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[英]How can I use Android DataBinding in a listview and still use a ViewHolder pattern?
[英]How to use viewHolder pattern to keep UI elements on scroll in listView?
我正在研究使用viewHolder模式來使我的UI元素在滾動listview時不會重置為默認值。 在調查之后,我不確定該如何處理。 我什至不確定我現有的代碼是否還會允許我使用viewHolder模式。 我是初學者,所以請詳細說明,不要略過細節。 謝謝
MainActivity.java
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.app.Activity;
import android.view.KeyEvent;
import android.view.View;
import android.view.inputmethod.EditorInfo;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import android.widget.ViewSwitcher;
import java.util.ArrayList;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final ArrayList<String> Chores = new ArrayList<>();
Chores.add("");
final ListAdapter MyAdapter = new CustomAdapter(this, Chores);
ListView listViewObject = (ListView)findViewById(R.id.customListView_ID);
listViewObject.setAdapter(MyAdapter);
listViewObject.setOnItemClickListener(
new AdapterView.OnItemClickListener(){
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id){
String ChoreString = String.valueOf(parent.getItemAtPosition(position));
}
}
);
final Button button = (Button) findViewById(R.id.button_ID);
button.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Chores.add("");
((ArrayAdapter)MyAdapter).notifyDataSetChanged();
}
});
}
}
CustomAdapter.java
import android.content.Context;
import android.content.DialogInterface;
import android.support.annotation.NonNull;
import android.support.v7.app.AlertDialog;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
import static com.example.emilythacker.chorelist.R.id.textView_ID;
class CustomAdapter extends ArrayAdapter{
public CustomAdapter(Context context, ArrayList choreText) {
super(context, R.layout.custon_listview_row, choreText);
}
@NonNull
@Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater myInflater = LayoutInflater.from(getContext());
View customView = myInflater.inflate(R.layout.custon_listview_row, parent, false);
ImageButton imageButton = (ImageButton) customView.findViewById(R.id.imageButton_ID);
final TextView textView = (TextView) customView.findViewById(textView_ID);
textView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//what happens when textView is clicked
AlertDialog alertDialog = new AlertDialog.Builder(getContext()).create();
final EditText input = new EditText(getContext());
input.setHint("hint");
alertDialog.setView(input);
alertDialog.setTitle("Set Chore");
alertDialog.setMessage("Alert message to be shown");
alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
//this will set text to "hello" only if user does not enter anything into input
//textView.setText("hello");
//this also will only work if there is no input entered into input...wich will change textView into empty space
textView.setText(input.getText().toString());
//works the same with or without dialog.dismiss();
dialog.dismiss();
}
});
alertDialog.show();
}
});
imageButton.setImageResource(R.drawable.clock);
return customView;
}
}
我發現本教程在學習使用ViewHolder模式時非常有用。 在解釋如何使用它方面非常清楚,但是可以隨時詢問是否感到卡住。
當您對任何列表項執行某些更改時,我們應該調用notifyDataSetChanged(),以便更新列表視圖。
回答您的問題:更新文本后,在textview.onClickListener()方法中調用notifyDataSetChanged()。
最好切換到RecyclerView,在這種情況下,當我們添加新項目時,我們可以只調用notifyItemAdded(position),它只會刷新該位置的視圖,而不刷新整個視圖。 當我們更新任何項目時,我們可以調用notifyItemChanged(position)。
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