以编程方式填充列表视图

问题描述：

我想在列表视图中显示存储在模拟器上的联系人。稍后，虽然它只是应用程序存储的一组选定联系人（需要对此存储和检索提出建议）。由于列表不能是一个硬编码的字符串数组我已经尝试以编程方式填充列表视图，但我得到一个错误。以编程方式填充列表视图

这里是代码PS：beginner android dev。

我已列入清单Reads_contacts ..必要的权限，所以这不是一个问题

public class settings_manager extends Activity{ 
/** Called when the activity is first created. */ 
@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.setting); 
    TabHost th = (TabHost)findViewById(R.id.tabhost); 
    th.setup(); 

    ContentResolver cr = getContentResolver(); 
    final Cursor cur = cr.query(ContactsContract.Contacts.CONTENT_URI, null, null, null, null); 


    TabSpec spec1 = th.newTabSpec("tag1"); 
    spec1.setIndicator("CONTACTS"); 
    if(!cur.moveToNext()){ 
    spec1.setContent(R.id.tab1); 
    } 
    else{ 
    spec1.setContent(new TabHost.TabContentFactory() { 
     public View createTabContent(String arg0) { 
      ListView contacts_list = new ListView(settings_manager.this); 
      String[] c_list = null; int i=0; 
      while(cur.moveToNext()) 
      { 
        int nameindex = cur.getColumnIndex(PhoneLookup.DISPLAY_NAME); 
        c_list[i] = cur.getString(nameindex); i++; 

      } 

      ArrayAdapter<String> contacts_adapter = new ArrayAdapter<String>(null,android.R.layout.simple_list_item_1, c_list); 
      return contacts_list; 
     } 
    }) ; 

    } 
    th.addTab(spec1); 


    TabSpec spec2 = th.newTabSpec("tag2"); 
    spec2.setContent(R.id.tab2); 
    spec2.setIndicator("tab2"); 
    th.addTab(spec2); 


    TabSpec spec3 = th.newTabSpec("tag3"); 
    spec3.setContent(R.id.tab3); 
    spec3.setIndicator("tab3"); 
    th.addTab(spec3); 
}

日志猫说：我真的不知道有什么表示什么所以我粘贴整件事

03-05 22:57:18.185: D/AndroidRuntime(232): Shutting down VM 
    03-05 22:57:18.185: W/dalvikvm(232): threadid=3: thread exiting with uncaught               exception (group=0x4001b188) 
    03-05 22:57:18.185: E/AndroidRuntime(232): Uncaught handler: thread main exiting due to uncaught exception 
    03-05 22:57:18.195: E/AndroidRuntime(232): java.lang.RuntimeException: Unable to start activity ComponentInfo{water.tank/water.tank.settings_manager}: java.lang.NullPointerException 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2496) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.app.ActivityThread.access$2200(ActivityThread.java:119) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.os.Handler.dispatchMessage(Handler.java:99) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.os.Looper.loop(Looper.java:123) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.app.ActivityThread.main(ActivityThread.java:4363) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at java.lang.reflect.Method.invokeNative(Native Method) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at java.lang.reflect.Method.invoke(Method.java:521) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at dalvik.system.NativeStart.main(Native Method) 
    03-05 22:57:18.195: E/AndroidRuntime(232): Caused by: java.lang.NullPointerException 
    03-05 22:57:18.195: E/AndroidRuntime(232): at water.tank.settings_manager$1.createTabContent(settings_manager.java:47) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.widget.TabHost$FactoryContentStrategy.getContentView(TabHost.java:617) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.widget.TabHost.setCurrentTab(TabHost.java:320) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.widget.TabHost.addTab(TabHost.java:213) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at water.tank.settings_manager.onCreate(settings_manager.java:57) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
    03-05 22:57:18.195: E/AndroidRuntime(232): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459) 
    03-05 22:57:18.195: E/AndroidRuntime(232): ... 11 more 
    03-05 22:57:18.215: I/dalvikvm(232): threadid=7: reacting to signal 3 
    03-05 22:57:18.215: E/dalvikvm(232): Unable to open stack trace file '/data/anr/traces.txt': Permission denied

首先Aseem，你的问题不清楚。添加您面临的问题的更多细节。你也可以添加logcat信息到这个问题。找出发生的事情会更容易。顺便说一句，你在项目的AndroidManifest.xml中添加了'READ_CONTACTS'权限？ – Gadenkan 2012-03-05 15:22:11

我已经提到关于许可已经 - 是的，我已经包括了这一点。 – 2012-03-05 15:32:36

好的。当应用程序崩溃时，logcat会说什么？ – Gadenkan 2012-03-05 15:51:56

答

你的代码有很多错误。 NPE只是第一个。

//Prevented cursor moving forward unnecessorily. 
if (cur.getCount() == 0) { 
    spec1.setContent(R.id.tab1); 
} else { 
    spec1.setContent(new TabHost.TabContentFactory() { 
     public View createTabContent(String arg0) { 
      ListView contacts_list = new ListView(settings_manager.this); 

      String[] c_list = new String[cur.getCount()];//NPE was here. 

      // use cur.getPosition() instead of int i = 0; i++; 
      while (cur.moveToNext()) { 
       c_list[cur.getPosition()] = cur.getString(cur 
         .getColumnIndex(PhoneLookup.DISPLAY_NAME)); 
      } 
      ArrayAdapter<String> contacts_adapter = new ArrayAdapter<String>(
        null, android.R.layout.simple_list_item_1, c_list); 

      //set listadaper 
      contacts_list.setAdapter(contacts_adapter); 
      return contacts_list; 
     } 
    }); 
}

以编程方式填充列表视图

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