Android 开发指南 翻译 User Interface -- Dialogs

User Interface -- Dialogs

A dialog is usually a small window that appears in front of the current Activity. The underlying Activity loses focus and the dialog accepts all user interaction. Dialogs are normally used for notifications that should interupt the user and to perform short tasks that directly relate to the application in progress (such as a progress bar or a login prompt).

对话框是出现在Activity前面的小窗口。其下面的Activity失去焦点，对话框接收所有用户操作。对话框通常用来通知用户，要去执行一个任务。

The Dialog class is the base class for creating dialogs. However, you typically should not instantiate a Dialog directly. Instead, you should use one of the following subclasses:

Dialog是对话框的基础类，然而，你通常不需要实例化Dialog，而是使用下面的子类：

AlertDialog

A dialog that can manage zero, one, two, or three buttons, and/or a list of selectable items that can include checkboxes or radio buttons. The AlertDialog is capable of constructing most dialog user interfaces and is the suggested dialog type. SeeCreating an AlertDialog below.

    AlertDialog可以有零个、一个、两个或三个按钮，一组包括复选框、单选框的可选项。AlertDialg是最常用的用户接口对话框。

ProgressDialog

A dialog that displays a progress wheel or progress bar. Because it's an extension of the AlertDialog, it also supports buttons. See Creating a ProgressDialog below.

    ProgressDialog显示一个旋转图标或进度条。因为扩展自AlertDialog，所以也支持按钮。

DatePickerDialog

A dialog that allows the user to select a date. See the Hello DatePicker tutorial.

    允许用户选择日期的对话框。

TimePickerDialog

A dialog that allows the user to select a time. See the Hello TimePicker tutorial.

    允许用户选择时间的对话框。

If you would like to customize your own dialog, you can extend the base Dialog object or any of the subclasses listed above and define a new layout. See the section on Creating a Custom Dialog below.

如果想自定义对话框，应该扩展Dialog类或任何子类，定义一个新的布局。

Dialog Design

For design guidelines, read Android Design's Dialogs guide.

Showing a Dialog 显示对话框

A dialog is always created and displayed as a part of an Activity. You should normally create dialogs from within your Activity's onCreateDialog(int) callback method. When you use this callback, the Android system automatically manages the state of each dialog and hooks them to the Activity, effectively making it the "owner" of each dialog. As such, each dialog inherits certain properties from the Activity. For example, when a dialog is open, the Menu key reveals the options menu defined for the Activity and the volume keys modify the audio stream used by the Activity.

对话框通常作为Activity的一部分创建和展示。你通常应该从Activity的onCreateDialog(int)回调方法中创建对话框。使用这个回调方法，Android系统自动管理每个对话框的状态，且连接到Activity,使Activity作为对话框的拥有者。这样，每个对话框可以从Activity继承特定属性。例如：对话框打开时，Menu键会调出Activity定义的可选菜单项，音量键可以修改Activity的音量。

Note: If you decide to create a dialog outside of the onCreateDialog() method, it will not be attached to an Activity. You can, however, attach it to an Activity withsetOwnerActivity(Activity).

注意：如果你决定在onCreateDialog()方法之外创建对话框，对话框不会连接到Acitivty。你可以使用setOwnerActivity(Activity)来连接Activity.

When you want to show a dialog, call showDialog(int) and pass it an integer that uniquely identifies the dialog that you want to display.

需要显示对话框时，调用showDialog(int),传递一个对话框的唯一标识整数。

When a dialog is requested for the first time, Android calls onCreateDialog(int) from your Activity, which is where you should instantiate the Dialog. This callback method is passed the same ID that you passed to showDialog(int). After you create the Dialog, return the object at the end of the method.

