Question

我正在尝试查询在我的应用中注册的所有parse.com用户。我按照指南编写了这个查询

try{
    name=Name.getText().toString();
    ParseQuery<ParseUser> query = ParseUser.getQuery();
    query.whereMatches("username", name);
    query.findInBackground(new FindCallback<ParseUser>() {
    public void done(List<ParseUser> objects, ParseException e) {
            if (e == null) {
                if (!objects.isEmpty()) {
                    show.setText(String.valueOf(objects.size()));
                    for (ParseUser singleobject : objects) {
                    mail[i] = singleobject.get("email").toString();
                    uname[i] = singleobject.get("username").toString();
                    i++;
                    }
                } else {
                    show.setText("No Tuples");
                }
            } else {
               Toast.makeText(getApplicationContext(), "Query Not Successful", Toast.LENGTH_LONG).show();
            }
        }
    });
  }catch (NullPointerException x){
        Toast.makeText(getApplicationContext(), "Null Pointer Exception", Toast.LENGTH_LONG);
    }}

当输入检索单个元组时，此查询很有效但当我提供检索多个元组的输入时，它会抛出一个像这样的NULL POINTER EXCEPTION

Process: com.example.nirmal.sportsparse, PID: 15097
java.lang.NullPointerException
        at com.example.nirmal.sportsparse.search_players$2.done(search_players.java:108)
        at com.example.nirmal.sportsparse.search_players$2.done(search_players.java:99)
        at com.parse.ParseTaskUtils$2$1.run(ParseTaskUtils.java:115)
        at android.os.Handler.handleCallback(Handler.java:808)
        at android.os.Handler.dispatchMessage(Handler.java:103)
        at android.os.Looper.loop(Looper.java:193)
        at android.app.ActivityThread.main(ActivityThread.java:5292)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:824)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:640)
        at dalvik.system.NativeStart.main(Native Method)

错误代码表示findInBackground()和for中有一个NULL指针在libcore.io.ErrnoException: close failed: EBADF (Bad file number) at libcore.io.Posix.close(Native Method) at libcore.io.BlockGuardOs.close(BlockGuardOs.java:75) at com.android.internal.os.ZygoteInit.closeServerSocket(ZygoteInit.java:220) at com.android.internal.os.ZygoteConnection.handleChildProc(ZygoteConnection.java:879) at com.android.internal.os.ZygoteConnection.runOnce(ZygoteConnection.java:242) at com.android.internal.os.ZygoteInit.runSelectLoop(ZygoteInit.java:700) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:636) at dalvik.system.NativeStart.main(Native Method)循环内。我确信我提供的输入必须检索至少2个元组。

有时它也会抛出此错误，我不知道这意味着什么

String name,mail[]=new String[100],uname[]=new String[100];

数组声明如下

Thread.setDefaultUncaughtExceptionHandler((Thread t, Throwable e) -> { System.out.println(t + " throws exception: " + e); });

谁能告诉我哪里出错？

Answer 1

在回调＆＃34;完成＆＃34; ，JSON API，通常允许2个步骤...

检查元素是否存在

Stringify元素

请注意

uname[i] = singleobject.get("username").toString();

尝试一次完成所有操作并在可能是＆＃34;未定义的列上抛出异常＆＃34;在返回的parse对象中。

先检查

然后stringify

Parse.com Query无法检索多个对象

1 个答案: