使用Fragment兼容Tablet和Handset

为了适应Handset和Tablet等不同分辨率的android设备，google在android3.0之后提供了一个新的API，也就是Fragment，大家可以查阅官方SDK的详细说明。

 

以下是摘自官方SDK 的一张设计图，很好地展示了Fragment在兼容Tablet和Handset设备的设计理念。

 

首先解释一下，上述的设计原理。

1.针对Tablet，Activity A中包含了Fragment A和Fragment B，而Handset中的Activity A中只包含了Fragment A，至于Fragment B则通过对Fragment A的事件监听，来启动新的Activity B（包含Fragment B）将Fragment B显示给用户。

既然这样的话就必须用到两个布局，layout目录下默认存放的是Handset的布局，layout-large目录下存放的则是Tablet的布局。

更详细的请参考：http://android-developers.blogspot.com/2011/07/new-tools-for-managing-screen-sizes.html

 

2.接着看如何在布局中定义Fragment

参考一下配置文件：

 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal" >

<fragment
    class="com.test.fragment.ItemActivity"
    android:id="@+id/item"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="3"
    />

<fragment
    class="com.test.fragment.ContentActivity"
    android:id="@+id/content"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_weight="1"
    />

</LinearLayout>

 

 

 

 3.系统内置了3种Fragment

DialogFragment：对话框式Fragment，管理模式类似与AlertDialog等对话框，允许用户返回之前的Fragment。

ListFragment：类似于ListActivity，并且提供了类似的功能，用法基本差不多。

PreferenceFragment：类似于PreferenceActivity，用法也差不多，可用来创建类似ipad的设置界面。

 

 

这里我们使用ListFragment来显示项目栏，内容栏通过Fragment来创建自定义布局。

直接上代码：

ItemActivity.java

package com.test.fragment;

import com.test.fragment.R;

import android.app.ListFragment;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

public class ItemActivity extends ListFragment{
	private ItemAdapter adapter;
	private ImageView mLastIndicate = null;
	private Context mContext = null;
	private String [] mArr = null;
	private static OnItemChangeListener onItemChangeListener;
	
	public interface OnItemChangeListener{
		void onItemChange(int position);
	}
	
	@Override
	public void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		mContext = getActivity();
		mArr = new String[]{"item1","item2","item3"}; 
		adapter = new ItemAdapter();
	}

	@Override
	public void onActivityCreated(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onActivityCreated(savedInstanceState);
		setListAdapter(adapter);
	}
	
	@Override
	public void onListItemClick(ListView l, View v, int position, long id) {
		// TODO Auto-generated method stub
		super.onListItemClick(l, v, position, id);
		if(mLastIndicate != null){
			mLastIndicate.setVisibility(View.GONE);
		}
		ImageView imageView = (ImageView)v.findViewById(R.id.item_indicate);
		imageView.setVisibility(View.VISIBLE);
		mLastIndicate = imageView;
		onItemChangeListener.onItemChange(position);
	}
	
	public static void setItemChangeListener(OnItemChangeListener l){
		onItemChangeListener = l;
	}

	public class ItemAdapter extends BaseAdapter{
		private ViewHolder mHolder = null;
		
		public ItemAdapter(){
		}

		public int getCount() {
			// TODO Auto-generated method stub
			return mArr.length;
		}

		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		public View getView(int position, View convertView, ViewGroup parent) {
			// TODO Auto-generated method stub
			if(convertView == null){
				LayoutInflater inflater = (LayoutInflater)mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
				convertView = inflater.inflate(R.layout.item_layout, parent, false);
				mHolder = new ViewHolder();
				mHolder.item_tv = (TextView)convertView.findViewById(R.id.item_tv);
				mHolder.item_indicate = (ImageView)convertView.findViewById(R.id.item_indicate);
				convertView.setTag(mHolder);
			}else{
				mHolder = (ViewHolder)convertView.getTag();
			}
			if(mLastIndicate == null){
				if(position == 0){
					mHolder.item_indicate.setVisibility(View.VISIBLE);
					mLastIndicate = mHolder.item_indicate;
				}
			}
			mHolder.item_tv.setText(mArr[position]);
			return convertView;
		}
		
		class ViewHolder{
			public TextView item_tv;
			public ImageView item_indicate;
		}
		
