ListView updated from EditText

风格不统一 提交于 2019-11-28 10:35:55
Mauker

Well, for what we discussed, you wanted something like this:

When you want to make a custom ListView, you have to write your own adapter. In this particular case I'm subclassing the BaseAdapter class.

This custom adapter will take hold of my data model, and will inflate the data to my ListView rows.

First, I'll create the XML of my custom row. You can see the code below.

item_mail.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    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">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Test text"
        android:id="@+id/tv_mail"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_centerVertical="true"/>

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/iv_icon"
        android:layout_alignParentTop="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:layout_centerVertical="true"
        android:src="@android:drawable/ic_menu_report_image" />
</RelativeLayout>

Here I've created a row that displays a text and an image.

Now, I'll create my custom adapter to handle this XML. As you can see below.

MailAdapter.java

public class MailAdapter extends BaseAdapter {

    private static final String LOG_TAG = MailAdapter.class.getSimpleName();

    private Context context_;
    private ArrayList<ArrayList<String>> mailitems;

    public MailAdapter(Context context, ArrayList<ArrayList<String>> mailitems) {
        this.context_ = context;
        this.mailitems = mailitems;
    }

    @Override
    public int getCount() {
        return mailitems.size();
    }

    @Override
    public Object getItem(int position) {
        return mailitems.get(position).get(0);
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            LayoutInflater mInflater = (LayoutInflater)
                    context_.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);

            convertView = mInflater.inflate(R.layout.item_mail, null);
        }

        TextView tv_mail = (TextView) convertView.findViewById(R.id.tv_mail);
        ImageView iv_icon = (ImageView) convertView.findViewById(R.id.iv_icon);

        String mail = mailitems.get(position).get(0);
        String icon = mailitems.get(position).get(1);

        Log.d(LOG_TAG,"Mail: " + mail + " mail_icon: " + icon);

        tv_mail.setText(mail);
        // iv_icon.setImageURI(); Here you can do whatever logic you want to update your image, using URI's, ID's, or something else.

        return convertView;
    }
}

Ok. Now we have everything to make this work. In your Activity class, do something like that:

activity_main.xml

<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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <TextView
        android:text="@string/hello_world"
        android:id="@+id/tv_header"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true" />

    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@+id/tv_header">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Add mail"
            android:id="@+id/button"
            android:layout_gravity="center" />

        <ListView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/listView" />
    </LinearLayout>

</RelativeLayout>

MainActivity.java

public class MainActivity extends ActionBarActivity {

    private int numMail = 1; // Dummy int to create my items with different numbers.

    private MailAdapter mailAdapter; // Your custom adapter.

    private ArrayList<ArrayList<String>> mailItems; // This is going to be your data structure, everytime you change it, call the notifyDataSetChanged() method.

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button bt = (Button) findViewById(R.id.button);
        ListView lv_mail = (ListView) findViewById(R.id.listView);
        mailItems = new ArrayList<>();
        mailAdapter = new MailAdapter(this,mailItems);
        lv_mail.setAdapter(mailAdapter);

        bt.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                addItem(); // The method I'm using to insert the item. Look for it below.
            }
        });
    }

    // Here I'm creating a new ArrayList, and appending it to my 'mailItems' Array. After that, I'm notifying the adapter that my data changed.
    private void addItem() {
        ArrayList<String> mail = new ArrayList<>();

        mail.add(0,"mail " + numMail++);
        mail.add(1,"path_to_image"); // Depending on what you want to do, put your path, URI, or whatever other way you want to store that image data.

        mailItems.add(mail); // Inserting the data on the ArrayList.
        mailAdapter.notifyDataSetChanged(); // Notifying the adapter that my ArrayList was modified.
    }
}

This should do the trick.

I guess your problem was that you weren't updating the same ArrayList that was in your custom adapter. That's why when you called notifyDataSetChanged()nothing happened, I mean. You were creating a new ArrayList, which wasn't the same that was in your adapter. So here's what I did... I've made the ArrayList global, and then I've used it in my custom adapter constructor. After that, when the user triggers the onClick() method of my button, I'm inserting some new data on my global Array, and then I'm notifying the adapter that the data changed.

You can read a little more about that here and I've found a similar question here, which you can read as well.

Edit: Another related question, which might be an interesting read.

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