像往常一样，这个问题来自 Android 的新用户。三周后，我会尽力解释这个问题。
首先，我从今天开始使用 Exlipse 3.7.1 和 SDK r15，因为我想我会尝试升级，也许这就是导致问题的原因，但在使用 r13 时似乎是一样的。
这是我的代码的工作副本:
主.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:gravity="center_horizontal"
android:id="@+id/llMain"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<LinearLayout
android:background="@drawable/header"
android:id="@+id/linearLayout1"
android:layout_height="50dp"
android:layout_width="fill_parent">
<ImageButton
android:background="@null"
android:id="@+id/ibHome"
android:layout_gravity="center_vertical"
android:layout_height="wrap_content"
android:layout_width="0dp"
android:layout_weight=".25"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:src="@drawable/trophy_cup" />
<ImageView
android:background="#000000"
android:id="@+id/imageView1"
android:layout_height="match_parent"
android:layout_width="1dp" />
<TextView
android:gravity="center_horizontal"
android:id="@+id/lblHome"
android:layout_height="50dp"
android:layout_width="0dp"
android:layout_weight="1"
android:paddingTop="14dp"
android:text="@string/helloHome"
android:textColor="@color/txtYellow"
android:textSize="18dp"
android:textStyle="bold"
android:typeface="serif" />
<ImageView
android:id="@+id/imageView2"
android:layout_height="match_parent" android:background="#000000"
android:layout_width="1dp" />
<ImageButton
android:background="@null"
android:focusable="true"
android:id="@+id/ibQuit"
android:layout_gravity="center_vertical"
android:layout_height="wrap_content"
android:layout_width="0dp"
android:layout_weight=".25"
android:paddingLeft="10dp"
android:paddingRight="10dp"
android:src="@drawable/yellow_flag" />
</LinearLayout>
<!-- Body code goes here -->
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="match_parent"
android:layout_height="300dp"
android:layout_weight="1"
android:gravity="center_horizontal" android:paddingTop="10dp">
<TextView
android:id="@+id/lblHeading"
android:layout_width="wrap_content"
android:layout_height="40dp"
android:layout_weight="0.17"
android:gravity="center_horizontal"
android:isScrollContainer="true"
android:text="Top"
android:textColor="@color/txtYellow"
android:textSize="22dp"
android:textStyle="bold" android:paddingTop="7dp" android:typeface="serif"/>
<Spinner
android:entries="@array/strArrTop"
android:id="@+id/spinTop"
android:layout_width="90dp"
android:layout_height="wrap_content"
android:layout_weight="0.44"
android:focusableInTouchMode="true"
android:longClickable="true"/>
</LinearLayout>
<LinearLayout
android:id="@+id/linearLayout3"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:layout_weight="1"
android:gravity="center_horizontal"
android:padding="25dp"
android:orientation="vertical" >
<ListView
android:id="@+id/list1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:isScrollContainer="true" />
</LinearLayout>
<!-- End Body code goes here -->
<LinearLayout
android:id="@+id/linearLayout4"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center_horizontal" >
<TextView
android:id="@+id/lblWidth"
android:layout_height="wrap_content"
android:layout_width="wrap_content" />
<ImageView
android:layout_height="120dp"
android:layout_width="201dp"
android:scaleType="fitXY"
android:src="@drawable/ddo_logo" />
<TextView
android:id="@+id/lblHeight"
android:layout_height="wrap_content"
android:layout_width="wrap_content" />
</LinearLayout>
</LinearLayout>
mylist.xml(自定义列表适配器)
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="wrap_content"
android:layout_weight="1"
android:layout_height="wrap_content" android:gravity="left|center">
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_horizontal">
<TextView
android:id="@+id/txt1"
android:layout_width="182dp"
android:layout_height="wrap_content"
android:layout_weight="0.21"
android:textColor="@color/txtYellow" />
<TextView
android:id="@+id/txt2"
android:layout_width="40dp"
android:layout_height="wrap_content"
android:textColor="@color/txtYellow" />
</LinearLayout>
</LinearLayout>
list 文件，使用minSDK 8.0
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.hunta.DDOFastestTimes"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk android:minSdkVersion="8" />
<uses-permission android:name="android.permission.INTERNET"/>
<supports-screens
android:normalScreens="true"
android:largeScreens="true" />
<application
android:icon="@drawable/ic_launcher"
android:label="@string/app_name" >
<activity
android:label="@string/app_name"
android:name=".DDOFastestTimesActivity" >
