简介:
为什么要用Fragment?使用Fragment可以在一个Activity中实现不同的界面。Fragment与Fragment之间的动画切换,远比Activity与Activity之间的动画切换变化方式多。很多时候,我们通过使用一个Activity,切换多个Fragment。本次博客,主要列举一下Fragment与它的Activity之间进行数据交换的方式。
1.Fragment中通过getActivity()然后进行强制转化,调用Activity中的公有方法
((XXXXActivity)getActivity()).fun();
2.Activity在切换Fragment的时候,通过setArguments向Fragment传递参数,Fragment通过getArguments();获得从activity中传递过来的值
3.Activity实现一个接口,Fragment在onAttach方法中,将该Activity转化为该接口,在需要调用的时候回调。
注意:本Demo是通过FragmentManager来管理Fragment的,通过FragmentManager管理,我们创建Fragment和销毁Fragment的时候,可以通过栈的方式:
a.FragmentTransaction的add方法,添加一个Fragment
b.FragmentTransaction的popBackStack()弹出该Fragment
演示实例:
fragment1.xml
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
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xmlns:tools="http://schemas.android.com/tools"
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android:layout_width="match_parent"
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android:layout_height="match_parent"
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android:background="#FFFFFFFF"
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android:paddingBottom="@dimen/activity_vertical_margin"
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android:paddingLeft="@dimen/activity_horizontal_margin"
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android:paddingRight="@dimen/activity_horizontal_margin"
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android:paddingTop="@dimen/activity_vertical_margin"
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tools:context="com.example.testfragment.MainActivity$PlaceholderFragment" >
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<TextView
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android:id="@+id/tv"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:layout_alignParentTop="true"
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android:text="fragment1" />
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<Button
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android:id="@+id/btn"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:layout_below="@id/tv"
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android:text="跳转到Fragment2" />
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</RelativeLayout>
MyFragment1.java
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package com.example.testfragment;
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import android.app.Activity;
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import android.os.Bundle;
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import android.support.v4.app.Fragment;
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import android.view.LayoutInflater;
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import android.view.View;
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import android.view.View.OnClickListener;
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import android.view.ViewGroup;
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import android.widget.Button;
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public class MyFragment1 extends Fragment {
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FragmentCallBack fragmentCallBack = null;
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Button btn;
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@Override
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public View onCreateView(LayoutInflater inflater, ViewGroup container,
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Bundle savedInstanceState) {
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View rootView = inflater.inflate(R.layout.fragment1, container,
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false);
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btn = (Button)rootView.findViewById(R.id.btn);
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btn.setOnClickListener(new OnClickListener() {
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@Override
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public void onClick(View v) {
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fragmentCallBack.callbackFun1(null);
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}
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});
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return rootView;
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}
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@Override
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public void onAttach(Activity activity) {
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super.onAttach(activity);
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fragmentCallBack = (MainActivity)activity;
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}
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}
fragment2.xml
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
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xmlns:tools="http://schemas.android.com/tools"
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android:layout_width="match_parent"
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android:layout_height="match_parent"
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android:background="#FFFFFFFF"
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android:paddingBottom="@dimen/activity_vertical_margin"
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android:paddingLeft="@dimen/activity_horizontal_margin"
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android:paddingRight="@dimen/activity_horizontal_margin"
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android:paddingTop="@dimen/activity_vertical_margin"
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tools:context="com.example.testfragment.MainActivity$PlaceholderFragment" >
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<TextView
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android:id="@+id/tv"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:layout_alignParentTop="true"
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android:text="fragment2" />
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<Button
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android:id="@+id/btn1"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:layout_below="@id/tv"
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android:text="直接调用Activity" />
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<Button
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android:id="@+id/btn2"
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android:layout_width="wrap_content"
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android:layout_height="wrap_content"
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android:layout_below="@id/btn1"
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android:text="回调Activity" />
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</RelativeLayout>
MyFragment2.java
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package com.example.testfragment;
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import android.app.Activity;
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import android.os.Bundle;
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import android.support.v4.app.Fragment;
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import android.view.LayoutInflater;
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import android.view.View;
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import android.view.View.OnClickListener;
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import android.view.ViewGroup;
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import android.widget.Button;
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import android.widget.Toast;
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public class MyFragment2 extends Fragment {
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FragmentCallBack fragmentCallBack = null;
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Button btn1;
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Button btn2;
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@Override
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public View onCreateView(LayoutInflater inflater, ViewGroup container,
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Bundle savedInstanceState) {
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View rootView = inflater.inflate(R.layout.fragment2, container,
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false);
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Bundle data = getArguments();
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Toast.makeText(getActivity(), data.getString("TEXT"), Toast.LENGTH_SHORT).show();
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btn1 = (Button)rootView.findViewById(R.id.btn1);
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btn1.setOnClickListener(new OnClickListener() {
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@Override
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public void onClick(View v) {
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((MainActivity)getActivity()).changeButtonColor();
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}
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});
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btn2 = (Button)rootView.findViewById(R.id.btn2);
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btn2.setOnClickListener(new OnClickListener() {
