我已完成此代码以在片段中显示警告对话框，但是当我单击按钮时，应用程序崩溃。 谢谢你以任何方式提供帮助。
fragment_disconnect.xml：
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:gravity="center_horizontal"
android:background="#EBB917" >
<Button
android:layout_margin="20dip"
android:id="@+id/button_disconnect_alert"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Disconnect"
android:onClick="onClick" />
</LinearLayout>
代码：
package com.example.poca2;
import android.app.AlertDialog;
import android.app.Fragment;
import android.content.DialogInterface;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class DisconnectFragment extends Fragment {
public DisconnectFragment(){}
public void onClick(View view)
{
AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(getActivity());
// set Title
alertDialogBuilder.setTitle("Disconnecting User");
//set Message
alertDialogBuilder.setMessage("Are You Sure You Want To Disconnect ? ").setCancelable(false).setPositiveButton("Yes",new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id){
// if button is clicked ,then go to into activity
//Intent intent = new Intent(getActivity(), IntroActivity.class);
//startActivity(intent);
}
}).setNegativeButton("No", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog,int id ){
// if button is clicked then close the alert box
dialog.cancel();
}
});
//create alert dialog
AlertDialog alertDialog = alertDialogBuilder.create();
//show alert box
alertDialog.show();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_disconnect, container, false);
return rootView;
}
}
日志：
04-03 11:37:22.684: D/skia(23439): new locale en-Latn-GB
04-03 11:37:22.854: D/libEGL(23439): loaded /vendor/lib/egl/libEGL_adreno.so
04-03 11:37:22.854: D/libEGL(23439): loaded /vendor/lib/egl/libGLESv1_CM_adreno.so
04-03 11:37:22.864: D/libEGL(23439): loaded /vendor/lib/egl/libGLESv2_adreno.so
04-03 11:37:22.864: I/Adreno-EGL(23439): <qeglDrvAPI_eglInitialize:316>: EGL 1.4 QUALCOMM build: (CL4169980)
04-03 11:37:22.864: I/Adreno-EGL(23439): OpenGL ES Shader Compiler Version: 17.01.10.SPL
04-03 11:37:22.864: I/Adreno-EGL(23439): Build Date: 09/26/13 Thu
04-03 11:37:22.864: I/Adreno-EGL(23439): Local Branch:
04-03 11:37:22.864: I/Adreno-EGL(23439): Remote Branch:
04-03 11:37:22.864: I/Adreno-EGL(23439): Local Patches:
04-03 11:37:22.864: I/Adreno-EGL(23439): Reconstruct Branch:
04-03 11:37:22.914: D/OpenGLRenderer(23439): Enabling debug mode 0
04-03 11:37:39.971: D/AndroidRuntime(23439): Shutting down VM
04-03 11:37:39.971: W/dalvikvm(23439): threadid=1: thread exiting with uncaught exception (group=0x41b2b898)
04-03 11:37:39.981: E/AndroidRuntime(23439): FATAL EXCEPTION: main
04-03 11:37:39.981: E/AndroidRuntime(23439): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.poca2/com.example.poca2.RegisterActivity}: java.lang.NullPointerException
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.app.ActivityThread.access$700(ActivityThread.java:159)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.os.Handler.dispatchMessage(Handler.java:99)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.os.Looper.loop(Looper.java:137)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.app.ActivityThread.main(ActivityThread.java:5419)
04-03 11:37:39.981: E/AndroidRuntime(23439): at java.lang.reflect.Method.invokeNative(Native Method)
04-03 11:37:39.981: E/AndroidRuntime(23439): at java.lang.reflect.Method.invoke(Method.java:525)
04-03 11:37:39.981: E/AndroidRuntime(23439): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
04-03 11:37:39.981: E/AndroidRuntime(23439): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
04-03 11:37:39.981: E/AndroidRuntime(23439): at dalvik.system.NativeStart.main(Native Method)
04-03 11:37:39.981: E/AndroidRuntime(23439): Caused by: java.lang.NullPointerException
04-03 11:37:39.981: E/AndroidRuntime(23439): at com.example.poca2.RegisterActivity.onCreate(RegisterActivity.java:33)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.app.Activity.performCreate(Activity.java:5372)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
04-03 11:37:39.981: E/AndroidRuntime(23439): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
04-03 11:37:39.981: E/AndroidRuntime(23439): ... 11 more