	}

}

在ItemActivity中设置onItemChangeListener监听器接口，在Item改变的时候，让MainActivity通过接口来刷新界面。

 

ContentActivity.java

package com.test.fragment;

import com.test.fragment.R;

import android.app.Fragment;
import android.content.Context;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

public class ContentActivity extends Fragment {
	private String [] arr = null;
	private String [] arr0 = {"item1:","item1:","item1:","item1:","item1:"};
	private String [] arr1 = {"item2:","item2:","item2:","item2:","item2:"};
	private String [] arr2 = {"item3:","item3:","item3:","item3:","item3:"};
	private ContentAdapter adapter = null;
	private ListView lv = null;
	private Context mContext = null;
	
	@Override
	public void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		Bundle bundle = getActivity().getIntent().getExtras();
		int position = 0;
		if(bundle == null){
			position = 0;
		}else{
			position = bundle.getInt(MainActivity.KEY_POSITION);
		}
		switch(position){
		case 0:
			arr = arr0;
			break;
		case 1:
			arr = arr1;
			break;
		case 2:
			arr = arr2;
			break;
		}
		mContext = getActivity();
	}

	@Override
	public View onCreateView(LayoutInflater inflater, ViewGroup container,
			Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		View view = inflater.inflate(R.layout.content_layout, container, false);
		lv = (ListView)view.findViewById(R.id.contentList);
		adapter = new ContentAdapter();
		lv.setAdapter(adapter);
		return view;
	}

	public void onUpdateContent(int position){
		switch(position){
		case 0:
			arr = arr0;
			break;
		case 1:
			arr = arr1;
			break;
		case 2:
			arr = arr2;
			break;
		}
		adapter.notifyDataSetChanged();
	}
	
	class ContentAdapter extends BaseAdapter{
		private ViewHolder mHolder;
		
		public ContentAdapter(){
			super();
		}

		public int getCount() {
			// TODO Auto-generated method stub
			return arr.length;
		}

		public Object getItem(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		public long getItemId(int position) {
			// TODO Auto-generated method stub
			return position;
		}

		public View getView(int position, View convertView, ViewGroup parent) {
			// TODO Auto-generated method stub
			if(convertView == null){
				LayoutInflater inflater = (LayoutInflater)mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
				convertView = inflater.inflate(R.layout.content_item_layout, parent, false);
				mHolder = new ViewHolder();
				mHolder.content_tv = (TextView)convertView.findViewById(R.id.content_tv);
				convertView.setTag(mHolder);
			}else{
				mHolder = (ViewHolder)convertView.getTag();
			}
			mHolder.content_tv.setText(arr[position]);
			return convertView;
		}
		
		class ViewHolder{
			public TextView content_tv;
		}
		
	}
}

 MainActivity.java

package com.test.fragment;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;

import com.test.fragment.ItemActivity.OnItemChangeListener;
import com.test.fragment.R;

public class MainActivity extends Activity implements OnItemChangeListener{
	private ContentActivity contentFragment = null;
//	private ItemActivity itemFragment = null;
	public static final String KEY_POSITION = "position";
	
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        contentFragment = (ContentActivity)getFragmentManager().findFragmentById(R.id.content);
		ItemActivity.setItemChangeListener(this);
    }

	public void onItemChange(int position) {
		// TODO Auto-generated method stub
		if(contentFragment == null){
			Intent intent = new Intent(this,Content.class);
			Bundle bundle = new Bundle();
			bundle.putInt(KEY_POSITION, position);
			intent.putExtras(bundle);
			startActivity(intent);
		}else{
			contentFragment.onUpdateContent(position);
		}
	}
}

MainActivity的实现了OnItemChangeListener监听器接口，那么首先就要在onCreate的时候将监听器注册到ItemActivity中，在实现的方法中分别针对Tablet和Handset设备做了不同的处理。

 

欲知更多fragment的使用技巧，请参考官方SDK。

 

代码下载，请看附件。