我正在编写这个用于货币转换的 android 代码，我得到 NullPointerException ：
这是代码，我的 logCat 说错误在第 73 行
public class Currency_convert extends Activity
{
public int to;
public int from;
public String [] val;
public String s;
public Handler handler;
public double am=0.0;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Spinner s1 = (Spinner) findViewById(R.id.spinner11);
Spinner s2 = (Spinner) findViewById(R.id.spinner22);
final EditText e=(EditText) findViewById(R.id.amountt);
// am=Double.parseDouble(e.getText().toString());
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(
this, R.array.name, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.select_dialog_singlechoice);
val = getResources().getStringArray(R.array.value);
s1.setAdapter(adapter);
s2.setAdapter(adapter);
s1.setOnItemSelectedListener(new spinOne(1));
s2.setOnItemSelectedListener(new spinOne(2));
Button b = (Button) findViewById(R.id.button11);
b.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
TextView t = (TextView) findViewById(R.id.textView44);
if(from == to)
{
Toast.makeText(getApplicationContext(), "Invalid", 4000).show();
}
else
{
try {
s = getJson("http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20yahoo.finance.xchange%20where%20pair%20in%20(%22"+val[from]+val[to]+"%22)&format=json&diagnostics=true&env=store%3A%2F%2Fdatatables.org%2Falltableswithkeys&callback=");
//s=getJson("http://www.google.com/ig/calculator?hl=en&q=1USD=?INR");
JSONObject jObj;
jObj = new JSONObject(s);
String exResult = jObj.getJSONObject("query").getJSONObject("results").getJSONObject("rate").getString("Rate");
am=Double.parseDouble(e.getText().toString());
double totalR=(Double.parseDouble(exResult))*am;
String r=String.valueOf(totalR);
t.setText(r);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
});
}
public String getJson(String url)throws ClientProtocolException, IOException {
StringBuilder build = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
HttpResponse response = client.execute(httpGet);
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String con;
while ((con = reader.readLine()) != null) {
build.append(con);
}
return build.toString();
}
private class spinOne implements OnItemSelectedListener
{
int ide;
spinOne(int i)
{
ide =i;
}
public void onItemSelected(AdapterView<?> parent, View view,
int index, long id) {
if(ide == 1)
from = index;
else if(ide == 2)
to = index;
}
public void onNothingSelected(AdapterView<?> arg0) {
// TODO Auto-generated method stub
}
}
}
错误是此行的运行时错误：
s2.setAdapter(adapter);
不知道怎么回事！！
这是日志猫：
11-07 10:25:22.194: E/AndroidRuntime(2004): FATAL EXCEPTION: main
11-07 10:25:22.194: E/AndroidRuntime(2004): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.dashboard_our/com.example.dashboard_our.Currency_convert}: java.lang.NullPointerException
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211)
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261)
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.app.ActivityThread.access$600(ActivityThread.java:141)
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256)
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.os.Handler.dispatchMessage(Handler.java:99)
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.os.Looper.loop(Looper.java:137)
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.app.ActivityThread.main(ActivityThread.java:5103)
11-07 10:25:22.194: E/AndroidRuntime(2004): at java.lang.reflect.Method.invokeNative(Native Method)
11-07 10:25:22.194: E/AndroidRuntime(2004): at java.lang.reflect.Method.invoke(Method.java:525)
11-07 10:25:22.194: E/AndroidRuntime(2004): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
11-07 10:25:22.194: E/AndroidRuntime(2004): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-07 10:25:22.194: E/AndroidRuntime(2004): at dalvik.system.NativeStart.main(Native Method)
11-07 10:25:22.194: E/AndroidRuntime(2004): Caused by: java.lang.NullPointerException
11-07 10:25:22.194: E/AndroidRuntime(2004): at com.example.dashboard_our.Currency_convert.onCreate(Currency_convert.java:73)
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.app.Activity.performCreate(Activity.java:5133)
11-07 10:25:22.194: E/AndroidRuntime(2004): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)