我正在练习一个带有php android的连接示例，该示例是通过JSON通信显示数据库中的名称和图片列表。
我发现的问题如下：
假设我的PHP或数据库位于以下地址：
http://example.com/phpdirection
我的应用程序连接到互联网，一切都很好。现在假设我的数据库被删除了，或者我的 PHP 的外壳被删除了，那么分配的地址是：http://example.com/phpdirection
停止操作。
通过测试，我发现了以下错误：
10-01 15:33:38.290: W/System.err(23332): java.net.UnknownHostException: Unable to resolve host "motaink.hol": No address associated with hostname
10-01 15:33:38.322: W/System.err(23332): at java.net.InetAddress.lookupHostByName(InetAddress.java:478)
10-01 15:33:38.322: W/System.err(23332): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:243)
10-01 15:33:38.322: W/System.err(23332): at java.net.InetAddress.getAllByName(InetAddress.java:220)
10-01 15:33:38.329: W/System.err(23332): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
10-01 15:33:38.329: W/System.err(23332): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
10-01 15:33:38.329: W/System.err(23332): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
10-01 15:33:38.329: W/System.err(23332): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
10-01 15:33:38.329: W/System.err(23332): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
10-01 15:33:38.329: W/System.err(23332): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
10-01 15:33:38.337: W/System.err(23332): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
10-01 15:33:38.337: W/System.err(23332): at com.prueba.bibliotecaappprueba.JSONParser.makeHttpRequest(JSONParser.java:62)
10-01 15:33:38.337: W/System.err(23332): at com.prueba.bibliotecaappprueba.LisCategAventActivity$Activity.doInBackground(LisCategAventActivity.java:122)
10-01 15:33:38.337: W/System.err(23332): at com.prueba.bibliotecaappprueba.LisCategAventActivity$Activity.doInBackground(LisCategAventActivity.java:1)
10-01 15:33:38.337: W/System.err(23332): at android.os.AsyncTask$2.call(AsyncTask.java:264)
10-01 15:33:38.337: W/System.err(23332): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
10-01 15:33:38.337: W/System.err(23332): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
10-01 15:33:38.337: W/System.err(23332): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
10-01 15:33:38.337: W/System.err(23332): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
10-01 15:33:38.337: W/System.err(23332): at java.lang.Thread.run(Thread.java:856)
10-01 15:33:38.337: W/System.err(23332): Caused by: libcore.io.GaiException: getaddrinfo failed: EAI_NODATA (No address associated with hostname)
10-01 15:33:38.337: W/System.err(23332): at libcore.io.Posix.getaddrinfo(Native Method)
10-01 15:33:38.337: W/System.err(23332): at libcore.io.ForwardingOs.getaddrinfo(ForwardingOs.java:55)
10-01 15:33:38.337: W/System.err(23332): at java.net.InetAddress.lookupHostByName(InetAddress.java:463)
10-01 15:33:38.337: W/System.err(23332): ... 18 more
10-01 15:33:38.345: E/Buffer Error(23332): Error converting result java.lang.NullPointerException
10-01 15:33:38.345: E/JSON Parser(23332): Error parsing data org.json.JSONException: End of input at character 0 of
10-01 15:33:38.345: W/dalvikvm(23332): threadid=11: thread exiting with uncaught exception (group=0x40a9f210)
10-01 15:33:38.345: E/AndroidRuntime(23332): FATAL EXCEPTION: AsyncTask #1
10-01 15:33:38.345: E/AndroidRuntime(23332): java.lang.RuntimeException: An error occured while executing doInBackground()
10-01 15:33:38.345: E/AndroidRuntime(23332): at android.os.AsyncTask$3.done(AsyncTask.java:278)
10-01 15:33:38.345: E/AndroidRuntime(23332): at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
10-01 15:33:38.345: E/AndroidRuntime(23332): at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
10-01 15:33:38.345: E/AndroidRuntime(23332): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
