详解Android应用中DialogFragment的基本用法

dialogfragment的基本用法
1. 创建dialogfragment

public class dialoga extends dialogfragment implements dialoginterface.onclicklistener {

 @override
 public dialog oncreatedialog(bundle savedinstancestate) {
  alertdialog.builder builder = new alertdialog.builder(getactivity());
  builder.setmessage(r.string.dialoga_title)
    .setpositivebutton(r.string.ok, this)
    .setnegativebutton(r.string.cancel, this);

  return builder.create();
 } 

 @override
 public void onclick(dialoginterface dialog, int id) {
  switch(id) {
   case alertdialog.button_negative:
    toast.maketext(getactivity(), "negative", toast.length_short).show();
    break;
   case alertdialog.button_positive:
    toast.maketext(getactivity(), "positive", toast.length_short).show();
    break;
   default:
    break;
  } 
 } 
}

说明：自定义一个dialogfragment，并重写它的oncreatedialog()方法。
2. 调用该dialogfragment
下面是在fragmentactivity中调用该dialogfragment对话框。

public class dialogtest extends fragmentactivity {

 @override
 public void oncreate(bundle savedinstancestate) {
  super.oncreate(savedinstancestate);
  setcontentview(r.layout.main);

  showdialog();
 }

 private void showdialog() {
  fragmentmanager fm = getsupportfragmentmanager();
  dialoga dialoga = new dialoga();
  dialoga.show(fm, "fragmenta");
 }
}

自定义dialogfragment布局
下面介绍自定义dialogfragment的布局的方法
点击查看：自定义dialogfragment布局的完整代码
1. 设置布局文件

<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical" >

 <textview
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:hint="@string/dialoga_intro" />

 <imageview
  android:id="@+id/image"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:src="@drawable/ic_action_video" />

</linearlayout>

2. 使用布局

public class dialoga extends dialogfragment implements dialoginterface.onclicklistener {

 @override
 public dialog oncreatedialog(bundle savedinstancestate) {
  alertdialog.builder builder = new alertdialog.builder(getactivity());
  layoutinflater inflater = getactivity().getlayoutinflater();
  builder.setview(inflater.inflate(r.layout.dialoga, null))
    .setmessage(r.string.dialoga_title)
    .setpositivebutton(r.string.ok, this)
    .setnegativebutton(r.string.cancel, this);

  return builder.create();
 }

 @override
 public void onclick(dialoginterface dialog, int id) {
  switch(id) {
   case alertdialog.button_negative:
    toast.maketext(getactivity(), "negative", toast.length_short).show();
    break;
   case alertdialog.button_positive:
    toast.maketext(getactivity(), "positive", toast.length_short).show();
    break;
   default:
    break;
  }
 }
}

dialogfragment和activity的交互
下面介绍自定义dialogfragment和activity交互的方法
点击查看：dialogfragment和activity交互的完整代码
1. 定义通信接口
在dialogfragment中定义它们之间的通信接口。

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");
 } 
} 

2. 在dialogfragment中调用该接口

@override
public void onclick(dialoginterface dialog, int id) {
 switch(id) {
  case alertdialog.button_positive:
   //toast.maketext(getactivity(), "negative", toast.length_short).show();
   mlistener.ondialogpositiveclick(dialoga.this);
   break;
  case alertdialog.button_negative:
   //toast.maketext(getactivity(), "positive", toast.length_short).show();
   mlistener.ondialognegativeclick(dialoga.this);
   break;
  default:
   break;
 } 
}

3. 在activity中实现该接口

public class dialogtest extends fragmentactivity 
 implements dialoga.noticedialoglistener {

 ...