<intent-filter >
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
最后是有问题的 java 文件:
package com.hunta.DDOFastestTimes;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
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.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.content.Context;
import android.net.ParseException;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
public class DDOFastestTimesActivity extends Activity implements OnClickListener {
/** JSON variables */
String jc1, jc2 = null;
/** END JSON variables */
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
/** JSON variables */
String result = null;
InputStream is = null;
StringBuilder sb = null;
/** END JSON variables */
ImageButton closeApp = (ImageButton) findViewById(R.id.ibQuit);
closeApp.setOnClickListener(this);
/** http://www.dcpagesapps.com/developer-resources/android/21-android-tutorial-spinners?start=1 */
/** Populating the spinner from that string-array */
Spinner s = (Spinner) findViewById( R.id.spinTop );
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource( this, R.array.strArrTop, android.R.layout.simple_spinner_item );
adapter.setDropDownViewResource( android.R.layout.simple_spinner_dropdown_item );
/** END Populating the spinner from that string-array */
/** Create a reference to our spinner */
s.setAdapter( adapter );
/** END Create a reference to our spinner */
/** END http://www.dcpagesapps.com/developer-resources/android/21-android-tutorial-spinners?start=1 */
s.setOnItemSelectedListener(new MyOnItemSelectedListener());
/** JSON code to initiate the php */
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
//http post
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://url-to-my-php-file/fastag.php");
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);
sb = new StringBuilder();
sb.append(reader.readLine() + "\n");
String line="0";
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());
}
//paring data
JSONArray jArray;
try{
jArray = new JSONArray(result);
JSONObject json_data=null;
// Adding the JSON data to the list view
int length = jArray.length();
List<String> listContents1 = new ArrayList<String>(length);
List<String> listContents2 = new ArrayList<String>(length);
// Convert ListString Array to an ArrayList
ArrayList<tblRecord> arrTxt = new ArrayList<tblRecord>();
// Changing the ListViews
for(int i=0;i<jArray.length();i++){
json_data = jArray.getJSONObject(i);
jc1 = json_data.getString("c1");
jc2 = json_data.getString("c2");
listContents1.add(json_data.getString("c1"));
listContents2.add(json_data.getString("c2"));
// Create an Array to pass to our custom view
tblRecord addRecord = new tblRecord(jc1, jc2);
arrTxt.add(addRecord);
}
ListView myListView1 = (ListView) findViewById(R.id.list1);
myListView1.setAdapter(new UserItemAdapter(this, android.R.layout.simple_list_item_1, arrTxt));
// END Adding the JSON data to the list view
}
catch(JSONException e1){
Toast.makeText(getBaseContext(), "No Results Found" ,Toast.LENGTH_LONG).show();
} catch (ParseException e1) {
e1.printStackTrace();
}
/** END JSON code to initiate the php */
}
/** End Called when the activity is first created. */
/** Using a custom List View */
public class UserItemAdapter extends ArrayAdapter<tblRecord> {
private ArrayList<tblRecord> arrList;
public UserItemAdapter(Context context, int textViewResourceId, ArrayList<tblRecord> arrList) {
super(context, textViewResourceId, arrList);
this.arrList = arrList;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.mylist, null);
}
tblRecord user = arrList.get(position);
if (user != null) {
TextView c1 = (TextView) v.findViewById(R.id.txt1);
TextView c2 = (TextView) v.findViewById(R.id.txt2);
if (c1 != null) {
c1.setText(user.c1);
}
if(c2 != null) {
c2.setText(user.c2);
}
}
return v;
}
}
public class tblRecord {
public String c1;
public String c2;
public tblRecord(String c1, String c2) {
this.c1 = c1;
this.c2 = c2;
}
}
/** END Using a custom List View */
/** Listener for the spinner, we will handle changes made to the spinner here */
public class MyOnItemSelectedListener implements OnItemSelectedListener {
public void onItemSelected(AdapterView<?> parent,
View v, int position, long id) {
Toast.makeText(parent.getContext(), "The top " +
parent.getItemAtPosition(position).toString(), Toast.LENGTH_LONG).show();
}
public void onNothingSelected(AdapterView<?> parent) {
// Do nothing.