当对话框第一个请求时，Android调用onCreateDialog(int)来实例化一个对话框。这个回调方法传递一个和showDialog(int)相同的ID。创建对话框后，返回该对话框对象。

Before the dialog is displayed, Android also calls the optional callback method onPrepareDialog(int, Dialog). Define this method if you want to change any properties of the dialog each time it is opened. This method is called every time a dialog is opened, whereas onCreateDialog(int) is only called the very first time a dialog is opened. If you don't defineonPrepareDialog(), then the dialog will remain the same as it was the previous time it was opened. This method is also passed the dialog's ID, along with the Dialog object you created inonCreateDialog().

在显示对话框之前，Android调用onPrepareDialog(int,Dialog)。如果你想在每次打开对话框时，改变对话框的任何属相，可以定义该方法。对话框每次打开都调用该方法，然而onCreateDialog(int)只是第一次打开时调用。如果不定义onPrepareDialog(),对话框总是和第一次打开时一样。这个方法也传入同样的对话框标识ID。

The best way to define the onCreateDialog(int) and onPrepareDialog(int, Dialog) callback methods is with a switch statement that checks the id parameter that's passed into the method. Each case should check for a unique dialog ID and then create and define the respective Dialog. For example, imagine a game that uses two different dialogs: one to indicate that the game has paused and another to indicate that the game is over. First, define an integer ID for each dialog:

static final int DIALOG_PAUSED_ID = 0;
static final int DIALOG_GAMEOVER_ID = 1;

Then, define the onCreateDialog(int) callback with a switch case for each ID:

protected Dialog onCreateDialog(int id) {
    Dialog dialog;
    switch(id) {
    case DIALOG_PAUSED_ID:
        // do the work to define the pause Dialog
        break;
    case DIALOG_GAMEOVER_ID:
        // do the work to define the game over Dialog
        break;
    default:
        dialog = null;
    }
    return dialog;
}

Note: In this example, there's no code inside the case statements because the procedure for defining your Dialog is outside the scope of this section. See the section below aboutCreating an AlertDialog, offers code suitable for this example.

When it's time to show one of the dialogs, call showDialog(int) with the ID of a dialog:

showDialog(DIALOG_PAUSED_ID);

Dismissing a Dialog 清除对话框

When you're ready to close your dialog, you can dismiss it by calling dismiss() on the Dialog object. If necessary, you can also call dismissDialog(int) from the Activity, which effectively calls dismiss() on the Dialog for you.

当你准备关闭对话框，你可以调用对话框的dismiss()方法。也可以调用Activity的dismissDialog(int)，它会调用对话框的dismiss()方法。

If you are using onCreateDialog(int) to manage the state of your dialogs (as discussed in the previous section), then every time your dialog is dismissed, the state of the Dialog object is retained by the Activity. If you decide that you will no longer need this object or it's important that the state is cleared, then you should call removeDialog(int). This will remove any internal references to the object and if the dialog is showing, it will dismiss it.

如果使用onCreateDialog(int)管理对话框的状态，每次对话框dismiss，对话框的状态会被Activity保留。如果不再需要这个对话框对象或清除对话框状态是很重要的，那么你可以调用removeDialog(int).它将清除对该对象的引用，如果对话框正在显示，也将dismiss对话框。

Using dismiss listeners 使用dismiss监听器

If you'd like your application to perform some procedures the moment that a dialog is dismissed, then you should attach an on-dismiss listener to your Dialog.

如果让应用在对话框消失时，执行一些过程，需要给Dialog加载on-dismiss监听。

First define the DialogInterface.OnDismissListener interface. This interface has just one method, onDismiss(DialogInterface), which will be called when the dialog is dismissed. Then simply pass your OnDismissListener implementation to setOnDismissListener().

首先定义DialogInterface.OnDismissListener接口，该接口只有一个方法onDismiss(DialogInterface),在对话框消失时调用。然后通过setOnDismissListener()加载你的实现。

However, note that dialogs can also be "cancelled." This is a special case that indicates the dialog was explicitly cancelled by the user. This will occur if the user presses the "back" button to close the dialog, or if the dialog explicitly calls cancel() (perhaps from a "Cancel" button in the dialog). When a dialog is cancelled, the OnDismissListener will still be notified, but if you'd like to be informed that the dialog was explicitly cancelled (and not dismissed normally), then you should register an DialogInterface.OnCancelListener with setOnCancelListener().

