首先,我三周前第一次接触到 Java,所以如果这段代码很糟糕,请耐心等待。这是学校的一项作业,我要在原型(prototype)应用程序的基础上构建并为其提供 UI,因此适配器基本上就是我对此所做的全部工作。
我的问题是,一旦我触摸滚动条,我就会被扔到列表的底部,并且无法向上滚动而不被推回。
/**
* VaxjoWeather.java
* Created: May 9, 2010
* Jonas Lundberg, LnU
*/
package dv106.weather;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.StringWriter;
import java.net.URL;
import java.net.URLConnection;
import java.util.ArrayList;
import java.util.List;
import android.app.ListActivity;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
/**
* This is a first prototype for a weather app. It is currently
* only downloading weather data for Växjo.
*
* This activity downloads weather data and constructs a WeatherReport,
* a data structure containing weather data for a number of periods ahead.
*
* The WeatherHandler is a SAX parser for the weather reports
* (forecast.xml) produced by www.yr.no. The handler constructs
* a WeatherReport containing meta data for a given location
* (e.g. city, country, last updated, next update) and a sequence
* of WeatherForecasts.
* Each WeatherForecast represents a forecast (weather, rain, wind, etc)
* for a given time period.
*
* The next task is to construct a list based GUI where each row
* displays the weather data for a single period.
*
*
* @author jlnmsi
*
*/
public class VaxjoWeather extends ListActivity {
//private InputStream input;
private WeatherReport report = null;
//private ArrayList<WeatherForecast> forecastList = new ArrayList<WeatherForecast>();
private WeatherAdapter adapter;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
adapter = new WeatherAdapter(this);
setListAdapter(adapter);
//getListView().setTranscriptMode(ListView.TRANSCRIPT_MODE_DISABLED);
try {
URL url = new URL("http://www.yr.no/sted/Sverige/Kronoberg/V%E4xj%F6/forecast.xml");
AsyncTask task = new WeatherRetriever().execute(url);
} catch (IOException ioe ) {
ioe.printStackTrace();
}
//adapter.notifyDataSetChanged();
}
private void PrintReportToConsole() {
if (this.report != null) {
/* Print location meta data */
//System.out.println(report);
/* Print forecasts */
int count = 0;
for (WeatherForecast forecast : report) {
count++;
adapter.add(forecast);
}
}
else {
System.out.println("Weather report has not been loaded.");
}
//adapter.notifyDataSetChanged();
}
private class WeatherRetriever extends AsyncTask<URL, Void, WeatherReport> {
protected WeatherReport doInBackground(URL... urls) {
try {
return WeatherHandler.getWeatherReport(urls[0]);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
protected void onProgressUpdate(Void... progress) {
}
protected void onPostExecute(WeatherReport result) {
report = result;
PrintReportToConsole();
}
}
// custom ArrayAdpater to show, weather icon, temperature, and precipation.
class WeatherAdapter extends ArrayAdapter<WeatherForecast> {
public WeatherAdapter(Context context) {
super(context,R.layout.forecast);
}
@Override // Called when updating the ListView
public View getView(int position, View convertView, ViewGroup parent) {
View row;
if (convertView == null) { // Create new row view object
LayoutInflater inflater = getLayoutInflater();
row = inflater.inflate(R.layout.forecast,parent,false);
}
else // reuse old row view to save time/battery
row = convertView;
// TextView for Temperature
TextView temperature = (TextView)row.findViewById(R.id.temperature);
temperature.setText(Integer.toString(this.getItem(position).getTemp())+" °C");
// TextView for out Precipation.
TextView precipation = (TextView)row.findViewById(R.id.rain);
precipation.setText(String.valueOf(this.getItem(position).getRain())+" mm");
// Image Icon for forecast.
ImageView icon = (ImageView)row.findViewById(R.id.icon);
String iconPath = "ic_";
if (this.getItem(position).getWeatherCode() <= 9){
iconPath = iconPath+"0"+(Integer.toString(this.getItem(position).getWeatherCode()));
}
else {
iconPath = iconPath+(Integer.toString(this.getItem(position).getWeatherCode()));
}
int resId = getResources().getIdentifier(iconPath, "drawable", getPackageName());
// If the resource ID is invalid, as in the image not existing, we'll add the postfix for periods.
if (resId == 0){
// Set the icon image source dependent on period code given.
if(this.getItem(position).getPeriodCode() == 3){
iconPath = iconPath +"n";
}
else if (this.getItem(position).getPeriodCode() == 2){
iconPath = iconPath +"d";
}
else {
iconPath = iconPath +"m";
}
resId = getResources().getIdentifier(iconPath, "drawable", getPackageName());
icon.setImageResource(resId);
}
// Or if everything checked out, we'll just run with the resource ID and find our Icon.
else {
icon.setImageResource(resId);
}
return row;
}
}
}
我尝试应用另一个标准数组适配器,实际上得到了相同的不需要的滚动结果,所以我不知道我遇到问题的是哪个部分。
最佳答案
实现方法是: 1:将ListView放在main.xml中 2:在您的 Activity 中像这样创建 ListView 对象 -> private ListView listView;在 onCreate 中将其连接到 main.xml,如下所示,listView = (ListView) R.id.listView1;//不管它叫什么
3:接下来创建一个ArrayList:-> private ArrayList arrayWeather = new ArrayList();
4:用天气数据填充数组列表,最后创建您创建的类的对象,并使其使用您的数组列表来显示数据。
示例: 公共(public)类 ListUser 扩展 BaseAdapter{
@Override
public int getCount() {
// TODO Auto-generated method stub
return arraylistData.size(); // the arraylist u created
}
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return arraylistData.get(position);
}
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return arraylistData.size();
}
@Override
public View getView(final int position, View v, ViewGroup parent) {
if(v == null){
LayoutInflater lf = (LayoutInflater) BuyPets.this.getSystemService( Context.LAYOUT_INFLATER_SERVICE);
v = lf.inflate(R.layout.forecast, null);
}
// setup here, done
return v;
}
}
关于java - Android - 无法向上滚动,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/26151463/