Question

当滚动列表时，每个项目上加载的图像被洗牌，并且到达下一个项目的每个项目的化身结束。我不知道我是否清楚，但我会用图像显示我的自定义适配器类

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.ArrayList;

public class CustomListAdapter extends BaseAdapter {
    private ArrayList listData;
    private LayoutInflater layoutInflater;

    public CustomListAdapter(Context context, ArrayList listData) {
        this.listData = listData;
        layoutInflater = LayoutInflater.from(context);
    }

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

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

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

    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            convertView = layoutInflater.inflate(R.layout.list_row_layout, null);
            holder = new ViewHolder();
            holder.headlineView = (TextView) convertView.findViewById(R.id.title);
            holder.reporterNameView = (TextView) convertView.findViewById(R.id.reporter);
            holder.reportedDateView = (TextView) convertView.findViewById(R.id.date);
            holder.imageView = (ImageView) convertView.findViewById(R.id.thumbImage);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        NewsItem newsItem = (NewsItem) listData.get(position);
        holder.headlineView.setText(newsItem.getHeadline());
        holder.reporterNameView.setText("By, " + newsItem.getReporterName());
        holder.reportedDateView.setText(newsItem.getDate());
        if (holder.imageView != null) {
            new ImageDownloaderTask(holder.imageView).execute(newsItem.getUrl());
        }
        return convertView;
    }

    static class ViewHolder {
        TextView headlineView;
        TextView reporterNameView;
        TextView reportedDateView;
        ImageView imageView;
    }
}

我的新闻项目

public class NewsItem {

    private String headline;
    private String reporterName;
    private String date;
    private String url;

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getHeadline() {
        return headline;
    }

    public void setHeadline(String headline) {
        this.headline = headline;
    }

    public String getReporterName() {
        return reporterName;
    }

    public void setReporterName(String reporterName) {
        this.reporterName = reporterName;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    @Override
    public String toString() {
        return "[ headline=" + headline + ", reporter Name=" + reporterName + " , date=" + date + "]";
    }
}

我的imageDownloaderTask

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.Drawable;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.ImageView;

import org.apache.http.HttpStatus;

import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.net.HttpURLConnection;
import java.net.URL;

class ImageDownloaderTask extends AsyncTask<String, Void, Bitmap> {
    private final WeakReference<ImageView> imageViewReference;

    public ImageDownloaderTask(ImageView imageView) {
        imageViewReference = new WeakReference<ImageView>(imageView);
    }

    @Override
    protected Bitmap doInBackground(String... params) {
        return downloadBitmap(params[0]);
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {
        if (isCancelled()) {
            bitmap = null;
        }

        if (imageViewReference != null) {
            ImageView imageView = imageViewReference.get();
            if (imageView != null) {
                if (bitmap != null) {
                    imageView.setImageBitmap(bitmap);
                } else {
                    Drawable placeholder = imageView.getContext().getResources().getDrawable(R.drawable.placeholder);
                    imageView.setImageDrawable(placeholder);
                }
            }
        }
    }
    private Bitmap downloadBitmap(String url) {
        HttpURLConnection urlConnection = null;
        try {
            URL uri = new URL(url);
            urlConnection = (HttpURLConnection) uri.openConnection();
            int statusCode = urlConnection.getResponseCode();
            if (statusCode != HttpStatus.SC_OK) {
                return null;
            }

            InputStream inputStream = urlConnection.getInputStream();
            if (inputStream != null) {
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                return bitmap;
            }
        } catch (Exception e) {
            urlConnection.disconnect();
            Log.w("ImageDownloader", "Error downloading image from " + url);
        } finally {
            if (urlConnection != null) {
                urlConnection.disconnect();
            }
        }
        return null;
    }
}

Answer 1

class Person(models.Model):
    first_name = models.CharField(max_length=30, null=False)
    last_name = models.CharField(max_length=30, null=False)

class Sensor(models.Model):
    person = models.ForeignKey(Person, on_delete=models.CASCADE)
    name = models.CharField(max_length=100, null=False)
    sensor_id = models.UUIDField(null=True, blank=True)

class DataPoint(models.Model):
    sensor = models.ForeignKey(Sensor, on_delete=models.CASCADE)
    date_time_instance = models.DateTimeField()
    value = models.DecimalField(max_digits=10, decimal_places=4)

Answer 2

试试这个。改变你的getView就像这样。

public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder holder;
     view=convertView;
    if (convertView == null) {
        view = layoutInflater.inflate(R.layout.list_row_layout, null);
        holder = new ViewHolder();
        holder.headlineView = (TextView) view.findViewById(R.id.title);
        holder.reporterNameView = (TextView) view.findViewById(R.id.reporter);
        holder.reportedDateView = (TextView) view.findViewById(R.id.date);
        holder.imageView = (ImageView) view.findViewById(R.id.thumbImage);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) view.getTag();
    }

    NewsItem newsItem = (NewsItem) listData.get(position);
    holder.headlineView.setText(newsItem.getHeadline());
    holder.reporterNameView.setText("By, " + newsItem.getReporterName());
    holder.reportedDateView.setText(newsItem.getDate());
    if (holder.imageView != null) {
        new ImageDownloaderTask(holder.imageView).execute(newsItem.getUrl());
    }
    return view;
}

并将View视图声明为类级别变量希望它有助于感谢。请参考这里 https://androidruler.wordpress.com/2016/02/21/android-custom-listview-example/

列表视图中的图像随机播放。滚动时

2 个答案: