Android常用适配器分析(如何制作简易Launcher)-Android系统开发

Android常用适配器分析

Android中适配器是连接后端数据和前端显示的适配器接口，是数据和UI之间重要的纽带。系统中常见的View有ListView、GridView都要用到Adapter.列表控件是扩展了android.widget.AdapterView的类，包括ListView、GridView、Spinner和Gallery。而AdapterView本身实际上扩展了android.widget.ViewGroup，这意味着ListView、GridView等都是容器控件，换句话说列表控件包含一组视图，适配器的用途是Adapter管理数据，并为其提供子视图。

下图是我在网上找到的比较全的Android适配器结构图：

这里面最常用的几个布局是ArrayAdapter、SimpleAdapter、CursorAdapter以及BaseAdapter。其中BaseAdapter是一个抽象类，需要子类继承并实现其中的接口才能使用，常用于用户自定义显示比较复杂的数据。

1）ArrayAdapter

ArrayAdapter数组适配器是Android中最简单的适配器，专门用于显示列表控件。常用构造方法如下：

public ArrayAdapter(Context context, int textViewResourceId, List objects);

public ArrayAdapter(Context context, int textViewResourceId, T[] objects);

Demo1:

public class MainActivity extends Activity {

	private ListView listView;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
//		setContentView(R.layout.activity_main);
		String[] strings = {"1", "2", "3", "4", "5"};
		ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item1, strings);
		listView = new ListView(this);
		listView.setAdapter(adapter);
		setContentView(listView);
	}
}

注意：这里资源上针对子布局资源ID的前缀为android,意味着系统不在本地/res目录中查找，会在系统自己的目录中查找。位于SDK文件的platforms/android-version/data/res/layout目录下，我们找到simple_list_item1.xml，其实际内容如下：

<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/text1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:textAppearance="?android:attr/textAppearanceListItemSmall"
    android:gravity="center_vertical"
    android:paddingStart="?android:attr/listPreferredItemPaddingStart"
    android:paddingEnd="?android:attr/listPreferredItemPaddingEnd"
    android:minHeight="?android:attr/listPreferredItemHeightSmall"
/>

这里strings可以是一个字符串数组，也可以是一个List集合。如：

private List<String> getData() {
	List<String> data = new ArratList<String>();
	data.add("one");
	data.add("two");
	data.add("three");
	data.add("four");
	data.add("three");
	return data;
}

在代码中我们的Activity可以直接继承于ListActivity，ListActivity类继承与Activity类，默认绑定了一个ListView界面组件，并提供一些与列表视图、处理相关的操作。

Demo2:

public class MainActivity extends ListActivity {

	private ListView listView;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		
		ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item1, getData());
		setListAdapter(adapter);
	}
	
	private List<String> getData() {
		List<String> data = new ArrayList<String>();
		data.add("one");
		data.add("two");
		data.add("three");
		return data;
	}

}

2)SimpleAdapter

simpleAdapter的扩展性最好，可以定义各种各样的布局，添加ImageView、Button、CheckBox等。

Demo:

simple_list.xml

<?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="wrap_content"
    android:orientation="horizontal" >

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:textIsSelectable="true" >
    </TextView>

    <ImageView
        android:id="@+id/img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="20sp" >
    </ImageView>

</LinearLayout>

MainActivity.java

public class MainActivity extends ListActivity {

	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		
		String [] strings = new String[] {"title", "img"};
		int[] ids = new int[] {R.id.textView, R.id.img};
		SimpleAdapter adapter = new SimpleAdapter(this, getData(), R.layout.simple_list, strings, ids);
		setListAdapter(adapter);
	}
	
	private List<Map<String, Object>> getData() {
		List<Map<String, Object>> list = new ArrayList<Map<String,Object>>();
		Map<String, Object> map = new HashMap<String, Object>();
		map.put("title", "Hello");
		map.put("img", R.drawable.iag);
		list.add(map);
		map = new HashMap<String, Object>();
		map.put("title", "world");
		map.put("img", R.drawable.ic_launcher);
		list.add(map);
		return list;
	}
}

3)CursorAdapter

一般要以数据库为数据源的时候才会使用SimpleCursorAdapter.这个适配器也需要在ListView中使用，通过游标向列表提供数据。

Demo:

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		
		Cursor  cursor = getContentResolver().query(People.CONTENT_URI, null, null, null, null);
		startManagingCursor(cursor);
		ListAdapter adapter = new SimpleCursorAdapter(this, R.layout.simple_list, cursor, 
				new String[] {People.NAME}, new int[] {R.id.textView});
		setListAdapter(adapter);
	}

