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标题: Android 使用Fragment界面向下跳转并一级级返回 [打印本页]

作者: jekeyhui99 时间: 2015-11-29 18:23
标题: Android 使用Fragment界面向下跳转并一级级返回
1.首先贴上项目结构图：

2.先添加一个接口文件BackHandledInterface.java,定义一个setSelectedFragment方法用于设置当前加载的Fragment在栈顶，主界面MainActivity须实现此接口，代码如下：

package com.example.testdemo;

public interface BackHandledInterface {

public abstract void setSelectedFragment(BackHandledFragment selectedFragment);
}
3.定义一个抽象类BackHandledFragment继承自Fragment，后面跳转的Fragment界面都要继承自BackHandledFragment。抽象类BackHandledFragment中定义一个返回值为boolean类型的onBackPressed方法，用于处理点击返回按键（物理Back键）时的逻辑，若该方法返回false，表示当前Fragment不消费返回事件，而由Fragment所属的FragmentActivity来处理这个事件。代码如下：

1 package com.example.testdemo;
2
3 import android.os.Bundle;
4 import android.support.v4.app.Fragment;
5
6 public abstract class BackHandledFragment extends Fragment {
7
8    protected BackHandledInterface mBackHandledInterface;
9
10    /**
11    * 所有继承BackHandledFragment的子类都将在这个方法中实现物理Back键按下后的逻辑
12    */
13    protected abstract boolean onBackPressed();
14
15    @Override
16    public void onCreate(Bundle savedInstanceState) {
17       super.onCreate(savedInstanceState);
18       if (!(getActivity() instanceof BackHandledInterface)) {
19          throw new ClassCastException(
20                   "Hosting Activity must implement BackHandledInterface");
21       } else {
22          this.mBackHandledInterface = (BackHandledInterface) getActivity();
23       }
24    }
25
26    @Override
27    public void onStart() {
28       super.onStart();
29       // 告诉FragmentActivity，当前Fragment在栈顶
30       mBackHandledInterface.setSelectedFragment(this);
31    }
32
33 }

4.主界面MainActivity要继承FragmentActivity才能调用getSupportFragmentManager()方法来处理Fragment。MainActivity还需重写onBackPressed方法用来捕捉返回键（Back Key）事件，代码如下：

1 package com.example.testdemo;
2
3 import android.os.Bundle;
4 import android.support.v4.app.FragmentActivity;
5 import android.support.v4.app.FragmentManager;
6 import android.support.v4.app.FragmentTransaction;
7 import android.view.View;
8 import android.view.View.OnClickListener;
9 import android.widget.Button;
10
11 public class MainActivity extends FragmentActivity implements
12       BackHandledInterface {
13    private static MainActivity mInstance;
14    private BackHandledFragment mBackHandedFragment;
15    private Button btnSecond;
16
17    @Override
18    public void onCreate(Bundle savedInstanceState) {
19       super.onCreate(savedInstanceState);
20       setContentView(R.layout.activity_main);
21       btnSecond = (Button) findViewById(R.id.btnSecond);
22       btnSecond.setOnClickListener(new OnClickListener() {
23
24          @Override
25          public void onClick(View v) {
26                FirstFragment first = new FirstFragment();
27                loadFragment(first);
28                btnSecond.setVisibility(View.GONE);
29          }
30       });
31
32    }
33
34    public static MainActivity getInstance() {
35       if (mInstance == null) {
36          mInstance = new MainActivity();
37       }
38       return mInstance;
39    }
40
41    public void loadFragment(BackHandledFragment fragment) {
42       BackHandledFragment second = fragment;
43       FragmentManager fm = getSupportFragmentManager();
44       FragmentTransaction ft = fm.beginTransaction();
45       ft.replace(R.id.firstFragment, second, "other");
46       ft.addToBackStack("tag");
47       ft.commit();
48    }
49
50    @Override
51    public void setSelectedFragment(BackHandledFragment selectedFragment) {
52       this.mBackHandedFragment = selectedFragment;
53    }
54
55    @Override
56    public void onBackPressed() {
57       if (mBackHandedFragment == null || !mBackHandedFragment.onBackPressed()) {
58          if (getSupportFragmentManager().getBackStackEntryCount() == 0) {
59                super.onBackPressed();
60          } else {
61                if (getSupportFragmentManager().getBackStackEntryCount() == 1) {
62                   btnSecond.setVisibility(View.VISIBLE);
63                }
64                getSupportFragmentManager().popBackStack();
65          }
66       }
67    }
68 }

