# Launcher3 一鍵改變Icon Shape 原理淺析
在Android O Launcher3 Google 團隊增加了一個新特性，可以在設(shè)置里面更改 桌面Icon 形狀恬总，分別可以改為系統(tǒng)默認讹俊、方形羽资、方圓形、圓形压汪、淚珠形牵囤。
在Android P Launcher3 Google團隊繼續(xù)保持這一神奇特性，那么欣舵，看上去好高大上神奇的特性是怎樣實現(xiàn)的呢擎鸠？帶著這個疑問，follow me》》》》》
下面我們基于Android P Launcher3 分析Launcher3 實現(xiàn)基本原理缘圈。
一.先看桌面設(shè)置中的菜單實現(xiàn)：
源碼位置 Launcher90\src\com\android\launcher3\SettingsActivity.java
Preference iconShapeOverride = findPreference(IconShapeOverride.KEY_PREFERENCE);
if (iconShapeOverride != null) {
if (IconShapeOverride.isSupported(getActivity())) {
IconShapeOverride.handlePreferenceUi((ListPreference) iconShapeOverride);
} else {
getPreferenceScreen().removePreference(iconShapeOverride);
}
}
可以看到isSupported方法是是否支持設(shè)置圖標形狀的判斷條件劣光。
public static boolean isSupported(Context context) {
if (!Utilities.ATLEAST_OREO) {
return false;
}
// Only supported when developer settings is enabled
if (Settings.Global.getInt(context.getContentResolver(),
Settings.Global.DEVELOPMENT_SETTINGS_ENABLED, 0) != 1) {
return false;
}
try {
if (getSystemResField().get(null) != Resources.getSystem()) {
// Our assumption that mSystem is the system resource is not true.
return false;
}
} catch (Exception e) {
// Ignore, not supported
return false;
}
return getConfigResId() != 0;
}
由源碼 可以看出 滿足幾個條件才能看到設(shè)置選項
1.判斷系統(tǒng)SDK 版本是否>=26
2.是否打開了開發(fā)者選項。如果開發(fā)者選項沒打開糟把，就看不到這個菜單绢涡。（至于為神馬開發(fā)者模式才可以看到待追蹤！Ｇ卜琛雄可！可能讓廠商在適配此特性吧）
3.大概意思就是獲取不到mSystem，如果獲取不到，說明當前系統(tǒng)存在問題滞项。
二.菜單出現(xiàn)后狭归，我們選擇其中一種形狀來設(shè)置：
<string-array translatable="false" name="icon_shape_override_paths_values">
<item></item>
<item>M50,0L100,0 100,100 0,100 0,0z</item>
<item>M50,0 C10,0 0,10 0,50 0,90 10,100 50,100 90,100 100,90 100,50 100,10 90,0 50,0 Z</item>
<item>M50 0A50 50,0,1,1,50 100A50 50,0,1,1,50 0</item>
<item>M50,0A50,50,0,0 1 100,50 L100,85 A15,15,0,0 1 85,100 L50,100 A50,50,0,0 1 50,0z</item>
</string-array>
<string-array translatable="false" name="icon_shape_override_paths_names">
<!-- Option to not change the icon shape on home screen. [CHAR LIMIT=50] -->
<item>@string/icon_shape_system_default</item>
<item>Square</item>
<item>Squircle</item>
<item>Circle</item>
<item>Teardrop</item>
</string-array>
發(fā)現(xiàn)每個Item對應(yīng)一個path 矢量圖的string值。
private static class PreferenceChangeHandler implements OnPreferenceChangeListener {
private final Context mContext;
private PreferenceChangeHandler(Context context) {
mContext = context;
}
@Override
public boolean onPreferenceChange(Preference preference, Object o) {
String newValue = (String) o;
if (!getAppliedValue(mContext).equals(newValue)) {
// Value has changed
ProgressDialog.show(mContext,
null /* title */,
mContext.getString(R.string.icon_shape_override_progress),
true /* indeterminate */,
false /* cancelable */);
new LooperExecuter(LauncherModel.getWorkerLooper()).execute(
new OverrideApplyHandler(mContext, newValue));
}
return false;
}
}
private static class OverrideApplyHandler implements Runnable {
private final Context mContext;
private final String mValue;
private OverrideApplyHandler(Context context, String value) {
mContext = context;
mValue = value;
}
@Override
public void run() {
// Synchronously write the preference.
prefs(mContext).edit().putString(KEY_PREFERENCE, mValue).commit();
// Clear the icon cache.
LauncherAppState.getInstance(mContext).getIconCache().clear();
// Wait for it
try {
Thread.sleep(PROCESS_KILL_DELAY_MS);
} catch (Exception e) {
Log.e(TAG, "Error waiting", e);
}
// Schedule an alarm before we kill ourself.