4)BaseAdapter

一般用于显示复杂的列表布局，由于BaseAdapter是一个抽象类，使用该类需要自己写一个适配器继承于该类，并重新一些方法。

如下Demo我们通过ApplicationInfoAdapter继承于BaseAdapter，实现一个简单的Launcher，通过PackageManager查询系统中Intent.ACTION_MAIN和Intent.CATEGORY_LAUNCHER的Activity并将其通过ListView的形式显示出来，然后点击某一项进入相应的Activity。

首先我们定义一个描述应用程序的类AppInfo:

public class AppInfo {
	private String appLabel;	// 应用程序标签
	private Drawable appIcon;	// 应用程序 的图像
	private Intent intent;	
 	private String pkgName;		// 应用程序所对应包名
	private Context context;
	
	public AppInfo(Context context) {
		this.context = context;
	}
	
	public String getAppLabel() {
		return appLabel;
	}
	public void setAppLabel(String appName) {
		this.appLabel = appName;
	}
	
	public Drawable getAppIcon() {
		return appIcon;
	}
	
	public void setAppIcon(Drawable appIcon) {
		this.appIcon = appIcon;
	}
	
	public Intent getIntent() {
		return intent;
	}
	
	public void setIntent(Intent intent) {
		this.intent = intent;
	}
	
	public String getPkgName() {
		return pkgName;
	}
	
	public void setPkgName(String pkgName) {
		this.pkgName = pkgName;
	}
}

然后我们定义一个ApplicationInfoAdapter 继承于BaseAdapter,并重写其getCount()，getItem()，getItemId()，getView()等函数。

public class ApplicationInfoAdapter extends BaseAdapter {

	private static final String TAG = "ApplicationInfoAdapter";
	private List<AppInfo> mListAppInfo = null;
	LayoutInflater infater = null;
	
	public ApplicationInfoAdapter(Context context, List<AppInfo> apps) {
		// TODO Auto-generated constructor stub
		infater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
		mListAppInfo = apps;
	}
	
	@Override
	public int getCount() {
		// TODO Auto-generated method stub
		Log.i(TAG, "size="+mListAppInfo.size());
		return mListAppInfo.size();
	}

	@Override
	public Object getItem(int arg0) {
		// TODO Auto-generated method stub
		return mListAppInfo.get(arg0);
	}

	@Override
	public long getItemId(int arg0) {
		// TODO Auto-generated method stub
		return 0;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup viewGroup) {
		// TODO Auto-generated method stub
		Log.i(TAG, "getView at" + position);
		View view = null;
		ViewHolder holder = null;
		
		if(convertView == null || convertView.getTag()==null) {
			view = infater.inflate(R.layout.app_list, null);
			holder = new ViewHolder(view);
			view.setTag(holder);
		} else {
			view = convertView;
			holder = (ViewHolder)convertView.getTag();
		}
		
		AppInfo appInfo = (AppInfo)getItem(position);
		holder.appIcon.setImageDrawable(appInfo.getAppIcon());
		holder.tvAppLabel.setText(appInfo.getAppLabel());
		holder.tvPktName.setText(appInfo.getPkgName());
		return view;
	}
	
	class ViewHolder {
		ImageView appIcon;
		TextView tvAppLabel;
		TextView tvPktName;
		
		public ViewHolder(View view) {
			this.appIcon = (ImageView)view.findViewById(R.id.imgApp);
			this.tvAppLabel = (TextView)view.findViewById(R.id.tvAppLabel);
			this.tvPktName = (TextView)view.findViewById(R.id.tvPkgName);
		}
	}
}

这里我们通过LAYOUT_INFLATER_SERVICE布局管理器服务动态加载app_list.xml用来显示每一个应用程序的信息

<?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="50dp"
    android:orientation="horizontal" >
    
    <ImageView android:id="@+id/imgApp"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent">
    </ImageView>
    
    <RelativeLayout 
        android:layout_width="fill_parent"
        android:layout_height="40dp"
        android:layout_marginLeft="10dp">
        
        <TextView android:id="@+id/tvLabel"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="AppLabel:">
        </TextView>
        
        <TextView android:id="@+id/tvAppLabel"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginLeft="3dp"
            android:text="Label"
            android:layout_toRightOf="@id/tvLabel"
            android:textColor="#ffD700">
        </TextView>
        
        <TextView android:id="@+id/tvName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/tvLabel"
            android:text="包名">
        </TextView>

        <TextView android:id="@+id/tvPkgName"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/tvAppLabel"
            android:layout_alignLeft="@id/tvAppLabel"
            android:textColor="#ffD700">
        </TextView>
    </RelativeLayout>"
</LinearLayout>

