android （13） Fragment使用下

一.Fragment使用：

    要在你的activity中管理Fragment，须要使用FragmentManager，能够通过getFragmentManager()，这里注意要是在v4包要用getSupportFragmentManager()方法。

FragmentManager能够开一个事物调用beginTransaction()方法返回FragmentTransaction对象，这是我们能够用FragmentTransaction去运行删除添加Fragment的一些操作：

(1).add():往activity加入一个Fragment。

(2).remove():从Activity移除一个Fragment，当这个Fragment没有加入进回退栈，则会被销毁。

当加入进入回退栈之后则会销毁视图层，在显示这个Fragment则会调用onDestoryView和onCreateView。

(3).replace():使用还有一个Fragment替换当前的Fragment，也就是remove操作和add合体运行。

(4).hide():隐藏当前的Fragment，不过设为不可见，并不会销毁。

(5).show():显示之前隐藏的Fragment。

(6).detach():会将view从UI中移除,和remove()不同,此时fragment的状态依旧由FragmentManager维护。

(7).attach():重建view视图。附加到UI上并显示。

(8).addToBackStack():加入Fragment事务到回退栈中。

传null表示当前Fragment。

(9).commit():提交事务。

注意当以使用了add加入Fragment之后，你不过想隐藏Fragment，并且保持当前Fragment输入的数据，你只须要用hide(),假设你不想用户在看到数据，直接使用replace()比使用add()在remove()方便的多。

二.怎样使用回退栈保持数据：

实现效果，当进入第一个Fragment后点击改变文字button，会把显示在屏幕中央的TextView内容改变，然后点击进入第二个Fragment，在点击返回button，屏幕中央的TextView内容会还原成未改变前的，这就是说明了退回栈把Fragment的视图销毁了，可是实例并没有销毁。假设你想要不把数据也销毁，则就像上面说的使用hide()和show().

图片就不上传了。大家但是自行測试源代码（要源代码留下邮箱，这个是在上篇文章基础上改动的）：

主Activity：

public class MainActivity extends Activity  {
	RelativeLayout r1;
	RelativeLayout r2;
	RelativeLayout r3;
	RelativeLayout view = null;

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

		r1 = (RelativeLayout) findViewById(R.id.layout1);
		r2 = (RelativeLayout) findViewById(R.id.layout2);
		r3 = (RelativeLayout) findViewById(R.id.layout3);

		setDefaultFragment();
	}
	private void setDefaultFragment() {
		FragmentManager fm = getFragmentManager();
		FragmentTransaction transaction = fm.beginTransaction();
		MyFragment my = new MyFragment();
		transaction.add(R.id.frame_layout1, my,"ONE");
		transaction.addToBackStack(null);
		transaction.commit();
	}
	
	
}

Fragment1：

public class MyFragment extends Fragment implements OnClickListener {

	private Button button1;
	private Button button2;
	private TextView textView1;

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		System.out.println("onCreateView");
		View view = inflater.inflate(R.layout.fragment_1, container, false);
		button1 = (Button) view.findViewById(R.id.button1);
		button1.setOnClickListener(this);
		button2 = (Button) view.findViewById(R.id.button2);
		button2.setOnClickListener(this);
		textView1 = (TextView) view.findViewById(R.id.textView1);
		return view;
	}
	
	@Override
	public void onClick(View arg0) {
		switch (arg0.getId()) {
		case R.id.button1:
			textView1.append("哈");
			break;
		case R.id.button2:
			MyFragment2 f2 = new MyFragment2();
			FragmentManager fm = getFragmentManager();
			FragmentTransaction tx = fm.beginTransaction();
			tx.replace(R.id.frame_layout1, f2, "TWO");
			tx.addToBackStack(null);
			tx.commit();
			break;
		}
	}

}

Fragment2：

public class MyFragment2 extends Fragment implements OnClickListener {
	private Button button1;
	private Button button2;
	private TextView textView1;

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		System.out.println("onCreateView");
		View view = inflater.inflate(R.layout.fragment_2, container, false);
		button1 = (Button) view.findViewById(R.id.button11);
		button1.setOnClickListener(this);
		button2 = (Button) view.findViewById(R.id.button21);
		button2.setOnClickListener(this);
		textView1 = (TextView) view.findViewById(R.id.textView2);
		return view;
	}
	
	@Override
	public void onClick(View arg0) {
		switch (arg0.getId()) {
		case R.id.button11:
			textView1.append("哈");
			break;
		case R.id.button21:
			MyFragment3 f3 = new MyFragment3();
			FragmentManager fm = getFragmentManager();
			FragmentTransaction tx = fm.beginTransaction();
			tx.hide(this);
			tx.add(R.id.frame_layout1, f3, "THREE");
	// tx.replace(R.id.id_content, fThree, "THREE");
			tx.addToBackStack(null);
			tx.commit();
			break;
		}
	}
	