10-01 15:33:38.345: E/AndroidRuntime(23332): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
10-01 15:33:38.345: E/AndroidRuntime(23332): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
10-01 15:33:38.345: E/AndroidRuntime(23332): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
10-01 15:33:38.345: E/AndroidRuntime(23332): at java.lang.Thread.run(Thread.java:856)
10-01 15:33:38.345: E/AndroidRuntime(23332): Caused by: java.lang.NullPointerException
10-01 15:33:38.345: E/AndroidRuntime(23332): at com.prueba.bibliotecaappprueba.LisCategAventActivity$Activity.doInBackground(LisCategAventActivity.java:125)
10-01 15:33:38.345: E/AndroidRuntime(23332): at com.prueba.bibliotecaappprueba.LisCategAventActivity$Activity.doInBackground(LisCategAventActivity.java:1)
10-01 15:33:38.345: E/AndroidRuntime(23332): at android.os.AsyncTask$2.call(AsyncTask.java:264)
10-01 15:33:38.345: E/AndroidRuntime(23332): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
10-01 15:33:38.345: E/AndroidRuntime(23332): ... 4 more
10-01 15:33:38.790: E/WindowManager(23332): Activity com.prueba.bibliotecaappprueba.LisCategAventActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@42367020 that was originally added here
10-01 15:33:38.790: E/WindowManager(23332): android.view.WindowLeaked: Activity com.prueba.bibliotecaappprueba.LisCategAventActivity has leaked window com.android.internal.policy.impl.PhoneWindow$DecorView@42367020 that was originally added here
10-01 15:33:38.790: E/WindowManager(23332): at android.view.ViewRootImpl.<init>(ViewRootImpl.java:355)
10-01 15:33:38.790: E/WindowManager(23332): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:267)
10-01 15:33:38.790: E/WindowManager(23332): at android.view.WindowManagerImpl.addView(WindowManagerImpl.java:215)
10-01 15:33:38.790: E/WindowManager(23332): at android.view.WindowManagerImpl$CompatModeWrapper.addView(WindowManagerImpl.java:140)
10-01 15:33:38.790: E/WindowManager(23332): at android.view.Window$LocalWindowManager.addView(Window.java:537)
10-01 15:33:38.790: E/WindowManager(23332): at android.app.Dialog.show(Dialog.java:284)
10-01 15:33:38.790: E/WindowManager(23332): at com.prueba.bibliotecaappprueba.LisCategAventActivity$Activity.onPreExecute(LisCategAventActivity.java:113)
10-01 15:33:38.790: E/WindowManager(23332): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:561)
10-01 15:33:38.790: E/WindowManager(23332): at android.os.AsyncTask.execute(AsyncTask.java:511)
10-01 15:33:38.790: E/WindowManager(23332): at com.prueba.bibliotecaappprueba.LisCategAventActivity.onCreate(LisCategAventActivity.java:61)
10-01 15:33:38.790: E/WindowManager(23332): at android.app.Activity.performCreate(Activity.java:4539)
10-01 15:33:38.790: E/WindowManager(23332): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
10-01 15:33:38.790: E/WindowManager(23332): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2013)
10-01 15:33:38.790: E/WindowManager(23332): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2083)
10-01 15:33:38.790: E/WindowManager(23332): at android.app.ActivityThread.access$600(ActivityThread.java:134)
10-01 15:33:38.790: E/WindowManager(23332): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1233)
10-01 15:33:38.790: E/WindowManager(23332): at android.os.Handler.dispatchMessage(Handler.java:99)
10-01 15:33:38.790: E/WindowManager(23332): at android.os.Looper.loop(Looper.java:137)
10-01 15:33:38.790: E/WindowManager(23332): at android.app.ActivityThread.main(ActivityThread.java:4697)
10-01 15:33:38.790: E/WindowManager(23332): at java.lang.reflect.Method.invokeNative(Native Method)
10-01 15:33:38.790: E/WindowManager(23332): at java.lang.reflect.Method.invoke(Method.java:511)
