在哪里定义OnClickListener以关闭Android中的自定义对话框视图？

Question

我定义了以下自定义对话框视图:

public class MyDialog extends Dialog {
    public MyDialog(Context context) {
        super(context);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_dialog);

        getWindow().setLayout(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    }
}

该对话框使用以下布局,其中仅包含"Dismiss Me"按钮:

<?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_horizontal" >

        <Button
            android:id="@+id/dismiss_btn"
            android:layout_width="100dip"
            android:layout_height="30dip"
            android:layout_centerHorizontal="true"
            android:text="Dismiss me"
            android:textSize="8dip"
            android:textColor="#ffffff" />
</RelativeLayout>

我MainActivity显示一个按钮,triggerDialogBtn按下时将显示我的对话框.我还为dismiss_btn我的对话框上的按钮定义了一个处理程序方法,用于在按下时关闭我的对话框.

public class MainActivity extends Activity{
    private Button triggerDialogBtn;
    private MyDialog myDialog;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        //initialize my dialog
        myDialog = new MyDialog(this);

        //the button which will trigger the dialog to pop up
        Button triggerDialogBtn = (Button)findViewById(R.id.trigger_btn);
        triggerDialogBtn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                myDialog.show(); //my dialog pop up
            }
        });

        // I would like to dismiss my dialog when the "Dismiss me" button on the dialog is pressed
        /**** BUT I GOT NULL POINTER EXCEPTION HERE ******/

        //This is the "Dismiss me" button defined on dialog layout
        Button dismissMeBtn = (Button)findViewById(R.id.dismiss_btn); 
        dismissMeBtn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                 myDialog.dismiss(); 
            }
        });
    }
}

布局main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <!-- The trigger button which will pop up my dialog when pressed -->
    <Button
        android:id="@+id/trigger_btn"
        android:layout_width="80dip"
        android:layout_height="20dip"
        android:text="Trigger dialog" />
</LinearLayout>

问题是如果我在里面定义了dismiss_btn(位于我的对话框中)的点击处理程序MainActivity,我dismiss_btn按下时不能忽略对话框; 它总是抛出NullPointerException.

那么,当按下对话框上的按钮时,我在哪里以及如何定义处理程序以关闭我的对话框？

更新

我还尝试将dismiss_btn处理程序放在我的自定义对话框视图类中,如下所示:

public class MyDialog extends Dialog {
    public MyDialog(Context context) {
        super(context);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.my_dialog);

        Button dismissMeBtn = (Button)findViewById(R.id.dismiss_btn);

        //ERROR: The method setOnClickListener(View.OnClickListener) in the 
        //       type View is not applicable 
        //       for the arguments (new DialogInterface.OnClickListener(){})

        dismissMeBtn.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View v) {
                ???.dismiss(); // What should replace "???"
            }
        });

        getWindow().setLayout(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
    }
}

我得到指示的错误,不知道用什么来代替问号.

Answer 1

您的活动的内容视图(在onCreate开头设置)是布局"main",从该活动您尝试完全访问另一个布局中的视图(dismiss_btn).尝试移动此代码:

  Button dismissMeBtn = (Button)findViewById(R.id.dismiss_btn); //This is the "Dismiss me" button defined on dialog layout
  dismissMeBtn.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View v) {
             /* Changed to reflect access from listener within MyDialog */
             MyDialog.this.dismiss(); 
        }
      });

进入对话框 - 根据需要进行编辑.