}

Fragment1布局：

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

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:text="第一个页面" />

       <Button
        android:id="@+id/button1"
        android:layout_width="fill_parent"
        android:layout_height="40dp"
        android:text="改变文字" />
    
    <Button
        android:id="@+id/button2"
        android:layout_width="fill_parent"
        android:layout_height="40dp"
        android:layout_below="@id/button1"
        android:text="跳转第二个界面" />

  

</RelativeLayout>

Fragment3：

public class MyFragment3 extends Fragment{
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
    		Bundle savedInstanceState) {
    	return inflater.inflate(R.layout.fragment_3, container, false);
    }
}

这样就ok了。

三.Activity与Fragment之间的回调：

由于要考虑Fragment的反复使用，所以必须减少Fragment与Activity的耦合，并且Fragment更不应该直接操作别的Fragment，毕竟Fragment操作应该由它的管理者Activity来决定。

就用上边的样例，第一种回调：

public class MyFragment extends Fragment implements OnClickListener {

	private Button button1;
	private Button button2;
	private TextView textView1;

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		System.out.println("onCreateView");
		View view = inflater.inflate(R.layout.fragment_1, container, false);
		button1 = (Button) view.findViewById(R.id.button1);
		button1.setOnClickListener(this);
		button2 = (Button) view.findViewById(R.id.button2);
		button2.setOnClickListener(this);
		textView1 = (TextView) view.findViewById(R.id.textView1);
		return view;
	}
	
	public interface MyFragmentOneClick{
		void onMyOneBtnClick();  
	}
	
	@Override
	public void onClick(View arg0) {
		switch (arg0.getId()) {
		case R.id.button1:
			textView1.append("哈");
			break;
		case R.id.button2:
			//第一种回调方式
			if (getActivity() instanceof MyFragmentOneClick)  
	        {  
	            ((MyFragmentOneClick) getActivity()).onMyOneBtnClick();  
	        }  
			break;
		}
	}

}

另外一种回调：

public class MyFragment2 extends Fragment implements OnClickListener {
	private Button button1;
	private Button button2;
	private TextView textView1;
	private MyFragmentTwoClick myFragmentTwoClick ;
	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		System.out.println("onCreateView");
		View view = inflater.inflate(R.layout.fragment_2, container, false);
		button1 = (Button) view.findViewById(R.id.button11);
		button1.setOnClickListener(this);
		button2 = (Button) view.findViewById(R.id.button21);
		button2.setOnClickListener(this);
		textView1 = (TextView) view.findViewById(R.id.textView2);
		return view;
	}
	
	public interface MyFragmentTwoClick{
		void onMyTwoBtnClick();  
	}
	
	//另外一种回调方式。设置回调接口  
    public void setMyTwoBtnClickListener(MyFragmentTwoClick myFragmentTwoClick)  
    {  
        this.myFragmentTwoClick = myFragmentTwoClick;  
    }  
	@Override
	public void onClick(View arg0) {
		switch (arg0.getId()) {
		case R.id.button11:
			textView1.append("哈");
			break;
		case R.id.button21:
			if(myFragmentTwoClick != null)  
	        {  
				myFragmentTwoClick.onMyTwoBtnClick();  
	        }  
			break;
		}
	}
	
}

主Activity实现：

public class MainActivity extends Activity implements MyFragmentOneClick,MyFragmentTwoClick {
	RelativeLayout r1;
	RelativeLayout r2;
	RelativeLayout r3;
	RelativeLayout view = null;
	MyFragment f1; 
	MyFragment2 f2 ;
	MyFragment3 f3; 
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.bottom_layout);

		r1 = (RelativeLayout) findViewById(R.id.layout1);
		r2 = (RelativeLayout) findViewById(R.id.layout2);
		r3 = (RelativeLayout) findViewById(R.id.layout3);

		setDefaultFragment();
	}
	private void setDefaultFragment() {
		FragmentManager fm = getFragmentManager();
		FragmentTransaction transaction = fm.beginTransaction();
		f1 = new MyFragment();
		transaction.add(R.id.frame_layout1, f1,"ONE");
		transaction.addToBackStack(null);
		transaction.commit();
	}
	

	@Override
	public void onMyOneBtnClick() {

		if (f2 == null)  
        {  
			f2 = new MyFragment2();  
			f2.setMyTwoBtnClickListener(this);  
        }  
		FragmentManager fm = getFragmentManager();
		FragmentTransaction tx = fm.beginTransaction();
		tx.replace(R.id.frame_layout1, f2, "TWO");
		tx.addToBackStack(null);
		tx.commit();
	}
	@Override
	public void onMyTwoBtnClick() {
		if (f3 == null)  
        {  
			f3 = new MyFragment3();  
  
        }  
		FragmentManager fm = getFragmentManager();
		FragmentTransaction tx = fm.beginTransaction();
		tx.hide(f2);
		tx.add(R.id.frame_layout1, f3, "THREE");
		tx.addToBackStack(null);
		tx.commit();		
	}
	
}

这样也实现了上述的功能。