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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; } } }
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。
android (13) Fragment使用下