效果 GIF

簡單介紹一下這個控件，像我們在實際的開發(fā)過程中，經(jīng)常性的會遇到這樣的場景，比如進入一個頁面先出來加載動畫，然后請求數(shù)據(jù)，如果網(wǎng)絡(luò)異常就顯示網(wǎng)絡(luò)異常的布局，數(shù)據(jù)異常、數(shù)據(jù)為空也有相應(yīng)的布局，以及當我們請求成功完畢數(shù)據(jù)后，根據(jù)返回的數(shù)據(jù)值去區(qū)分不同VIP等級的用戶顯示不同的頁面，這里我放了兩張圖，我的女神，迪麗熱巴和俞飛鴻，就當做我們在業(yè)務(wù)開發(fā)中的 Layout ，把布局全部寫在 xml，然后控制顯示隱藏就有點不優(yōu)雅了，基于這個問題，就有了這個控件。

下面是自定義 View 的自定義屬性：

<declare-styleable name="EasyStateView">

        // 是否使用過渡動畫
        <attr name="esv_use_anim" format="boolean"/>

        // 加載動畫 View
        <attr name="esv_loadingView" format="reference" />

        // 數(shù)據(jù)異常，加載失敗 View
        <attr name="esv_errorDataView" format="reference" />

        // 網(wǎng)絡(luò)異常 View
        <attr name="esv_errorNetView" format="reference" />

        // 空白頁面 View
        <attr name="esv_emptyView" format="reference" />

        // 設(shè)置當前顯示的 viewState
        <attr name="esv_viewState" format="enum">
            <enum name="content" value="0" />
            <enum name="loading" value="-1" />
            <enum name="error_data" value="-2" />
            <enum name="error_net" value="-3" />
            <enum name="empty" value="-4" />
        </attr>

    </declare-styleable>

Java代碼：

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.animation.ObjectAnimator;
import android.content.Context;
import android.content.res.TypedArray;
import android.os.Parcel;
import android.os.Parcelable;
import android.util.AttributeSet;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.FrameLayout;

public class EasyStateView extends FrameLayout {

    // 內(nèi)容 View
    public static final int VIEW_CONTENT = 0;
    // 加載 View
    public static final int VIEW_LOADING = -1;
    // 數(shù)據(jù)異常( 數(shù)據(jù)異常指原本應(yīng)該是有數(shù)據(jù)，但是服務(wù)器返回了錯誤的、不符合格式的數(shù)據(jù) ) View
    public static final int VIEW_ERROR_DATA = -2;
    // 網(wǎng)絡(luò)異常 View
    public static final int VIEW_ERROR_NET = -3;
    // 數(shù)據(jù)為空 View
    public static final int VIEW_EMPTY = -4;
    // View 的 Tag 標簽值
    private static final int VIEW_TAG = -5;
    // 用來存放 View
    private SparseArray<View> mViews;
    // 是否使用過渡動畫
    private boolean mUseAnim;
    // 是否處于動畫中
    private boolean isAniming;
    // 當前顯示的 ViewTag
    private int mCurrentState;
    private Context mContext;
    private StateViewListener mListener;
    // content View 是否被添加到隊列
    private boolean isAddContent;

    public interface StateViewListener {
        void onStateChanged(int state);
    }

    public void setStateChangedListener(StateViewListener listener) {
        this.mListener = listener;
    }

    public EasyStateView(Context context) {
        this(context, null);
    }

    public EasyStateView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public EasyStateView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(context, attrs);
    }

    private void init(Context context, AttributeSet attrs) {
        mContext = context;
        mViews = new SparseArray<>();
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.EasyStateView);
        mCurrentState = typedArray.getInt(R.styleable.EasyStateView_esv_viewState, VIEW_CONTENT);
        int emptyResId = typedArray.getResourceId(R.styleable.EasyStateView_esv_emptyView, VIEW_TAG);
        if (emptyResId != VIEW_TAG) {
            View view = LayoutInflater.from(getContext()).inflate(emptyResId, this, false);
            addViewToHash(view, VIEW_EMPTY);
            addViewInLayout(view, -1, view.getLayoutParams());
        }
        int errorDataResId = typedArray.getResourceId(R.styleable.EasyStateView_esv_errorDataView, VIEW_TAG);
        if (errorDataResId != VIEW_TAG) {
            View view = LayoutInflater.from(getContext()).inflate(errorDataResId, this, false);
            addViewToHash(view, VIEW_ERROR_DATA);
            addViewInLayout(view, -1, view.getLayoutParams());
        }
        int errorNetResId = typedArray.getResourceId(R.styleable.EasyStateView_esv_errorNetView, VIEW_TAG);
        if (errorNetResId != VIEW_TAG) {
            View view = LayoutInflater.from(getContext()).inflate(errorNetResId, this, false);
            addViewToHash(view, VIEW_ERROR_NET);
            addViewInLayout(view, -1, view.getLayoutParams());
        }
        int loadingResId = typedArray.getResourceId(R.styleable.EasyStateView_esv_loadingView, VIEW_TAG);
        if (loadingResId != VIEW_TAG) {
            View view = LayoutInflater.from(getContext()).inflate(loadingResId, this, false);
            addViewToHash(view, VIEW_LOADING);
            addViewInLayout(view, -1, view.getLayoutParams());
        }
        mUseAnim = typedArray.getBoolean(R.styleable.EasyStateView_esv_use_anim, true);
        typedArray.recycle();
    }

    @Override
    public void addView(View child) {
        addContentV(child);
        super.addView(child);
    }

    private boolean isContentView(View child) {
        if (!isAddContent && null != child
                && null == child.getTag()) {
            return true;
        }
        return false;
    }

    private void addContentV(View child) {
        if (isContentView(child)) {
            addViewToHash(child, VIEW_CONTENT);
            isAddContent = true;
        }
    }

    private void addViewToHash(View child, int viewTag) {
        child.setTag(viewTag);
        if (viewTag != mCurrentState) {
            child.setVisibility(GONE);
        }
        mViews.put(viewTag, child);
    }

    @Override
    public void addView(View child, int index) {
        addContentV(child);
        super.addView(child, index);
    }

    @Override
    public void addView(View child, int index, ViewGroup.LayoutParams params) {
        addContentV(child);
        super.addView(child, index, params);
    }

    @Override
    public void addView(View child, ViewGroup.LayoutParams params) {
        addContentV(child);
        super.addView(child, params);
    }

    @Override
    public void addView(View child, int width, int height) {
        addContentV(child);
        super.addView(child, width, height);
    }

    @Override
    protected boolean addViewInLayout(View child, int index, ViewGroup.LayoutParams params) {
        addContentV(child);
        return super.addViewInLayout(child, index, params);
    }

    @Override
    protected boolean addViewInLayout(View child, int index, ViewGroup.LayoutParams params, boolean preventRequestLayout) {
        addContentV(child);
        return super.addViewInLayout(child, index, params, preventRequestLayout);
    }


    @Override
    protected Parcelable onSaveInstanceState() {
        Parcelable parcelable = super.onSaveInstanceState();
        int useAnim = 0;
        if (mUseAnim) {
            useAnim = 1;
        }
        return new SaveState(parcelable, mCurrentState, useAnim);
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {
        SaveState saveState = (SaveState) state;
        if (saveState.useAnim == 1) {
            mUseAnim = true;
        } else {
            mUseAnim = false;
        }
        // 因為應(yīng)用方向改變觸發(fā)重繪后，重新初始化讀取的 ViewState 是不準確的，所以要隱藏掉
        if (saveState.viewState != mCurrentState) {
            getStateView(mCurrentState).setVisibility(GONE);
            showViewState(saveState.viewState);
        }
        super.onRestoreInstanceState(saveState.getSuperState());
    }

    private static class SaveState extends BaseSavedState {

        private int viewState;
        /**
         * 布爾值存儲居然沒有api，只能存儲布爾數(shù)組，故改成 int 記錄
         * 1 使用動畫
         * 2 不使用動畫
         */
        private int useAnim;

        private SaveState(Parcel source) {
            super(source);
            viewState = source.readInt();
        }

        private SaveState(Parcelable superState, int viewState, int useAnim) {
            super(superState);
            this.viewState = viewState;
            this.useAnim = useAnim;
        }

        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeInt(viewState);
            out.writeInt(useAnim);
        }

        public static final Parcelable.Creator<SaveState> CREATE = new Parcelable.Creator<SaveState>() {

            @Override
            public SaveState createFromParcel(Parcel source) {
                return new SaveState(source);
            }

            @Override
            public SaveState[] newArray(int size) {
                return new SaveState[size];
            }
        };
    }

    /**
     * 切換默認狀態(tài)的 View
     *
     * @param state
     */
    public void showViewState(int state) {
        if (!checkState(state)) {
            showViewAnim(state, VIEW_TAG);
        }
    }

    /**
     * 切換 view 時用 loading view 過渡
     *
     * @param state
     */
    public void afterLoadingState(int state) {
        if (!checkState(state)) {
            if (mCurrentState == VIEW_LOADING) {
                showViewAnim(state, VIEW_TAG);
            } else {
                showViewAnim(VIEW_LOADING, state);
            }
        }
    }

    /**
     * 檢查狀態(tài)是否合法
     * true 表示不合法，不往下執(zhí)行
     * false 表示該狀態(tài)和當前狀態(tài)不同，并合法數(shù)值狀態(tài)
     *
     * @param state
     * @return
     */
    private boolean checkState(int state) {
        if (state <= VIEW_TAG) {
            throw new RuntimeException("ViewState 不在目標范圍");
        }
        if (state == mCurrentState) {
            return true;
        } else if (isAniming) {
            return true;
        }
        return false;
    }

    public void setUseAnim(boolean useAnim) {
        this.mUseAnim = useAnim;
    }

    private void showViewAnim(int showState, int afterState) {
        if (!isAniming) {
            isAniming = true;
        }
        View showView = getStateView(showState);
        if (null == showView) {
            isAniming = false;
            return;
        }
        View currentView = getStateView(mCurrentState);
        if (mUseAnim) {
            showAlpha(showState, afterState, showView, currentView);
        } else {
            currentView.setVisibility(GONE);
            if (showView.getAlpha() == 0) {
                showView.setAlpha(1f);
            }
            showView.setVisibility(VISIBLE);
            mCurrentState = showState;
            if (null != mListener) {
                mListener.onStateChanged(showState);
            }
            isAniming = false;
        }
    }

    /**
     * 參數(shù)依次為：顯示的狀態(tài)、顯示之后的狀態(tài)碼、要顯示的 View、當前的 View
     *
     * @param showState
     * @param afterState
     * @param showView
     * @param currentView
     */
    private void showAlpha(final int showState, final int afterState, final View showView,
                           final View currentView) {
        ObjectAnimator currentAnim = ObjectAnimator.ofFloat(currentView, "alpha", 1, 0);
        currentAnim.setDuration(250L);
        final ObjectAnimator showAnim = ObjectAnimator.ofFloat(showView, "alpha", 0, 1);
        showAnim.setDuration(250L);
        showAnim.addListener(new AnimatorListenerAdapter() {

            @Override
            public void onAnimationEnd(Animator animation) {
                super.onAnimationEnd(animation);
                if (null != mListener) {
                    mListener.onStateChanged(showState);
                }
                if (afterState != VIEW_TAG) {
                    showViewAnim(afterState, VIEW_TAG);
                } else {
                    isAniming = false;
                }
            }
        });
        currentAnim.addListener(new AnimatorListenerAdapter() {

            @Override
            public void onAnimationEnd(Animator animation) {
                super.onAnimationEnd(animation);
                currentView.setVisibility(GONE);
                showView.setVisibility(VISIBLE);
                showAnim.start();
                mCurrentState = showState;
            }
        });
        currentAnim.start();
    }

    public int getCurrentState() {
        return mCurrentState;
    }

    public View getStateView(int state) {
        if (state <= VIEW_TAG) {
            throw new RuntimeException("ViewState 不在目標范圍");
        }
        return mViews.get(state);
    }

    public void addUserView(int state, int layId) {
        setUserDefView(state, null, layId);
    }

    public void addUserView(int state, View view) {
        setUserDefView(state, view, -1);
    }

    private void setUserDefView(int state, View view, int layId) {
        if (state <= 0) {
            throw new RuntimeException("自定義的 ViewState TAG 必須大于 0");
        }
        if (null == view && layId != -1) {
            view = LayoutInflater.from(mContext).inflate(layId, this, false);
        }
        addViewToHash(view, state);
        addViewInLayout(view, -1, view.getLayoutParams());
    }

}

簡單說明一下，繼承 FrameLayout 是因為幀布局是效率最高的布局，添加 View 到布局中用的是addViewInLayout，這里解釋一下為什么不用addView，因為addView會觸發(fā) requestLayout，addViewInLayout會先添加進去，然后再統(tǒng)一觸發(fā)布局，這個控件的用法非常簡單，控件里面已經(jīng)內(nèi)置了很多常用的場景類型，你可以通過 addUserView()這個方法來添加你的 View，目前只有一個過渡動畫，后續(xù)考慮迭代。

項目的 Github 地址 https://github.com/MarkRaoAndroid/EasyStateView