Intent homeIntent = new Intent(Intent.ACTION_MAIN)
.addCategory(Intent.CATEGORY_HOME)
.setPackage(mContext.getPackageName())
.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
PendingIntent pi = PendingIntent.getActivity(mContext, RESTART_REQUEST_CODE,
homeIntent, PendingIntent.FLAG_CANCEL_CURRENT | PendingIntent.FLAG_ONE_SHOT);
mContext.getSystemService(AlarmManager.class).setExact(
AlarmManager.ELAPSED_REALTIME, SystemClock.elapsedRealtime() + 50, pi);
// Kill process
android.os.Process.killProcess(android.os.Process.myPid());
}
}
設(shè)置的時候執(zhí)行上面代碼文判，主要將設(shè)置的保存到本地过椎，清除圖標緩存，然后kill Launcher process 重啟launcher戏仓。
三.怎樣通過矢量圖工作的：
源碼位置 ：Launcher90\src\com\android\launcher3\graphics\IconShapeOverride.java
IconShapeOverride.apply(getContext());
private static int getConfigResId() {
return Resources.getSystem().getIdentifier("config_icon_mask", "string", "android");
}
public static void apply(Context context) {
if (!Utilities.isAtLeastO()) {
return;
}
String path = getAppliedValue(context);
if (TextUtils.isEmpty(path)) {
return;
}
if (!isSupported(context)) {
return;
}
// magic
try {
Resources override =
new ResourcesOverride(Resources.getSystem(), getConfigResId(), path);
getSystemResField().set(null, override);
} catch (Exception e) {
Log.e(TAG, "Unable to override icon shape", e);
// revert value.
prefs(context).edit().remove(KEY_PREFERENCE).apply();
}
}
其中ResourcesOverride是繼承了Resources疚宇，并且重寫了getString方法。
private static class ResourcesOverride extends Resources {
private final int mOverrideId;
private final String mOverrideValue;
@SuppressWarnings("deprecated")
public ResourcesOverride(Resources parent, int overrideId, String overrideValue) {
super(parent.getAssets(), parent.getDisplayMetrics(), parent.getConfiguration());
mOverrideId = overrideId;
mOverrideValue = overrideValue;
}
@NonNull
@Override
public String getString(int id) throws NotFoundException {
if (id == mOverrideId) {
return mOverrideValue;
}
return super.getString(id);
}
}
在根據(jù)源碼看下getSystemResField方法：
private static Field getSystemResField() throws Exception {
Field staticField = Resources.class.getDeclaredField("mSystem");
staticField.setAccessible(true);
return staticField;
}
這個方法是反射系統(tǒng)Resources中mSystem變量赏殃。
小結(jié)：
從Launcher 源代碼可以看出大概的意思就是Launcher中將Resources 的mSystem設(shè)置成了ResourcesOverride對象敷待，
也就是說Resources的getSystem方法獲取的是我們重寫的ResourcesOverride，當調(diào)用getString方法的時候仁热，走的也是重寫的方法榜揖。getString方法里面判斷了如果string id 是config_icon_mask這個的時候，返回我們傳入的mOverrideValue抗蠢，這個mOverrideValue就是用戶選擇的圖標形狀值举哟。
追蹤下 AdaptiveIconDrawable的構(gòu)造方法：
/**
* The one constructor to rule them all. This is called by all public
* constructors to set the state and initialize local properties.
*/
AdaptiveIconDrawable(@Nullable LayerState state, @Nullable Resources res) {
mLayerState = createConstantState(state, res);
if (sMask == null) {
sMask = PathParser.createPathFromPathData(
Resources.getSystem().getString(R.string.config_icon_mask));
}
mMask = PathParser.createPathFromPathData(
Resources.getSystem().getString(R.string.config_icon_mask));
mMaskMatrix = new Matrix();
mCanvas = new Canvas();
mTransparentRegion = new Region();
}
此方法的Resources.getSystem().getString(R.string.config_icon_mask)，通過getString方法迅矛，如果id是config_icon_mask妨猩，則返回的是mOverrideValue，mOverrideValue就是上面5種里面的一種秽褒。
四.Launcher是如何獲取應(yīng)用圖標的:
public Drawable getFullResIcon(LauncherActivityInfo info) {
return mIconProvider.getIcon(info, mIconDpi);
}
public Drawable getIcon(LauncherActivityInfo info, int iconDpi) {
return info.getIcon(iconDpi);
}
最終調(diào)用到LauncherActivityInfo的getIcon方法
/**
* Returns the icon for this activity, without any badging for the profile
* @param density The preferred density of the icon, zero for default density. Use
* density DPI values from {@link DisplayMetrics}.
* @see #getBadgedIcon(int)
* @see DisplayMetrics
* @return The drawable associated with the activity.
*/
public Drawable getIcon(int density) {
// TODO: Go through LauncherAppsService
final int iconRes = mActivityInfo.getIconResource();
Drawable icon = null;
// Get the preferred density icon from the app's resources
if (density != 0 && iconRes != 0) {
try {
final Resources resources
= mPm.getResourcesForApplication(mActivityInfo.applicationInfo);
icon = resources.getDrawableForDensity(iconRes, density);
} catch (NameNotFoundException | Resources.NotFoundException exc) {
}
}
// Get the default density icon
if (icon == null) {
icon = mActivityInfo.loadIcon(mPm);
}
return icon;
}
通過以上步驟可以看出壶硅，Launcher獲取應(yīng)用圖標的時候時候，如果該應(yīng)用是支持AdaptiveIcon的話销斟，返回的圖標就是根據(jù)形狀裁剪出來的AdaptiveIconDrawable庐椒，Launcher從系統(tǒng)拿到的圖標已經(jīng)是想要的形狀圖標了。
這就是在把launcher進程kill掉蚂踊，重啟 launcher 重新獲取加載就是被裁減過的Icon形狀了扼睬。
