android textview在AlertDialog中得到了NullPointerException

Question

When I tried to customize a AlertDialog with a TextView, I got a NullPointerException. I wonder why it happens? It seems that the TextView hasn't initialized when I call setText method. If so, when the TextView will be initialized if using LayoutInflater?

Thanks a lot!

Here is Java code:

   listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
            LayoutInflater layoutInflater = getLayoutInflater();
            View layout = layoutInflater.inflate(R.layout.dialog_desc, null);
            AlertDialog.Builder alertDialog = new AlertDialog.Builder(MainActivity.this).setTitle("Description");
            alertDialog.setView(layout);

            TextView descTextView = (TextView) findViewById(R.id.desc_text);
            String descString = itemData.get(position).get("desc");
            descTextView.setText(descString);

            alertDialog.show();
        }
    });

The AlertDialog works fine if I comment "descTextView.setText(descString)". Besides, descString is fine.

Here is XML:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/desc_dialog_layout">

    <TextView
        android:id="@+id/desc_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="New Text"
     />
</LinearLayout>

Here is the exception info:

04-28 13:27:44.794  12896-12896/com.example.chanson.listview E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException
        at com.example.chanson.listview.main.MainActivity$5.onItemClick(MainActivity.java:99)
        at android.widget.AdapterView.performItemClick(AdapterView.java:298)
        at android.widget.AbsListView.performItemClick(AbsListView.java:1147)
        at android.widget.AbsListView$PerformClick.run(AbsListView.java:2979)
        at android.widget.AbsListView$1.run(AbsListView.java:3755)
        at android.os.Handler.handleCallback(Handler.java:615)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:153)
        at android.app.ActivityThread.main(ActivityThread.java:5000)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:821)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:584)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

Change

 TextView descTextView = (TextView) findViewById(R.id.desc_text);

to

 TextView descTextView = (TextView) layout.findViewById(R.id.desc_text);

Answer 2

This

TextView descTextView = (TextView) findViewById(R.id.desc_text);

Should be replaced by

TextView descTextView = (TextView) layout.findViewById(R.id.desc_text);