Question

我想将数据从 DatabaseBon 传递到ListView。我想在不使用ListViewActivity的情况下执行此操作。

我发现我应该使用cursorAdapter，但还有其他方法（没有ListViewActivity）吗？我实现了CursorAdapter，但得到了一个空指针异常。

我的活动如下：

      public class BlackNumbersBlockDb extends Activity {
        String TAG;
       @Override
   protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.blocknumbersdb);
    @SuppressWarnings("unused")
    Button imBT= (Button)findViewById(R.id.importBL);
    DataBaseBON info= new DataBaseBON(this);
    info.open();
    Cursor cursor=info.getcursor();
    startManagingCursor(cursor);
    ContactCursorAdapter adapter = new ContactCursorAdapter(null, cursor);
    ListView contactLV = (ListView) findViewById(R.id.listviewblDB);
    contactLV.setAdapter(adapter);
    info.close();
        imBT.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            Intent i= new Intent ("android.intent.action.IMPORTM");
            startActivity(i);   
        }
    });

我的cursoradapter看起来像：

            import vahid.engineer.com.DataBaseBON
            import android.content.Context;
            import android.database.Cursor;
            import android.view.LayoutInflater;
    public class ContactCursorAdapter extends CursorAdapter  {
  public ContactCursorAdapter(Context context, Cursor c) {  
    super(context, c);
}

@Override
public void bindView(View view, Context context, Cursor cursor) {
    TextView name = (TextView)view.findViewById(R.id.blacklistDB1);
    name.setText(cursor.getString(cursor.getColumnIndex(DataBaseBON.N_NAME)));
    TextView phone = (TextView)view.findViewById(R.id.blacklistDB2); 
    phone.setText(cursor.getString(cursor.getColumnIndex(DataBaseBON.KEY_NUMBER)));}

@Override
public View newView(Context context, Cursor cursor, ViewGroup parent) {
    LayoutInflater inflater = LayoutInflater.from(context);
    View v = inflater.inflate(R.layout.lv, parent, false);
    bindView(v, context, cursor);
    return v;

我的Xml文件（是否阻止）看起来像

   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical" >

  <ListView
      android:id="@+id/listviewblDB"
      android:layout_width="match_parent"
      android:layout_height="499dp"
      android:layout_weight="0.72" >
  </ListView>

  <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="129dp"
    android:gravity="bottom|center_horizontal|fill|top"
    android:orientation="horizontal" >

    <Button
        android:id="@+id/importBL"
        android:layout_width="100dp"
        android:layout_height="90dp"
        android:layout_marginLeft="10sp"
        android:layout_marginTop="20sp"
        android:ems="10"
        android:text="Import"
        android:textSize="20sp"/>

    </LinearLayout>

我的xml文件LV如下所示：

            <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical" >

  <TextView
          android:id="@+id/blacklistDB1"
          android:layout_width="33dp"
          android:layout_height="wrap_content"
          android:text="Large Text"
          />
   <TextView
        android:id="@+id/blacklistDB2"
        android:layout_width="19dp"
        android:layout_height="wrap_content"
        android:text="Large Text"
        />
   </LinearLayout>

我的错误看起来像是

    FATAL EXCEPTION: main
    java.lang.NullPointerException
at android.view.LayoutInflater.from(LayoutInflater.java:171)
at vahid.engineer.com.ContactCursorAdapter.newView
at android.widget.CursorAdapter.getView(CursorAdapter.java:182)
at android.widget.AbsListView.obtainView(AbsListView.java:1315)
at android.widget.ListView.makeAndAddView(ListView.java:1727)
    at android.widget.ListView.fillDown(ListView.java:652)
at android.widget.ListView.fillFromTop(ListView.java:709)
at android.widget.ListView.layoutChildren(ListView.java:1580)
at android.widget.AbsListView.onLayout(AbsListView.java:1147)
at android.view.View.layout(View.java:7035)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:
at android.widget.LinearLayout.onLayout(LinearLayout.java:1042)
at android.view.View.layout(View.java:7035)

Answer 1

ContactCursorAdapter adapter = new ContactCursorAdapter(null, cursor);

看起来它与它有关。该参数调用您的活动的上下文，而不是null。您为数据库实例化做得很好。以下应该有效。

ContactCursorAdapter adapter = new ContactCursorAdapter(BlackNumbersBlockDb.this, cursor);

ListView和cursorAdapter给出一个空指针异常

1 个答案: