如何將數據從列表適配器發送到 android 中的活動？

Question

我有一個自定義列表適配器，我想將此列表適配器中的值傳遞給我設置適配器的活動。 這是我的適配器代碼。

public class RoleList extends ArrayAdapter<String>
{
    private ArrayList<String> name;
    private ArrayList<String> username;
    private ArrayList<String>  password;
    private ArrayList<String>  role;
    private Activity context;

    private MyActionCallback callback;
public RoleList(Activity context, ArrayList<String> name, ArrayList<String> username, ArrayList<String> password, ArrayList<String> role, MyActionCallback callback)
{
    super(context, R.layout.role_list,name);
    this.context = context;
    this.name = name;
    this.username =username;
    this.password = password;
    this.role = role;
    this.callback = callback;
}

    @Override
    public View getView(final int position, View convertView, ViewGroup parent)
    {
        LayoutInflater inflater = context.getLayoutInflater();
        final View listViewItem = inflater.inflate(R.layout.role_list, null, true);
        final TextView textViewName = (TextView) listViewItem.findViewById(R.id.tv_empname);
        final TextView textViewusername = (TextView) listViewItem.findViewById(R.id.tv_empusername);
        final TextView textViewPass = (TextView) listViewItem.findViewById(R.id.tv_emppassword);
        final TextView textViewRole = (TextView) listViewItem.findViewById(R.id.tv_emprole);
        Button edit = (Button) listViewItem.findViewById(R.id.btn_editRole);
        Button delete = (Button) listViewItem.findViewById(R.id.btn_delRole);


        delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                name.remove(position);
                username.remove(position);
                password.remove(position);
                role.remove(position);
                callback.onActionPerformed(position);
                notifyDataSetChanged();
            }
        });
        edit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v)
            {
                Log.d("Emp Info", name.get(position) + " " + username.get(position) + " " + password.get(position) + " " + role.get(position));

                final Dialog dialog = new Dialog(getContext());
                dialog.setContentView(R.layout.userreg);
                dialog.setTitle("Edit Employee " + name.get(position) + " details");
                final String[] arraySpinner = new String[]{"Manager","Stockist","Cashier","Accountant"};
                dialog.setCancelable(false);
                dialog.setCanceledOnTouchOutside(false);
                final EditText emp_name = (EditText) dialog.findViewById(R.id.editTextName);
                final EditText emp_uname = (EditText) dialog.findViewById(R.id.editTextUserName);
                final EditText emp_pw = (EditText) dialog.findViewById(R.id.editTextPassword);
                final Spinner emp_role = (Spinner) dialog.findViewById(R.id.spinner_role);
                final TextView textRole = (TextView) dialog.findViewById(R.id.tv_selected_role);
                ArrayAdapter<String> adapter = new ArrayAdapter<String>(getContext(),android.R.layout.simple_spinner_item, arraySpinner);
                emp_role.setAdapter(adapter);
                emp_role.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                    @Override
                    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                        Toast.makeText(getContext(), "Role Selected is " + arraySpinner[position], Toast.LENGTH_SHORT).show();

                        String employee_role = arraySpinner[position];
                        textRole.setText(employee_role);

                    }

                    @Override
                    public void onNothingSelected(AdapterView<?> parent) {

                    }
                });


                emp_name.setText(name.get(position));
                emp_uname.setText(username.get(position));
                emp_pw.setText(password.get(position));
                emp_role.setSelection(position);

                Button buttoncancel = (Button) dialog.findViewById(R.id.buttonCancel);
                buttoncancel.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        dialog.dismiss();
                    }
                });

                Button  buttonChange = (Button) dialog.findViewById(R.id.buttonRegister);
                buttonChange.setText("Change");
                buttonChange.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v)
                    {
                        textViewName.setText(emp_name.getText().toString());
                        textViewusername.setText(emp_uname.getText().toString());
                        textViewPass.setText(emp_pw.getText().toString());
                        textViewRole.setText(textRole.getText());
                        dialog.dismiss();

                    }
                });



                dialog.show();
            }
        });


        textViewName.setText(name.get(position));
        textViewusername.setText(username.get(position));
        textViewPass.setText(password.get(position));
        textViewRole.setText(role.get(position));

        return listViewItem;
    }
public interface MyActionCallback{
 void onActionPerformed(int position);
}
   }

記錄空指針異常。

04-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：致命異常：主要 04-23 14:59:16.462 24919-24919/org.combordettime/AndroidRuntime進程：org.bordetuts.com.goldmine，PID：24919 04-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：java.lang.NullPointerException 04-29216459 -24919/org.bordetuts.com.goldmine E/AndroidRuntime：在 org.bordetuts.com.goldmine.adapter.RoleList$1.onClick(RoleList.java:67) 04-23 14:59:16.462 24919-24919/org. bordetuts.com.goldmine E/AndroidRuntime：在 android.view.View.performClick(View.java:4444) 04-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：在 android。 view.View$PerformClick.run(View.java:18440) 04-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：在 android.os.Handler.handleCallback(Handler.java: 733) 04-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：在 android.os.Handler.dispatchMessage(Handler.java:95) 0 4-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：在 android.os.Looper.loop(Looper.java:136) 04-23 14:59:16.462 249199-2 org.bordetuts.com.goldmine E/AndroidRuntime：在 android.app.ActivityThread.main(ActivityThread.java:5028) 04-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：在java.lang.reflect.Method.invokeNative(Native Method) 04-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：在 java.lang.reflect.Method.invoke(Method.java) :515) 04-23 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：在 com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java4-783) 0 14:59:16.462 24919-24919/org.bordetuts.com.goldmine E/AndroidRuntime：在 com.android.internal.os.ZygoteInit.main(ZygoteInit.java:604) 04-23 14:59:16.4192-24444 /org.bordetuts.com.goldmine E/AndroidRuntime：在 dalvik.system.NativeStart.main(Native Method)

我想通知活動適配器內部發生了一些變化。例如。 某個位置按下了刪除鍵。 任何建議、幫助或指示都會有所幫助。謝謝。

Answer 1

您的活動：

public class MainActivity extends AppCompatActivity implements YourCustomAdapter.MyActionCallback {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    // or something like that
    ListView listView = findViewById(R.id.my_list_view);
    listView.setAdapter(new YourCustomAdapter(this));
}



@Override
public void onActionPerformed(int position) {
    //do here something with your data

}

你的適配器：

public class YourCustomAdapter extends BaseAdapter {

public YourCustomAdapter(
        MyActionCallback actionCallback) {
    mActionCallback = actionCallback;
}

private MyActionCallback mActionCallback;

@Override
public int getCount() {
    return 0;
}

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

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

@Override
public View getView(final int position, View convertView, ViewGroup parent) {
    // your case specific code
    // don't forget to implement view re-using properly,
    // don't inflate view each time
    delete.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v)
        {
            name.remove(position);
            username.remove(position);
            password.remove(position);
            role.remove(position);
            //pass position of deleted object or any other thing you want
            mActionCallback.onActionPerformed(position);
            notifyDataSetChanged();
        }
    });
    return null;
}

public interface MyActionCallback{
    void onActionPerformed(int position);
}

您也可以使用事件總線，例如 Otto，但我認為對於您的情況，只需自定義回調就足夠了。 這取決於。