ListView 中的错误 android

Question

我有一个大小为 50 个元素的数组，但有些东西是空的，所以在创建列表视图时它显示错误，如

02-07 06:37:25.589: E/AndroidRuntime(1898): FATAL EXCEPTION: main
02-07 06:37:25.589: E/AndroidRuntime(1898): java.lang.NullPointerException
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:394)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.ArrayAdapter.getView(ArrayAdapter.java:362)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.AbsListView.obtainView(AbsListView.java:2267)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.ListView.makeAndAddView(ListView.java:1769)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.ListView.fillDown(ListView.java:672)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.ListView.fillFromTop(ListView.java:733)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.ListView.layoutChildren(ListView.java:1622)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.AbsListView.onLayout(AbsListView.java:2102)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.View.layout(View.java:13754)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewGroup.layout(ViewGroup.java:4362)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.View.layout(View.java:13754)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewGroup.layout(ViewGroup.java:4362)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.View.layout(View.java:13754)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewGroup.layout(ViewGroup.java:4362)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.View.layout(View.java:13754)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewGroup.layout(ViewGroup.java:4362)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.View.layout(View.java:13754)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewGroup.layout(ViewGroup.java:4362)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1866)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1687)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.Choreographer.doCallbacks(Choreographer.java:555)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.Choreographer.doFrame(Choreographer.java:525)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.os.Handler.handleCallback(Handler.java:615)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.os.Handler.dispatchMessage(Handler.java:92)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.os.Looper.loop(Looper.java:137)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at android.app.ActivityThread.main(ActivityThread.java:4745)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at java.lang.reflect.Method.invokeNative(Native Method)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at java.lang.reflect.Method.invoke(Method.java:511)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-07 06:37:25.589: E/AndroidRuntime(1898):     at dalvik.system.NativeStart.main(Native Method)

这是我创建列表视图的代码

 String[] summary = new String[5];
    summary = obj.getAllSummary();
    ListView listView1 = (ListView) findViewById(R.id.listView1);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
    android.R.layout.simple_list_item_1, summary);     
    listView1.setAdapter(adapter);

我的 getAllSummary 函数

 private String[] summary = new String[5];  
    //here some function that will set the `summary` array size. i will be        from 0 to 5
    public String[] getAllSummary(){
    return summary;
    }

这个 summary 数组有一些字段为空。一旦我想删除它们。我的意思是我需要动态创建字符串数组。或者我应该在检查数组元素是否为空后添加到列表视图中。如何做到这一点请帮助我！

Answer 1

public String[] getAllSummary(){

        int k=0;
       for(int i=0;i<summary.length;i++){
           if(summary[i]!=null)
          k++;
         }

       String[] summary2 = new String[k];
       for(int i=0;i<summary.length;i++){
           if(summary[i]!=null)
         summary2[i]=summary[i];
         }
      return summary2;
   }

Answer 2

正如您所说，数据项随时动态变化，1 或 2 或 5 等，因此您应该使用 ArrayList 而不是 String 数组。在 arrayList 中不需要定义大小。根据要求，它的大小可以增加或减少。

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