Question

我有一个ListView的主要活动。然后，我有第二个活动，其中包含用于用户输入的文本框和一个按钮。当用户输入输入并单击按钮时，它应该将项目添加到主活动中的ListView，但由于某种原因，ListView不会使用新数据刷新。关于如何解决这个问题的任何想法？

Answer 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();
}


 }

在您的活动中 // Crate MyAdapter实例分配给listview，如 -

listView,setAdapter(adapter);

Item item= new Item();

//在item中添加必要的属性。并将项目添加到列表中。

adapter.addItem(item);

这是整体想法。环顾四周。应该工作。

Answer 2

您的第二个活动B无法在活动a中看到您的数据资源，因此，当您在活动B中添加新项目时，您必须通知活动A

发生了变化。这可以使用broadcastreceive获得。当您将活动B中的项目sendBroadcastreceive添加到活动A. 活动A收到更改后将其添加到dataresource，并且仅在通知您的适配器后。

请参阅下面的示例。它有效！

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（您的活动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>

Android中的ListView刷新

2 个答案: