHelper$insert.doInBackground(DataHelper.java:563)
    at com.westat.nopus.util.data.DataHelper$insert.doInBackground(DataHelper.java:1)
    at android.os.AsyncTask$2.call(AsyncTask.java:288)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
    at java.lang.Thread.run(Thread.java:841)
 Error inserting 
 android.database.sqlite.SQLiteException: near "null": syntax error (code 1): , while compiling: INSERT INTO TrackingLog(null) VALUES (NULL)
    at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
    at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
    at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
    at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
    at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
    at android.database.sqlite.SQLiteStatement.<init>(SQLiteStatement.java:31)
    at android.database.sqlite.SQLiteDatabase.insertWithOnConflict(SQLiteDatabase.java:1467)
    at android.database.sqlite.SQLiteDatabase.insert(SQLiteDatabase.java:1339)
    at com.westat.nopus.util.data.DataHelper$insert.doInBackground(DataHelper.java:563)
    at com.westat.nopus.util.data.DataHelper$insert.doInBackground(DataHelper.java:1)
    at android.os.AsyncTask$2.call(AsyncTask.java:288)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)

调用AsyncTask的完整方法：

         void Tableinsert(TableNames tableName,ContentValues val){

     val.put("Exported_Flag", "F");

    if (debug) {
        Log.i(tag, "TableInsert.  Size: " + String.valueOf(val.size()));
        //This returns 26 - Which is the correct size of the ContentValues
    }
    try {
        new insert(tableName).execute(val); //Doesn't work
    //  new insert(tableName).execute(val).get; //Works
    } 
    catch (Exception e) {
        if (MyApplication.SEND_HANDLED_EXCEPTIONS) {
            ACRA.getErrorReporter().handleSilentException(e);
        }
        e.printStackTrace();
    }
}

Answer 1

谢谢大家，但在阅读完评论后，我发现了我的问题。

当我创建内容值，值并将它们传递到AsyncTask时，主线程的下一行是values.clear（）。显然，这会在AsyncTask将它们插入数据库之前清空值。这解释了为什么它使用了execute（）。get（）。

再次感谢...

Answer 2

在标题

中

 private class insert extends AsyncTask<ContentValues, Object, Long>{ ...

将Long替换为Void，并使用

执行相同操作

protected Long doInBackground(ContentValues... values) {

太。现在你不再需要返回值了。

如果没有execute（），Android AsyncTask无法正常工作.get（）

2 个答案: