我对android开发很陌生。我正在尝试从 sdcard 解析 json。我几乎花了一个星期来解决它，但我无法解决错误。如果有人帮助解决或使其工作，那就太好了。以下是所需的代码。对不起我的英语。
Baby1.java
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import org.json.JSONObject;
import com.kabelash.salesgossip02.util.ExternalStorage;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Menu;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.SimpleAdapter;
public class Baby1 extends Activity {
private final String JSON_file = "country.json";
File jsonFile;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.baby1_1);
/** Getting Cache Directory */
File cDir = ExternalStorage.getSDCacheDir( this, "json_files" );
/** Getting a reference to temporary file, if created earlier */
jsonFile = new File(cDir.getPath() + "/" + JSON_file) ;
String strLine="";
StringBuilder strJson = new StringBuilder();
/** Reading contents of the temporary file, if already exists */
try {
FileReader fReader = new FileReader(jsonFile);
BufferedReader bReader = new BufferedReader(fReader);
/** Reading the contents of the file , line by line */
while( (strLine=bReader.readLine()) != null ){
strJson.append(strLine);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}catch(IOException e){
e.printStackTrace();
}
System.out.println(strLine);
/** The parsing of the xml data is done in a non-ui thread */
// ListViewLoaderTask listViewLoaderTask = new ListViewLoaderTask();
/** Start parsing xml data */
new ListViewLoaderTask().execute(strLine);
}
private class ListViewLoaderTask extends AsyncTask<String, Void, SimpleAdapter>{
JSONObject jObject;
/** Doing the parsing of xml data in a non-ui thread */
@Override
protected SimpleAdapter doInBackground(String... strJson) {
try{
jObject = new JSONObject(strJson[0]);
CountryJSONParser countryJsonParser = new CountryJSONParser();
countryJsonParser.parse(jObject);
}catch(Exception e){
Log.d("JSON Exception1",e.toString());
}
CountryJSONParser countryJsonParser = new CountryJSONParser();
List<HashMap<String, String>> countries = null;
try{
/** Getting the parsed data as a List construct */
countries = countryJsonParser.parse(jObject);
}catch(Exception e){
Log.d("Exception",e.toString());
}
/** Keys used in Hashmap */
String[] from = { "country","flag","details"};
/** Ids of views in listview_layout */
int[] to = { R.id.tv_country,R.id.iv_flag,R.id.tv_country_details};
/** Instantiating an adapter to store each items
* R.layout.listview_layout defines the layout of each item
*/
SimpleAdapter adapter = new SimpleAdapter(getBaseContext(), countries, R.layout.lv_layout, from, to);
return adapter;
}
/** Invoked by the Android system on "doInBackground" is executed completely */
/** This will be executed in ui thread */
@Override
protected void onPostExecute(SimpleAdapter adapter) {
/** Getting a reference to listview of main.xml layout file */
ListView listView = ( ListView ) findViewById(R.id.lv_countries);
/** Setting the adapter containing the country list to listview */
listView.setAdapter(adapter);
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
countryJSONParser.java
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
public class CountryJSONParser {
/** Receives a JSONObject and returns a list */
public List<HashMap<String,String>> parse(JSONObject jObject){
JSONArray jCountries = null;
try {
/** Retrieves all the elements in the 'countries' array */
jCountries = jObject.getJSONArray("countries");
} catch (JSONException e) {
e.printStackTrace();
}
/** Invoking getCountries with the array of json object
* where each json object represent a country
*/
return getCountries(jCountries);
}
private List<HashMap<String, String>> getCountries(JSONArray jCountries){
int countryCount = jCountries.length();
List<HashMap<String, String>> countryList = new ArrayList<HashMap<String,String>>();
HashMap<String, String> country = null;
/** Taking each country, parses and adds to list object */
for(int i=0; i<countryCount;i++){
try {
/** Call getCountry with country JSON object to parse the country */
country = getCountry((JSONObject)jCountries.get(i));
countryList.add(country);
} catch (JSONException e) {
e.printStackTrace();
}
}
return countryList;
}
/** Parsing the Country JSON object */
private HashMap<String, String> getCountry(JSONObject jCountry){
HashMap<String, String> country = new HashMap<String, String>();
String countryName = "";
String flag="";
String language = "";
String capital = "";
String currencyCode = "";
String currencyName = "";
try {
countryName = jCountry.getString("countryname");
flag = jCountry.getString("flag");
language = jCountry.getString("language");
capital = jCountry.getString("capital");
currencyCode = jCountry.getJSONObject("currency").getString("code");
currencyName = jCountry.getJSONObject("currency").getString("currencyname");
String details = "Language : " + language + "\n" +
"Capital : " + capital + "\n" +
"Currency : " + currencyName + "(" + currencyCode + ")";
country.put("country", countryName);
country.put("flag", flag);
country.put("details", details);