}
}
/** END Listener for the spinner, we will handle changes made to the spinner here */
@Override
public void onClick(View v) {
int id = v.getId();
// Intent myIntent;
switch (id) {
case R.id.ibQuit:
finish();
break;
}
}
}
到目前为止一切正常，如果不是 100% 至少它可以正常工作，但现在我需要尝试在用户更改微调器时动态更改 ListView 的内容。
模拟器在其运行配置中使用 -dns-server xxx.xxx.xxx.xxx 我正在运行 3.7in WVGA
现在，经过 8 小时的尝试找到一种方法来做到这一点，这是我所能得到的，但它只是崩溃了:
package com.hunta.DDOFastestTimes;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
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.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ListActivity;
import android.content.Context;
import android.net.ParseException;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
public class DDOFastestTimesActivity extends ListActivity implements OnClickListener {
private UserItemAdapter myAdapter;
private ArrayList<tblRecord> arrTxt = null;
private Runnable viewJSON;
/** JSON variables */
String jc1, jc2, result = null;
InputStream is = null;
StringBuilder sb = null;
/** END JSON variables */
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ImageButton closeApp = (ImageButton) findViewById(R.id.ibQuit);
closeApp.setOnClickListener(this);
/** http://www.dcpagesapps.com/developer-resources/android/21-android-tutorial-spinners?start=1 */
/** Populating the spinner from that string-array */
Spinner s = (Spinner) findViewById( R.id.spinTop );
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource( this, R.array.strArrTop, android.R.layout.simple_spinner_item );
adapter.setDropDownViewResource( android.R.layout.simple_spinner_dropdown_item );
/** END Populating the spinner from that string-array */
/** Create a reference to our spinner */
s.setAdapter( adapter );
/** END Create a reference to our spinner */
/** END http://www.dcpagesapps.com/developer-resources/android/21-android-tutorial-spinners?start=1 */
s.setOnItemSelectedListener(new MyOnItemSelectedListener());
arrTxt = new ArrayList<tblRecord>();
this.myAdapter = new UserItemAdapter(this, R.layout.mylist, arrTxt);
setListAdapter(this.myAdapter);
viewJSON = new Runnable(){
@Override
public void run() {
arrTxt = MyJSONFetch(0);
}
};
Thread thread = new Thread(null, viewJSON, "MagentoBackground");
thread.start();
ListView myListView1 = (ListView) findViewById(R.id.list1);
myListView1.setAdapter(new UserItemAdapter(this, android.R.layout.simple_list_item_1, arrTxt));
}
/** End Called when the activity is first created. */
private Runnable returnRes = new Runnable() {
@Override
public void run() {
if(arrTxt != null && arrTxt.size() > 0){
myAdapter.notifyDataSetChanged();
for(int i=0;i<arrTxt.size();i++)
myAdapter.add(arrTxt.get(i));
}
myAdapter.notifyDataSetChanged();
}
};
/** Using a custom List View */
public class UserItemAdapter extends ArrayAdapter<tblRecord> {
private ArrayList<tblRecord> arrTxt;
public UserItemAdapter(Context context, int textViewResourceId, ArrayList<tblRecord> arrTxt) {
super(context, textViewResourceId, arrTxt);
this.arrTxt = arrTxt;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
View v = convertView;
if (v == null) {
LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);
v = vi.inflate(R.layout.mylist, null);
}
tblRecord user = arrTxt.get(position);
if (user != null) {
TextView c1 = (TextView) v.findViewById(R.id.txt1);
TextView c2 = (TextView) v.findViewById(R.id.txt2);
if (c1 != null) {
c1.setText(user.c1);
}
if(c2 != null) {
c2.setText(user.c2);
}
}
return v;
}
}
public class tblRecord {
public String c1;
public String c2;
public tblRecord(String c1, String c2) {
this.c1 = c1;
this.c2 = c2;
}
}
/** END Using a custom List View */