10-01 15:33:38.790: E/WindowManager(23332): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:787)
10-01 15:33:38.790: E/WindowManager(23332): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:554)
10-01 15:33:38.790: E/WindowManager(23332): at dalvik.system.NativeStart.main(Native Method)
然后应用程序关闭。在这种情况下，我该怎么办？如果我想显示另一个带有消息"数据库中的问题"的活动，谢谢！
这是我的代码：
public class LisCategAventActivity extends Activity {
private ProgressDialog pDialog;
public int i = 0;
JSONParser jParser = new JSONParser();
ArrayList<HashMap<String, String>> DaftarRS = new ArrayList<HashMap<String, String>>();
private static String url_daftar_rs = "http://example.com/phpdirection";
public static final String TAG_SUCCESS = "success";
public static final String TAG_DAFTAR_RS = "daftar_rs";
public static final String TAG_ID_RS = "id_rs";
public static final String TAG_NOMBRE_RS = "nombre_rs";
public static final String TAG_LINK_IMAGE_RS = "link_image_rs";
public static final String TAG_AUTOR_RS = "autor_rs";
public static final String TAG_CATEG_RS = "categ_rs";
public static final String TAG_LINK_DESCARGA_RS = "link_descarga_rs";
JSONArray daftar_rs = null;
ListView list;
ListAdapter adapter;
private LisCategAventActivity activity;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.cat_av);
DaftarRS = new ArrayList<HashMap<String, String>>();
new Activity().execute();
activity = this;
list = (ListView) findViewById(R.id.list_cat_av);
list.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
String id_rs = ((TextView) view
.findViewById(R.id.id_rs)).getText().toString();
Intent in = new Intent(getApplicationContext(),
DetallesActivity.class);
in.putExtra(TAG_ID_RS, id_rs);
startActivityForResult(in, 100);
}
});
}
public void SetListViewAdapter(ArrayList<HashMap<String, String>> daftar) {
adapter = new ListAdapter(activity, daftar);
list.setAdapter(adapter);
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);
if (resultCode == 100) {
Intent intent = getIntent();
finish();
startActivity(intent);
}
}
class Activity extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(LisCategAventActivity.this);
pDialog.setMessage("Cargando Biblioteca...");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
protected String doInBackground(String... args) {
Conexion();
if (i == 0){
List<NameValuePair> params = new ArrayList<NameValuePair>();
JSONObject json = jParser.makeHttpRequest(url_daftar_rs, "GET",
params);
Log.d("All Products: ", json.toString());
try {
int success = json.getInt(TAG_SUCCESS);
if (success == 1) {
daftar_rs = json.getJSONArray(TAG_DAFTAR_RS);
for (int i = 0; i < daftar_rs.length(); i++) {
JSONObject c = daftar_rs.getJSONObject(i);
String id_rs = c.getString(TAG_ID_RS);
String nama_rs = c.getString(TAG_NOMBRE_RS);
String link_image_rs = c
.getString(TAG_LINK_IMAGE_RS);
String alamat_rs = c.getString(TAG_AUTOR_RS);
String telepon_rs = c.getString(TAG_CATEG_RS);
HashMap<String, String> map = new HashMap<String, String>();
map.put(TAG_ID_RS, id_rs);
map.put(TAG_NOMBRE_RS, nama_rs);
map.put(TAG_LINK_IMAGE_RS, link_image_rs);
map.put(TAG_AUTOR_RS, alamat_rs);
map.put(TAG_CATEG_RS, telepon_rs);
DaftarRS.add(map);
}
} else {
}
} catch (JSONException e) {
Intent nohay= new Intent(LisCategAventActivity.this, noActivity.class);
onStop();
i = 1;
startActivity(nohay);
e.printStackTrace();
}
}
else{finish();}
return null;
}
protected void onPostExecute(String file_url) {
pDialog.dismiss();
runOnUiThread(new Runnable() {
public void run() {
SetListViewAdapter(DaftarRS);
}
});
}
} }
尝试在logcat上显示id_rs、nama_rs等内容，使用android Log类，或者只使用System.out.println()，检查它是否为空。
您应该进行如下检查：
if (json!=null) { // this is from 'JSONObject json = ...'
//parse json and insert data to list
} else { //json==null
//display `database error`
}
希望这有帮助，祝你好运
里德