Dialogs

dialog 是对话框的基类，应避免直接使用dialog而应使用dialog的子类AlertDialog 和DatePickerDialog以及TimePickerDialog.
要使用DialogFragment 作为dialog的容器.
一般情况下应该事先DialogFragment 的子类，然后在onCreateDialog中创建AlertDialog，如下所示:
public class FireMissilesDialogFragment extends DialogFragment {
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Use the Builder class for convenient dialog construction
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(R.string.dialog_fire_missiles)
               .setPositiveButton(R.string.fire, new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                       // FIRE ZE MISSILES!
                   }
               })
               .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                       // User cancelled the dialog
                   }
               });
        // Create the AlertDialog object and return it
        return builder.create();
    }
}
然后调用builder.show()方法就可以把dialog 显示出来.
public void confirmFireMissiles() {
    DialogFragment newFragment = new FireMissilesDialogFragment();
    newFragment.show(getSupportFragmentManager(), "missiles");
}


新建一个AlertDialog的时候，可以通过AlertDialog.Builder 的setMessage和setTitle方法来改变dialog的message和title，如下所示：
// 1. Instantiate an AlertDialog.Builder with its constructor
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());


// 2. Chain together various setter methods to set the dialog characteristics
builder.setMessage(R.string.dialog_message)
       .setTitle(R.string.dialog_title);


// 3. Get the AlertDialog from create()
AlertDialog dialog = builder.create();
还可以通过setPositiveButton() 和setNegativeButton（）来为dialog添加button.
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
// Add the buttons
builder.setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
               // User clicked OK button
           }
       });
builder.setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
               // User cancelled the dialog
           }
       });
还可以增加一个Neutral button


AlertDialog 中可以使用single-choice list,single-choice list(radio buttons),mutiple-choice list(checkboxes)
可以通过setItems（）或者setAdapter（）提供可选选项，如下所示：
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    builder.setTitle(R.string.pick_color)
           .setItems(R.array.colors_array, new DialogInterface.OnClickListener() {
               public void onClick(DialogInterface dialog, int which) {
               // The 'which' argument contains the index position
               // of the selected item
           }
    });
    return builder.create();
}
用setMutiChoiceItems（）和setSingleChoiceItems 为ingle-choice list(radio buttons)和mutiple-choice list(checkboxes)提供选项.
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    mSelectedItems = new ArrayList();  // Where we track the selected items
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    // Set the dialog title
    builder.setTitle(R.string.pick_toppings)
    // Specify the list array, the items to be selected by default (null for none),
    // and the listener through which to receive callbacks when items are selected
           .setMultiChoiceItems(R.array.toppings, null,
                      new DialogInterface.OnMultiChoiceClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int which,
                       boolean isChecked) {
                   if (isChecked) {
                       // If the user checked the item, add it to the selected items
                       mSelectedItems.add(which);
                   } else if (mSelectedItems.contains(which)) {
                       // Else, if the item is already in the array, remove it
                       mSelectedItems.remove(Integer.valueOf(which));
                   }
               }
           })
    // Set the action buttons
           .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int id) {
                   // User clicked OK, so save the mSelectedItems results somewhere
                   // or return them to the component that opened the dialog
                   ...
               }
           })
           .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int id) {
                   ...
               }
           });


    return builder.create();
}


可以通过setView为AlertDialog 设置一个自定义的layout.
layout文件保存在res/layout/dialog_signin.xml
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    <ImageView
        android:src="@drawable/header_logo"
        android:layout_width="match_parent"
        android:layout_height="64dp"
        android:scaleType="center"
        android:background="#FFFFBB33"
        android:contentDescription="@string/app_name" />
    <EditText
        android:id="@+id/username"
        android:inputType="textEmailAddress"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:layout_marginLeft="4dp"
        android:layout_marginRight="4dp"
        android:layout_marginBottom="4dp"
        android:hint="@string/username" />
    <EditText
        android:id="@+id/password"
        android:inputType="textPassword"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="4dp"
        android:layout_marginLeft="4dp"
        android:layout_marginRight="4dp"
        android:layout_marginBottom="16dp"
        android:fontFamily="sans-serif"
        android:hint="@string/password"/>
</LinearLayout>
可知这个AlertDialog 包含一个ImageView，两个EditText.
然后调用inflate 来展开这个layout.
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
    // Get the layout inflater
    LayoutInflater inflater = getActivity().getLayoutInflater();


    // Inflate and set the layout for the dialog
    // Pass null as the parent view because its going in the dialog layout
    builder.setView(inflater.inflate(R.layout.dialog_signin, null))
    // Add action buttons
           .setPositiveButton(R.string.signin, new DialogInterface.OnClickListener() {
               @Override
               public void onClick(DialogInterface dialog, int id) {
                   // sign in the user ...
               }
           })
           .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
               public void onClick(DialogInterface dialog, int id) {
                   LoginDialogFragment.this.getDialog().cancel();
               }
           });
    return builder.create();
}
也可以通过将Activity的主题设成dialog来做上面相同的事情
<activity android:theme="@android:style/Theme.Holo.Dialog" >


