Android 开发教程 DialogFragment

本文介绍如何在Android应用中使用DialogFragment来创建对话框。通过继承DialogFragment类并重写onCreateDialog方法,可以轻松构建带有自定义标题和按钮的对话框,并处理用户交互。

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本章节翻译自《Beginning-Android-4-Application-Development》,如有翻译不当的地方,敬请指出。

原书购买地址http://www.amazon.com/Beginning-Android-4-Application-Development/dp/1118199545/


我们也可以创建另外一种碎片——DialogFragment。顾名思义,DialogFragment就是一个浮动在Activity上面的Fragment。当需要用户的反馈时,DialogFragment就会派上用场。与使用ListFragment类似,需要继承DialogFragment基类。

下面将会展示如何使用DialogFragment。

1. 创建一个工程:DialogFragmentExample。

2. 在包路径下面新建一个类,Fragment1。

  1. public class Fragment1 extends DialogFragment { 
  2.  
  3.     static Fragment1 newInstance(String title) { 
  4.         Fragment1 fragment = new Fragment1(); 
  5.         Bundle args = new Bundle(); 
  6.         args.putString("title", title); 
  7.         fragment.setArguments(args); 
  8.         return fragment; 
  9.     } 
  10.  
  11.     @Override 
  12.     public Dialog onCreateDialog(Bundle savedInstanceState) { 
  13.         String title = getArguments().getString("title"); 
  14.         return new AlertDialog.Builder(getActivity()) 
  15.         .setIcon(R.drawable.ic_launcher) 
  16.         .setTitle(title) 
  17.         .setPositiveButton("OK"
  18.                 new DialogInterface.OnClickListener() { 
  19.             public void onClick(DialogInterface dialog,  
  20.                     int whichButton) { 
  21.                 ((DialogFragmentExampleActivity) 
  22.                         getActivity()).doPositiveClick(); 
  23.             } 
  24.         }) 
  25.         .setNegativeButton("Cancel"
  26.                 new DialogInterface.OnClickListener() { 
  27.             public void onClick(DialogInterface dialog,  
  28.                     int whichButton) { 
  29.                 ((DialogFragmentExampleActivity) 
  30.                         getActivity()).doNegativeClick(); 
  31.             } 
  32.         }).create(); 
  33.     }         
  34.  
public class Fragment1 extends DialogFragment {

	static Fragment1 newInstance(String title) {
		Fragment1 fragment = new Fragment1();
		Bundle args = new Bundle();
		args.putString("title", title);
		fragment.setArguments(args);
		return fragment;
	}

	@Override
	public Dialog onCreateDialog(Bundle savedInstanceState) {
		String title = getArguments().getString("title");
		return new AlertDialog.Builder(getActivity())
		.setIcon(R.drawable.ic_launcher)
		.setTitle(title)
		.setPositiveButton("OK",
				new DialogInterface.OnClickListener() {
			public void onClick(DialogInterface dialog, 
					int whichButton) {
				((DialogFragmentExampleActivity)
						getActivity()).doPositiveClick();
			}
		})
		.setNegativeButton("Cancel",
				new DialogInterface.OnClickListener() {
			public void onClick(DialogInterface dialog, 
					int whichButton) {
				((DialogFragmentExampleActivity)
						getActivity()).doNegativeClick();
			}
		}).create();
	}        

}
3. DialogFragmentExampleActivity.java中的代码。

  1. public class DialogFragmentExampleActivity extends Activity { 
  2.     /** Called when the activity is first created. */ 
  3.     @Override 
  4.     public void onCreate(Bundle savedInstanceState) { 
  5.         super.onCreate(savedInstanceState); 
  6.         setContentView(R.layout.main); 
  7.          
  8.         Fragment1 dialogFragment = Fragment1.newInstance( 
  9.                 "Are you sure you want to do this?"); 
  10.             dialogFragment.show(getFragmentManager(), "dialog");    
  11.     } 
  12.      
  13.     public void doPositiveClick() { 
  14.         //---perform steps when user clicks on OK--- 
  15.         Log.d("DialogFragmentExample", "User clicks on OK"); 
  16.     } 
  17.  
  18.     public void doNegativeClick() { 
  19.         //---perform steps when user clicks on Cancel--- 
  20.         Log.d("DialogFragmentExample", "User clicks on Cancel"); 
  21.     } 
  22.  
public class DialogFragmentExampleActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        Fragment1 dialogFragment = Fragment1.newInstance(
                "Are you sure you want to do this?");
            dialogFragment.show(getFragmentManager(), "dialog");   
    }
    
    public void doPositiveClick() {
        //---perform steps when user clicks on OK---
        Log.d("DialogFragmentExample", "User clicks on OK");
    }

    public void doNegativeClick() {
        //---perform steps when user clicks on Cancel---
        Log.d("DialogFragmentExample", "User clicks on Cancel");
    }

