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我是新來的android，我試圖把我的mysql服務器的信息放到android的listview中。列表項中有文字和圖片。如果我嘗試僅添加文本，它將起作用。錯誤：從mysql錯誤填充Android列表錯誤
06-22 22:54:43.215: E/AndroidRuntime(32644): FATAL EXCEPTION: main
06-22 22:54:43.215: E/AndroidRuntime(32644): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.rolab37.lostpet/com.rolab37.lostpet.DashboardActivity}: java.lang.NullPointerException
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.app.ActivityThread.access$700(ActivityThread.java:159)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.os.Handler.dispatchMessage(Handler.java:99)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.os.Looper.loop(Looper.java:176)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.app.ActivityThread.main(ActivityThread.java:5419)
06-22 22:54:43.215: E/AndroidRuntime(32644): at java.lang.reflect.Method.invokeNative(Native Method)
06-22 22:54:43.215: E/AndroidRuntime(32644): at java.lang.reflect.Method.invoke(Method.java:525)
06-22 22:54:43.215: E/AndroidRuntime(32644): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1046)
06-22 22:54:43.215: E/AndroidRuntime(32644): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:862)
06-22 22:54:43.215: E/AndroidRuntime(32644): at dalvik.system.NativeStart.main(Native Method)
06-22 22:54:43.215: E/AndroidRuntime(32644): Caused by: java.lang.NullPointerException
06-22 22:54:43.215: E/AndroidRuntime(32644): at com.rolab37.lostpet.DashboardActivity.connect(DashboardActivity.java:201)
06-22 22:54:43.215: E/AndroidRuntime(32644): at com.rolab37.lostpet.DashboardActivity.onCreate(DashboardActivity.java:67)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.app.Activity.performCreate(Activity.java:5372)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
06-22 22:54:43.215: E/AndroidRuntime(32644): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
06-22 22:54:43.215: E/AndroidRuntime(32644): ... 11 more
因此，這裏是我的代碼： DashboardActivity.java
package com.example.dashboard;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.List;
import java.util.Vector;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.http.AndroidHttpClient;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.StrictMode;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.webkit.URLUtil;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import com.rolab37.lostpet.library.UserFunctions;
public class DashboardActivity extends Activity {
UserFunctions userFunctions;
Button btnLogout;
TextView text;
ListView listView;
private StockAdaptor stockAdaptor;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
/**
* Dashboard Screen for the application
* */
// Check login status in database
userFunctions = new UserFunctions();
if(userFunctions.isUserLoggedIn(getApplicationContext())){
setContentView(R.layout.dashboard);
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
connect();
btnLogout = (Button) findViewById(R.id.btnLogout);
btnLogout.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
// TODO Auto-generated method stub
userFunctions.logoutUser(getApplicationContext());
Intent login = new Intent(getApplicationContext(), LoginActivity.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
// Closing dashboard screen
finish();
}
});
}else{
// user is not logged in show login screen
Intent login = new Intent(getApplicationContext(), LoginActivity.class);
login.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(login);
// Closing dashboard screen
finish();
}
}
private class StockAdaptor extends BaseAdapter { //The stocks list adaptor
class ViewHolder {
TextView name;
TextView price;
ImageView image;
}
private LayoutInflater layoutInflater;
private StockInformation[] stocks = null; //Array of stocks
private ListView stocksListView = null;
public StockAdaptor(Context context) {
super();
layoutInflater = LayoutInflater.from(context);
}
public void setStockList(StockInformation[] stocksinfo) {
this.stocks = stocksinfo;// //////////////LITERALLY THIS
}
@Override
public int getCount() {
return stocks.length;
}
@Override
public Object getItem(int position) {
return stocks[position];
}
public StockInformation[] getAll() { //Return the array of stocks
return stocks;
}
@Override
public long getItemId(int position) {
return 0;
}
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder holder; //New holder
if (convertView == null) {
convertView = layoutInflater.inflate(R.layout.dashboard,
null);
holder = new ViewHolder();
// Creates the new viewholder define above, storing references to the children
holder.name = (TextView) convertView.findViewById(R.id.name);
holder.price = (TextView) convertView.findViewById(R.id.location);
holder.image = (ImageView) convertView.findViewById(R.id.image);
stocksListView = (ListView) findViewById(android.R.id.list);
if (holder.image != null) {
if (holder.image.getDrawable() == null) {
new ImageDownloaderTask(holder.image, null) .execute(stocks[position].imageurl); //Download the image using the imageurl
}
}
convertView.setTag(holder);
} else {
stocksListView = (ListView) findViewById(android.R.id.list);
holder = (ViewHolder) convertView.getTag();
}
holder.name.setText(stocks[position].name);
holder.price.setText(stocks[position].location);
return convertView;
}
}
private void connect() {
String data;
