android - 显示几秒钟后，如何将 ListView 项目标记为“已读”？

Question

我想用粗体将新添加的项目标记到我的列表中。一旦用户看到这个项目（即它在屏幕上显示 3 秒），我想将其标记为已读（即删除粗体）。我知道如何用粗体标记一些项目。但是当用户看到该项目时如何捕捉事件呢？

这个问题非常接近我正在寻找的内容。但它没有公认的答案。并且不太清楚如何等待 3 秒。

Answer 1

Hints:

• Your adapter has a getView().

• Your adapter has a data source (a list, content provider, etc. of some sort).

• Your adapter knows which position(s) are visible (because the list asked for those).

• Combined with an OnScrollListener, you can tell when the list is moving.

• If you use a view holder pattern (and you should) in your adapter, you can tell when views are being reused.

• You can also set a 3 sec timer that will "flag" the items as read, as long as they remain visible.

• You can tell if an item is visible by asking the list (getFirstVisiblePosition() and the last counterpart).

That's a starting point.

Answer 2

在您的 getView 方法上启动一个线程。

1. 检查是否已读取项目。
2. 如果没有，请将标识符设置为视图的标记。
3. 开始你的话题。
4. 后为前。4 秒睡眠。检查该视图标签是否仍然等于标识符。
5. 如果是，请更改视图样式。并将项目设置为在您的数据结构中读取。

email.xml（项目布局）：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/background"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="100dp" 
        android:background="@android:color/transparent" />

</LinearLayout>

EMail.java（项目类）：

public class EMail {

    public String title;
    public boolean read;

    public EMail(String title, boolean read) {
        this.title = title;
        this.read = read;
    }
}

活动 onCreate 方法：

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

        ListView lv = (ListView)findViewById(R.id.listView1);

        ListAdapter emails = new ListAdapter(this, 0, new ArrayList<EMail>());
        emails.add(new EMail("Email 1", false));
        emails.add(new EMail("Email 2", false));
        emails.add(new EMail("Email 3", true));
        emails.add(new EMail("Email 4", true));
        emails.add(new EMail("Email 5", false));
        emails.add(new EMail("Email 6", false));
        emails.add(new EMail("Email 7", true));
        emails.add(new EMail("Email 8", false));
        emails.add(new EMail("Email 9", false));
        emails.add(new EMail("Email 10", true));
        emails.add(new EMail("Email 11", false));
        emails.add(new EMail("Email 12", false));
        emails.add(new EMail("Email 13", false));
        emails.add(new EMail("Email 14", true));
        emails.add(new EMail("Email 15", false));
        emails.add(new EMail("Email 16", false));
        emails.add(new EMail("Email 17", false));
        emails.add(new EMail("Email 18", false));
        emails.add(new EMail("Email 19", false));
        emails.add(new EMail("Email 20", false));

        lv.setAdapter(emails);
    }

适配器：

import java.util.ArrayList;
import java.util.Timer;
import java.util.TimerTask;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.TextView;


public class ListAdapter extends ArrayAdapter<EMail> {

    private Timer timer = new Timer();
    private int identifier = 0;

    public ListAdapter(Context context, int textViewResourceId, 
            ArrayList<EMail> items) {
        super(context, textViewResourceId, items);
    }

    @Override
    public View getView(final int position, View v, ViewGroup parent) {

        if (v == null) {
            LayoutInflater vi = (LayoutInflater)getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            v = vi.inflate(R.layout.email, null);
        }

        final int id = identifier++;
        v.setTag(id);

        TextView titleTextView = (TextView)v.findViewById(R.id.title);
        final LinearLayout back = (LinearLayout)v.findViewById(R.id.background);
        final EMail e = getItem(position);

        titleTextView.setText(e.title);

        if (e.read)
            back.setBackgroundColor(getContext().getResources().getColor(R.color.gray));
        else
        {
            back.setBackgroundColor(getContext().getResources().getColor(R.color.white));

            final View view = v;

            TimerTask task = new TimerTask() {
                public void run() {
                    if (view.getTag().toString().equals(id+""))
                    {
                        e.read = true;
                        ((Activity) getContext()).runOnUiThread(new Runnable() {
                            public void run() {
                                back.setBackgroundColor(getContext().getResources().getColor(R.color.gray));
                            }
                        });
                    }
                }
            };

            timer.schedule(task, 3000);
        }

        return v;
    }
}

Answer 3

You can set OnScrollListener to your ListView and check when user scrolls to your new items.