適配器模式

時間 2019-11-17

標籤適配器模式简体版

原文原文鏈接

適配器模式

定義

適配器模式把一個類的接口變換成客戶端所期待的另外一個接口，從而使本來因接口不匹配而沒法在一塊兒工做的兩個類可以在一塊兒工做 ##使用場景bash

系統須要使用現有的類，而此類的接口不符合系統的須要，即接口不支持
想要創建一個能夠重複使用的類，用於與一些彼此之間沒有太大關聯的一些類，包括一些可能在未來引進的類一塊兒工做
須要一個統一的輸出接口，而輸入端的類型不可預知

##模式組成ide

Target 目標角色，也就是所期待獲得的接口
Adaptee 如今須要適配的接口
adapter 適配器角色是適配器模式的核心，適配器把源接口轉換成目標接口。承擔這一角色不多是接口，而必須是具體類

##適配器模式種類適配器模式能夠分爲2種函數

類適配器模式佈局

類適配器模式是經過實現 Target 接口以及繼承 Adaptee 類來實現接口轉換ui
對象適配器模式this

對象適配器模式不是使用繼承關係鏈接到 Adaptee 類，而是使用代理關係鏈接到 Adaptee 類spa

##簡單實現實現一個簡單圓形菜單功能3d

public class MenuItem {

    public int imageId;
    public  String title;

    public MenuItem(int imageId, String title) {
        this.imageId = imageId;
        this.title = title;
    }
}
複製代碼

MenuItem 爲菜單內容實體類，用於存儲菜單項圖標和文本信息代理

public class CircleMenuLayout extends ViewGroup {

    //  圓形直徑
    private int mRadius;

    // 容器內 child item 的默認尺寸
    private static final float RADIO_DEFAULT_CHILD_DIMENSION = 1 / 4f;

    //容器的內邊距
    private static final float RADIO_PADDING_LAYOUT = 1 / 12f;

    private float mPadding;

    //佈局時的開始角度
    private double mStartAngel = 0;


    private Adapter adapter;


    private OnMenuItemClickListener onItemClickListener;

    public CircleMenuLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }


    public void setAdapter(Adapter adapter) {
        this.adapter = adapter;
    }

    public void setOnItemClickListener(OnMenuItemClickListener onItemClickListener) {
        this.onItemClickListener = onItemClickListener;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

        measureSelf(widthMeasureSpec, heightMeasureSpec);

        measureChildViews();
    }


    private void measureSelf(int widthMeasureSpec, int heightMeasureSpec) {
        int resWidth = 0;
        int resHeight = 0;

        int width = MeasureSpec.getSize(widthMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);

        int height = MeasureSpec.getSize(heightMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);

        if (widthMode != MeasureSpec.EXACTLY || heightMode != MeasureSpec.EXACTLY) {
            //設置背景圖的高度
            resWidth = getSuggestedMinimumWidth();
            resWidth = resWidth == 0 ? getDefaultWidth() : resWidth;

            //若是未設置背景圖片，則設置爲屏幕寬高的默認值
            resHeight = getSuggestedMinimumHeight();
            resHeight = resHeight == 0 ? getDefaultWidth() : resHeight;
        } else {
            resWidth = resHeight = Math.min(width, height);
        }

        setMeasuredDimension(resWidth, resHeight);
    }

    private void measureChildViews() {

        //得到半徑
        mRadius = Math.max(getMeasuredWidth(), getMeasuredHeight());

        final int count = getChildCount();

        int childSize = (int) (mRadius * RADIO_DEFAULT_CHILD_DIMENSION);

        int childMode = MeasureSpec.EXACTLY;


        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() == GONE) {
                continue;
            }
            int makeMeasureSpec = MeasureSpec.makeMeasureSpec(childSize, childMode);
            child.measure(makeMeasureSpec, makeMeasureSpec);
        }

        mPadding = RADIO_PADDING_LAYOUT * mRadius;
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b) {

        final int childCount = getChildCount();
        int left, top;
        int itemWidth = (int) (mRadius * RADIO_DEFAULT_CHILD_DIMENSION);

        //計算 item 的佈局佔用角度
        float angelDelay = 360 / childCount;

        for (int i = 0; i < adapter.getCount(); i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() == GONE) {
                continue;
            }
            mStartAngel %= 360;
            //計算中心點到 menu item 的距離
            float distancefromCenter = mRadius / 2f - itemWidth / 2 - mPadding;
            //menu item 中心點的 left 座標
            left = (int) (mRadius / 2 + Math.round(distancefromCenter * Math.cos(Math.toRadians(mStartAngel)) - 1 / 2f * itemWidth));
            // menu item 的中心點的 縱座標
            top = (int) (mRadius / 2 + Math.round(distancefromCenter * Math.sin(Math.toRadians(mStartAngel)) - 1 / 2f * itemWidth));
            //layout child item
            child.layout(left, top, left + itemWidth, top + itemWidth);
            // 疊加尺寸, 調整初始角度
            mStartAngel += angelDelay;
        }
    }

