Android之自定义LoadingViewHelper

针对ListView有setEmpty方法来设置加载失败时的默认显示页面，但扩展性太差。有没有通用性更强，适用为任意布局添加加载中等状态布局的方法呢？

答案是肯定的，接下来我们就去实现这样一个帮助类。申明LoadingViewHelper类，由于加载成功显示的布局为目标显示界面，所以采用构造方法注入。对于加载中以及加载失败显示的布局，申明为抽象方法，由子类决定是否实现，这样增加了扩展性。

updateLoadingView方法负责根据mLoadingStatus切换显示对应的布局，其中针对View的获取进行了优化，以免重复实例化loadingView和failedView。

changeLoadingStatus为外界提供访问接口，在业务层可控制显示加载状态对应的View。

/**
 * Created by Administrator on 2016/6/22.
 * 加载View时各种情况下的View显示
 * 未考虑提示View的宽高超出SucceedView的情况，需要自定义控制非SucceedView的宽高在SuceedView内部
 */
public abstract class LoadingViewHelper {
    public static final UtilsLog lg = UtilsLogFactory.getLogger(LoadingViewHelper.class);
    private View loadingView;
    private View succeedView;//绑定的布局，用于加载成功时显示
    private View failedView;
    private ViewGroup parentViewGroup;//父布局
    private LoadingStatus mLoadingStatus;//默认为加载中

    /**
     * 不支持SucceedView的父布局为
     *
     * @param succeedView
     */
    public LoadingViewHelper(View succeedView) {
        this.succeedView = succeedView;
        this.parentViewGroup = (ViewGroup) succeedView.getParent();
        if (parentViewGroup == null) {
            //此时succeedView为getDecorView，需要调整
            lg.e("ParentViewGroup is null:当前View为getWindow().getDecorView()");
            this.parentViewGroup = (ViewGroup) (succeedView.findViewById(android.R.id.content));
            this.succeedView = this.parentViewGroup.getChildAt(0);
        }
        this.mLoadingStatus = LoadingStatus.Loading;
        updateLoadingView();
    }

    /**
     * 根据LoadingStatus切换View显示
     */
    private void updateLoadingView() {
        switch (mLoadingStatus) {
            case Loading:
                lg.e("updateLoadingView:Loading");
                if (loadingView == null) {
                    loadingView = getLoadingView();
                    /*添加至布局中*/
                    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，则切换显示方式
     *
     * @param view
     * @param visibility
     * @return
     */
    private LoadingViewHelper settingViewVisibilityIfViewNotNull(View view, int visibility) {
        if (view != null) {
            view.setVisibility(visibility);
        }
        return this;
    }

    /**
     * 切换更新状态
     *
     * @param loadingStatus
     */
    public void changeLoadingStatus(LoadingStatus loadingStatus) {
        if (loadingStatus != null) {
            this.mLoadingStatus = loadingStatus;
            updateLoadingView();
        }
    }

    public enum LoadingStatus {
        Loading, Success, Faild;
    }

    /**
     * 获取加载状态中显示的布局
     *
     * @return
     */
    public abstract View getLoadingView();

    /**
     * 获取加载失败显示的布局
     *
     * @param succeedView
     * @return
     */
    public abstract View getFailedView(View succeedView);
}

具体在业务层的使用方式如下，postDelayed模拟请求数据的耗时操作，这里的getFailedView方法中自定义请求重试事件。

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("点击重试");
        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，这下所有的View都能添加加载状态的View显示效果了。

来自为知笔记(Wiz)