android - 只获取一个项目到微调器

Question

public class MainActivity extends AppCompatActivity {
ArrayList al = new ArrayList(20);
public static final String SharedPref = "MyPreferences";
SharedPreferences settings=null;
Spinner sp;
ArrayAdapter aa;
Intent i;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    sp = (Spinner) findViewById(R.id.spinner);
    settings=getSharedPreferences(SharedPref,0);

    Toast.makeText(this, al.size()+"", Toast.LENGTH_SHORT).show();

    aa = new ArrayAdapter(this, R.layout.support_simple_spinner_dropdown_item, al);
    sp.setAdapter(aa);

}

public void onResume()
    {
        super.onResume();
        int j=0;
        String s =settings.getString("NewTask","");
        try {
            for(j=0;j<20;j++) {
                aa.insert(s,j);
                aa.notifyDataSetChanged();
                j++;
                Toast.makeText(this, al.size()+"", Toast.LENGTH_SHORT).show();
                sp.setAdapter(aa);
            }
        }
        catch(Exception e)
        {
            Log.e("Array",e+"");
        }
    }



public  void add1(View v)
{
   i = new Intent(this,second.class);
    startActivityForResult(i,1);

}} 

我需要从其他 Activity 获取项目。我正在通过单击添加按钮移动到第二个 Activity。通过 edittext 添加项目并单击添加按钮。然后我只得到一个我添加的项目，但我需要所有之前添加的项目。请帮助我。我的要求是使用两种布局。(我知道将一个布局中的项目添加到微调器)。 arraylist 的大小在这里没有增加。如何修复我的 Arraylist 大小。

Answer 1

You can use startActivityForResult to pass data to activity

For example call startActivityResult from first activity

Intent i = new Intent(FirstActivity.this, SecondActivity.class);
startActivityForResult(i, 1);

And in second activity set data you want to return back like below

Intent returnIntent = new Intent();
returnIntent.putExtra("data",result);
setResult(Activity.RESULT_OK,returnIntent);
finish();

And in your first activity override the onActivityResult() method to get data

 @Override
protected void onActivityResult(int requestCode, int resultCode, Intent 
  data) {
  if (requestCode == 1) {
    if(resultCode == Activity.RESULT_OK)
      {
        String result=data.getStringExtra("data");

     }
    if (resultCode == Activity.RESULT_CANCELED)
     {

    }

    }
}

Hope this will help