[英]Populate list view
我正在開發一個最后一年的項目,我陷入了困境。 我必須從我的數據庫(MySQL數據庫)中檢索醫生的名字,並在列表視圖中顯示它。 我能夠與服務器建立連接並檢索值,但是當我嘗試在列表視圖中顯示值時,應用程序崩潰了!
我嘗試了[Hello,Views,List View] [4]中給出的相同示例。
它適用於預定義的數組,如
private String lv_arr[]={"Android","iPhone","BlackBerry","AndroidPeople"};
但對於從數據庫檢索的字符串數組,它顯示運行時異常。 有什么辦法可以實現嗎?
package com.proj;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.widget.*;
import android.app.ListActivity;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.LinearLayout;
import android.widget.TextView;
public class proj extends ListActivity {
/** Called when the activity is first created. */
public int n=0;
public int t=0;
public int i=0;
public String name[]=new String[30];
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Create a crude view - this should really be set via the layout resources
// but since its an example saves declaring them in the XML.
TextView txt=(TextView)findViewById(R.id.tv);;
//Call the method to run the data retrieval
getServerData(KEY_121);
setListAdapter(new ArrayAdapter(this,
android.R.layout.simple_list_item_1, name));
}
public static final String KEY_121 = "http://10.0.2.2/doc.php"; //I use my real IP address here.
private String getServerData(String returnString) {
InputStream is = null;
String result = "";
//The year data to send.
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("year","1970"));
//HTTP post
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(KEY_121);
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}
catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
//Convert response to string
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result=sb.toString();
}
catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
//Parse JSON data
try {
JSONArray jArray = new JSONArray(result);
for(i=0;i<jArray.length();i++)
{
JSONObject json_data = jArray.getJSONObject(i);
n=jArray.length();
name[i]=json_data.getString("name");
//Get an output to the screen
returnString += "\n\t" + jArray.getJSONObject(i);
}
}
catch(JSONException e)
{
Log.e("log_tag", "Error parsing data "+e.toString());
e.printStackTrace();
}
return returnString;
}
}
您正在使用
1.)
android:id="@+id/list"
在ListView中,但如果您通過ListActivity擴展活動,則必須使用
android:id = "@android:id/list"
2.)
你在這里返回一個String[]
,而不是String
private String[] getServerData(String returnString) {
.......
JSONArray jArray = new JSONArray(result);
name = new String[jArray.length()];
for(i=0;i<jArray.length();i++)
{
JSONObject json_data = jArray.getJSONObject(i);
name[i]=json_data.getString("name");
}
return name;
}
在ArrayAdapter中,這樣做:
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, getServerData(KEY_121));
setListAdapter(adapter);
public String name[];
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Create a crude view - this should really be set via the layout resources
// but since its an example saves declaring them in the XML.
TextView txt=(TextView)findViewById(R.id.tv);;
...
...
try {
JSONArray jArray = new JSONArray(result);
name[]=new String[jArray.length()];
for(i=0;i<jArray.length();i++)
{
JSONObject json_data = jArray.getJSONObject(i);
n=jArray.length();
name[i]=json_data.getString("name");
//Get an output to the screen
returnString += "\n\t" + jArray.getJSONObject(i);
}
}
catch(JSONException e)
{
Log.e("log_tag", "Error parsing data "+e.toString());
e.printStackTrace();
}
似乎初始化name[]
的大小為30可能太小。
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