} catch (JSONException e) {
e.printStackTrace();
}
return country;
}
}
baby1_1.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<ListView
android:id="@+id/lv_countries"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
tools:context=".Baby1" />
</RelativeLayout>
lv_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="@+id/tv_country"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerHorizontal="true"
android:textSize="20dp"
android:textStyle="bold"
/>
<ImageView
android:id="@+id/iv_flag"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@id/tv_country"
android:layout_centerVertical="true"
android:padding="4dp"
android:contentDescription="@string/str_iv_flag" />
<TextView
android:id="@+id/tv_country_details"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/iv_flag"
android:layout_below="@id/tv_country"
/>
</RelativeLayout>
国家.json
{ "countries":[
{
"countryname": "India",
"flag": "R.drawable.sample_0",
"language": "Hindi",
"capital": "New Delhi",
"currency": [
"code": "INR",
"currencyname": "Rupee"
]
}
]}
日志猫
08-16 11:43:27.852: D/JSON Exception1(1667): org.json.JSONException: End of input at character 0 of
08-16 11:43:27.863: D/Exception(1667): java.lang.NullPointerException
08-16 11:43:27.952: D/AndroidRuntime(1667): Shutting down VM
08-16 11:43:27.962: W/dalvikvm(1667): threadid=1: thread exiting with uncaught exception (group=0x414c4700)
08-16 11:43:28.022: E/AndroidRuntime(1667): FATAL EXCEPTION: main
08-16 11:43:28.022: E/AndroidRuntime(1667): java.lang.NullPointerException
08-16 11:43:28.022: E/AndroidRuntime(1667): at android.widget.SimpleAdapter.getCount(SimpleAdapter.java:93)
08-16 11:43:28.022: E/AndroidRuntime(1667): at android.widget.ListView.setAdapter(ListView.java:463)
08-16 11:43:28.022: E/AndroidRuntime(1667): at com.kabelash.sg02.Baby1$ListViewLoaderTask.onPostExecute(Baby1.java:120)
08-16 11:43:28.022: E/AndroidRuntime(1667): at com.kabelash.sg02.Baby1$ListViewLoaderTask.onPostExecute(Baby1.java:1)
08-16 11:43:28.022: E/AndroidRuntime(1667): at android.os.AsyncTask.finish(AsyncTask.java:631)
08-16 11:43:28.022: E/AndroidRuntime(1667): at android.os.AsyncTask.access$600(AsyncTask.java:177)
08-16 11:43:28.022: E/AndroidRuntime(1667): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
08-16 11:43:28.022: E/AndroidRuntime(1667): at android.os.Handler.dispatchMessage(Handler.java:99)
08-16 11:43:28.022: E/AndroidRuntime(1667): at android.os.Looper.loop(Looper.java:137)
08-16 11:43:28.022: E/AndroidRuntime(1667): at android.app.ActivityThread.main(ActivityThread.java:5103)
08-16 11:43:28.022: E/AndroidRuntime(1667): at java.lang.reflect.Method.invokeNative(Native Method)
08-16 11:43:28.022: E/AndroidRuntime(1667): at java.lang.reflect.Method.invoke(Method.java:525)
08-16 11:43:28.022: E/AndroidRuntime(1667): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
08-16 11:43:28.022: E/AndroidRuntime(1667): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-16 11:43:28.022: E/AndroidRuntime(1667): at dalvik.system.NativeStart.main(Native Method)
08-16 11:43:31.892: I/Process(1667): Sending signal. PID: 1667 SIG: 9
新的Logcat：
08-17 18:25:04.815: D/AndroidRuntime(14216): Shutting down VM
08-17 18:25:04.815: W/dalvikvm(14216): threadid=1: thread exiting with uncaught exception (group=0x40ee22a0)
08-17 18:25:04.875: E/AndroidRuntime(14216): FATAL EXCEPTION: main
08-17 18:25:04.875: E/AndroidRuntime(14216): java.lang.NullPointerException
08-17 18:25:04.875: E/AndroidRuntime(14216): at android.widget.SimpleAdapter.getCount(SimpleAdapter.java:93)
08-17 18:25:04.875: E/AndroidRuntime(14216): at android.widget.ListView.setAdapter(ListView.java:466)
08-17 18:25:04.875: E/AndroidRuntime(14216): at com.kabelash.sg02.Jeans$ListViewLoaderTask.onPostExecute(Jeans.java:119)
08-17 18:25:04.875: E/AndroidRuntime(14216): at com.kabelash.sg02.Jeans$ListViewLoaderTask.onPostExecute(Jeans.java:1)
08-17 18:25:04.875: E/AndroidRuntime(14216): at android.os.AsyncTask.finish(AsyncTask.java:631)
08-17 18:25:04.875: E/AndroidRuntime(14216): at android.os.AsyncTask.access$600(AsyncTask.java:177)
08-17 18:25:04.875: E/AndroidRuntime(14216): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
08-17 18:25:04.875: E/AndroidRuntime(14216): at android.os.Handler.dispatchMessage(Handler.java:99)
08-17 18:25:04.875: E/AndroidRuntime(14216): at android.os.Looper.loop(Looper.java:137)
08-17 18:25:04.875: E/AndroidRuntime(14216): at android.app.ActivityThread.main(ActivityThread.java:4898)
08-17 18:25:04.875: E/AndroidRuntime(14216): at java.lang.reflect.Method.invokeNative(Native Method)
08-17 18:25:04.875: E/AndroidRuntime(14216): at java.lang.reflect.Method.invoke(Method.java:511)
08-17 18:25:04.875: E/AndroidRuntime(14216): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
08-17 18:25:04.875: E/AndroidRuntime(14216): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
08-17 18:25:04.875: E/AndroidRuntime(14216): at dalvik.system.NativeStart.main(Native Method)
08-17 18:25:04.940: I/Process(14216): Sending signal. PID: 14216 SIG: 9