Android之Fragment

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Fragment是在Activity的托管下才能具有显示视图的能力；

**fragment_crime.xml**<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical" >    <EditText         android:id="@+id/et"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:hint="请输入标题！"        />    <Button         android:id="@+id/btn"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="显示标题"/></LinearLayout>**CrimeFragment.java**package com.duolyn.test07;import android.os.Bundle;import android.support.v4.app.Fragment;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.Button;import android.widget.EditText;import android.widget.Toast;public class CrimeFragment extends Fragment{    Button btn;    EditText et;    @Override    public void onCreate(Bundle savedInstanceState) {        // TODO Auto-generated method stub        super.onCreate(savedInstanceState);    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,            Bundle savedInstanceState) {        //inflate是在xml中找到布局为R.layout.fragment_crime        View v = inflater.inflate(R.layout.fragment_crime, container, false);        et = (EditText) v.findViewById(R.id.et);        btn = (Button) v.findViewById(R.id.btn);        btn.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                // TODO Auto-generated method stub                Toast.makeText(getActivity(), et.getText().toString(), Toast.LENGTH_SHORT).show();            }        });        return v;    }}

**activity_crime.xml**<FrameLayout  xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    //R.id.fragmentContainer是托管Fragment的Activity的id    android:id="@+id/fragmentContainer"    android:layout_width="match_parent"    android:layout_height="wrap_content"></FrameLayout>**CrimeActivity.java**public class CrimeActivity extends FragmentActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_crime);        //以下几行代码是使Fragment在Activity的托管下生效，即Fragment在Activity下显示视图        FragmentManager fm = getSupportFragmentManager();        Fragment fragment = fm.findFragmentById(R.id.fragmentContainer);        if(fragment == null){            fragment =  new CrimeFragment();            fm.beginTransaction().add(R.id.fragmentContainer, fragment).commit();        }    }    @Override    public boolean onCreateOptionsMenu(Menu menu) {        // Inflate the menu; this adds items to the action bar if it is present.        getMenuInflater().inflate(R.menu.crime, menu);        return true;    }}

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