将值从 EditText 获取到 AWS DynamoDB 中的表中

Question

我想将用户写入的文本框中的新项目放入 DynamoDB 的现有表中。但是，我遇到了一些我不太了解的错误。以下是我的代码：

添加方法

public class Add_Item
{
    private String title;
    private AmazonDynamoDBClient client;
    String tableName = "Tesis_FTSM";
    public void DynamoDBLoad() throws IOException
    {
        AWSCredentials credentials = new PropertiesCredentials(DynamoDBClient.class.getClassLoader().getResourceAsStream("AWSCredentials.properties"));
        client = new AmazonDynamoDBClient(credentials);
        client.setRegion(Region.getRegion(Regions.US_WEST_2));
    }
    public void add()
        {
          
            final EditText title = (EditText)findViewById(R.id.text1);
            String tajuk = title.getText().toString();
          
            Map<String, AttributeValue> item = new HashMap<String, AttributeValue>();
            try {
               item.put("Id", new AttributeValue().withS(tajuk));
                PutItemRequest itemRequest = new PutItemRequest().withTableName(
                        tableName).withItem(item);
                client.putItem(itemRequest);
                item.clear();
            } catch (Exception e) {
                System.err.println("Create items failed.");
                System.err.println(e.getMessage());
            }
        }

主活动

public class Task extends AsyncTask<String, Void, String> {
        @Override
        protected String doInBackground(String... params) {
            Looper.prepare();
            try
            {
                Add_Item db = new Add_Item();
                db.DynamoDBLoad();
                db.add();
                  
            } catch (Exception e)
            {
                e.printStackTrace();
            }
            Looper.myLooper().quit();
            return null;
        }
        protected void onPostExecute(String page)
        {
            //onPostExecute
        }
    }

日志猫错误

06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕java.lang.NullPointerException
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at android.app.Activity.findViewById(Activity.java:1957)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at com.af.ftsm.testing.Add_Item.<init>(Add_Item.java:26)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at com.af.ftsm.testing.MainActivity$Task.doInBackground(MainActivity.java:50)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at com.af.ftsm.testing.MainActivity$Task.doInBackground(MainActivity.java:39)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at android.os.AsyncTask$2.call(AsyncTask.java:288)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at java.util.concurrent.FutureTask.run(FutureTask.java:237)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
06-15 10:33:33.938  16885-17179/com.af.ftsm.testing W/System.err﹕ at java.lang.Thread.run(Thread.java:841)

我向表中添加项目的方法是否错误或其他方法？谢谢。

Answer 1

根据这些信息，我相信资源 R.id.text1 不存在，所以 findViewById 返回 null。在 null 上强制转换的类型将引发 NPE。如果没有，请告诉我们Add_Item.java的第 26 行的内容。

PS：您最好避免在生产级Android应用程序中使用PropertiesCredentials。 CognitoCachingCredentialsProvider是获取AWS凭证的推荐方法。有关更多详细信息，请参阅亚马逊认知身份。