關於 RemoteViews 跨程式資源訪問的勘誤

玉剛說發表於2019-01-13
REMView

看到《Android開發藝術探索》書中 P241 頁提到RemoteViews跨程式資源訪問的限制，我在跨程式的實際使用時，證實是沒有限制的，可以跨程式使用，RemoteViews原始碼如下：

public RemoteViews(String packageName, int layoutId) {
    this(getApplicationInfo(packageName, UserHandle.myUserId()), layoutId);
}

protected RemoteViews(ApplicationInfo application, int layoutId) {
    mApplication = application;
    ...
}
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RemoteViews例項化的時候會儲存一個mApplication的變數，用於跨程式訪問資源。

/** @hide */
public View apply(Context context, ViewGroup parent, OnClickHandler handler) {
    ...
    final Context contextForResources = getContextForResources(context);
    Context inflationContext = new ContextWrapper(context) {
        @Override
        public Resources getResources() {
            return contextForResources.getResources();
        }
        @Override
        public Resources.Theme getTheme() {
            return contextForResources.getTheme();
        }
        @Override
        public String getPackageName() {
            return contextForResources.getPackageName();
        }
    };

    LayoutInflater inflater = (LayoutInflater)
            context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    ...
}

private Context getContextForResources(Context context) {
    if (mApplication != null) {
        if (context.getUserId() == UserHandle.getUserId(mApplication.uid)
                && context.getPackageName().equals(mApplication.packageName)) {
            return context;
        }
        try {
            return context.createApplicationContext(mApplication,
                    Context.CONTEXT_RESTRICTED);
        } catch (NameNotFoundException e) {
            Log.e(LOG_TAG, "Package name " + mApplication.packageName + " not found");
        }
    }

    return context;
}
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感謝網友 magazmj@gmail.com 的反饋，希望對大家有所幫助。

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