/** Reload JSON Database from onclick listener */
public ArrayList<tblRecord> MyJSONFetch(int position)
{
ArrayList<tblRecord> arrTxt = new ArrayList<tblRecord>();
String tmpUrl = null;
/** JSON code to initiate the php */
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
//http post
try{
HttpClient httpclient = new DefaultHttpClient();
switch (position)
{
case 0:
tmpUrl = "http://smutlow.comp-degree.uhi.ac.uk/UG409713/DDOFastestTimes/fastag.php";
break;
case 1:
tmpUrl = "http://smutlow.comp-degree.uhi.ac.uk/UG409713/DDOFastestTimes/fastas.php";
break;
}
HttpPost httppost = new HttpPost(tmpUrl);
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);
sb = new StringBuilder();
sb.append(reader.readLine() + "\n");
String line="0";
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());
}
//paring data
JSONArray jArray;
try{
jArray = new JSONArray(result);
JSONObject json_data=null;
// Adding the JSON data to the list view
int length = jArray.length();
List<String> listContents1 = new ArrayList<String>(length);
List<String> listContents2 = new ArrayList<String>(length);
// Changing the ListViews
for(int i=0;i<jArray.length();i++){
json_data = jArray.getJSONObject(i);
jc1 = json_data.getString("c1");
jc2 = json_data.getString("c2");
listContents1.add(json_data.getString("c1"));
listContents2.add(json_data.getString("c2"));
// Create an Array to pass to our custom view
tblRecord addRecord = new tblRecord(jc1, jc2);
arrTxt.add(addRecord);
}
// END Adding the JSON data to the list view
}
catch(JSONException e1){
Toast.makeText(getBaseContext(), "No Results Found" ,Toast.LENGTH_LONG).show();
} catch (ParseException e1) {
e1.printStackTrace();
}
/** END Reload JSON Database from onclick listener */
runOnUiThread(returnRes);
return arrTxt;
}
/** Listener for the spinner, we will handle changes made to the spinner here */
public class MyOnItemSelectedListener implements OnItemSelectedListener {
public void onItemSelected(AdapterView<?> parent,
View v, int position, long id) {
MyJSONFetch(position);
Toast.makeText(parent.getContext(), "The top " + parent.getItemAtPosition(position).toString(), Toast.LENGTH_LONG).show();
MyJSONFetch(position);
}
public void onNothingSelected(AdapterView<?> parent) {
// Do nothing.
}
}
/** END Listener for the spinner, we will handle changes made to the spinner here */
@Override
public void onClick(View v) {
int id = v.getId();
// Intent myIntent;
switch (id) {
case R.id.ibQuit:
finish();
break;
}
}
}
基本上我已经尝试将 JSON 代码从 onCreate 中分离出来，并将其放入自己的公共(public)方法中，以便我可以从 MyOnItemSelectedListener 中调用它，但我没有想法，并且已经证明我完全不了解 java。
如果您的回答尽量简单化。
提前谢谢你。
附注抱歉，如果布局不是它应该的样子，这是我的第一篇文章
最佳答案
所以我找到了一个解决方案，也许有人会提供更好的解决方案，但我是这样做的:
我没有尝试从微调器中触发我需要的 PHP，而是选择使用微调器加载一个新的 Intent，其中包含我想使用的 PHP 的相关 URL 添加到 Bundle。
if (position == 0) {
Bundle myBundle = new Bundle();
Intent myIntent;
myBundle.putString("myPHP", "http://url-to-my-php-file/fastag.php");
myIntent = new Intent(getBaseContext(), DDOFastestGuilds.class);
myIntent.putExtras(myBundle);
startActivity(myIntent);
onLowMemory();
finish();
}
然后我添加了两个与第一个文件几乎相同的新 .java 文件，在开头添加了两行:
Bundle myBundle = getIntent().getExtras();
String tmpPHP = myBundle.getString("myPHP");
我修改了调用 HttpPost 的行以指向我刚刚创建的变量 tmpPHP 而不是我在原始文件中使用的文字 URL:
HttpPost httppost = new HttpPost(tmpPHP);
最后更改微调器选择以反射(reflect)用户最后选择的选项，如果微调器中有两个以上的选项，我会使用 bundle 传递最后选择的索引，但在我的示例中我只有两个选项所以我知道所选索引是 0 或 1，具体取决于我想要打开的 Intent。 (确保它直接在 setAdapter 方法之后):
s.setSelection(1);
希望 future 有一种替代方法。 如果有人能提出一种只需要使用一个 Activity 就可以获得相同结果的方法，我将不胜感激。
关于json - 使用自定义 ListViewAdapter 从 JSON 对象动态更新 ListView，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/8195708/