Android5.1 设置壁纸流程简析

这里只是简单分析一下5.1里是如何设置壁纸的；这个流程和4.4有一些不同。但基本都是找个地方存放壁纸文件，需要的时候读取，设置的时候更新

这里只看设置的过程。权当参考。

 

机器使用launcher3，在桌面上长按，底部显示设置壁纸的入口。

进入设置壁纸界面，观察log可知，此界面属于Trebuchet。也是launcher3

点击设置壁纸按钮，发现整个标题栏都有响应。在以下文件中可以找到相关定义：

/*--- ↓ --- WallpaperPickerActivity.java *********/

// Action bar
// Show the custom action bar view
final ActionBar actionBar = getActionBar();
actionBar.setCustomView(R.layout.actionbar_set_wallpaper);
actionBar.getCustomView().setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mSelectedTile != null) {
WallpaperTileInfo info = (WallpaperTileInfo) mSelectedTile.getTag();
info.onSave(WallpaperPickerActivity.this);
} else {
// no tile was selected, so we just finish the activity and go back
setResult(Activity.RESULT_OK);
finish();
}
}
});
mSetWallpaperButton = findViewById(R.id.set_wallpaper_button);
/*--- ↑ --- (packages/apps/Trebuchet/WallpaperPicker/src/com/android/launcher3/) *********/

整个 actionBar都拿来响应点击。info是 WallpaperTileInfo抽象类的对象，有5个子类。

这样系统能根据图片来选择使用哪一个子类。再调用 onSave方法。以FileWallpaperInfo类为例。

它复写了 onSave方法

/*--- ↓ --- WallpaperPickerActivity.java *********/
@Override
public void onSave(WallpaperPickerActivity a) {
a.setWallpaper(Uri.fromFile(mFile), true);
}
/*--- ↑ --- (packages/apps/Trebuchet/WallpaperPicker/src/com/android/launcher3/) *********/

因为WallpaperPickerActivity 继承自 WallpaperCropActivity

setWallpaper方法在 WallpaperCropActivity中找到；传入了Uri和一个boolean值

/*↓ --- WallpaperCropActivity.java *********/
protected void setWallpaper(Uri uri, final boolean finishActivityWhenDone) {
int rotation = getRotationFromExif(this, uri);
BitmapCropTask cropTask = new BitmapCropTask(
this, uri, null, rotation, 0, 0, true, false, null);
final Point bounds = cropTask.getImageBounds();
Runnable onEndCrop = new Runnable() {
public void run() {
updateWallpaperDimensions(bounds.x, bounds.y);
if (finishActivityWhenDone) {
setResult(Activity.RESULT_OK);
finish();
}
}
};
cropTask.setOnEndRunnable(onEndCrop);
cropTask.setNoCrop(true);
cropTask.execute();
}
/*↑ --- (packages/apps/trebuchet/wallpaperpicker/src/com/android/launcher3) *********/

以上代码可以看出，它启动了一个异步任务  BitmapCropTask extends AsyncTask ；把一些列参数都传入了cropTask

启动一个线程onEndCrop，等待任务结束

进入BitmapCropTask看，系统做了什么工作

这是setWallpaper使用的构造方法

/*↓ --- WallpaperCropActivity.java *********/
public BitmapCropTask(Context c, Uri inUri,
RectF cropBounds, int rotation, int outWidth, int outHeight,
boolean setWallpaper, boolean saveCroppedBitmap, Runnable onEndRunnable) {
mContext = c;
mInUri = inUri;
init(cropBounds, rotation,
outWidth, outHeight, setWallpaper, saveCroppedBitmap, onEndRunnable);
}
// ......
private void init(RectF cropBounds, int rotation, int outWidth, int outHeight,
boolean setWallpaper, boolean saveCroppedBitmap, Runnable onEndRunnable) {
Log.d("rust","init after bitmapcroptask");
mCropBounds = cropBounds;
mRotation = rotation;    //    传入各项参数
mOutWidth = outWidth;
mOutHeight = outHeight;
mSetWallpaper = setWallpaper;
mSaveCroppedBitmap = saveCroppedBitmap;
mOnEndRunnable = onEndRunnable;
}
// ...... 在这里处理任务，启动 cropBitmap()
@Override
protected Boolean doInBackground(Void... params) {
return cropBitmap();
}
// ......
public boolean cropBitmap() {
boolean failure = false;

WallpaperManager wallpaperManager = null;
if (mSetWallpaper) {
wallpaperManager = WallpaperManager.getInstance(mContext.getApplicationContext());
}

if (mSetWallpaper && mNoCrop) {
try {
InputStream is = regenerateInputStream();  // 获得InputStream
if (is != null) {
wallpaperManager.setStream(is);    // 把is写进去，从这里进入到wallpaperManager
Utils.closeSilently(is);
}
} catch (IOException e) {
Log.w(LOGTAG, "cannot write stream to wallpaper", e);
failure = true;
}
return !failure;
} else { // 顺利的话不会进入这里
// ......
// Helper to setup input stream
private InputStream regenerateInputStream() {
if (mInUri == null && mInResId == 0 && mInFilePath == null && mInImageBytes == null) {
Log.w(LOGTAG, "cannot read original file, no input URI, resource ID, or " +
"image byte array given");
} else {
try {
String filepath = mInFilePath;
if(mInUri != null){
filepath = DrmHelper.getFilePath(mContext, mInUri);
}
if(DrmHelper.isDrmFile(filepath)){
byte[] bytes = DrmHelper.getDrmImageBytes(filepath);
return new ByteArrayInputStream(bytes);    //    返回一个ByteArray
}
/*↑ --- (packages/apps/trebuchet/wallpaperpicker/src/com/android/launcher3) *********/