如果将用户在dialog中的选择item传递给host呢？
一般情况下会定义一个interface,host 来实现这个interface，然后再DialogFragment 的子类中调用这个interface就可以callback会host.
如下所示：
public class NoticeDialogFragment extends DialogFragment {


    /* The activity that creates an instance of this dialog fragment must
     * implement this interface in order to receive event callbacks.
     * Each method passes the DialogFragment in case the host needs to query it. */
    public interface NoticeDialogListener {
        public void onDialogPositiveClick(DialogFragment dialog);
        public void onDialogNegativeClick(DialogFragment dialog);
    }


    // Use this instance of the interface to deliver action events
    NoticeDialogListener mListener;


    // Override the Fragment.onAttach() method to instantiate the NoticeDialogListener
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        // Verify that the host activity implements the callback interface
        try {
            // Instantiate the NoticeDialogListener so we can send events to the host
            mListener = (NoticeDialogListener) activity;
        } catch (ClassCastException e) {
            // The activity doesn't implement the interface, throw exception
            throw new ClassCastException(activity.toString()
                    + " must implement NoticeDialogListener");
        }
    }
    ...
}
再来看看host 如何实现这个interface
public class MainActivity extends FragmentActivity
                          implements NoticeDialogFragment.NoticeDialogListener{
    ...


    public void showNoticeDialog() {
        // Create an instance of the dialog fragment and show it
        DialogFragment dialog = new NoticeDialogFragment();
        dialog.show(getSupportFragmentManager(), "NoticeDialogFragment");
    }


    // The dialog fragment receives a reference to this Activity through the
    // Fragment.onAttach() callback, which it uses to call the following methods
    // defined by the NoticeDialogFragment.NoticeDialogListener interface
    @Override
    public void onDialogPositiveClick(DialogFragment dialog) {
        // User touched the dialog's positive button
        ...
    }


    @Override
    public void onDialogNegativeClick(DialogFragment dialog) {
        // User touched the dialog's negative button
        ...
    }
}
这样我们就可以在用户按下确定或者取消按钮是调用mListener，如下所示:
public class NoticeDialogFragment extends DialogFragment {
    ...


    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Build the dialog and set up the button click handlers
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(R.string.dialog_fire_missiles)
               .setPositiveButton(R.string.fire, new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                       // Send the positive button event back to the host activity
                       mListener.onDialogPositiveClick(NoticeDialogFragment.this);
                   }
               })
               .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                       // Send the negative button event back to the host activity
                       mListener.onDialogNegativeClick(NoticeDialogFragment.this);
                   }
               });
        return builder.create();
    }
}
如果你想要一个嵌入式的dialogFragment，需要定义一个dialog ui的layout文件，然后调用onCreateView方法来显示.
下面是个例子.
public class CustomDialogFragment extends DialogFragment {
    /** The system calls this to get the DialogFragment's layout, regardless
        of whether it's being displayed as a dialog or an embedded fragment. */
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        // Inflate the layout to use as dialog or embedded fragment
        return inflater.inflate(R.layout.purchase_items, container, false);
    }


    /** The system calls this only when creating the layout in a dialog. */
    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // The only reason you might override this method when using onCreateView() is
        // to modify any dialog characteristics. For example, the dialog includes a
        // title by default, but your custom layout might not need it. So here you can
        // remove the dialog title, but you must call the superclass to get the Dialog.
        Dialog dialog = super.onCreateDialog(savedInstanceState);
        dialog.requestWindowFeature(Window.FEATURE_NO_TITLE);
        return dialog;
    }
}
调用下面的方法show
public void showDialog() {
    FragmentManager fragmentManager = getSupportFragmentManager();
    CustomDialogFragment newFragment = new CustomDialogFragment();


    if (mIsLargeLayout) {
        // The device is using a large layout, so show the fragment as a dialog
        newFragment.show(fragmentManager, "dialog");
    } else {
        // The device is smaller, so show the fragment fullscreen
        FragmentTransaction transaction = fragmentManager.beginTransaction();
        // For a little polish, specify a transition animation
        transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
        // To make it fullscreen, use the 'content' root view as the container
        // for the fragment, which is always the root view for the activity
        transaction.add(android.R.id.content, newFragment)
                   .addToBackStack(null).commit();
    }
}
可以在xml中定义mIsLargeLayout
<!-- Large screen boolean values -->
<resources>
    <bool name="large_layout">true</bool>
</resources>
然后在onCreate（）方法中获得这个值
boolean mIsLargeLayout;


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


    mIsLargeLayout = getResources().getBoolean(R.bool.large_layout);
}
如果想要在大屏上将Activity 以dialog的方式显示出来，可以用下面主题
<activity android:theme="@android:style/Theme.Holo.DialogWhenLarge" >


可以调用dismiss（）方法来手动让dialog消失.