    @Override
    protected void onAttachedToWindow() {
        if (adapter != null) {
            buildMenuItems();
        }
        super.onAttachedToWindow();
    }

    private void buildMenuItems() {
        for (int i = 0; i < adapter.getCount(); i++) {
            final View viewItem = adapter.getView(i, null, this);
            final int position = i;
            viewItem.setOnClickListener(new OnClickListener() {
                @Override
                public void onClick(View v) {
                    if (onItemClickListener != null) {
                        onItemClickListener.onItemClick(viewItem, position);
                    }
                }
            });

            addView(viewItem);
        }
    }

    /**
     * 得到該 layout 的尺寸
     *
     * @return
     */
    public int getDefaultWidth() {
        WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics outMetrics = new DisplayMetrics();
        wm.getDefaultDisplay().getMetrics(outMetrics);
        return Math.min(outMetrics.widthPixels, outMetrics.heightPixels);
    }

    public interface OnMenuItemClickListener {
        void onItemClick(View view, int position);
    }
}

複製代碼

CircleMenuLayout 爲自定義圓形菜單View，該類關聯了一個Adapter 對象 adapter，Adapter是ListView、RecyclerView等View的共同父類，也就是說說適用於ListView或者RecyclerView的Adapter數據一樣也適用於該View。code

CircleMenuLayout在 onAttachedToWindow 函數中調用 Adapter 的 getCount 函數獲取菜單項的數目，而後經過 getView 函數獲取每一個 View，最後將這些 View 添加到圓形菜單中

整個過程當中，CircleMenuLayout 不知道菜單項的具體佈局和因此成員，對 CircleMenuLayout 來講無論菜單項怎麼變化，它終將是一個 view ，菜單項的具體 view 是什麼樣子，交由 Adapter 去實現

public class CircleMenuAdapter extends BaseAdapter {

    List<MenuItem> mMenuItems = new ArrayList<>();


    public CircleMenuAdapter(List<MenuItem> mMenuItems) {
        this.mMenuItems = mMenuItems;
    }

    @Override
    public int getCount() {
        return mMenuItems.size();
    }

    @Override
    public MenuItem getItem(int position) {
        if (position > mMenuItems.size()) {

        }
        return mMenuItems.get(position);
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater mInflater = LayoutInflater.from(parent.getContext());
        View itemView = mInflater.inflate(R.layout.circle_menu_item, parent, false);
        initMenuItem(itemView, position);
        return itemView;
    }

    /**
     * 初始化菜單項佈局
     *
     * @param itemView 菜單view
     * @param position 菜單項所在位置
     */
    private void initMenuItem(View itemView, int position) {
        MenuItem t = getItem(position);
        TextView tv = itemView.findViewById(R.id.circle_tv);
        ImageView iv = itemView.findViewById(R.id.circle_iv);
        iv.setImageResource(t.imageId);
        tv.setText(t.title);

    }
}

複製代碼

CircleMenuAdapter 爲getView中加載每一項菜單的佈局文件，而且綁定數據等。最終將菜單 View 返回，而後這個 View 就會被添加到 CircleMenuLayout 中。

public class TestAdapterActy extends AppCompatActivity {

    private CircleMenuLayout mLayout;

    private List<MenuItem> mMenuItems = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_testadapter_acty);

        mockMenuItems();

        mLayout = findViewById(R.id.lv);
        CircleMenuAdapter adapter = new CircleMenuAdapter(mMenuItems);

        mLayout.setOnItemClickListener(new CircleMenuLayout.OnMenuItemClickListener() {
            @Override
            public void onItemClick(View view, int position) {
                Toast.makeText(TestAdapterActy.this, mMenuItems.get(position).title, Toast.LENGTH_SHORT).show();
            }
        });

        mLayout.setAdapter(adapter);
    }

    private List<MenuItem> mockMenuItems() {

        MenuItem item0 = new MenuItem(R.mipmap.ic_launcher_round, "動漫");
        MenuItem item1 = new MenuItem(R.mipmap.ic_launcher, "電視劇");
        MenuItem item2 = new MenuItem(R.mipmap.ic_launcher_round, "電影");
        MenuItem item3 = new MenuItem(R.mipmap.ic_launcher, "音樂");
        MenuItem item4 = new MenuItem(R.mipmap.ic_launcher_round, "綜藝");

        mMenuItems.add(item0);
        mMenuItems.add(item1);
        mMenuItems.add(item2);
        mMenuItems.add(item3);
        mMenuItems.add(item4);

        return mMenuItems;
    }
}

複製代碼

運行結果以下: