frament

在第一个界面first frgment中点击按钮show next page将跳转进入第二个界面second fragent,再次单击按钮show next page跳转进入第三个界面first fragment.首先做好三个布局界面的设计，其次再运用java来实现三个界面的跳转。

第一个主要布局代码如下

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"

tools:context="com.example.mpyypm.chacha1.FragmentActivity">


<LinearLayout
android:id="@+id/W"
android:layout_width="match_parent"
android:layout_height="0dp"
android:orientation="vertical"
android:layout_weight="3">

<Button
    android:id="@+id/action0"
    android:layout_width="250dp"
    android:layout_height="wrap_content"
    android:text="SHOW NEXT PAGE"
    android:textSize="25dp"
    android:layout_gravity="center_horizontal"
    android:gravity="center"
    android:onClick="onClick"
    /></LinearLayout>


</LinearLayout>

第二个主要代码：

<LinearLayout
    android:id="@+id/w"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:orientation="vertical"
    android:layout_weight="1">

</LinearLayout>

<LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1">

    <Buttonandroid:id="@+id/action0"
        android:layout_width="250dp"
        android:layout_height="wrap_content"
        android:text="@string/action0"
        android:layout_gravity="center_horizontal"
        android:gravity="center"
        android:onClick="onClick"
        />
</LinearLayout>

第三段代码：

<TextView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/holo_blue_light"
    android:gravity="center"
    android:textSize="25sp"
    android:text="@string/first_fragment" />
 </FrameLayout>

第四段代码：

<TextView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorAccent"
    android:gravity="center"
    android:text="@string/second_fragment"
    android:textSize="25sp" /></FrameLayout>

第五段代码：

public class FragmentActivity extends AppCompatActivity implements View.OnClickListener{
FirstFragment firstFragment;
SecondFragment secondFragment;
private boolean a=true;    
boolean e=false;       
@Override
protected void onCreate(Bundle savedInstanceState)  {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_fragment);

    FragmentManager manager = getFragmentManager();
    FragmentTransaction transaction = manager.beginTransaction();
        firstFragment = new FirstFragment();
        transaction.add(R.id.show,firstFragment);
        transaction.commit();
}

@Override
public void onClick(View view) {
    if(view.getId()==R.id.action0){
        e=true; 
            FragmentManager manager = getFragmentManager();
            FragmentTransaction transaction = manager.beginTransaction();
            if (secondFragment == null){
                secondFragment = new SecondFragment();
                transaction.replace(R.id.show,secondFragment);
                transaction.commit();
                a=false;    
            } else{
                transaction.replace(R.id.show,secondFragment);
                transaction.commit();
                a=false;    
            }
        }else{
            Toast.makeText(this,"This is second fragment",Toast.LENGTH_SHORT).show();
        }
    }
}

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(event.getKeyCode()==KeyEvent.KEYCODE_BACK&&e){
            FragmentManager manager = getFragmentManager();
            FragmentTransaction transaction = manager.beginTransaction();
            a=true;     
            e=false;    
            transaction.replace(R.id.show,firstFragment);
            transaction.commit();
                return  false;
        } else {
        finish();
          }
    return super.onKeyDown(keyCode, event);
}
}