如果我们必须使用自定义适配器创建第二个活动，如何更改启动器活动？

Question

我想更改我的启动器活动。我的第一个创建的活动有可选择的列表视图。当用户第一次打开应用程序时；他将选择人员然后我的第二个创建的活动，这些选定的人员来到我的自定义列表视图。我的问题是；如何更改启动器活动，因为在我的第二个活动有自定义列表视图，如果用户不点击任何人，我的第二个活动将为空，因此我收到错误消息。我该如何解决这个问题？

我的第一个活动：

public class MainActivity extends AppCompatActivity {

ArrayList<String> selectedlistisim = new ArrayList<>();

    int girisyazısıcount = 2 ;
    ArrayList<String> listte = new ArrayList<String>();
    String phonenumber;
ArrayList<String> selectedlist = new ArrayList<>();
    ListView chosinglist;
Button kaydet ;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
      kaydet = (Button) findViewById(R.id.kaydet);
   chosinglist = (ListView) findViewById(R.id.chosing);
        chosinglist.setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);

        getNumber(this.getContentResolver());


 }

    private void getNumber(ContentResolver contentResolver) {
        Cursor phones = contentResolver.query(ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null,null,null, null);
        while (phones.moveToNext())
        {

            String name=phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME));
            phonenumber = phones.getString(phones.getColumnIndex(ContactsContract.CommonDataKinds.Phone.NUMBER));

            System.out.println(".................."+phonenumber);



            listte.add(phonenumber);
        }
        phones.close();// close cursor
        final ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.checkrow,
                R.id.checkedTextView2,listte);


kaydet.setEnabled(false);
        chosinglist.setAdapter(adapter);
        chosinglist.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                String selecteditem = ((TextView)view).getText().toString();


                if (selectedlist.contains(selecteditem)){
                    selectedlist.remove(selecteditem);

                }else selectedlist.add(selecteditem);




                if (selectedlist.size() >= 5 && selectedlist.size() < 16 ) {


                    kaydet.setEnabled(true);
                }
                 if (selectedlist.size() == 16){
                     kaydet.setEnabled(false);

                 }
if (selectedlist.size() == 4){
    kaydet.setEnabled(false);
}


kaydet.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
Intent i = new Intent(MainActivity.this, AnaMenu.class);
i.putStringArrayListExtra("listem",selectedlist);
        startActivity(i);

        Toast.makeText(MainActivity.this, "abc.", Toast.LENGTH_LONG).show();

        MainActivity.this.finish();
    }
});
            }
        });
    }


}

我的第二个活动：

public class AnaMenu extends AppCompatActivity {
    public static final int MENU_Ara = Menu.FIRST + 1;
    OyunTextView oyunTextView;
    static final int AnketDegerlendirmesi = 1337;
   int selectedPosition ;
    String[] afteractivitydialogitems;
    int toplamaislemi;
    String[] dialogdegerleri;

    boolean[] dialogcheckeditems;

    String toast;

    TextView sayılar;
    ListView liste;

int a = 60 ;
    ArrayList<String> kullanıcısayıdegerlistesi = new ArrayList<>();

    ArrayList<Integer> mUserselecteditems = new ArrayList<>();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ana_menu);
        liste = (ListView) findViewById(R.id.oyun);
        //Adapter im.




        oyunTextView = new OyunTextView();

        liste.setAdapter(oyunTextView);

        registerForContextMenu(liste);

        afteractivitydialogitems = getResources().getStringArray(R.array.anket);

        dialogcheckeditems = new boolean[afteractivitydialogitems.length];

        dialogdegerleri = getResources().getStringArray(R.array.anketdeğer);



//show the first activity when First time launched application. 
        SharedPreferences prefs = this.getSharedPreferences("MyAppPrefs", MODE_PRIVATE);
        boolean settingsFilled = prefs.getBoolean("SettingsFilled", false);

        if (!settingsFilled){
            Intent sa = new Intent(AnaMenu.this,MainActivity.class);
            startActivity(sa);



            SharedPreferences pr = this.getSharedPreferences("MyAppPrefs", MODE_PRIVATE);
            SharedPreferences.Editor editor = prefs.edit();
            editor.putBoolean("SettingsFilled", true);
            editor.commit();
        }




    }


    class OyunTextView extends BaseAdapter {


        @Override
        public int getCount() {
            Intent i = getIntent();
            final ArrayList<String> secilmis = i.getStringArrayListExtra("listem");


            return secilmis.size();
        }

        @Override
        public Object getItem(int position) {
            return null;
        }

        @Override
        public long getItemId(int position) {
            return 0;
        }

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            convertView = getLayoutInflater().inflate(R.layout.oyuntextview, null);
            TextView namesbox = (TextView) convertView.findViewById(R.id.isim);
            sayılar = (TextView) convertView.findViewById(R.id.sayı);
            Intent i = getIntent();
            final ArrayList<String> secilmis = i.getStringArrayListExtra("listem");

            for (int defa = 0; defa < secilmis.size(); defa++) {
                kullanıcısayıdegerlistesi.add("50");
 //   if (kullanıcısayıdegerlistesi.contains("50")){sayılar.setTextColor(getResources().getColor(R.color.elli));}




            }
            namesbox.setText(secilmis.get(position));
            sayılar.setText(kullanıcısayıdegerlistesi.get(position));
                   sayılar.setTextColor(getResources().getColor(R.color.elli));
convertView.setBackgroundColor(getResources().getColor(R.color.yüz));
            return convertView;
        }
    }

Answer 1

所以要修复 空列表错误，只需尝试这样做：

    kaydet.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
             if(selectedlist.size()>0){
                   Intent i = new Intent(MainActivity.this, AnaMenu.class);
                   i.putStringArrayListExtra("listem",selectedlist);
                   startActivity(i);

                   Toast.makeText(MainActivity.this, "abc.", Toast.LENGTH_LONG).show();

               MainActivity.this.finish();
             }else{
               Toast.makeText(MainActivity.this, "No itens added", Toast.LENGTH_LONG).show();

              }
  }
    });

如果 list 没有 itens 并且如果没有显示文本，则此 检查 如果是，则转到下一个 活动.

对于 open 第二个活动 而不是 first，如果用户第二次启动活动，请在 first 中执行此逻辑在 super.oncreate() 之前的活动 检查数据库是否有数据 如果是则开始第二个活动，如果数据库为空则什么也不做。

我的逻辑示例：

@Override
    protected void onCreate(Bundle savedInstanceState) {
        //here you check if database has data

        if(hasdata){
           //start second activity
        }

        super.onCreate(savedInstanceState);

       //Or if you want you can put logic here is the same

        setContentView(R.layout.activity_loginactivity);

        //Not put here below setcontentview!!!!
    }

所以 before 创建 activity 检查 database 是否有数据，如果有则转到其他 activity，因为activity 未创建且 layout 未添加，因为用户与单击启动器图标时打开第二个 Activity 相同。

Answer 2

公共类 LoginActivity 扩展 Activity {

最能帮助您的是尝试在 Oncreate 中添加与此处相同的以下行。
这将检查列表是否为空，如果是，则重定向到列表活动，否则继续。

 @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       //add some code to detect if parent is selected
       if (parent == null){
           Intent in = new Intent(SecondActivity.this, PersonAcrivity.class);
           startActivity(in);
       }