然而，对话框可以被取消。这是对话框被用户明确地取消的一种情况。用户按“back”键关闭对话框或对话框调用cancel()方法。当对话框被取消，onDismissListener会被通知，如果cancel是被通知，可以用setOnCancelListener注册DialogInterface.OnCancelListener.

Creating an AlertDialog 创建AlertDialog

An AlertDialog is an extension of the Dialog class. It is capable of constructing most dialog user interfaces and is the suggested dialog type. You should use it for dialogs that use any of the following features:

AlertDialog继承了Dialog类，它有能力构造大多数用户接口对话框。可以使用如下属性：

• A title 标题
• A text message 文本信息
• One, two, or three buttons 1,2,3个按钮
• A list of selectable items (with optional checkboxes or radio buttons)可选项列表

To create an AlertDialog, use the AlertDialog.Builder subclass. Get a Builder with AlertDialog.Builder(Context) and then use the class's public methods to define all of the AlertDialog properties. After you're done with the Builder, retrieve the AlertDialog object with create().

创建一个AlertDialog,可以使用AlertDialog.Builder子类。通过AlertDialog.Bulder(Context)获得一个Builder，然后使用该类的公共犯非法来定义AlertDialog的属性。定义好后，使用Builder.create()获得AlertDialog。

The following topics show how to define various properties of the AlertDialog using the AlertDialog.Builder class. If you use any of the following sample code inside your onCreateDialog()callback method, you can return the resulting Dialog object to display the dialog.

下列各节显示了如何使用AlertDialog.Buider类定义AlertDialog的属性。如果在onCreateDialog()中使用下面的代码，你可以返回结果Dialog对象来显示。

Adding buttons 添加按钮

To create an AlertDialog with side-by-side buttons like the one shown in the screenshot to the right, use the set...Button() methods:

使用set...Button()方法：

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setMessage("Are you sure you want to exit?")
       .setCancelable(false)
       .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                MyActivity.this.finish();
           }
       })
       .setNegativeButton("No", new DialogInterface.OnClickListener() {
           public void onClick(DialogInterface dialog, int id) {
                dialog.cancel();
           }
       });
AlertDialog alert = builder.create();

First, add a message for the dialog with setMessage(CharSequence). Then, begin method-chaining and set the dialog to be not cancelable (so the user cannot close the dialog with the back button) with setCancelable(boolean). For each button, use one of the set...Button() methods, such as setPositiveButton(), that accepts the name for the button and aDialogInterface.OnClickListener that defines the action to take when the user selects the button.

首先，使用setMessage(CharSequence)增加信息。然后，使用方法链setCancelable(boolean)设置对话框不可取消，使用set...Button()方法，如setPositiveButton()接收按钮的名字和DialogInterface.OnClickListener方法。

Note: You can only add one of each button type to the AlertDialog. That is, you cannot have more than one "positive" button. This limits the number of possible buttons to three: positive, neutral, and negative. These names are technically irrelevant to the actual functionality of your buttons, but should help you keep track of which one does what.

注意：每种按钮只能在AlertDialog中添加一个。就是说，你不能有多于一个的"positive"按钮。有三种可能的按钮：positive(正),neutral(中立),negative(负)。这些名字和实际功能是不相干的。

Adding a list 添加列表

To create an AlertDialog with a list of selectable items like the one shown to the right, use the setItems() method:

使用setItems()方法产生可选择的列表。

final CharSequence[] items = {"Red", "Green", "Blue"};

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Pick a color");
builder.setItems(items, new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int item) {
        Toast.makeText(getApplicationContext(), items[item], Toast.LENGTH_SHORT).show();
    }
});
AlertDialog alert = builder.create();

First, add a title to the dialog with setTitle(CharSequence). Then, add a list of selectable items with setItems(), which accepts the array of items to display and aDialogInterface.OnClickListener that defines the action to take when the user selects an item.

