问题
I have a main activity with a ListView. I then have a second activity with a text box for the user input and a button. When the user enters the input and clicks on the button, it should add the item to the ListView in the main activity but for some reason the ListView doesn't refresh with the new data. Any idea on how to go about this ?
回答1:
Create an adapter class for your listView.
class MyAdapter extends BaseAdapter {
ArrayList<Item> items;
// Override all other needed methods.
//Add method to add items to list from outside.
public void addItems(Item item) {
items.add(item);
adapter.notifyDataSetChanged();
}
}
Inside your activity // Crate MyAdapter instance an assign to listview like-
listView,setAdapter(adapter);
Item item= new Item();
//Add necessary properties in item. and add item to list.
adapter.addItem(item);
This is the overall idea . Look around this. Should work.
回答2:
Your second activity B, can't see your data resource in activity a, therefore, when you add new item in activity B you must notify activity A
that a change has occurred. This you can obtain using broadcastreceive. When you add a item in activity B sendBroadcastreceive to activity A. Activity A receive the change add it to dataresource and only after notify your adapter.
See the example below. it work!
MainActivity.java
public class MainActivity extends AppCompatActivity {
static String[] bike = new String[]{
"Ducati", "Honda", "BMW", "Bimota", "Kawasaky", "Yahamaha", "Suzuky", "Harlay-Davinson",
"Fantic", "Morini", "Hasquarna", "Aprilia", "Guzzi", "Beta", "Borile", "Buell", "Kymco", "Ktm"
};
ArrayList<String> alBike = new ArrayList<>(Arrays.asList(bike));
private ArrayAdapter adapter ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView listView = (ListView) findViewById(R.id.listView);
Button button = (Button) findViewById(R.id.button2);
adapter = new myadapter(getBaseContext(),0);
listView.setAdapter(adapter);
IntentFilter intentFilter =new IntentFilter();
intentFilter.addAction("ITEM_ADDED");
BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
// Log.i("bogo",action);
switch (action) {
case "ITEM_ADDED":
String newitem = intent.getStringExtra("newitem");
alBike.add(newitem);
adapter.notifyDataSetChanged();
break;
}
}
};
registerReceiver(broadcastReceiver, intentFilter);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
startActivity(new Intent(getApplicationContext(),FormActivity.class));
}
});
}
public class myadapter extends ArrayAdapter<String> {
public myadapter(Context context, int resource) {
super(context, resource);
}
@Override
public int getCount() {
return alBike.size();
}
@Override
public long getItemId(int position) {
return 0;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
LayoutInflater inflater = (LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View row = inflater.inflate(R.layout.listviewrow, parent, false);
TextView textView = (TextView) row.findViewById(R.id.textView);
textView.setText(alBike.get(position));
return row;
}
}
}
main_activity.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="bogo.com.additemtolistview.MainActivity">
<Button
style="?android:attr/buttonStyleSmall"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="new item"
android:id="@+id/button2"
android:layout_above="@+id/listView"
android:layout_alignParentEnd="true"
android:layout_marginEnd="198dp" />
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/listView"
android:layout_alignParentEnd="true"
android:layout_alignParentTop="true" />
</LinearLayout>
FormActivity.java (YOUR ACTIVITY B)
package bogo.com.additemtolistview;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class FormActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_form);
Button button = (Button) findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
EditText editText = (EditText) findViewById(R.id.editText);
String newitem = editText.getText().toString();
Intent intent = new Intent("ITEM_ADDED");
intent.putExtra("newitem",newitem);
sendBroadcast(intent);
finish();
}
});
}
}
activity_form.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="bogo.com.additemtolistview.FormActivity">
<EditText
android:layout_width="220dp"
android:layout_height="wrap_content"
android:id="@+id/editText"
android:layout_alignParentTop="true"
android:layout_alignParentStart="true"
android:layout_marginStart="78dp"
android:layout_marginTop="60dp" />
<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="New Button"
android:id="@+id/button"
android:layout_centerVertical="true"
android:layout_alignStart="@+id/editText" />
</RelativeLayout>
listviewrow.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent">
<LinearLayout
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="48dp">
<TextView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="New Text"
android:textColor="@android:color/black"
android:id="@+id/textView" />
</LinearLayout>
</LinearLayout>
来源：https://stackoverflow.com/questions/34836188/listview-refresh-in-android