我使用customadapter实现了自定义列表视图。当我按下刷新按钮时，数据从数据库中获取并在列表视图中更新。但在我的情况下，项目会在前面的项目之后附加，即如果我在数据库中有2个项目而我按下刷新按钮而不更改数据库项目，则会追加相同的项目并显示4个列表项目。需要快速帮助。 notifyDatasetChanged()用于代码中。但我不知道它是否正确。
以下是MainActivity.java的代码
public class MainActivity extends Activity {
ListView lv;
TextView tv1,tv2,tv3;
ArrayList<String> a=new ArrayList<String>();
ArrayList<String> b=new ArrayList<String>();
ArrayList<String> c=new ArrayList<String>();
ArrayList<String> d=new ArrayList<String>();
String mydata,name,name1,society,date,venue;
public String[] s1 = new String[50];
public String[] s2=new String[50];
public String[] s3=new String[50];
public String[] s4=new String[50];
public int[] img = {R.drawable.rty, R.drawable.sf, R.drawable.rty};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
tv1=(TextView)findViewById(R.id.textView);
lv = (ListView) findViewById(R.id.listView);
ConnectionDetector cd = new ConnectionDetector(getApplicationContext());
Boolean isInternetPresent = cd.isConnectingToInternet(); // true or false
if(isInternetPresent) {
new MyData().execute();
}
else
Toast.makeText(MainActivity.this,"No Internet Connection",Toast.LENGTH_SHORT).show();
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
Intent in = new Intent(MainActivity.this, listclick.class);
in.putExtra("position", position);
startActivity(in);
}
});
}
public void abc(View v)
{
Intent in=new Intent(MainActivity.this,webform.class);
startActivity(in);
}
public void ref(View v)
{
ConnectionDetector cd = new ConnectionDetector(getApplicationContext());
Boolean isInternetPresent = cd.isConnectingToInternet();
if(isInternetPresent) {
new MyData().execute();
}
else
Toast.makeText(MainActivity.this,"No Internet Connection",Toast.LENGTH_SHORT).show();
}
public class MyData extends AsyncTask<String,String,String>
{
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(String s) {
super.onPostExecute(s);
CustomAdapter cad = new CustomAdapter(MainActivity.this, s1, img,s2,s3,s4);
lv.setAdapter(cad);
cad.notifyDataSetChanged();
}
@Override
protected String doInBackground(String... params) {
getData();
return null;
}
}
public void getData()
{
try {
HttpClient httpClient=new DefaultHttpClient();
HttpPost httpPost=new HttpPost("http://collegeevents.esy.es/abc.php");
HttpResponse response=httpClient.execute(httpPost);
HttpEntity httpEntity=response.getEntity();
InputStream is=httpEntity.getContent();
BufferedReader reader=new BufferedReader(new InputStreamReader(is,"utf-8"),8);
StringBuilder strbuilder=new StringBuilder();
String line=null;
while ((line=reader.readLine())!=null)
{
strbuilder.append(line);
}
is.close();
mydata=strbuilder.toString();
JSONArray obj=new JSONArray(mydata);
for(int i=0;i<obj.length();i++)
{
JSONObject obj1=obj.getJSONObject(i);
a.add(i,obj1.getString("Name"));
b.add(i,obj1.getString("society"));
c.add(i,obj1.getString("venue"));
d.add(i,obj1.getString("date"));
}
String[] s = new String[a.size()];
s=a.toArray(s);
s1 = s;
String[] soc = new String[b.size()];
soc=b.toArray(soc);
s2 = soc;
String[] ven = new String[c.size()];
ven=c.toArray(ven);
s3 = ven;
String[] dat = new String[d.size()];
dat=d.toArray(dat);
s4 = dat;
}
catch (Exception e)
{
}
}
}
这是CustomAdapter.java
public class CustomAdapter extends ArrayAdapter<String> {
Context c1;
String s1[],soc[],ven[],dat[];
int s2[];
CustomAdapter(Context c,String s[],int s3[],String society[],String venue[],String date[])
{
super(c, R.layout.listcustom, s);
this.c1=c;
this.s1=s;
this.s2=s3;
this.soc=society;
this.ven=venue;
this.dat=date;
}
@Override
public View getView(int position, View v, ViewGroup parent) {
LayoutInflater li=(LayoutInflater) c1.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v=li.inflate(R.layout.listcustom,parent,false);
TextView tv=(TextView)v.findViewById(R.id.textView);
TextView tv1=(TextView)v.findViewById(R.id.society);
TextView tv2=(TextView)v.findViewById(R.id.venue);
TextView tv3=(TextView)v.findViewById(R.id.date);
tv.setText(s1[position]);
tv1.setText(soc[position]);
tv2.setText(ven[position]);
tv3.setText(dat[position]);
if(position%2==0) {
tv.setTextColor(Color.parseColor("#01579B"));
tv3.setTextColor(Color.parseColor("#01579B"));
}
else{
tv.setTextColor(Color.parseColor("#00897B"));
tv3.setTextColor(Color.parseColor("#00897B"));
}
v.setTag(position);
//notifyDataSetChanged();
return v;
}
}
答案 0 :(得分：1)
我终于明白了。您的简短回答是问题 - 您尚未清除default: calc
calc.o: calc.c calc.h
gcc -Wall -std=c99 -o calc calc.c -lm
clean:
rm calc.o
cleanall: clean
rm calc
，a，b，c d。因此，每个ArrayList调用都会添加数据，而之前的数据仍然存在。因此，您应该在getData()的开头添加a.clear()，b.clear() ...等。
但我建议做出以下改进：
的AsyncTask：
getData的活动：
public class MyData extends AsyncTask<String, String, Event[]> {
@Override
protected Event[] doInBackground(String... params) {
return getData();
}
@Override
protected void onPostExecute(Event[] s) {
cad.clear();
cad.addAll(s)
}
}
CustomAdapter：
public class MainActivity extends Activity {
private CustomAdapter cad;
@Override
protected void onCreate(Bundle savedInstanceState) {
...
lv = (ListView) findViewById(R.id.listView);
cad = new CustomAdapter(getApplicationContext());
}
}
请勿使用public class CustomAdapter extends ArrayAdapter<Event> {
private final LayoutInflater inflater;
public CustomAdapter(Context c, Event ev[]) {
super(context, ev[]);
inflate = LayoutInflater.from(context);
}
CustomAdapter(Context c) {
this(context, new Event[0]);
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
final View v;
if(convertView == null) {
v = inflater.inflate(...)
} else {
v = convertView;
}
// find views or event better — use ViewHolder pattern
Event evt = getItem(position);
tv.setText(evt.getName());
...
return v;
}
}
标记。请改用view＃setOnClickListener。 onClick绑定布局和活动实施，但这并不好。
使用明确的名称。像onClick而不是LoadDataTask。