Adding checkboxes and radio buttons 添加多选或单选按钮

To create a list of multiple-choice items (checkboxes) or single-choice items (radio buttons) inside the dialog, use the setMultiChoiceItems() andsetSingleChoiceItems() methods, respectively. If you create one of these selectable lists in the onCreateDialog() callback method, Android manages the state of the list for you. As long as the Activity is active, the dialog remembers the items that were previously selected, but when the user exits the Activity, the selection is lost.

Note: To save the selection when the user leaves or pauses the Activity, you must properly save and restore the setting throughout the activity lifecycle. To permanently save the selections, even when the Activity process is completely shutdown, you need to save the settings with one of theData Storage techniques.

To create an AlertDialog with a list of single-choice items like the one shown to the right, use the same code from the previous example, but replace thesetItems() method with setSingleChoiceItems():

final CharSequence[] items = {"Red", "Green", "Blue"};

AlertDialog.Builder builder = new AlertDialog.Builder(this);
builder.setTitle("Pick a color");
builder.setSingleChoiceItems(items, -1, new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int item) {
        Toast.makeText(getApplicationContext(), items[item], Toast.LENGTH_SHORT).show();
    }
});
AlertDialog alert = builder.create();

The second parameter in the setSingleChoiceItems() method is an integer value for the checkedItem, which indicates the zero-based list position of the default selected item. Use "-1" to indicate that no item should be selected by default.

Creating a ProgressDialog 创建进度对话框

A ProgressDialog is an extension of the AlertDialog class that can display a progress animation in the form of a spinning wheel, for a task with progress that's undefined, or a progress bar, for a task that has a defined progression. The dialog can also provide buttons, such as one to cancel a download.

Opening a progress dialog can be as simple as calling ProgressDialog.show(). For example, the progress dialog shown to the right can be easily achieved without managing the dialog through the onCreateDialog(int) callback, as shown here:

ProgressDialog dialog = ProgressDialog.show(MyActivity.this, "", 
                        "Loading. Please wait...", true);

The first parameter is the application Context, the second is a title for the dialog (left empty), the third is the message, and the last parameter is whether the progress is indeterminate (this is only relevant when creating a progress bar, which is discussed in the next section).

The default style of a progress dialog is the spinning wheel. If you want to create a progress bar that shows the loading progress with granularity, some more code is required, as discussed in the next section.

Showing a progress bar

To show the progression with an animated progress bar:

1. Initialize the ProgressDialog with the class constructor, ProgressDialog(Context).
2. Set the progress style to "STYLE_HORIZONTAL" with setProgressStyle(int) and set any other properties, such as the message.
3. When you're ready to show the dialog, call show() or return the ProgressDialog from the onCreateDialog(int) callback.
4. You can increment the amount of progress displayed in the bar by calling either setProgress(int) with a value for the total percentage completed so far or incrementProgressBy(int) with an incremental value to add to the total percentage completed so far.

For example, your setup might look like this:

ProgressDialog progressDialog;
progressDialog = new ProgressDialog(mContext);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Loading...");
progressDialog.setCancelable(false);

The setup is simple. Most of the code needed to create a progress dialog is actually involved in the process that updates it. You might find that it's necessary to create a second thread in your application for this work and then report the progress back to the Activity's UI thread with a Handler object. If you're not familiar with using additional threads with a Handler, see the example Activity below that uses a second thread to increment a progress dialog managed by the Activity.

 Example ProgressDialog with a second thread

Creating a Custom Dialog 创建客户化对话框

If you want a customized design for a dialog, you can create your own layout for the dialog window with layout and widget elements. After you've defined your layout, pass the root View object or layout resource ID to setContentView(View).