调用了wallpaperManager.setStream(is);进入 WallpaperManager.java 看看

/*↓ --- WallpaperManager.java *********/

public void setStream(InputStream data) throws IOException {  //luncher3 里直接调用了这个方法
if (sGlobals.mService == null) {                          //WallpaperCropActivity 调用
Log.w(TAG, "WallpaperService not running");
return;
}
try {
ParcelFileDescriptor fd = sGlobals.mService.setWallpaper(null);  // 利用service得到fd
if (fd == null) {    // 这里要去WallpaperManagerService里找到对应方法
return;
}
FileOutputStream fos = null;
try {
fos = new ParcelFileDescriptor.AutoCloseOutputStream(fd);
setWallpaper(data, fos);    // 写入壁纸数据
} finally {
if (fos != null) {
fos.close();
}
}
} catch (RemoteException e) {
// Ignore
}
}
// ...... 在这里写入壁纸，写入过程结束，Manager完成任务
private void setWallpaper(InputStream data, FileOutputStream fos)
throws IOException {
byte[] buffer = new byte[32768];
int amt;
while ((amt=data.read(buffer)) > 0) {
fos.write(buffer, 0, amt);
}
}
/*↑ --- (framework/base/core/java/android/app) *********/

再来看Globals extends IWallpaperManagerCallback.Stub

包含成员变量 IWallpaperManager mService，通过

Globals(Looper looper) {
IBinder b = ServiceManager.getService(Context.WALLPAPER_SERVICE);
mService = IWallpaperManager.Stub.asInterface(b);
}

调用 WallpaperManagerService.java 里的setWallpaper方法

Service的作用

进入WallpaperManagerService看看，是如何返回ParcelFileDescriptor值的

/*↓ --- WallpaperManagerService.java *********/
public ParcelFileDescriptor setWallpaper(String name) {    //  供 WallpaperManager 调用
checkPermission(android.Manifest.permission.SET_WALLPAPER);
synchronized (mLock) {
if (DEBUG) Slog.v(TAG, "setWallpaper");
int userId = UserHandle.getCallingUserId();
WallpaperData wallpaper = mWallpaperMap.get(userId);
if (wallpaper == null) {
throw new IllegalStateException("Wallpaper not yet initialized for user " + userId);
}
final long ident = Binder.clearCallingIdentity();
try {
ParcelFileDescriptor pfd = updateWallpaperBitmapLocked(name, wallpaper);
if (pfd != null) {// 启动下面的方法
wallpaper.imageWallpaperPending = true;
}
return pfd;    // 返回ParcelFileDescriptor值给WallpaperManager
} finally {
Binder.restoreCallingIdentity(ident);
}
}
}

ParcelFileDescriptor updateWallpaperBitmapLocked(String name, WallpaperData wallpaper) {
if (name == null) name = "";
try {
File dir = getWallpaperDir(wallpaper.userId);  // 找到壁纸
if (!dir.exists()) {
dir.mkdir();
FileUtils.setPermissions(
dir.getPath(),
FileUtils.S_IRWXU|FileUtils.S_IRWXG|FileUtils.S_IXOTH,
-1, -1);
}
File file = new File(dir, WALLPAPER); //创建一个新的文件
ParcelFileDescriptor fd = ParcelFileDescriptor.open(file,
MODE_CREATE|MODE_READ_WRITE|MODE_TRUNCATE);
if (!SELinux.restorecon(file)) {
return null;
}
wallpaper.name = name;
return fd;    // 返回ParcelFileDescriptor值
} catch (FileNotFoundException e) {
Slog.w(TAG, "Error setting wallpaper", e);
}
return null;
}

private static File getWallpaperDir(int userId) {  // 取得壁纸文件
return Environment.getUserSystemDirectory(userId);
}
/*↑ --- (framework/base/services/core/java/com/android/server/wallpaper/) *********/

至此一个简单的流程就结束了

我们可反过来看

壁纸文件是存在 Environment.getUserSystemDirectory(userId) 这个路径下

WallpaperManagerService取到这个文件后，将其打开为ParcelFileDescriptor形式，交给WallpaperManager

WallpaperManager把launcher传来的数据写入这个文件中

小结一下：

选定壁纸，点击按钮，launcher把壁纸信息给WallpaperManager；

WallpaperManagerService把存放壁纸的文件打开，交给WallpaperManager

WallpaperManager把壁纸信息写入；一次设置壁纸的动作就完成了

这里传输数据使用到engine，一个挺有意思的东西。