Question

大家好我需要在listview中填充数据库元素。我得到空指针异常和数组适配器错误。我做了以下几种方式： 1）创建一个大小为行数的字符串数组2）在数组中存储数据库值3）在listview中合并。我试了很久但我找不到它。编码：

    Cursor c = db.rawQuery("select * from stopwatch"  , null);
    if (c != null ) {
    if  (c.moveToFirst()) {
      do {
        counter=counter+1;   // finding no of rows in table.
      }while (c.moveToNext());
    }
    } 
    array=new String[counter];


    counter1=0;
    Cursor c1 = db.rawQuery("select * from stopwatch"  , null);
    if (c1 != null ) {
    if  (c1.moveToFirst()) {
      do {
           array[counter1]=String.valueOf(c1.getInt(0))+":"+String.valueOf(c1.getInt(1))+":"+String.valueOf(c1.getInt(2));

计数器=计数+ 1; } while（c1.moveToNext（））; } } db.close（）;

    // populating in listview as follows
     list1.setAdapter(new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1, array));

我的logcat：

   05-12 18:52:30.853: ERROR/AndroidRuntime(8330): java.lang.NullPointerException
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:351)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.ArrayAdapter.getView(ArrayAdapter.java:323)
   05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.AbsListView.obtainView(AbsListView.java:1254)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.ListView.measureHeightOfChildren(ListView.java:1142)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.ListView.onMeasure(ListView.java:1055)
   05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.View.measure(View.java:7117)
   05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:2929)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:888)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:619)
   05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at  android.widget.LinearLayout.onMeasure(LinearLayout.java:280)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.View.measure(View.java:7117)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:2929)
05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.View.measure(View.java:7117)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.LinearLayout.measureVertical(LinearLayout.java:464)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.LinearLayout.onMeasure(LinearLayout.java:278)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.View.measure(View.java:7117)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:2929)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.View.measure(View.java:7117)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.ViewRoot.performTraversals(ViewRoot.java:713)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1504)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.os.Handler.dispatchMessage(Handler.java:99)
   05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at  android.os.Looper.loop(Looper.java:123)
  05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at android.app.ActivityThread.main(ActivityThread.java:3948)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at java.lang.reflect.Method.invokeNative(Native Method)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at  java.lang.reflect.Method.invoke(Method.java:521)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:782)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:540)
 05-12 18:52:30.853: ERROR/AndroidRuntime(8330):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

你用计数器计算记录了。使用cursor.getCount();

并使用SimpleCursorAdapter代替ArrayAdapter。它会方便你。

查看this Answer

Answer 2

尝试使用SQLiteOpenHelper 创建数据帮助

实现这样的功能：

public List<List<String>> getData(){
       Cursor cursor = this.db.query(TABLE_NAME,new String[] { "value1", "value2" }, null, null, null, null, "code asc");
       List<List<String>> list = new ArrayList<List<String>>();
       if (cursor.moveToFirst()){
           do{
               List<String> temp = new ArrayList<String>();
               temp.add(cursor.getString(0));
               temp.add(cursor.getString(1));
               list.add(temp);
           }while (cursor.moveToNext());
       }
       return list;
   }

然后在另一个班级电话中：

private List<List<String>> liItems;
liItems = dh.getData();

/** create an array in the proper length */
String[] rgItems = new String[liItems.size()];

/** Fill the array with data */
for (int i=0; i < liItems.size(); i++){
        List<String> temp = liItems.get(i);
        rgItems[i] = temp.get(0) + " - " + temp.get(1);
    }
    /** Populate ListView with list */
    ArrayList<String> customerList = new ArrayList<String>();
    customerList.addAll( Arrays.asList(rgItems) );
    adItemAdapter = new ArrayAdapter<String>(this, R.layout.itemlisttext, rgItems);
    lvItemListview.setAdapter(adItemAdapter);

itemlisttext是带有textview的xmlLayout

这对我来说很好，希望它可以帮助你。

问题 - 在android中将数据库填充到listview中

2 个答案: