我如何在配接器類中呼叫MainActivityMethod

這是我的 MainActivity，我在其中定義了 dataRefresh 方法，該方法在從資料庫中插入或洗掉資料時重繪 到配接器

public class MainActivity extends AppCompatActivity {
EditText phone, name;
ListView list;
MyDatabase db;
CustomAdapter ad;
ArrayList<contact> cont;
Button add;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    list=findViewById(R.id.list_item);
    db=new MyDatabase(this);
    cont=new ArrayList<>();
    cont=db.showData();
    ad=new CustomAdapter(this,cont;
    list.setAdapter(ad);
}


 public  void  dataRefresh(){
    cont.clear();
    cont.addAll(db.showData());
    ad.notifyDataSetChanged();
}

上面是一個dataRefresh方法

這是我的配接器類，我在其中呼叫洗掉方法從資料庫資料中洗掉資料

    public class CustomAdapter extends ArrayAdapter {
    ArrayList<contact> phnecontact;
    MyDatabase db;
    LinearLayout horizon;
    Context context;

    public CustomAdapter(@NonNull Context context, ArrayList<contact> 
    phonecontact) {
    super(context,R.layout.customlayout,phonecontact);
    this.context = context;
    this.phnecontact = phonecontact;
    }

    public contact getItem(int position) {
    return phnecontact.get(position);
   }

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

  @NonNull
  @Override
  public View getView(int position, View i, ViewGroup parent) {
    View view = 
  LayoutInflater.from(context).inflate(R.layout.customlayout, parent, 
  false);
    contact s1 = phnecontact.get(position);
    db=new MyDatabase(context);
    TextView name=view.findViewById(R.id.cmname);
    horizont=view.findViewById(R.id.horizontal);
    TextView number=view.findViewById(R.id.cmphone);
    ImageView sms=view.findViewById(R.id.message);
    ImageView call=view.findViewById(R.id.phone);
    ImageView photo=view.findViewById(R.id.cmphoto);
    number.setText(String.valueOf(s1.getPhone()));
    name.setText(s1.getName());
    horizont.setOnLongClickListener(v -> {
       AlertDialog.Builder builder=new AlertDialog.Builder(context);
       builder.setTitle("Are you sure to delete");
       builder.setPositiveButton("yes", new 
       DialogInterface.OnClickListener() {
           @Override
           public void onClick(DialogInterface dialog, int which) {
               int i =db.Deletioncontact(s1.getPhone());

我想在 if 條件之后呼叫 Mainactivity 的 dataRefresh 方法

               if(i==1)
               {

                   Toast.makeText(context, "contact is deleted", 
      Toast.LENGTH_SHORT).show();
               }
               else
               {
                   Toast.makeText(context, "contact not deleted", 
  Toast.LENGTH_SHORT).show();
               }
           }
       });

如果我通過 Mainactivity 的 make 物件呼叫此方法，則我的應用程式已崩潰

uj5u.com熱心網友回復：

除了呼叫方法之外，mainActivity還有一些可以改進的地方。

您不必傳入context配接器，要使用內部getView()方法，您可以從中獲取背景關系parent viewGroup

@Override
  public View getView(int position, View i, ViewGroup parent) {
    View view = 
  LayoutInflater.from(parent.getContext()).inflate(R.layout.customlayout, parent, 
  false);

您可以將您的所有clickListeners和longClickListeneners邏輯移動到您的activity, 并用于interface觸發這些方法。通過這種方式，將讓您的配接器類松耦合的activity，你可以使用這個adapter在另一個activity或fragment過。

clickInterface在您的配接器類中創建

public interface ClickListeners {
     public void onItemlongClickListener(int phone);
}

現在interface在您的活動中覆寫它

public class MainActivity extends AppCompatActivity implements CustomAdapter.ClickListener{
    //

    @Override
    protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         //
         ad = new CustomAdapter(this, cont); // pass interface instance to the adapter
         //
    }

    @Override
    public void onItemlongClickListener(int phone) {
        // add your dialog confirmation 
        // and item deletion code here
    }

}

更改CustomAdaper建構式以獲取介面實體

public CustomAdapter(ClickListeners clickListeners, ArrayList<contact> 
    phonecontact) {
    super(context,R.layout.customlayout,phonecontact);
    this.clickListeners = clickListeners;
    this.phnecontact = phonecontact;
    }

onItemlongClickListener當用戶長按專案時觸發

horizon.setOnLongClickListener(v -> {
      clickListeners.onItemlongClickListener(s1.getPhone()); // call interface method
}

uj5u.com熱心網友回復：

**在你的 onclick 方法中試試這個 **

public void onClick(DialogInterface dialog, int which) {

int i =db.Deletioncontact(s1.getPhone());

Iterator<Integer> itr = numbers.iterator();
while(itr.hasNext()) { 
   Phone phone = itr.next(); 
   if (phone == s1.getPhone()) {  
      s1.remove(phone); 
   } 
}
notifyDataSetChange();
}

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