返回包含来自REST API的项目的列表。

huangapple
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英文:

Problem to return list which contains items from rest api

问题

我在Android中的一个方法中遇到了问题，该方法应该返回从REST API接收到的项目列表。我能够在该方法中调试这些项目，因为我在onCreate方法中编写了该方法的声明。但是，问题出现在我尝试将这些项目（在该方法中）添加到列表中，以便该方法可以返回它们时。我收到了以下错误消息：

  1. Caused by: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

应该返回项目的方法如下：

  1. public List<Categories> displayDataaaa(List<Categories> categoriesList) {
  3.     this.categoriesList = new ArrayList<Categories>();
  4.     // ...
  5.     String cat_name = "";
  7.     this.categoriesList.add(new Categories(1, categoriesList.get(0).getCategoriesName()));
  9.     for (int i = 0; i < categoriesList.size(); i++) {
  10.         cat_name = categoriesList.get(i).getCategoriesName();
  11.         Log.d("displayDataaaaa-cat_name", "displayDataaaaa-cat_name" + cat_name);
  12.         this.categoriesList.addAll(categoriesList);
  13.     }
  15.     return this.categoriesList;
  16. }

请问是否可以提供一些提示？谢谢。

英文:

I've got a problem with a method in Android which should return a list of items which are received from rest api. I am able to debug these items in that method - because I wrote declaration of this method in the onCreate method. But the problem occurs once I try to add these items (in that method) to the list, so the method could return these. I receive an error like:

  1. Caused by: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

the method which should return items:

  1. public List&lt;Categories&gt; displayDataaaa(List&lt;Categories&gt; categoriesList) {
  3.     this.categoriesList = new ArrayList&lt;Categories&gt;();
  4.     /
  5.     String cat_name = &quot;&quot;;
  7.     // this.categoriesList.add(new Categories(1,&quot;lkajsdflk&quot;));
  8.     this.categoriesList.add(new Categories(1, categoriesList.get(0).getCategoriesName()));
  11.     for (int i = 0; i &lt; categoriesList.size(); i++) {
  12.          cat_name = categoriesList.get(i).getCategoriesName();
  13.       //    this.categoriesList.add(new Categories(i, cat_name));
  14.         Log.d(&quot;displayDataaaaa-cat_name&quot;, &quot;displayDataaaaa-cat_name&quot; + cat_name);
  16.         this.categoriesList.addAll(categoriesList);
  17.     }
  18.  //   this.categoriesList.add(new Categories(1, cat_name));
  20.     return this.categoriesList;
  21. }

Could I ask you for some hint, please?
Thank you.

Log:

  1.  java.lang.RuntimeException: Unable to start activity ComponentInfo{dev4passion.partyj10/dev4passion.partyj10.MainActivity}: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
  2.     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2913)
  3.     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)
  4.     at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
  5.     at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
  6.     at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
  7.     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)
  8.     at android.os.Handler.dispatchMessage(Handler.java:106)
  9.     at android.os.Looper.loop(Looper.java:193)
  10.     at android.app.ActivityThread.main(ActivityThread.java:6669)
  11.     at java.lang.reflect.Method.invoke(Native Method)
  12.     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
  13.     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)
  14.  Caused by: java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
  15.     at java.util.ArrayList.get(ArrayList.java:437)
  16.     at dev4passion.partyj10.MainActivity.displayDataaaa(MainActivity.java:189)
  17.     at dev4passion.partyj10.MainActivity.onCreate(MainActivity.java:94)
  18.     at android.app.Activity.performCreate(Activity.java:7136)
  19.     at android.app.Activity.performCreate(Activity.java:7127)
  20.     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1271)
  21.     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2893)
  22.     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3048)&#160;
  23.     at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)&#160;
  24.     at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)&#160;
  25.     at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)&#160;
  26.     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1808)&#160;
  27.     at android.os.Handler.dispatchMessage(Handler.java:106)&#160;
  28.     at android.os.Looper.loop(Looper.java:193)&#160;
  29.     at android.app.ActivityThread.main(ActivityThread.java:6669)&#160;
  30.     at java.lang.reflect.Method.invoke(Native Method)&#160;
  31.     at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)&#160;
  32.     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)&#160;

答案1

得分: 1

这是您的问题行。当categoriesList为空时，categoriesList.get(0)会引发异常。

英文: 
  1. this.categoriesList.add(new Categories(1, categoriesList.get(0).getCategoriesName()));

This is your problem line. categoriesList.get(0) will throw an exception when categoriesList is empty.

huangapple
  • 本文由 发表于 2020年8月9日 04:18:31
  • 转载请务必保留本文链接：https://go.coder-hub.com/63319868.html
  • android
  • java
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