然后我们在MainActivity中通过PackageManager查询系统中所有的ACTION_MAIN和 CATEGORY_LAUNCHER的属性的Activity，通过ApplicationInfoAdapter适配器显示到ListView上。

public class MainActivity extends Activity implements OnItemClickListener {

	private static final String LOG_TAG = "MainActivity";
	private static final int MSG_SUCCESS = 0;
	
	private ListView listView = null;
	private List<AppInfo> mListAppInfos = null;
	Handler mHandler = null;
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		listView = (ListView) this.findViewById(R.id.listView);
		mListAppInfos = new ArrayList<AppInfo>();

		mHandler = new Handler() {
			public void handleMessage(android.os.Message msg) {
				switch (msg.what) {
				case MSG_SUCCESS:
					ApplicationInfoAdapter applicationInfoAdapter = new ApplicationInfoAdapter(
							MainActivity.this, mListAppInfos); 
					listView.setAdapter(applicationInfoAdapter);
					listView.setOnItemClickListener(MainActivity.this);
					break;

				default:
					break;
				}
			};
		};
		
		new Thread(new Runnable() {
			
			@Override
			public void run() {
				// TODO Auto-generated method stub
				queryAppInfo(); // 查询所有应用程序信息
				mHandler.obtainMessage(MSG_SUCCESS).sendToTarget();
			}
		}).start();
	}

	public void queryAppInfo() {
		
		PackageManager pm = this.getPackageManager();

/* 		List<ApplicationInfo> listApplications = pm.getInstalledApplications(PackageManager.GET_UNINSTALLED_PACKAGES);
 		Collections.sort(listApplications, new ApplicationInfo.DisplayNameCoamparator(pm));
 		for(ApplicationInfo app : listApplications) {
 			if((app.flags & ApplicationInfo.FLAG_SYSTEM) > 0) {	// 系统程序

 			} else if( (app.flags & ApplicationInfo.FLAG_SYSTEM) <= 0) {	// 第三方程序
 				
 			} else if((app.flags & ApplicationInfo.FLAG_UPDATED_SYSTEM_APP) != 0) {	// 系统程序被用户更新了
 				
 			} else if((app.flags & ApplicationInfo.FLAG_EXTERNAL_STORAGE) != 0) {	// 安装在SD卡程序
 				
 			}
 		}*/
		
		
		Intent mainIntent = new Intent(Intent.ACTION_MAIN, null);
		mainIntent.addCategory(Intent.CATEGORY_LAUNCHER);
		
		// 查询获得所有ResolveInfo对象
		List<ResolveInfo> resolveInfos = pm.queryIntentActivities(mainIntent, PackageManager.MATCH_DEFAULT_ONLY);
		
		for(ResolveInfo reInfo : resolveInfos) {
			Log.e(LOG_TAG, "name:"+reInfo.activityInfo.name + "pkg:"+reInfo.activityInfo.packageName);
		}
		
		// 根据name排序
		Collections.sort(resolveInfos, new ResolveInfo.DisplayNameComparator(pm));
		
		for(ResolveInfo reInfo : resolveInfos) {
			Log.e(LOG_TAG, "name:"+reInfo.activityInfo.name + "pkg:"+reInfo.activityInfo.packageName);
		}
		
		if(mListAppInfos != null) {
			
			mListAppInfos.clear();
		
			for(ResolveInfo reInfo : resolveInfos) {
				
				String activityName = reInfo.activityInfo.name;		// 获得应用程序启动Activity的name
				String pkgName = reInfo.activityInfo.packageName;	// 获得应用程序的包名
				String appLabel = (String)reInfo.loadLabel(pm);		// 获得应用程序的Label
				Drawable icon = reInfo.loadIcon(pm);				// 获得应用程序的图标
				
				// 为应用程序的启动Activity准备Intent
				Intent launchIntent = new Intent();
				launchIntent.setComponent(new ComponentName(pkgName, activityName));
				
				// 创建一个 AppInfo 对象
				AppInfo appInfo = new AppInfo(this);
				appInfo.setAppLabel(appLabel);
				appInfo.setAppIcon(icon);
				appInfo.setPkgName(pkgName);
				appInfo.setIntent(launchIntent);
				
				mListAppInfos.add(appInfo);
				
				Log.i(LOG_TAG, "ActivityName:"+activityName+ "pkgName:"+pkgName);
			}	
		}
	}

	@Override
	public void onItemClick(AdapterView<?> adapter, View view, int arg2, long arg3) {
		// TODO Auto-generated method stub
		Intent intent = mListAppInfos.get(arg2).getIntent();
		Log.d(LOG_TAG, "intent:"+intent.toString());
		startActivity(intent);
	}

}