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@Override
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public void onClick(View v) {
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fragmentCallBack.callbackFun2(null);
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}
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});
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return rootView;
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}
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@Override
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public void onAttach(Activity activity) {
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super.onAttach(activity);
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fragmentCallBack = (MainActivity)activity;
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}
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}
回调接口:
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package com.example.testfragment;
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import android.os.Bundle;
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public interface FragmentCallBack {
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public void callbackFun1(Bundle arg);
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public void callbackFun2(Bundle arg);
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}
main.xml
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<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
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xmlns:tools="http://schemas.android.com/tools"
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android:layout_width="match_parent"
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android:layout_height="match_parent"
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android:paddingBottom="@dimen/activity_vertical_margin"
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android:paddingLeft="@dimen/activity_horizontal_margin"
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android:paddingRight="@dimen/activity_horizontal_margin"
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android:paddingTop="@dimen/activity_vertical_margin" >
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<Button
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android:id="@+id/btn"
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android:layout_width="match_parent"
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android:layout_height="wrap_content"
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android:layout_alignParentBottom="true"
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android:text="切换" />
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<RelativeLayout
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android:id="@+id/rl_container"
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android:layout_width="match_parent"
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android:layout_height="wrap_content"
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android:layout_above="@id/btn" />
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</RelativeLayout>
MainActivity.java
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package com.example.testfragment;
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import android.graphics.Color;
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import android.os.Bundle;
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import android.support.v4.app.Fragment;
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import android.support.v4.app.FragmentManager;
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import android.support.v4.app.FragmentTransaction;
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import android.support.v7.app.ActionBarActivity;
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import android.view.View;
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import android.view.View.OnClickListener;
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import android.widget.Button;
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public class MainActivity extends ActionBarActivity implements FragmentCallBack{
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private Button btn;
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private MyFragment1 fragment1;
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private MyFragment2 fragment2;
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private FragmentManager fragmentManager;
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private Fragment currentFragment;
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@Override
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protected void onCreate(Bundle savedInstanceState) {
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super.onCreate(savedInstanceState);
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setContentView(R.layout.activity_main);
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fragmentManager = getSupportFragmentManager();
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FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
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fragmentTransaction.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);
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fragment1 = new MyFragment1();
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Bundle data = new Bundle();
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data.putString("TEXT", "这是Activiy通过Bundle传递过来的值");
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fragment1.setArguments(data);
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fragmentTransaction.add(R.id.rl_container,fragment1);
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fragmentTransaction.addToBackStack(null);
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fragmentTransaction.commitAllowingStateLoss();
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currentFragment = fragment1;
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btn = (Button)findViewById(R.id.btn);
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btn.setOnClickListener(new OnClickListener() {
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@Override
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public void onClick(View v) {
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if(currentFragment instanceof MyFragment1){
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switchFragment();
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}else{
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fragmentManager.popBackStack();
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currentFragment = fragment1;
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}
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}
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});
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}
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private void switchFragment(){
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if(null == fragment2){
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fragment2 = new MyFragment2();
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}
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Bundle data = new Bundle();
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data.putString("TEXT", "传递给fragment2");
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fragment2.setArguments(data);
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FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
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fragmentTransaction.setCustomAnimations(android.R.anim.fade_in, android.R.anim.fade_out);
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fragmentTransaction.add(R.id.rl_container,fragment2);
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fragmentTransaction.addToBackStack(null);
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fragmentTransaction.commitAllowingStateLoss();
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currentFragment = fragment2;
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}
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public void changeButtonColor(){
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btn.setBackgroundColor(Color.RED);
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}
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@Override
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public void callbackFun1(Bundle arg) {
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switchFragment();
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}
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@Override
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public void callbackFun2(Bundle arg) {
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changeButtonColor();
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}
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}
初始画面
切换到第二个Fragment之后,通过Fragment2回调,改变按钮背景后的截图。
注意:
1.直接在Fragment中通过getActivity然后强转Activity的方式调用Activity的方法,这个方式不推荐!因为这会使Fragment的适配性变差。
解决方法:在使用之前,使用instanceof 判断一下Activity的类型
2.FragmentTransaction通过使用setCustomAnimations方法,可以为Fragment的切换增添各种不同的动画。变化方式远比Activity与Activity之间的切换动画要多。
3.多个Fragment之间,可以通过Activity复用很多代码,提高效率。
4.我们还可以通过ViewPager来管理Fragment,通过Adapter添加多个Fragment,然后通过setcurrentitem进行切换。我们同样可以通过setArguments向Fragment传递数据。