android fill_parent和match_parent 的区别

三个属性都用来适应视图的水平或垂直大小，一个以视图的内容或尺寸为基础的布局比精确地指定视图范围更加方便。

1）fill_parent

设置一个构件的布局为fill_parent将强制性地使构件扩展，以填充布局单元内尽可能多的空间。这跟Windows控件的dockstyle属性大体一致。设置一个顶部布局或控件为fill_parent将强制性让它布满整个屏幕。

2） wrap_content

设置一个视图的尺寸为wrap_content将强制性地使视图扩展以显示全部内容。以TextView和ImageView控件为例，设置为wrap_content将完整显示其内部的文本和图像。布局元素将根据内容更改大小。设置一个视图的尺寸为wrap_content大体等同于设置Windows控件的Autosize属性为True。

3）match_parent
   Android2.2中match_parent和fill_parent是一个意思 .两个参数意思一样，match_parent更贴切，于是从2.2开始两个词都可以用。那么如果考虑低版本的使用情况你就需要用fill_parent了

android.view.ViewGroup.LayoutParams

/**
* Special value for the height or width requested by a View.
* FILL_PARENT means that the view wants to be as big as its parent,
* minus the parent's padding, if any. This value is deprecated
* starting in API Level 8 and replaced by {@link #MATCH_PARENT}.
*/
@SuppressWarnings({"UnusedDeclaration"})
@Deprecated
public static final int FILL_PARENT = -1;

/**
* Special value for the height or width requested by a View.
* MATCH_PARENT means that the view wants to be as big as its parent,
* minus the parent's padding, if any. Introduced in API Level 8.
*/
public static final int MATCH_PARENT = -1;

/**
* Special value for the height or width requested by a View.
* WRAP_CONTENT means that the view wants to be just large enough to fit
* its own internal content, taking its own padding into account.
*/
public static final int WRAP_CONTENT = -2;

    public static class LayoutParams {
        /**
         * Special value for the height or width requested by a View.
         * FILL_PARENT means that the view wants to be as big as its parent,
         * minus the parent's padding, if any. This value is deprecated
         * starting in API Level 8 and replaced by {@link #MATCH_PARENT}.
         */
        @SuppressWarnings({"UnusedDeclaration"})
        @Deprecated
        public static final int FILL_PARENT = -1;

        /**
         * Special value for the height or width requested by a View.
         * MATCH_PARENT means that the view wants to be as big as its parent,
         * minus the parent's padding, if any. Introduced in API Level 8.
         */
        public static final int MATCH_PARENT = -1;

        /**
         * Special value for the height or width requested by a View.
         * WRAP_CONTENT means that the view wants to be just large enough to fit
         * its own internal content, taking its own padding into account.
         */
        public static final int WRAP_CONTENT = -2;

        /**
         * Information about how wide the view wants to be. Can be one of the
         * constants FILL_PARENT (replaced by MATCH_PARENT ,
         * in API Level 8) or WRAP_CONTENT. or an exact size.
         */
        @ViewDebug.ExportedProperty(category = "layout", mapping = {
            @ViewDebug.IntToString(from = MATCH_PARENT, to = "MATCH_PARENT"),
            @ViewDebug.IntToString(from = WRAP_CONTENT, to = "WRAP_CONTENT")
        })
        public int width;

        /**
         * Information about how tall the view wants to be. Can be one of the
         * constants FILL_PARENT (replaced by MATCH_PARENT ,
         * in API Level 8) or WRAP_CONTENT. or an exact size.
         */
        @ViewDebug.ExportedProperty(category = "layout", mapping = {
            @ViewDebug.IntToString(from = MATCH_PARENT, to = "MATCH_PARENT"),
            @ViewDebug.IntToString(from = WRAP_CONTENT, to = "WRAP_CONTENT")
        })
        public int height;

        /**
         * Used to animate layouts.
         */
        public LayoutAnimationController.AnimationParameters layoutAnimationParameters;

        /**
         * Creates a new set of layout parameters. The values are extracted from
         * the supplied attributes set and context. The XML attributes mapped
         * to this set of layout parameters are:
         *
         * <ul>
         *   <li><code>layout_width</code>: the width, either an exact value,
         *   {@link #WRAP_CONTENT}, or {@link #FILL_PARENT} (replaced by
         *   {@link #MATCH_PARENT} in API Level 8)</li>
         *   <li><code>layout_height</code>: the height, either an exact value,
         *   {@link #WRAP_CONTENT}, or {@link #FILL_PARENT} (replaced by
         *   {@link #MATCH_PARENT} in API Level 8)</li>
         * </ul>
         *
         * @param c the application environment
         * @param attrs the set of attributes from which to extract the layout
         *              parameters' values
         */
        public LayoutParams(Context c, AttributeSet attrs) {
            TypedArray a = c.obtainStyledAttributes(attrs, R.styleable.ViewGroup_Layout);
            setBaseAttributes(a,
                    R.styleable.ViewGroup_Layout_layout_width,
                    R.styleable.ViewGroup_Layout_layout_height);
            a.recycle();
        }

        /**
         * Creates a new set of layout parameters with the specified width
         * and height.
         *
         * @param width the width, either {@link #WRAP_CONTENT},
         *        {@link #FILL_PARENT} (replaced by {@link #MATCH_PARENT} in
         *        API Level 8), or a fixed size in pixels
         * @param height the height, either {@link #WRAP_CONTENT},
         *        {@link #FILL_PARENT} (replaced by {@link #MATCH_PARENT} in
         *        API Level 8), or a fixed size in pixels
         */
        public LayoutParams(int width, int height) {
            this.width = width;
            this.height = height;
        }

        /**
         * Copy constructor. Clones the width and height values of the source.
         *
         * @param source The layout params to copy from.
         */
        public LayoutParams(LayoutParams source) {
            this.width = source.width;
            this.height = source.height;
        }

        /**
         * Used internally by MarginLayoutParams.
         * @hide
         */
        LayoutParams() {
        }

        /**
         * Extracts the layout parameters from the supplied attributes.
         *
         * @param a the style attributes to extract the parameters from
         * @param widthAttr the identifier of the width attribute
         * @param heightAttr the identifier of the height attribute
         */
        protected void setBaseAttributes(TypedArray a, int widthAttr, int heightAttr) {
            width = a.getLayoutDimension(widthAttr, "layout_width");
            height = a.getLayoutDimension(heightAttr, "layout_height");
        }

        /**
         * Returns a String representation of this set of layout parameters.
         *
         * @param output the String to prepend to the internal representation
         * @return a String with the following format: output +
         *         "ViewGroup.LayoutParams={ width=WIDTH, height=HEIGHT }"
         *
         * @hide
         */
        public String debug(String output) {
            return output + "ViewGroup.LayoutParams={ width="
                    + sizeToString(width) + ", height=" + sizeToString(height) + " }";
        }

        /**
         * Converts the specified size to a readable String.
         *
         * @param size the size to convert
         * @return a String instance representing the supplied size
         *
         * @hide
         */
        protected static String sizeToString(int size) {
            if (size == WRAP_CONTENT) {
                return "wrap-content";
            }
            if (size == MATCH_PARENT) {
                return "match-parent";
            }
            return String.valueOf(size);
        }
    }