调用 getSupportFragmentManager().getFragments().get(1) 给出错误 Invalid index 1, size is 1

Question

在两种不同的情况下，我将变量从 MainActivity 传递到 HomeFragment，如下所示：

首先我在MainActivity中调用这个方法：

buttonCreator(d, Name);

然后我将变量“d”和“Name”发送到 HomeFragment，如下所示：

public void buttonCreator(Drawable d,String a) {
    int fragsize = getSupportFragmentManager().getFragments().size();
    Log.d("tag_name", "Size of Home Fragment" + fragsize);
    HomeFragment homeFragment = (HomeFragment)getSupportFragmentManager().getFragments().get(1);
    homeFragment.createButton(d, a);
}

我第一次调用 buttonCreator(d,Name) 时没有收到任何错误。 我第二次尝试通过 buttonCreator 将变量传递给 HomeFragment 时，出现错误“IndexOutOfBoundsException: Invalid index 1, size is 1”。 我认为这与 HomeFragment 的数组大小有关，但我在这里并不完全理解片段和数组之间的联系。

我知道我第一次尝试访问 HomeFragment 时会调用：

int fragsize = getSupportFragmentManager().getFragments().size();

我得到“3”的输出，第二次调用它（当它崩溃时），我得到“1”的输出。 谁能解释一下为什么会发生这种情况以及我可以如何解决这个问题？

如果有帮助，这是我的完整 MainActivity。我第一次调用 buttonCreator 是在“RepeaterTask”中，第二次（当它崩溃时）是通过 onCreate()，通过“else”语句。

public class MainActivity extends FragmentActivity implements HomeFragment.ButtonCreator {


private Thread repeatTaskThread;
private byte[] byteArray;
private static Context mContext;
private Cursor c;

@Override
public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);

   mContext = getApplicationContext();

   DatabaseStructure database = new DatabaseStructure(mContext);
   database.checkDatabase();


   // if database is empty (checkDatabase == false) Open empty HomeFragment
   if (!database.checkDatabase()) {

       Log.d("tag_name", "Database is Empty: Open HomeFragment");

       FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
       ft.replace(R.id.container, new HomeFragment(),"Home_Fragment")
               .addToBackStack("Home_Fragment").commit();
   }

   else {

       DatabaseStructure appDatabase = new DatabaseStructure(this);
       c = appDatabase.getApps();
       c.moveToFirst();

       String Name = c.getString(0);
       Log.d("tag_name", "String from Database" + appName);
       byte[] image = c.getBlob(1);
       Log.d("tag_name", "Image from Database" + image);


       Bitmap bitmap = BitmapFactory.decodeByteArray(image, 0, image.length);
       Drawable d = new BitmapDrawable(Resources.getSystem(), bitmap);
       Log.d("tag_name", "Drawable from Database" + d);

       buttonCreator(d, Name);
   }

   RepeatTask();

}


public void buttonCreator(Drawable d,String a) {
    int fragsize = getSupportFragmentManager().getFragments().size();
    Log.d("tag_name", "Size of Home Fragment" + fragsize);
    HomeFragment homeFragment = (HomeFragment)getSupportFragmentManager().getFragments().get(1);
    homeFragment.createButton(d, a);
}



public void RepeatTask() {

    repeatTaskThread = new Thread() {
        public void run() {

            while (true) {

                try {

                    Socket socket = new Socket("192.168.0.26", 5050);

                    // Get data sent through socket
                    DataInputStream DIS = new DataInputStream(socket.getInputStream());

                    System.out.println("DataInputStream Started");
                    final String Name = DIS.readUTF();
                    int len = DIS.readInt();
                    final byte[] data = new byte[len];

                    DIS.readFully(data, 0, data.length);

                    Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);

                    final Drawable d = new BitmapDrawable(getResources(), Bitmap.createScaledBitmap(bitmap, 90, 90, true));


                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {

                            buttonCreator(d, Name);

                            DatabaseStructure database = new DatabaseStructure(mContext);
                            database.addEntry(Name, data);

                        }
                    });


                    socket.close();

                } catch (Exception e) {

                    System.out.println("Exception is " + e.toString());
                }

                try {
                    // Sleep for 5 seconds
                    Thread.sleep(5000);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }

        ;
    };
    repeatTaskThread.start();
}

}

Answer 1

数组和列表的索引从零开始（第一个索引是 0 而不是 1）所以试试

HomeFragment homeFragment = 
      (HomeFragment)getSupportFragmentManager().getFragments().get(0);