作者: jekeyhui99 时间: 2015-11-29 18:25
5.分别添加两个子级Fragment，FirstFragment.java和SecondFragment.java,代码分别如下：

FirstFragment.java

1 package com.example.testdemo;
2
3 import android.os.Bundle;
4 import android.support.annotation.Nullable;
5 import android.support.v4.app.FragmentManager;
6 import android.support.v4.app.FragmentTransaction;
7 import android.view.LayoutInflater;
8 import android.view.View;
9 import android.view.View.OnClickListener;
10 import android.view.ViewGroup;
11 import android.widget.Button;
12
13 public class FirstFragment extends BackHandledFragment {
14    private View myView;
15    private Button btnSecond;
16
17    @Override
18    public View onCreateView(LayoutInflater inflater,
19          @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
20       myView = inflater.inflate(R.layout.fragment_first, null);
21       initView();
22       return myView;
23    }
24
25    private void initView() {
26       btnSecond = (Button) myView.findViewById(R.id.btnSecond);
27       btnSecond.setOnClickListener(new OnClickListener() {
28
29          @Override
30          public void onClick(View v) {
31                SecondFragment second = new SecondFragment();
32                FragmentManager fm = getFragmentManager();
33                FragmentTransaction ft = fm.beginTransaction();
34                ft.replace(R.id.firstFragment, second);
35                ft.addToBackStack("tag");
36                ft.commit();
37          }
38       });
39    }
40
41    @Override
42    protected boolean onBackPressed() {
43       return false;
44    }
45
46 }

SecondFragment.java

1 package com.example.testdemo;
2
3 import android.os.Bundle;
4 import android.support.annotation.Nullable;
5 import android.view.LayoutInflater;
6 import android.view.View;
7 import android.view.ViewGroup;
8
9 public class SecondFragment extends BackHandledFragment {
10
11    private View mView;
12
13    @Override
14    public View onCreateView(LayoutInflater inflater,
15          @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
16       mView = inflater.inflate(R.layout.fragment_second, null);
17       return mView;
18    }
19
20    @Override
21    protected boolean onBackPressed() {
22       return false;
23    }
24
25 }

6.三个布局文件代码如下：
activity_main.xml

1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
2    xmlns:tools="http://schemas.android.com/tools"
3    android:layout_width="match_parent"
4    android:layout_height="match_parent"
5    android:orientation="vertical" >
6
7    <TextView
8       android:layout_width="wrap_content"
9       android:layout_height="wrap_content"
10       android:layout_centerInParent="true"
11       android:text="FragmentActivity 父界面"
12       android:textSize="26sp" />
13
14    <Button
15       android:id="@+id/btnSecond"
16       android:layout_width="wrap_content"
17       android:layout_height="wrap_content"
18       android:layout_alignParentBottom="true"
19       android:text="跳转到FirstFragment" />
20
21    <FrameLayout
22       android:id="@+id/firstFragment"
23       android:layout_width="match_parent"
24       android:layout_height="match_parent" >
25    </FrameLayout>
26
27 </RelativeLayout>

fragment_first.xml

<?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:background="#e5e5e5"
android:orientation="vertical" >

<TextView
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_centerInParent="true"
      android:text="FirstFragment"
      android:textColor="#000000"
      android:textSize="26sp" />

<Button
      android:id="@+id/btnSecond"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_alignParentBottom="true"
      android:text="打开SecondFragment" />

</RelativeLayout>

fragment_second.xml

1 <?xml version="1.0" encoding="utf-8"?>
2 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
3    android:layout_width="match_parent"
4    android:layout_height="match_parent"
5    android:background="#e5e5e5"
6    android:orientation="vertical" >
7
8    <TextView
9       android:layout_width="wrap_content"
10       android:layout_height="wrap_content"
11       android:layout_centerInParent="true"
12       android:text="SecondFragment"
13       android:textColor="#000000"
14       android:textSize="26sp" />
15
16 </RelativeLayout>

7.最后奉上实例链接：

http://files.cnblogs.com/_ymw/TestDemo

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