最近组织上派遣了我一个任务，最终目的只有一个，就是看看launcher你的wallpaper设置的流程。

废话不多说，直接看源码。

tips：在com.android.launcher2.Launcher类内有一个方法叫做startWallpaper(),很明显此方法就是设置壁纸的关键所在。

要说我是怎么知道的，大概老外起名字也不是随便起的，要是找类似的功能，比如创建快捷方式，在Launcher类里

按快捷键CTRL+O 键入对应的英文比如（*shortcut*），列出来的方法看名字也能猜出来对吧。同上，wallpaper就是这么找到的。

private void startWallpaper() {

        showWorkspace(true);         final Intent pickWallpaper = new Intent(Intent.ACTION_SET_WALLPAPER);         Intent chooser = Intent.createChooser(pickWallpaper,                 getText(R.string.chooser_wallpaper));         // NOTE: Adds a configure option to the chooser if the wallpaper supports it         //       Removed in Eclair MR1 //        WallpaperManager wm = (WallpaperManager) //                getSystemService(Context.WALLPAPER_SERVICE); //        WallpaperInfo wi = wm.getWallpaperInfo(); //        if (wi != null && wi.getSettingsActivity() != null) { //            LabeledIntent li = new LabeledIntent(getPackageName(), //                    R.string.configure_wallpaper, 0); //            li.setClassName(wi.getPackageName(), wi.getSettingsActivity()); //            chooser.putExtra(Intent.EXTRA_INITIAL_INTENTS, new Intent[] { li }); //        }         startActivityForResult(chooser, REQUEST_PICK_WALLPAPER);     }

 

以上代码中Intent的chooser静态方法没有使用过，没有关系，看对应的api就是了。

public static  createChooser ( target,  title)

Added in 

Convenience function for creating a  Intent.

Builds a new  Intent that wraps the given target intent, also optionally supplying a title. If the target intent has specified or , then these flags will also be set in the returned chooser intent, with its ClipData set appropriately: either a direct reflection of  if that is non-null, or a new ClipData build from .

Parameters

target	The Intent that the user will be selecting an activity to perform.
title	Optional title that will be displayed in the chooser.

Returns

• Return a new Intent object that you can hand to  and related methods.

很明显这个方法是将该IntentFIlter中符合该Intent的activity全都列出来，然后第二个参数就是展示的chooser的标题。

当点击对应的item就会打开对应的activity，而launcher源码中存在一个对应的activity，清单文件中有提及到。

 

因此顺藤摸瓜，看看设置壁纸是如何实现的。找到WallpaperChooser类，查看源码

public class WallpaperChooser extends Activity {    private static final String TAG = "Launcher.WallpaperChooser";    @Override    public void onCreate(Bundle icicle) {        super.onCreate(icicle);        setContentView(R.layout.wallpaper_chooser_base);        Fragment fragmentView =                getFragmentManager().findFragmentById(R.id.wallpaper_chooser_fragment);        Log.i(TAG, "wallpaper"+(fragmentView==null));        // TODO: The following code is currently not exercised. Leaving it here in case it        // needs to be revived again.        if (fragmentView == null) {            /* When the screen is XLarge, the fragment is not included in the layout, so show it             * as a dialog             */            DialogFragment fragment = WallpaperChooserDialogFragment.newInstance();            fragment.show(getFragmentManager(), "dialog");        }    }}

事实上在对应的layout上有如下

实际是使用了WallpaperChooserDialogFragment，注释说了如果是Xlarge屏幕，没有显示该fragment，则获得WallpaperChooserDialogFragment对象

大概看到应该是在倒数第二句话中使用了一个fragment 选择壁纸。继续找到WallpaperChooserDialogFragment.类，果然

private void selectWallpaper(int position) {        try {            WallpaperManager wpm = (WallpaperManager) getActivity().getSystemService(                    Context.WALLPAPER_SERVICE);            wpm.setResource(mImages.get(position));            Activity activity = getActivity();            activity.setResult(Activity.RESULT_OK);            activity.finish();        } catch (IOException e) {            Log.e(TAG, "Failed to set wallpaper: " + e);        }    }    // Click handler for the Dialog's GridView    @Override    public void onItemClick(AdapterView
     parent, View view, int position, long id) {        selectWallpaper(position);    }

这一段就是真正的实现壁纸设置的方法。使用WallpaperManager.setResource(arg0)设置。   

  activity.setResult(Activity.RESULT_OK);将会在Launcher你的onActivityResult方法接收到，

此时也就是设置了对应的壁纸。