fragment的使用-优快云博客

本文详细介绍了如何使用XML布局文件和Java代码动态生成Fragment，包括Fragment的生命周期和如何实现Fragment间的通讯，通过实例展示了通过Activity来管理Fragment并进行数据交换的方法。

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一、fragment的静态生成

第一步，main.xml

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

    <fragment 
        android:id="@+id/fragment1"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:name="com.example.fragment1demo.Fragment1"/>
    <fragment 
        android:id="@+id/fragment2"
        android:layout_width="match_parent"
        android:layout_height="200dp"
        android:name="com.example.fragment1demo.Fragment2"/>

</LinearLayout>

其中name对应于Fragment1和Fragment2两个.java文件。我的理解是调用了这两个文件里的onCreateView方法

第二步，Fragment1.java

public class Fragment1 extends Fragment {
	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		View view = inflater.inflate(R.layout.fragment1, null);
		return view;
	}
}

二、Fragment动态生成

MainActivity.java

public class MainActivity extends Activity {

	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		Fragment1 fragment1 = new Fragment1();
		Fragment2 fragment2 = new Fragment2();
		
		FragmentManager manager = getFragmentManager();
		FragmentTransaction transaction = manager.beginTransaction();
		//把id为linearLayout的布局替换为fragment1
		transaction.replace(android.R.id.content, fragment1);  
		//记得commit
		transaction.commit();
	}
}

三、Fragment生命周期

由于Fragment是依附于Activity上，所以其生命周期执行必然落后于Activity。

Activity:onCreate 创建时被调用
fragment:onattach
fragment:oncreate
fragment:oncreateView
fragment:onActivityCreated
Activity:onstart 用户可见时调用
fragment:onStart
Activity:onresume 获得焦点时调用
fragment:onResume

fragment:onPause
Activity:onpause 失去焦点时调用
fragment:onstop
Activity:onStop 界面消失时调用
fragment:ondestroyView
fragment:ondestroy
fragment:onDetach
Activity:onDestroy 销毁时调用

四、Fragment之间通讯

案例：通过Fragment1的Button来修改Fragment2的TextView

Fragment1.java

public class Fragment1 extends Fragment {
	private Button button;
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		View view = inflater.inflate(R.layout.fragment1, null);
		button = (Button) view.findViewById(R.id.button);
		button.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				Fragment2 fragment2 = (Fragment2) getActivity().getFragmentManager().findFragmentById(R.id.fragment2);
				fragment2.setText("hello world");
			}
		});
		return view;
	}
}

两个Fragment通讯的桥梁是他们的Activity。通过该Activity来获得Fragment2的对象

Fragment2.java

public class Fragment2 extends Fragment {
	private TextView tv;
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		View view = inflater.inflate(R.layout.fragment2, null);
		tv = (TextView) view.findViewById(R.id.textView);
		return view;
	}
	public void setText(String str){
		tv.setText(str);
	}
}

暴露出setText方法，在Fragment1.java中能进行调用