我不知道为什么我会一次又一次地收到这个错误。任何帮助将不胜感激。我已经检查了 manifest.xml ..没有问题是 ..请检查并在可能的情况下提供解决方案
package com.example.helloworld;
import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
public class List extends ListActivity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
String[] numbers = {"one","two","three","four"};
this.setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item,R.id.new_list,numbers));
ListView lv = getListView();
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
TextView textitem =(TextView)findViewById(R.id.new_list);
String num = ((TextView) textitem).getText().toString();
Intent i = new Intent("com.example.helloworld.CHECKBOX");
i.putExtra("number", num);
startActivity(i);
}
});
}
}
这是manifest.xml ..
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.helloworld"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="10"
android:targetSdkVersion="17" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.example.helloworld.Splash"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.example.helloworld.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.example.helloworld.MAINACTIVITY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.example.helloworld.List"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.example.helloworld.LIST" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.example.helloworld.Menu"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.example.helloworld.MENU" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.example.helloworld.CheckPermissions"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.example.helloworld.CHECKPERMISSIONS" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.example.helloworld.TextPlay"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.example.helloworld.TEXTPLAY" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.example.helloworld.CheckboxCursorAdapter"
android:label="@string/app_name" >
<intent-filter>
<action android:name="com.example.helloworld.CHECKBOXCURSORADAPTER" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
<activity
android:name="com.example.helloworld.CheckBox"
android:label="@string/title_activity_check_box" >
<intent-filter>
<action android:name="com.example.helloworld.CHECKBOX" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
最后是 checkbox.java
package com.example.helloworld;
import java.util.ArrayList;
import java.util.List;
import android.os.Bundle;
import android.app.ListActivity;
import android.util.SparseBooleanArray;
import android.widget.ArrayAdapter;
public class CheckBox extends ListActivity {
String classes[] = { "MainActivity","CheckPermissions","TextPlay","example3","example4","example5","example6"};
//ListView lView ;
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
this.setListAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice, classes));
}
List<Integer> checkedIDs = new ArrayList<Integer>();
// Get all of the items that have been clicked - either on or off
final SparseBooleanArray checkedItems = getListView().getCheckedItemPositions();
{
for (int i = 0; i < checkedItems.size(); i++){
// And this tells us the item status at the above position
final boolean isChecked = checkedItems.valueAt(i);
if (isChecked){
// This tells us the item position we are looking at
final int position = checkedItems.keyAt(i);
// Put the value of the id in our list
checkedIDs.add(position);
}
}
}
}
这是原木猫
04-22 15:14:00.236: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:00.616: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:00.656: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.336: D/dalvikvm(1615): GC_FOR_ALLOC freed 71K, 7% free 2515K/2704K, paused 54ms, total 58ms
04-22 15:14:01.596: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.596: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.618: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.636: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.748: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.756: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.768: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.857: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.857: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.866: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.866: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.866: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.866: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:01.896: D/gralloc_goldfish(1615): Emulator without GPU emulation detected.
04-22 15:14:02.356: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:02.426: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:04.646: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:04.796: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:04.796: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:05.136: D/dalvikvm(1615): GC_CONCURRENT freed 15K, 5% free 2903K/3056K, paused 6ms+135ms, total 322ms
04-22 15:14:05.556: D/dalvikvm(1615): GC_FOR_ALLOC freed 8K, 5% free 2975K/3112K, paused 91ms, total 98ms
04-22 15:14:05.609: I/dalvikvm-heap(1615): Grow heap (frag case) to 3.624MB for 635812-byte allocation
04-22 15:14:05.766: D/dalvikvm(1615): GC_FOR_ALLOC freed <1K, 4% free 3596K/3736K, paused 156ms, total 156ms
04-22 15:14:06.046: D/dalvikvm(1615): GC_CONCURRENT freed 1K, 4% free 3610K/3736K, paused 11ms+110ms, total 282ms
04-22 15:14:06.206: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.236: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.336: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.366: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.476: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.618: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.626: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.646: I/Choreographer(1615): Skipped 81 frames! The application may be doing too much work on its main thread.
