1
請看看下面的代碼NullPointException ListView中
activity_form.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".Form" >
<ImageView
android:id="@+id/logo"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:src="@drawable/logo" />
<TextView
android:id="@+id/title"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_below="@+id/logo"
android:layout_marginTop="10dp"
android:text="@string/title" />
<ListView
android:id="@+id/list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/title"
android:layout_marginTop="10dp"
/>
</RelativeLayout>
list_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="horizontal" >
<ImageView
android:id="@+id/listImage"
android:layout_width="50dp"
android:layout_height="50dp"
android:src="@drawable/star" />
<TextView
android:id="@+id/listText"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:paddingLeft="5dp"
android:paddingTop="10dp"
android:text="Large Text"
android:textAppearance="?android:attr/textAppearanceLarge" />
</LinearLayout>
Form.java
package com.example.callmanager;
import android.os.Bundle;
import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
public class Form extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_form);
ListView lv = (ListView)findViewById(android.R.id.list);
String arr[] = getResources().getStringArray(R.array.branch_list);
lv.setAdapter(new MyAdapter(this,android.R.layout.simple_list_item_1,R.id.listText,arr));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_form, menu);
return true;
}
private class MyAdapter extends ArrayAdapter
{
public MyAdapter(Context context, int resource, int textViewResourceId,
Object[] objects) {
super(context, resource, textViewResourceId, objects);
// TODO Auto-generated constructor stub
}
@Override
public View getView(int position, View contentView, ViewGroup parent)
{
LayoutInflater inflater = (LayoutInflater)getSystemService(LAYOUT_INFLATER_SERVICE);
View view = inflater.inflate(R.layout.list_layout, parent,false);
TextView tv = (TextView)findViewById(R.id.listText);
ImageView iv = (ImageView)findViewById(R.id.listImage);
String arr[] = getResources().getStringArray(R.array.branch_list);
tv.setText(arr[position]);
if(arr[position].equals("Anuradhapura"))
iv.setImageResource(R.drawable.star);
return view;
}
}
}
的strings.xml
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">Esoft Call Manager</string>
<string name="hello_world">Hello world!</string>
<string name="menu_settings">Settings</string>
<string name="title"><b>Select a Branch To Call</b></string>
<string-array name="branch_list">
<item>Anuradhapura</item>
<item>Avissawella</item>
</string-array>
</resources>
當我運行這段代碼，我得到了 'NullPointException'。我加入這裏的完整的日誌文件
02-08 21:04:01.463: D/dalvikvm(490): GC_EXTERNAL_ALLOC freed 43K, 53% free 2551K/5379K, external 1949K/2137K, paused 82ms
02-08 21:04:01.713: D/AndroidRuntime(490): Shutting down VM
02-08 21:04:01.713: W/dalvikvm(490): threadid=1: thread exiting with uncaught exception (group=0x40015560)
02-08 21:04:01.733: E/AndroidRuntime(490): FATAL EXCEPTION: main
02-08 21:04:01.733: E/AndroidRuntime(490): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.callmanager/com.example.callmanager.Form}: java.lang.NullPointerException
02-08 21:04:01.733: E/AndroidRuntime(490): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
02-08 21:04:01.733: E/AndroidRuntime(490): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
02-08 21:04:01.733: E/AndroidRuntime(490): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
02-08 21:04:01.733: E/AndroidRuntime(490): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
02-08 21:04:01.733: E/AndroidRuntime(490): at android.os.Handler.dispatchMessage(Handler.java:99)
02-08 21:04:01.733: E/AndroidRuntime(490): at android.os.Looper.loop(Looper.java:123)
02-08 21:04:01.733: E/AndroidRuntime(490): at android.app.ActivityThread.main(ActivityThread.java:3683)
02-08 21:04:01.733: E/AndroidRuntime(490): at java.lang.reflect.Method.invokeNative(Native Method)
02-08 21:04:01.733: E/AndroidRuntime(490): at java.lang.reflect.Method.invoke(Method.java:507)
02-08 21:04:01.733: E/AndroidRuntime(490): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
02-08 21:04:01.733: E/AndroidRuntime(490): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-08 21:04:01.733: E/AndroidRuntime(490): at dalvik.system.NativeStart.main(Native Method)
02-08 21:04:01.733: E/AndroidRuntime(490): Caused by: java.lang.NullPointerException
02-08 21:04:01.733: E/AndroidRuntime(490): at com.example.esoftcallmanager.Form.onCreate(Form.java:24)
02-08 21:04:01.733: E/AndroidRuntime(490): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
02-08 21:04:01.733: E/AndroidRuntime(490): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
02-08 21:04:01.733: E/AndroidRuntime(490): ... 11 more
我加入下面是否有幫助
爲什麼我收到此錯誤的文件夾結構？如何解決這個問題？請幫忙！
'這裏是我有的所有代碼，問題在哪裏'很不好尋求幫助...... – WarrenFaith 2013-02-08 15:51:10
您仍然錯過了在代碼中引用NullPointer的地方標記行的部分。簡而言之：你張貼的方式超過需要，仍然錯過了重要的東西。 – WarrenFaith 2013-02-08 16:58:14