}
4. 按F11在模拟器上调试。会看到一个对话框,点击OK或Cancel按钮会弹出消息。


要创建一个DialogFragment,首先要继承DialogFragment基类:

  1. public class Fragment1 extends DialogFragment{ 
public class Fragment1 extends DialogFragment{
}
在这个例子中,我没创建一个警告对话框,它包含一条警告消息和两个可供点击的按钮。在Fragment1类中,我们定义了一个newInstance()方法:

  1. static Fragment1 newInstance(String title) { 
  2.         Fragment1 fragment = new Fragment1(); 
  3.         Bundle args = new Bundle(); 
  4.         args.putString("title", title); 
  5.         fragment.setArguments(args); 
  6.         return fragment; 
  7.     } 
static Fragment1 newInstance(String title) {
		Fragment1 fragment = new Fragment1();
		Bundle args = new Bundle();
		args.putString("title", title);
		fragment.setArguments(args);
		return fragment;
	}
这个newInstance()方法允许创建一个碎片的实例对象,同时,它也可以接受一个指定的字符串参数,这个参数就是对话框中的消息。title对象被存储在一个Bundle对象中,之后会用到它。

接下来,我们定义了onCreateDialog()方法,这个方法在onCreate()之后,onCreateView()之前被调用:

  1.        @Override 
  2. public Dialog onCreateDialog(Bundle savedInstanceState) { 
  3.     String title = getArguments().getString("title"); 
  4.     return new AlertDialog.Builder(getActivity()) 
  5.     .setIcon(R.drawable.ic_launcher) 
  6.     .setTitle(title) 
  7.     .setPositiveButton("OK"
  8.             new DialogInterface.OnClickListener() { 
  9.         public void onClick(DialogInterface dialog,  
  10.                 int whichButton) { 
  11.             ((DialogFragmentExampleActivity) 
  12.                     getActivity()).doPositiveClick(); 
  13.         } 
  14.     }) 
  15.     .setNegativeButton("Cancel"
  16.             new DialogInterface.OnClickListener() { 
  17.         public void onClick(DialogInterface dialog,  
  18.                 int whichButton) { 
  19.             ((DialogFragmentExampleActivity) 
  20.                     getActivity()).doNegativeClick(); 
  21.         } 
  22.     }).create(); 
  23. }         
        @Override
	public Dialog onCreateDialog(Bundle savedInstanceState) {
		String title = getArguments().getString("title");
		return new AlertDialog.Builder(getActivity())
		.setIcon(R.drawable.ic_launcher)
		.setTitle(title)
		.setPositiveButton("OK",
				new DialogInterface.OnClickListener() {
			public void onClick(DialogInterface dialog, 
					int whichButton) {
				((DialogFragmentExampleActivity)
						getActivity()).doPositiveClick();
			}
		})
		.setNegativeButton("Cancel",
				new DialogInterface.OnClickListener() {
			public void onClick(DialogInterface dialog, 
					int whichButton) {
				((DialogFragmentExampleActivity)
						getActivity()).doNegativeClick();
			}
		}).create();
	}        
然后,我们可以创建两个按钮OK和Cancel。对话框的标题是从Bunddle对象中取出来的。

想要把对话框碎片显示出来,我们创建一个它的实例,然后调用show()方法即可:

  1. Fragment1 dialogFragment = Fragment1.newInstance( 
  2.                 "Are you sure you want to do this?"); 
  3.             dialogFragment.show(getFragmentManager(), "dialog");   
Fragment1 dialogFragment = Fragment1.newInstance(
                "Are you sure you want to do this?");
            dialogFragment.show(getFragmentManager(), "dialog");  
同时,我们需要实现两个回调方法,doPositiveClick()和doNegativeClick(),通过这两个方法去处理用户的输入事件:

  1. public void doPositiveClick() { 
  2.         //---perform steps when user clicks on OK--- 
  3.         Log.d("DialogFragmentExample", "User clicks on OK"); 
  4.     } 
  5.  
  6.     public void doNegativeClick() { 
  7.         //---perform steps when user clicks on Cancel--- 
  8.         Log.d("DialogFragmentExample", "User clicks on Cancel"); 
  9.     } 
public void doPositiveClick() {
        //---perform steps when user clicks on OK---
        Log.d("DialogFragmentExample", "User clicks on OK");
    }

    public void doNegativeClick() {
        //---perform steps when user clicks on Cancel---
        Log.d("DialogFragmentExample", "User clicks on Cancel");
    }

注:在Android 4.0版本以后,官方推荐使用DialogFragment去替换Dialog。大家可以看看Android 4.0的Launcher等源码,这些源码中大量使用了Fragment类。


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