Android之自定義LoadingViewHelper

針對ListView有setEmpty方法來設置加載失敗時的默認顯示頁面，但擴展性太差。有沒有通用性更強，適用爲任意佈局添加加載中等狀態佈局的方法呢？

答案是確定的，接下來咱們就去實現這樣一個幫助類。申明LoadingViewHelper類，因爲加載成功顯示的佈局爲目標顯示界面，因此採用構造方法注入。對於加載中以及加載失敗顯示的佈局，申明爲抽象方法，由子類決定是否實現，這樣增長了擴展性。

updateLoadingView方法負責根據mLoadingStatus切換顯示對應的佈局，其中針對View的獲取進行了優化，以避免重複實例化loadingView和failedView。

changeLoadingStatus爲外界提供訪問接口，在業務層可控制顯示加載狀態對應的View。

/**
 * Created by Administrator on 2016/6/22.
 * 加載View時各類狀況下的View顯示
 * 未考慮提示View的寬高超出SucceedView的狀況，須要自定義控制非SucceedView的寬高在SuceedView內部
 */
public abstract class LoadingViewHelper {
    public static final UtilsLog lg = UtilsLogFactory.getLogger(LoadingViewHelper.class);
    private View loadingView;
    private View succeedView;//綁定的佈局，用於加載成功時顯示
    private View failedView;
    private ViewGroup parentViewGroup;//父佈局
    private LoadingStatus mLoadingStatus;//默認爲加載中

    /**
     * 不支持SucceedView的父佈局爲
     *
     * @param succeedView
     */
    public LoadingViewHelper(View succeedView) {
        this.succeedView = succeedView;
        this.parentViewGroup = (ViewGroup) succeedView.getParent();
        if (parentViewGroup == null) {
            //此時succeedView爲getDecorView，須要調整
            lg.e("ParentViewGroup is null:當前View爲getWindow().getDecorView()");
            this.parentViewGroup = (ViewGroup) (succeedView.findViewById(android.R.id.content));
            this.succeedView = this.parentViewGroup.getChildAt(0);
        }
        this.mLoadingStatus = LoadingStatus.Loading;
        updateLoadingView();
    }

    /**
     * 根據LoadingStatus切換View顯示
     */
    private void updateLoadingView() {
        switch (mLoadingStatus) {
            case Loading:
                lg.e("updateLoadingView:Loading");
                if (loadingView == null) {
                    loadingView = getLoadingView();
                    /*添加至佈局中*/
                    if (loadingView != null) {
                        ViewGroup.LayoutParams layoutParams = succeedView.getLayoutParams();
                        parentViewGroup.addView(loadingView, layoutParams);
                    }
                }
                settingViewVisibilityIfViewNotNull(loadingView, View.VISIBLE)
                        .settingViewVisibilityIfViewNotNull(succeedView, View.GONE)
                        .settingViewVisibilityIfViewNotNull(failedView, View.GONE);
                break;
            case Success:
                lg.e("updateLoadingView:Success");
                settingViewVisibilityIfViewNotNull(loadingView, View.GONE)
                        .settingViewVisibilityIfViewNotNull(succeedView, View.VISIBLE)
                        .settingViewVisibilityIfViewNotNull(failedView, View.GONE);
                break;
            case Faild:
                lg.e("updateLoadingView:Faild");
                if (failedView == null) {
                    failedView = getFailedView(succeedView);
                    if (failedView != null) {
                        ViewGroup.LayoutParams layoutParams = succeedView.getLayoutParams();
                        parentViewGroup.addView(failedView, layoutParams);
                    }
                }
                settingViewVisibilityIfViewNotNull(loadingView, View.GONE)
                        .settingViewVisibilityIfViewNotNull(succeedView, View.GONE)
                        .settingViewVisibilityIfViewNotNull(failedView, View.VISIBLE);
                break;
        }
    }

    /**
     * 若View非空，則切換顯示方式
     *
     * @param view
     * @param visibility
     * @return
     */
    private LoadingViewHelper settingViewVisibilityIfViewNotNull(View view, int visibility) {
        if (view != null) {
            view.setVisibility(visibility);
        }
        return this;
    }

    /**
     * 切換更新狀態
     *
     * @param loadingStatus
     */
    public void changeLoadingStatus(LoadingStatus loadingStatus) {
        if (loadingStatus != null) {
            this.mLoadingStatus = loadingStatus;
            updateLoadingView();
        }
    }

    public enum LoadingStatus {
        Loading, Success, Faild;
    }

    /**
     * 獲取加載狀態中顯示的佈局
     *
     * @return
     */
    public abstract View getLoadingView();

    /**
     * 獲取加載失敗顯示的佈局
     *
     * @param succeedView
     * @return
     */
    public abstract View getFailedView(View succeedView);
}

具體在業務層的使用方式以下，postDelayed模擬請求數據的耗時操做，這裏的getFailedView方法中自定義請求重試事件。

final LoadingViewHelper loadingViewHelper = new LoadingViewHelper(btnActCahngeSkinShowStyle) {
    @Override
    public View getLoadingView() {
        ImageView imageView = new ImageView(getCurActivity());
        imageView.setImageResource(R.mipmap.ic_famer_help_seize);
        imageView.setBackgroundColor(Color.RED);
        return imageView;
    }

    @Override
    public View getFailedView(View succeedView) {
        Button btn = new Button(getCurActivity());
        btn.setText("點擊重試");
        btn.setBackgroundColor(Color.YELLOW);
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                changeLoadingStatus(LoadingStatus.Loading);
                AppHelper.getInstance().getLooperHandler().postDelayed(new Runnable() {
                    @Override
                    public void run() {
                        changeLoadingStatus(LoadingStatus.Success);
                    }
                }, 10000);
            }
        });
        return btn;
    }
};

AppHelper.getInstance().getLooperHandler().postDelayed(new Runnable() {
    @Override
    public void run() {
        loadingViewHelper.changeLoadingStatus(LoadingViewHelper.LoadingStatus.Faild);
    }
}, 10000);

ok，這下全部的View都能添加加載狀態的View顯示效果了。

來自爲知筆記(Wiz)