Fragment
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1、Fragment知识概要
Android3.0引入了Fragment,主要目的是用在大屏幕设备上,支持更加动态和灵活的UI设计。Fragment在你的应用中应当是一个模块化和可重用的组件,因为Fragment定义了它自己的布局,以及通过使用它自己的声明周期回调回调方法定义了它自己的行为,可以将Fragment包含到多个Activity中。
(1)Fragment可以作为Activity界面的一部分组成出现;
(2)可以在一个Activity中同时出现多个Fragment,并且一个Fragment也可以在多个Activity中使用;
(3)在Activity运行过程中,可以添加、移除或替换Fragment;
(4)Fragment可以响应自己的输入事件,并且有自己的声明周期,它们的生命周期受宿主Activity的生命周期影响;
(5)Fragment在第一次绘制它的用户界面时,系统会调用onCreateView()方法,此方法返回一个View。(如果不显示UI,返回null);
Fragment两种加载方式:静态加载、动态加载。
2、准备阶段:
本文以及后续将使用一个APP来讲解关于Fragment的知识,大致布局如下:
values添加color.xml:
<!--{cke_protected}{C}%3C!%2D%2D%3Fxml%20version%3D%
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<resources>
<color name=
"gray"
>#
88000000
</color>
<color name=
"white"
>#ffffff</color>
</resources>
<?xml version=
"1.0"
encoding=
"utf-8"
?>
<selector xmlns:android=
"http://schemas.android.com/apk/res/android"
>
<item android:drawable=
"@color/gray"
android:state_checked=
"true"
></item>
<item android:drawable=
"@color/white"
android:state_pressed=
"true"
></item>
<item android:drawable=
"@color/white"
></item>
</selector>
<!--{cke_protected}{C}%3C!%2D%2D%3Fxml%20version%3D%
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<relativelayout xmlns:android=
"http://schemas.android.com/apk/res/android"
android:layout_width=
"match_parent"
android:layout_height=
"match_parent"
>
<linearlayout android:id=
"@+id/frame"
android:layout_width=
"match_parent"
android:layout_height=
"wrap_content"
android:orientation=
"vertical"
>
</linearlayout>
<radiogroup android:id=
"@+id/radiogroup"
android:layout_width=
"match_parent"
android:layout_height=
"wrap_content"
android:layout_alignparentbottom=
"true"
android:gravity=
"center_horizontal"
android:orientation=
"horizontal"
>
<radiobutton android:id=
"@+id/first"
android:layout_width=
"0dp"
android:layout_height=
"wrap_content"
android:layout_weight=
"1"
android:background=
"@drawable/radio_pressed"
android:button=
"@null"
android:drawabletop=
"@drawable/ic_launcher"
android:gravity=
"center_horizontal"
android:text=
"静态加载"
>
<radiobutton android:id=
"@+id/second"
android:layout_width=
"0dp"
android:layout_height=
"wrap_content"
android:layout_weight=
"1"
android:background=
"@drawable/radio_pressed"
android:button=
"@null"
android:drawabletop=
"@drawable/ic_launcher"
android:gravity=
"center_horizontal"
android:text=
"动态加载"
>
<radiobutton android:id=
"@+id/thrid"
android:layout_width=
"0dp"
android:layout_height=
"wrap_content"
android:layout_weight=
"1"
android:background=
"@drawable/radio_pressed"
android:button=
"@null"
android:drawabletop=
"@drawable/ic_launcher"
android:gravity=
"center_horizontal"
android:text=
"生命周期"
>
<radiobutton android:id=
"@+id/fourth"
android:layout_width=
"0dp"
android:layout_height=
"wrap_content"
android:layout_weight=
"1"
android:background=
"@drawable/radio_pressed"
android:button=
"@null"
android:drawabletop=
"@drawable/ic_launcher"
android:gravity=
"center_horizontal"
android:text=
"传值通信"
>
</radiobutton></radiobutton></radiobutton></radiobutton></radiogroup>
</relativelayout>
package
com.example.fragment;
import
android.os.Bundle;
import
android.app.Activity;
import
android.view.Menu;
import
android.widget.RadioGroup;
import
android.widget.RadioGroup.OnCheckedChangeListener;
public
class
MainActivity
extends
Activity
implements
OnCheckedChangeListener {
private
RadioGroup group;
@Override
protected
void
onCreate(Bundle savedInstanceState) {
super
.onCreate(savedInstanceState);
setContentView(R.layout.main);
group=(RadioGroup) findViewById(R.id.radiogroup);
group.setOnCheckedChangeListener(
this
);
}
@Override
public
boolean
onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return
true
;
}
@Override
public
void
onCheckedChanged(RadioGroup group,
int
checkedId) {