04-22 15:14:06.656: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.666: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.876: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:06.956: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.006: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.077: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.147: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.147: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.206: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.206: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.526: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.598: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.598: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.666: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.676: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.676: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:07.977: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.306: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.306: I/Choreographer(1615): Skipped 75 frames! The application may be doing too much work on its main thread.
04-22 15:14:08.306: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.306: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.396: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.407: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.436: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.436: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.496: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:08.496: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:09.929: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:09.937: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.021: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.086: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.086: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.097: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.207: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.207: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.286: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.296: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.588: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.588: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.616: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.686: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.686: W/Trace(1615): Unexpected value from nativeGetEnabledTags: 0
04-22 15:14:10.696: D/AndroidRuntime(1615): Shutting down VM
04-22 15:14:10.696: W/dalvikvm(1615): threadid=1: thread exiting with uncaught exception (group=0x40a70930)
04-22 15:14:10.846: E/AndroidRuntime(1615): FATAL EXCEPTION: main
04-22 15:14:10.846: E/AndroidRuntime(1615): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.helloworld/com.example.helloworld.CheckBox}: java.lang.NullPointerException
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.ActivityThread.access$600(ActivityThread.java:141)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.os.Handler.dispatchMessage(Handler.java:99)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.os.Looper.loop(Looper.java:137)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.ActivityThread.main(ActivityThread.java:5039)
04-22 15:14:10.846: E/AndroidRuntime(1615): at java.lang.reflect.Method.invokeNative(Native Method)
04-22 15:14:10.846: E/AndroidRuntime(1615): at java.lang.reflect.Method.invoke(Method.java:511)
04-22 15:14:10.846: E/AndroidRuntime(1615): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
04-22 15:14:10.846: E/AndroidRuntime(1615): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
04-22 15:14:10.846: E/AndroidRuntime(1615): at dalvik.system.NativeStart.main(Native Method)
04-22 15:14:10.846: E/AndroidRuntime(1615): Caused by: java.lang.NullPointerException
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.Activity.setContentView(Activity.java:1881)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.ListActivity.ensureList(ListActivity.java:312)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.ListActivity.getListView(ListActivity.java:297)
04-22 15:14:10.846: E/AndroidRuntime(1615): at com.example.helloworld.CheckBox.<init>(CheckBox.java:26)
04-22 15:14:10.846: E/AndroidRuntime(1615): at java.lang.Class.newInstanceImpl(Native Method)
04-22 15:14:10.846: E/AndroidRuntime(1615): at java.lang.Class.newInstance(Class.java:1319)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
04-22 15:14:10.846: E/AndroidRuntime(1615): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
04-22 15:14:10.846: E/AndroidRuntime(1615): ... 11 more
04-22 15:14:14.096: I/Process(1615): Sending signal. PID: 1615 SIG: 9
更新代码：list.java
lv.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// selected item
//String num = ((TextView) view).getText().toString();
// Launching new Activity on selecting single List Item
Intent i = new Intent("com.example.helloworld.CHECKBOX");
// sending data to new activity
//i.putExtra("number", num);
startActivity(i);
}
复选框.java
this.setListAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_multiple_choice, classes));
List<Integer> checkedIDs = new ArrayList<Integer>();
// Get all of the items that have been clicked - either on or off
final SparseBooleanArray checkedItems = getListView().getCheckedItemPositions();
{
for (int i = 0; i < checkedItems.size(); i++){
// And this tells us the item status at the above position
final boolean isChecked = checkedItems.valueAt(i);
if (isChecked){
// This tells us the item position we are looking at
final int position = checkedItems.keyAt(i);
// Put the value of the id in our list
checkedIDs.add(position);
}
}
}