当我开始以下活动时，我正在使用android我在我的android模拟器上有一个强制关闭。我认为这是由于getstringExtra（）中的null值，但我无法正确找到它。任何人都可以说这个活动中的错误是什么
public class Cancel_parkActivity extends Activity implements LocationListener{
String p_u_name;
HttpPost httppost;
StringBuffer buffer;
HttpResponse response;
HttpClient httpclient;
List<NameValuePair> nameValuePairs;
ProgressDialog dialog = null;
LocationManager locManager;
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.cancel_park);
Intent in = getIntent();
p_u_name = in.getExtras().getString("KEY_USERNAME");
System.out.println(" Cancel_park : your name is"+p_u_name);
dialog = ProgressDialog.show(Cancel_parkActivity.this, "",
"Cancel parking...", true);
new Thread(new Runnable() {
public void run() {
cancelpark();
}
}).start();
}
public void cancelpark(){
try{
httpclient=new DefaultHttpClient();
httppost= new HttpPost("http://10.0.2.2/test_login/deletepark.php");
nameValuePairs = new ArrayList<NameValuePair>(2);
String KEY_DELETE = "delete";
nameValuePairs.add(new BasicNameValuePair(KEY_DELETE,""));
nameValuePairs.add(new BasicNameValuePair("username",p_u_name.trim()));
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
ResponseHandler<String> responseHandler = new BasicResponseHandler();
final String response = httpclient.execute(httppost, responseHandler);
System.out.println("Response : " + response);
runOnUiThread(new Runnable() {
public void run() {
System.out.println("Response from PHP : " + response);
dialog.dismiss();
}
});
if(response.equalsIgnoreCase("Success")){
runOnUiThread(new Runnable() {
public void run() {
Toast.makeText(Cancel_parkActivity.this,"Last parking canceled", Toast.LENGTH_SHORT).show();
}
});
// startActivity(new Intent(LoginActivity.this, MainActivity.class));
}else{
Toast.makeText(Cancel_parkActivity.this,"fucking", Toast.LENGTH_SHORT).show();
}
}catch(Exception e){
dialog.dismiss();
System.out.println("Exception : " + e.getMessage());
}
}
public void showAlert(){
Cancel_parkActivity.this.runOnUiThread(new Runnable() {
public void run() {
AlertDialog.Builder builder = new AlertDialog.Builder(Cancel_parkActivity.this);
builder.setTitle("Parking Error.");
builder.setMessage("Try again?.")
.setCancelable(false)
.setPositiveButton("OK", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
Intent r = new Intent(getApplicationContext(),Park_HereActivity.class);
startActivity(r);
}
});
AlertDialog alert = builder.create();
alert.show();
}
});
}
public void onLocationChanged(Location arg0) {
// TODO Auto-generated method stub
}
public void onProviderDisabled(String provider) {
// TODO Auto-generated method stub
}
public void onProviderEnabled(String provider) {
// TODO Auto-generated method stub
}
public void onStatusChanged(String provider, int status, Bundle extras) {
// TODO Auto-generated method stub
}
}
我得到了像这样的nullpointer异常
10-20 17:42:50.044: E/AndroidRuntime(1983): FATAL EXCEPTION: main
10-20 17:42:50.044: E/AndroidRuntime(1983): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.oranz.epark/com.oranz.epark.Cancel_parkActivity}: java.lang.NullPointerException
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.app.ActivityThread.access$600(ActivityThread.java:122)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.os.Handler.dispatchMessage(Handler.java:99)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.os.Looper.loop(Looper.java:137)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.app.ActivityThread.main(ActivityThread.java:4340)
10-20 17:42:50.044: E/AndroidRuntime(1983): at java.lang.reflect.Method.invokeNative(Native Method)
10-20 17:42:50.044: E/AndroidRuntime(1983): at java.lang.reflect.Method.invoke(Method.java:511)
10-20 17:42:50.044: E/AndroidRuntime(1983): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
10-20 17:42:50.044: E/AndroidRuntime(1983): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
10-20 17:42:50.044: E/AndroidRuntime(1983): at dalvik.system.NativeStart.main(Native Method)
10-20 17:42:50.044: E/AndroidRuntime(1983): Caused by: java.lang.NullPointerException
10-20 17:42:50.044: E/AndroidRuntime(1983): at com.oranz.epark.Cancel_parkActivity.onCreate(Cancel_parkActivity.java:43)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.app.Activity.performCreate(Activity.java:4465)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
10-20 17:42:50.044: E/AndroidRuntime(1983): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919)
10-20 17:42:50.044: E/AndroidRuntime(1983): ... 11 more
答案 0 :(得分：1)
在代码中检查此行：
Cancel_parkActivity.java:43
也许getIntent（）。getExtras（）为空？
答案 1 :(得分：1)
Intent myIntent= getIntent(); // gets the previously created intent
String firstKeyName = intent.getStringExtra("KEY_USERNAME");
试试这种方式。
由于
答案 2 :(得分：0)
p_u_name = getIntent().getStringExtra("KEY_USERNAME");
p_u_name throw NullPointer so please check the before Activity class
Example :
Intent intent = new Intent(this, Cancel_parkActivity.class);
intent.putExtra("KEY_USERNAME", your_Value);
startActivity(intent);
请检查以上编码，然后您可以轻松找到解决方案