如果你想客户化对话框，你可以创建你自己的layout和控件。然后通过setContentView(View)传递根view或layout资源ID。

For example, to create the dialog shown to the right:

1. Create an XML layout saved as custom_dialog.xml:

   <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
                 android:id="@+id/layout_root"
                 android:orientation="horizontal"
                 android:layout_width="fill_parent"
                 android:layout_height="fill_parent"
                 android:padding="10dp"
                 >
       <ImageView android:id="@+id/image"
                  android:layout_width="wrap_content"
                  android:layout_height="fill_parent"
                  android:layout_marginRight="10dp"
                  />
       <TextView android:id="@+id/text"
                 android:layout_width="wrap_content"
                 android:layout_height="fill_parent"
                 android:textColor="#FFF"
                 />
   </LinearLayout>

   This XML defines an ImageView and a TextView inside a LinearLayout.

2. Set the above layout as the dialog's content view and define the content for the ImageView and TextView elements:

   Context mContext = getApplicationContext();
   Dialog dialog = new Dialog(mContext);
   
   dialog.setContentView(R.layout.custom_dialog);
   dialog.setTitle("Custom Dialog");
   
   TextView text = (TextView) dialog.findViewById(R.id.text);
   text.setText("Hello, this is a custom dialog!");
   ImageView image = (ImageView) dialog.findViewById(R.id.image);
   image.setImageResource(R.drawable.android);

   After you instantiate the Dialog, set your custom layout as the dialog's content view with setContentView(int), passing it the layout resource ID. Now that the Dialog has a defined layout, you can capture View objects from the layout with findViewById(int) and modify their content.

   
   

3. That's it. You can now show the dialog as described in Showing A Dialog.

A dialog made with the base Dialog class must have a title. If you don't call setTitle(), then the space used for the title remains empty, but still visible. If you don't want a title at all, then you should create your custom dialog using the AlertDialog class. However, because an AlertDialog is created easiest with the AlertDialog.Builder class, you do not have access to the setContentView(int) method used above. Instead, you must use setView(View). This method accepts a View object, so you need to inflate the layout's root View object from XML.

一个继承自Dialog的对话框必须有一个标题。如果你不调用setTitle(),标题为空，但仍然可见。如果根本不想显示标题，你需要使用AlertDialog创建自己的客户化对话框.然而，因为AlertDialog可以使用AlertDialgo.Builder方便的建立，没有setContentView(int)方法。你必须使用setView(View)来代替。这个方法接收View对象，所以你需要从xml构造根view。

To inflate the XML layout, retrieve the LayoutInflater with getLayoutInflater() (or getSystemService()), and then call inflate(int, ViewGroup), where the first parameter is the layout resource ID and the second is the ID of the root View. At this point, you can use the inflated layout to find View objects in the layout and define the content for the ImageView and TextView elements. Then instantiate the AlertDialog.Builder and set the inflated layout for the dialog with setView(View).

构造XML布局，通过getLayoutInflater()获取LayoutInflater,然后调用inflate(int,ViewGroup),第一个参数是布局资源ID，第二个参数是根View的ID。你可以查找View对象，来定义ImageView和TextView的内容。然后实例化AlertDialog.Builder对象，使用setView(View)指定infalted的视图。

Here's an example, creating a custom layout in an AlertDialog:

AlertDialog.Builder builder;
AlertDialog alertDialog;

Context mContext = getApplicationContext();
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(LAYOUT_INFLATER_SERVICE);
View layout = inflater.inflate(R.layout.custom_dialog,
                               (ViewGroup) findViewById(R.id.layout_root));

TextView text = (TextView) layout.findViewById(R.id.text);
text.setText("Hello, this is a custom dialog!");
ImageView image = (ImageView) layout.findViewById(R.id.image);
image.setImageResource(R.drawable.android);

builder = new AlertDialog.Builder(mContext);
builder.setView(layout);
alertDialog = builder.create();

Using an AlertDialog for your custom layout lets you take advantage of built-in AlertDialog features like managed buttons, selectable lists, a title, an icon and so on.

使用AlertDialog来客户化对话框，可以利用AlertDialog的内建特性，如：按钮、可选的列表、标题和图标等。

For more information, refer to the reference documentation for the Dialog and AlertDialog.Builder classes.