List<String> r = new ArrayList<String>();
ArrayAdapter<String>adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1,r);
ListView list=(ListView)findViewById(R.id.list);
try {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet("http://localhost/list.php");
HttpResponse response = client.execute(request);
HttpEntity entity=response.getEntity();
data=EntityUtils.toString(entity);
Log.e("STRING", data);
try {
JSONArray json=new JSONArray(data);
Vector<StockInformation> vstocks = new Vector<StockInformation>();
Log.e("debug", "aici");
for (int i = 0; i < json.length(); i++) {
JSONObject obj=json.getJSONObject(i);
StockInformation stock = new StockInformation();
stock.name = obj.optString("name");
stock.location = obj.optString("location");
stock.imageurl = obj.getString("imageurl");
Log.e("StockLog", stock.name + stock.location + stock.imageurl);
vstocks.add(stock);
}
StockInformation[] stocks = new StockInformation[json.length()];
int stockscount = json.length();
for (int n = 0; n < stockscount; n++)
{
stocks[n] = vstocks.get(n);
}
stockAdaptor.setStockList(stocks);
list.setAdapter(stockAdaptor);
/*
for(int i=0;i<json.length(); i++) {
JSONObject obj=json.getJSONObject(i);
String name=obj.getString("name");
String year=obj.getString("year");
String age=obj.getString("age");
Log.e("STRING", name);
r.add(name);
r.add(year);
r.add(age);
list.setAdapter(adapter);
}*/
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (ClientProtocolException e) {
Log.d("DashboardActivity", e.getLocalizedMessage());
} catch (IOException e) {
Log.d("DashboardActivity", e.getLocalizedMessage());
}
}
private class ImageDownloaderTask extends AsyncTask<String, Void, Bitmap> {
private final WeakReference<ImageView> imageViewReference;
public ImageDownloaderTask(ImageView imageView, View view) {
imageViewReference = new WeakReference<ImageView>(imageView);
}
@Override
// Actual download method, run in the task thread
protected Bitmap doInBackground(String... params) {
// params comes from the execute() call: params[0] is the url.
return downloadBitmap(params[0]);
}
@Override
// Once the image is downloaded, associates it to the imageView
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 {
//
}
}
}
}
Bitmap downloadBitmap(String url) {
if(URLUtil.isValidUrl(url)){
final AndroidHttpClient client = AndroidHttpClient.newInstance("Android");
final HttpGet getRequest = new HttpGet(url);
try {
HttpResponse response = client.execute(getRequest);
final int statusCode = response.getStatusLine().getStatusCode();
if (statusCode != HttpStatus.SC_OK) {
Log.w("ImageDownloader", "Error " + statusCode
+ " while retrieving bitmap from " + url);
return null;
}
final HttpEntity entity = response.getEntity();
if (entity != null) {
InputStream inputStream = null;
try {
inputStream = entity.getContent();
try {
byte[] buffer = new byte[8192];
int bytesRead;
ByteArrayOutputStream output = new ByteArrayOutputStream();
while ((bytesRead = inputStream.read(buffer)) != -1) {
output.write(buffer, 0, bytesRead);
}
return BitmapFactory.decodeByteArray(output.toByteArray(), 0, output.toByteArray().length);
} catch (IllegalArgumentException e) {
e.printStackTrace();
Log.i("IAE", "in stocks");
return null;
}
} finally {
if (inputStream != null) {
inputStream.close();
}
entity.consumeContent();
}
}
} catch (Exception e) {
getRequest.abort();
Log.w("ImageDownloader", "Error while retrieving bitmap from " + url);
} finally {
if (client != null) {
client.close();
}
}
return null;
}
return null;
}
}
}
StockInformation.java 包com.example.dashboard;
public class StockInformation {
public String name;
public String location;
public String imageurl;
}
dashboard.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:background="#3b3b3b">
<TextView android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="WELCOME"
android:textSize="40dip"
android:gravity="center"
android:layout_marginTop="20dip"/>
<ListView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true" >
</ListView>
<Button android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Logout Me"
android:textSize="20dip"
android:textColor="#21dbd4"
android:textStyle="bold"
android:id="@+id/btnLogout"
android:layout_marginTop="80dip"
android:background="@null"/>
</LinearLayout>
和dashboardlist.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:minHeight="50dp"
android:orientation="vertical" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:orientation="horizontal" >
<ImageView
android:id="@+id/image"
android:layout_width="70dp"
android:layout_height="70dp" />
<TextView
android:id="@+id/name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:lineSpacingExtra="3dp"
android:paddingLeft="5dp"
android:paddingTop="5dp"
android:text="" />
<TextView
android:id="@+id/location"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingLeft="5dp"
android:paddingTop="5dp"
android:text="" />
</LinearLayout>
</LinearLayout>
這是JSON
[{"name":"Nicu","location":"1983","imageurl":"http:\/\/www.fancyicons.com\/free-icons\/103\/flags\/png\/256\/romania_flag_256.png"},{"name":"Adina","location":"1987","imageurl":"http:\/\/icons.iconarchive.com\/icons\/custom-icon-design\/flag-3\/256\/United-Kingdom-flag-icon.png"}]
希望你能幫助
好的，接下來我該怎麼做。 「stocks」看起來像是有值 – user3765406
您應該在DashboardActivity的onCreate方法中爲stockAdapter變量賦值，如：stockAdapter = new StockAdaptor（this）; –