04-03 11:37:44.545: D/skia(23761): new locale en-Latn-GB
04-03 11:37:44.776: D/libEGL(23761): loaded /vendor/lib/egl/libEGL_adreno.so
04-03 11:37:44.786: D/libEGL(23761): loaded /vendor/lib/egl/libGLESv1_CM_adreno.so
04-03 11:37:44.786: D/libEGL(23761): loaded /vendor/lib/egl/libGLESv2_adreno.so
04-03 11:37:44.786: I/Adreno-EGL(23761): <qeglDrvAPI_eglInitialize:316>: EGL 1.4 QUALCOMM build: (CL4169980)
04-03 11:37:44.786: I/Adreno-EGL(23761): OpenGL ES Shader Compiler Version: 17.01.10.SPL
04-03 11:37:44.786: I/Adreno-EGL(23761): Build Date: 09/26/13 Thu
04-03 11:37:44.786: I/Adreno-EGL(23761): Local Branch:
04-03 11:37:44.786: I/Adreno-EGL(23761): Remote Branch:
04-03 11:37:44.786: I/Adreno-EGL(23761): Local Patches:
04-03 11:37:44.786: I/Adreno-EGL(23761): Reconstruct Branch:
04-03 11:37:44.836: D/OpenGLRenderer(23761): Enabling debug mode 0
04-03 11:37:48.069: D/AndroidRuntime(23761): Shutting down VM
04-03 11:37:48.069: W/dalvikvm(23761): threadid=1: thread exiting with uncaught exception (group=0x41b2b898)
04-03 11:37:48.069: E/AndroidRuntime(23761): FATAL EXCEPTION: main
04-03 11:37:48.069: E/AndroidRuntime(23761): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.poca2/com.example.poca2.RegisterActivity}: java.lang.NullPointerException
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.app.ActivityThread.access$700(ActivityThread.java:159)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.os.Handler.dispatchMessage(Handler.java:99)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.os.Looper.loop(Looper.java:137)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.app.ActivityThread.main(ActivityThread.java:5419)
04-03 11:37:48.069: E/AndroidRuntime(23761): at java.lang.reflect.Method.invokeNative(Native Method)
04-03 11:37:48.069: E/AndroidRuntime(23761): at java.lang.reflect.Method.invoke(Method.java:525)
04-03 11:37:48.069: E/AndroidRuntime(23761): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1187)
04-03 11:37:48.069: E/AndroidRuntime(23761): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)
04-03 11:37:48.069: E/AndroidRuntime(23761): at dalvik.system.NativeStart.main(Native Method)
04-03 11:37:48.069: E/AndroidRuntime(23761): Caused by: java.lang.NullPointerException
04-03 11:37:48.069: E/AndroidRuntime(23761): at com.example.poca2.RegisterActivity.onCreate(RegisterActivity.java:33)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.app.Activity.performCreate(Activity.java:5372)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
04-03 11:37:48.069: E/AndroidRuntime(23761): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257)
04-03 11:37:48.069: E/AndroidRuntime(23761): ... 11 more
04-03 11:37:54.265: I/Process(23761): Sending signal. PID: 23761 SIG: 9
当我点击按钮时，应用程序崩溃了。 thnx寻求帮助
答案 0 :(得分：0)
你有一个空指针异常@ RegisterActivity.onCreate（），RegisterActivity.java第33行
无论您在此处访问哪些变量，都需要在使用它们之前检查它们是否为空。
基本的调试方法是对该行上使用的每个引用/变量执行类似的操作。
if (variable == null)
{
Log.d(TAG, "variable is null")
}
一旦你发现什么是null，那么你就可以找到原因，一旦你知道原因，就可以解决它并从中吸取经验。
答案 1 :(得分：0)
试试这个：
假设这是你的片段：
public class SomeFragment extends Fragment {
public SomeFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.activity_main, container,
false);
return rootView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onActivityCreated(savedInstanceState);
Button btn = (Button) getActivity().findViewById(
button_disconnect_alert);
btn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
AlertDialog.Builder builder = new AlertDialog.Builder(
getActivity());
builder.setIcon(getResources().getDrawable(
R.drawable.ic_launcher));
builder.setTitle("Some title");
builder.setMessage("Some Message");
builder.setPositiveButton("Yes",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int which) {
Toast.makeText(getActivity(),
"Positive clicked", Toast.LENGTH_SHORT)
.show();
Intent intent = new Intent(getActivity(),
IntroActivity.class);
getActivity().startActivity(intent);
}
});
builder.setNegativeButton("No",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog,
int which) {
Toast.makeText(getActivity(),
"Negative clicked", Toast.LENGTH_SHORT)
.show();
}
});
builder.setCancelable(false);
AlertDialog alert = builder.create();
alert.show();
}
});
}
}
希望这会有所帮助.. :)