 @override
 public void ondialogpositiveclick(dialogfragment dialog) {
  toast.maketext(this, "positive callback", toast.length_short).show();
 }
 @override
 public void ondialognegativeclick(dialogfragment dialog) {
  toast.maketext(this, "negative callback", toast.length_short).show();
 }
}

dialog与dialogfragment的对比
从代码的编写角度看，dialog使用起来要更为简单，但是google则是推荐尽量使用dialogfragment（对于android 3.0以下的版本，可以结合使用support包中提供的dialogfragment以及fragmentactivity）。今天试着用这两种方式来创建对话框，发现dialogfragment果然有一个非常好的特性（在手机配置变化，导致activity需要重新创建时，例如旋屏，基于dialogfragment的对话框将会由fragmentmanager自动重建，然而基于dialog实现的对话框则没有这样的能力）。

下面是两段实例代码：

他们使用的界面都一样：（dialog.xml）

<?xml version="1.0" encoding="utf-8"?>
<linearlayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:orientation="vertical" >
 
 <imageview
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:src="@drawable/ic_launcher" />
 
</linearlayout>

1.基于dialog实现的对话框

public class mainactivity extends activity {
 private button clk;
 private dialog dialog;
 @override
 protected void oncreate(bundle savedinstancestate) {
  super.oncreate(savedinstancestate);
  setcontentview(r.layout.activity_main);
   
  clk = (button) findviewbyid(r.id.clk);
  dialog = new dialog(this);
  dialog.setcontentview(r.layout.dialog);
  clk.setonclicklistener(new onclicklistener() {
    
   @override
   public void onclick(view v) {
    dialog.show();
   }
  });
 }
}

当我们点击按钮时，会弹出对话框（内容为android logo），当我们旋转屏幕后，activity重新创建，整个activity的界面没有问题，而对话框消失了。
除此之外，其实还有一个问题，就是在logcat中会看到异常信息：android..leaked .. window，这是因为在activity结束之前，android要求所有的dialog必须要关闭。我们旋屏后，activity会被重建，而上面的代码逻辑并没有考虑到对话框的状态以及是否已关闭。

于是将上述代码修改为：

public class mainactivity extends activity {
 private button clk;
 private dialog dialog;
 @override
 protected void oncreate(bundle savedinstancestate) {
  super.oncreate(savedinstancestate);
  setcontentview(r.layout.activity_main);
   
  clk = (button) findviewbyid(r.id.clk);
  dialog = new dialog(this);
  dialog.setcontentview(r.layout.dialog);
  clk.setonclicklistener(new onclicklistener() {
    
   @override
   public void onclick(view v) {
    dialog.show();
   }
  });
 
  //用户恢复对话框的状态
  if(savedinstancestate != null && savedinstancestate.getboolean("dialog_show"))
   clk.performclick();
 }
 
 /**
  * 用于保存对话框的状态以便恢复
  */
 @override
 protected void onsaveinstancestate(bundle outstate) {
  super.onsaveinstancestate(outstate);
  if(dialog != null && dialog.isshowing())
   outstate.putboolean("dialog_show", true);
  else
   outstate.putboolean("dialog_show", false);
 }
 
 /**
  * 在activity销毁之前，确保对话框以关闭
  */
 @override
 protected void ondestroy() {
  super.ondestroy();
  if(dialog != null && dialog.isshowing())
   dialog.dismiss();
 }
}

2. 基于dialogfragment的对话框

与上面的对话框使用同样的界面布局，此处仅仅展现一个简单对话框，因此只重写了oncreateview方法

public class mydialogfragment extends dialogfragment {
 @override
 public view oncreateview(layoutinflater inflater, viewgroup container,
   bundle savedinstancestate) {
  view v = inflater.inflate(r.layout.dialog, container, false);
  return v;
 }
}

public class mainactivity extends fragmentactivity {
 private button clk;
 @override
 protected void oncreate(bundle savedinstancestate) {
  super.oncreate(savedinstancestate);
  setcontentview(r.layout.activity_main);
   
  clk = (button) findviewbyid(r.id.clk);
  clk.setonclicklistener(new onclicklistener() {
    
   @override
   public void onclick(view v) {
    mydialogfragment mdf = new mydialogfragment();
    fragmenttransaction ft = getsupportfragmentmanager().begintransaction();
    ft.settransition(fragmenttransaction.transit_fragment_fade);
    mdf.show(ft, "df");
   }
  });
 }
}

这两段代码可以实现第一种方式的同样功能，此处我们并没有去关心对话框的重建，以及activity销毁前对话框是否已关闭，这一切都是由fragmentmanager来管理。
其实dialogfragment还拥有fragment的优点，即可以在一个activity内部实现回退（因为fragmentmanager会管理一个回退栈）