Android 設計模式之原型模式

標籤：

簡介：在系統中要建立大量的對象，這些對象之間具有幾乎完全相同的功能，只是在細節上有一點兒差別

用原型執行個體指定建立對象的種類，並且通過拷貝這些原型建立新的對象   

example 1：

我們需要一張Bitmap的幾種不同格式：ARGB_8888、RGB_565、ARGB_4444、ALAPHA_8等。那我們就可以先建立一個ARGB_8888的Bitmap作為原型，在它的基礎上，通過調用Bitmap.copy(Config)來建立出其它幾種格式的Bitmap

  /**     * Tries to make a new bitmap based on the dimensions of this bitmap,     * setting the new bitmap‘s config to the one specified, and then copying     * this bitmap‘s pixels into the new bitmap. If the conversion is not     * supported, or the allocator fails, then this returns NULL.  The returned     * bitmap initially has the same density as the original.     *     * @param config    The desired config for the resulting bitmap     * @param isMutable True if the resulting bitmap should be mutable (i.e.     *                  its pixels can be modified)     * @return the new bitmap, or null if the copy could not be made.     */    public Bitmap copy(Config config, boolean isMutable) {        checkRecycled("Can‘t copy a recycled bitmap");        Bitmap b = nativeCopy(mNativeBitmap, config.nativeInt, isMutable);        if (b != null) {            b.setPremultiplied(mRequestPremultiplied);            b.mDensity = mDensity;        }        return b;    }

另外一個例子就是Java中所有對象都有的一個名字叫clone的方法

   /**     * Copy constructor.     */    public Intent(Intent o) {        this.mAction = o.mAction;        this.mData = o.mData;        this.mType = o.mType;        this.mPackage = o.mPackage;        this.mComponent = o.mComponent;        this.mFlags = o.mFlags;        this.mContentUserHint = o.mContentUserHint;        if (o.mCategories != null) {            this.mCategories = new ArraySet<String>(o.mCategories);        }        if (o.mExtras != null) {            this.mExtras = new Bundle(o.mExtras);        }        if (o.mSourceBounds != null) {            this.mSourceBounds = new Rect(o.mSourceBounds);        }        if (o.mSelector != null) {            this.mSelector = new Intent(o.mSelector);        }        if (o.mClipData != null) {            this.mClipData = new ClipData(o.mClipData);        }    }    @Override    public Object clone() {        return new Intent(this);    }

 

Android 設計模式之原型模式