// TODO Auto-generated method stub
switch
(checkedId) {
case
R.id.first:
//演示静态加载
break
;
case
R.id.second:
//演示动态加载
break
;
case
R.id.thrid:
//演示生命周期
break
;
case
R.id.fourth:
//演示传值通信
break
;
}
}
}
3、静态加载
在Activity的layout文件中声明Fragment(特别注意:在标签中的android: name属性中指定了在layout中实例化的Fragment类),标识Fragment的方法:A.android: id 属性提供一个唯一ID;B.android: tag属性提供一个唯一字符串;
添加fragment.xml:
<!--{cke_protected}{C}%3C!%2D%2D%3Fxml%20version%3D%
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<linearlayout 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/text"
android:layout_width=
"wrap_content"
android:layout_height=
"wrap_content"
android:text=
"我的Fragment"
><button android:layout_width=
"wrap_content"
android:layout_height=
"wrap_content"
android:id=
"@+id/button"
></button></textview></linearlayout>
package
com.example.fragment;
import
android.app.Fragment;
import
android.os.Bundle;
import
android.view.LayoutInflater;
import
android.view.View;
import
android.view.View.OnClickListener;
import
android.view.ViewGroup;
import
android.widget.Button;
import
android.widget.TextView;
public
class
MyFragment
extends
Fragment {
@Override
public
View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// layout布局文件转换成View对象
/**
* inflater.inflate(resource, root, attachToRoot)
* resource:Fragment需要加载的布局文件
* root:加载layout的父ViewGroup
* attactToRoot:false,不返回父ViewGroup
*/
View view = inflater.inflate(R.layout.fragment, container,
false
);
TextView text = (TextView) view.findViewById(R.id.text);
Button button = (Button) view.findViewById(R.id.button);
text.setText(
"静态加载Fragment"
);
button.setText(
"获取内容"
);
button.setOnClickListener(
new
OnClickListener() {
@Override
public
void
onClick(View v) {
// TODO Auto-generated method stub
// String value = getAaa();
// Toast.makeText(getActivity(), "value="+value,
// Toast.LENGTH_SHORT).show();
}
});
return
view;
}
}
<!--{cke_protected}{C}%3C!%2D%2D%3Fxml%20version%3D%
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<linearlayout xmlns:android=
"http://schemas.android.com/apk/res/android"
android:layout_width=
"match_parent"
android:layout_height=
"match_parent"
android:orientation=
"vertical"
>
<!--{cke_protected}{C}%3C!%2D%2D%20android%3Aid%EF%BC%9A%E9%9D%
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%E6%
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80
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%2D%2D%3E-->
<!--{cke_protected}{C}%3C!%2D%2D%20android%3Aname%EF%BC%9A%E5%AE%8C%E6%
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%B4%E5%8C%
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<fragment android:id=
"@+id/fragment"
android:layout_width=
"wrap_content"
android:layout_height=
"wrap_content"
android:name=
"com.example.fragment.MyFragment"
>
</fragment></linearlayout>
添加JingTaiActivity类:
public
class
JingTaiActivity
extends
Activity {
private
TextView tv;
@Override
protected
void
onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super
.onCreate(savedInstanceState);
setContentView(R.layout.jingtai);
Button button=(Button) findViewById(R.id.button);
tv=(TextView) findViewById(R.id.text);
button.setText(
"改变"
);
button.setOnClickListener(
new
OnClickListener() {
@Override
public
void
onClick(View v) {
// TODO Auto-generated method stub
tv.setText(
"TextView改变了"
);
}
});
}
}
主MainActivity中演示静态加载部分添加:
case
R.id.first:
//演示静态加载
Intent jingtaiIntent=
new
Intent(MainActivity.
this
,JingTaiActivity.
class
);
startActivity(jingtaiIntent);
break
;
MainActivity跳转到JingTaiActivity,里面加载了一个,而其中android:name属性是com.example.fragment.MyFragment,在这个MyFragment中又有自己的text、button布局。再回到JingTaiActivity,在其中加载了jingtai.xml,并且可以直接通过findViewById找到MyFragment的布局文件fragment中的text、button。
也就是说,当一个布局文件中通过静态加载Fragment加载到Activity中来,Fragment中的布局文件对Activity也是共享的。
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