以下将为大家简单的分析一下源代码中luncher修改壁纸的过程（一下代码均来自Luncher源代码）：
一.当我们在luncher界面按下menu的时候，第三个选项就是Wallpaper，定义如下（源码1116行，局部），menu.add第二项既是选择wallpaper：
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public boolean onCreateOptionsMenu(Menu menu) {
if (isWorkspaceLocked()) {
return false;
}
super.onCreateOptionsMenu(menu);
menu.add(MENU_GROUP_ADD, MENU_ADD, 0, R.string.menu_add)
.setIcon(android.R.drawable.ic_menu_add)
.setAlphabeticShortcut('A');
menu.add(MENU_GROUP_WALLPAPER, MENU_WALLPAPER_SETTINGS, 0, R.string.menu_wallpaper)
.setIcon(android.R.drawable.ic_menu_gallery)
.setAlphabeticShortcut('W');
public boolean onCreateOptionsMenu(Menu menu) {
if (isWorkspaceLocked()) {
return false;
}
super.onCreateOptionsMenu(menu);
menu.add(MENU_GROUP_ADD, MENU_ADD, 0, R.string.menu_add)
.setIcon(android.R.drawable.ic_menu_add)
.setAlphabeticShortcut('A');
menu.add(MENU_GROUP_WALLPAPER, MENU_WALLPAPER_SETTINGS, 0, R.string.menu_wallpaper)
.setIcon(android.R.drawable.ic_menu_gallery)
.setAlphabeticShortcut('W');
二.当我们按下Wallpaper触发什么事件呢？看一下代码(源代码1171行）:
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@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case MENU_ADD:
addItems();
return true;
case MENU_WALLPAPER_SETTINGS:
startWallpaper();
return true;
case MENU_SEARCH:
onSearchRequested();
return true;
case MENU_NOTIFICATIONS:
showNotifications();
return true;
}
return super.onOptionsItemSelected(item);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case MENU_ADD:
addItems();
return true;
case MENU_WALLPAPER_SETTINGS:
startWallpaper();
return true;
case MENU_SEARCH:
onSearchRequested();
return true;
case MENU_NOTIFICATIONS:
showNotifications();
return true;
}
return super.onOptionsItemSelected(item);
}
我们看到：
而它调用的事件是
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startWallpaper();
startWallpaper();
你们看到的图片跟我的都不一样，呵呵，这是因为我写了一个很简单的demo，然后就系统给调用了，所以你们看到一个比你们多了一个wallpaperdemo。在下一篇日志中，我会说下这个demo是如何实现的。
三.下面让我们看下startWallpaper（）这个方法（源代码1370行）：
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private void startWallpaper() {
closeAllApps(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);
}
private void startWallpaper() {
closeAllApps(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);
}
很多人可能会对他是如何实现跳转设置的呢？Intent.createChooser()这个方法的实现原理赶到好奇，因为你在Luncher源代码里面找不到Live Wallpapers和Galleryde的实现。因为他是通过一个类似广播的机制。
