Question

我有一个自定义类CustomDialog 有一个show（）函数，它应该显示一个包含listview内容的对话框，对话框一直很好，直到我添加列表部分。

这里是elements_view的XML代码：

   <?xml version="1.0" encoding="utf-8"?>
 <ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/lvElements"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/circuit_board" >
</ListView>

这里是element_layout：

   <?xml version="1.0" encoding="utf-8"?>
   <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content" 
android:layout_gravity="center"
android:background="@drawable/circuit_board">
   <TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentLeft="true"
    android:layout_alignParentTop="true"
    android:layout_marginLeft="21dp"
    android:layout_marginTop="14dp"
    android:text="Medium Text"
    />

   <ImageView
    android:id="@+id/imageView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentRight="true"
    android:layout_alignParentTop="true"
    android:src="@drawable/ic_launcher" />

    </RelativeLayout>

这是我的CustomDialog类：

package com.example.control;
import java.util.ArrayList;
import com.example.control.R;
import android.app.ActionBar.LayoutParams;
import android.app.Activity;
import android.app.Dialog;
import android.content.Context;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.ArrayAdapter;
import android.widget.ListView;


public class CustomDialog {

private Context con;
    private Activity act;
ListView list;
    private ArrayList<String> listData;
static final String[] str = new String[] { "Apple", "Avocado", "Banana",
    "Blueberry", "Coconut", "Durian", "Guava", "Kiwifruit",
    "Jackfruit", "Mango", "Olive", "Pear", "Sugar-apple" };

    CustomDialog(Activity activity) throws Exception{
this.act = activity;
this.con = activity;
}

    void show() throws Exception{
try{

       try{
 list = (ListView) act.findViewById(R.id.lvElements);


ArrayAdapter<String> ad = new ArrayAdapter<String>(con,R.layout.element_layout,str);
    list.setAdapter(ad);
    }
     catch(Exception ex){
 android.util.Log.e("Control", "problem in list ");
 android.util.Log.e("Control", ex.toString());

     }

     final Dialog dialog = new Dialog(con);
        dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
        dialog.setContentView(R.layout.elements_view);
        final Window window = dialog.getWindow();
        window.setLayout(WindowManager.LayoutParams.MATCH_PARENT,         WindowManager.LayoutParams.MATCH_PARENT);
        window.clearFlags(WindowManager.LayoutParams.FLAG_DIM_BEHIND);
        window.setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
        dialog.show();
}
catch(Exception ex){
     throw ex;

}

   }


   }//ends the class

内部尝试导致在logcat中获取此对话框时不显示该对话框：

01-17 01:54:50.122: E/Control(29502): problem in list 
01-17 01:54:50.122: E/Control(29502): java.lang.NullPointerException
01-17 01:54:50.152: D/dalvikvm(29502): GC_FOR_ALLOC freed 3096K, 43% free 10009K/17364K,    paused 24ms, total 27ms
01-17 01:54:50.162: I/dalvikvm-heap(29502): Grow heap (frag case) to 16.203MB for       3464956-byte allocation
01-17 01:54:50.202: D/dalvikvm(29502): GC_CONCURRENT freed 18K, 36% free 13374K/20748K,     paused 5ms+2ms, total 42ms
01-17 01:54:50.272: D/AbsListView(29502): Get MotionRecognitionManager
01-17 01:54:50.292: D/dalvikvm(29502): GC_CONCURRENT freed 3386K, 32% free  11922K/17368K, paused 2ms+15ms, total 36ms
01-17 01:54:50.302: D/AbsListView(29502): unregisterIRListener() is called 
01-17 01:54:50.312: D/AbsListView(29502): unregisterIRListener() is called 
01-17 01:54:50.352: D/AbsListView(29502): unregisterIRListener() is called

Answer 1

在你的Activity onCreate（）中，我假设你用setContentView夸大了'elements_view.xml'以外的东西。在show（）中，通过搜索R.id.lvElements的Activity的视图层次结构来设置'list'：

list = (ListView) act.findViewById(R.id.lvElements);

You Activity的布局不包含R.id.lvElements，因此list设置为null，因此当您尝试在其上设置适配器时，Null Pointer Exception。

您的列表视图在elements_view.xml中定义，您将其视为对话框的视图层次结构。将list的设置和用法移动到dialog.setContentView（）之后的某个点并在对话框中调用findViewById（），而不是执行：

dialog.setContentView(R.layout.elements_view);
list = (ListView) dialog.findViewById(R.id.lvElements);

Answer 2

首先，您需要Inflate Dialog Layout如下所示：

private static LayoutInflater inflater = null;
inflater = (LayoutInflater) activity
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);

现在，在全球范围内创建Dialog个对象：

Dialog main_dialog;

现在，给Dialog Layout View充气并设置为Dialog：

final View DialogView = inflater.inflate(
            R.layout.elements_view, null);

main_dialog = new Dialog(Splash.this,R.style.Theme_Dialog);

main_dialog.setContentView(DialogView);

现在，您的列表视图在elements_view.xml中定义，您将其视为对话框的视图层次结构。从DialogView

中查找列表视图

list = (ListView)DialogView.findViewById(R.id.lvElements);

然后设置适配器或类似的东西。试试这个

在对话框中添加列表视图

2 个答案: