如何解决android中的Null指针异常
| 我有一个问题，我在button.setOnClickListner上收到nullpointer异常。 我不知道为什么。请建议我解决这个问题。Error:
05-27 20:22:24.194: ERROR/AndroidRuntime(336): java.lang.RuntimeException: Unable to start activity ComponentInfo{org.shopzilla.android.common/org.shopzilla.android.product.ProductShareActivity}: java.lang.NullPointerException
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.os.Handler.dispatchMessage(Handler.java:99)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.os.Looper.loop(Looper.java:123)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.ActivityThread.main(ActivityThread.java:3683)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at java.lang.reflect.Method.invokeNative(Native Method)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at java.lang.reflect.Method.invoke(Method.java:507)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at dalvik.system.NativeStart.main(Native Method)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): Caused by: java.lang.NullPointerException
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at org.shopzilla.android.product.ProductShareActivity.onCreateDialog(ProductShareActivity.java:39)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.Activity.onCreateDialog(Activity.java:2482)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.Activity.createDialog(Activity.java:882)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.Activity.showDialog(Activity.java:2557)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.Activity.showDialog(Activity.java:2524)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at org.shopzilla.android.product.ProductShareActivity.onCreate(ProductShareActivity.java:24)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
05-27 20:22:24.194: ERROR/AndroidRuntime(336): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
package org.shopzilla.android.product;
import org.shopzilla.android.common.R;
import android.app.Activity;
import android.app.Dialog;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class ProductShareActivity extends Activity{
Dialog dialog;
Dialog dialog1;
Button btn_ok;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.more_background);
showDialog(0);
}
//Dialog Creation
protected Dialog onCreateDialog(int id) {
switch(id) {
case 0: dialog = new Dialog(ProductShareActivity.this);
dialog.setContentView(R.layout.sms);
dialog.setTitle(\"Please Enter Phone Number\");
final EditText txt_sms = (EditText)findViewById(R.id.txt_sms);
btn_ok = (Button)dialog.findViewById(R.id.btn_sms_ok);
btn_ok.setOnClickListener(new View.OnClickListener() {
public void onClick(View arg0) {
// TODO Auto-generated method stub
Intent intent = new Intent(Intent.ACTION_VIEW,Uri.parse( \"sms:\" + txt_sms.getText().toString()));
intent.putExtra(\"sms_body\",\"Title: \"+ProductComparisonActivity.s_title+\"\\n\"+\"Description: \"+ProductComparisonActivity.s_des+\"\\n\"+\"\\n\"+\"Max Price: \"+ProductComparisonActivity.s_max+\"\\n\"+\"Min Price: \"+ProductComparisonActivity.s_min);
startActivity(intent);
}
});
default:
dialog = null;
}
return dialog;
}
}
解决方法
您必须以\'break \'结束\'case 0：\'，现在它继续下降到\'dialog = null \';
, 关于该方法中唯一可能导致NullPointerException的事情是findViewById（）方法。您应确保您为
Dialog
case 0:
dialog.findViewById(R.id.btn_sms_ok)
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