ActionMode簡介

Android 3.0以前，我們處理列表的長按事件經(jīng)常使用Context Menu，Android3.0以后，我們有了新的選擇：ActionMode。

Android開發(fā)者應該都熟悉Context Menu了，Context Menu是懸浮在操作項之上的視圖，ActionMode是臨時占據(jù)了ActionBar的位置。

ActionMode使用步驟

實現(xiàn)ActionMode.Callbak接口，并處理其生命周期方法即可

1.public boolean onCreateActionMode(ActionMode mode, Menu menu)

2.public boolean onPrepareActionMode(ActionMode mode, Menu menu)

3.public boolean onActionItemClicked(ActionMode mode, MenuItem item)

4.public void onDestroyActionMode(ActionMode mode)

重寫ActionMode

package com.example.simpleexplore;

import android.app.Activity;

import android.support.v7.view.ActionMode;

import android.view.Menu;

import android.view.MenuItem;

import android.view.Window;

/**

* Created by Administrator on 2017/8/5 0005.

*/

public class ActionModeCallback implements ActionMode.Callback{

    private Activity activity;

    private Window window;

    private ActionListener mActionListener;

    private ActionMode actionMode;

    private boolean isShowing = true;

    public ActionModeCallback(Activity activity,ActionListener listener){

        this.activity = activity;

        this.window = activity.getWindow();

        mActionListener = listener;

    }

    @Override

    public boolean onCreateActionMode(ActionMode mode, Menu menu) {

        actionMode = mode;

        mode.getMenuInflater().inflate(R.menu.menu_item_top,menu);

        return true;

    }

    @Override

    public boolean onPrepareActionMode(ActionMode mode, Menu menu) {

        return false;

    }

    @Override

    public boolean onActionItemClicked(ActionMode mode, MenuItem item) {

        if(item.getItemId() == R.id.menu_item_done){

            if(mActionListener != null){

                mActionListener.onFinishAction();

            }

        }else if(item.getItemId() == R.id.menu_item_delete){

          if(mActionListener != null){

              mActionListener.onDeleteAction();

          }

        }

        mode.finish();

        return false;

    }

    @Override

    public void onDestroyActionMode(ActionMode mode) {

        isShowing = false;

        if(mActionListener != null){

            mActionListener.onDismissAction();

        }

    }

    /**

    * 更新title

    * @param count

    */

    public void updateTitleSelectItemCount(int count){

        if(actionMode != null){

            actionMode.setTitle(count + (count > 1?"items":"item") + "selected");

        }

    }

    /**

    * 退出actionMode

    */

    public void dismiss(){

        if(actionMode != null){

            actionMode.finish();

        }

    }

    /**

    * ActionmMode 是否開啟

    */

    public boolean isShowing(){

        return isShowing;

    }

    /**

    * 設置ActionMode的開啟

    * @param showing

    */

    public void setShowing(boolean showing){

        isShowing = showing;

    }

    /**

    * actionMode的監(jiān)聽者

    */

    public interface ActionListener {

        void onFinishAction();

        void onDismissAction();

        void onDeleteAction();

    }

}

```

###定義文件model

```

public class FileWraper {

    /**

    * 文件

    */

    public File file;

    /**

    * 是否選中

    */

    public boolean isSelected = false;

    public FileWraper(){

    }

    public FileWraper(File file){

        this.file = file;

    }

    public FileWraper(File file,boolean isSelected){

        this.file = file;

        this.isSelected = isSelected;

    }

}

```

###定義堆棧

存儲每次瀏覽時訪問節(jié)點的記錄

```

public class FileTreeStack {

    //棧頂節(jié)點

    private Node mTopNode;

    //棧內(nèi)元素個數(shù)

    private int mSize;

    //入棧

    public void push(FileShotSnap shotSnap){

        Node node = new Node();

        node.shotSnap = shotSnap;

        node.next = mTopNode;

        mTopNode = node;//尾插法

        mSize++;

    }

    //出棧

    public FileShotSnap pop(){

        if(mTopNode == null) return null;

        FileShotSnap shotSnap = mTopNode.shotSnap;

        mTopNode = mTopNode.next;

        mSize--;

        return shotSnap;

    }

    /**

    * 返回堆棧大小

    * @return

    */

    public int size(){

        return mSize;

    }

    //訪問節(jié)點

    class Node {

        FileShotSnap shotSnap;

        Node next;//指向下一個節(jié)點

    }

    public static class FileShotSnap {

        //母文件夾

        public File parent;

        //此文件夾下的文件

        public List files;

        //y上的滑動距離

        public int ScrollY;

    }

}

```

###MainActvity

```

public class FileExploreActivity extends BaseActivity {

    @BindView(R.id.recycler_view)

    RecyclerView recyclerView;

    private int position;

    //根目錄

    private File rootFile = Environment.getExternalStorage();

    //文件訪問棧

    private FileTreeStack mFileStack;

    private ActionModeCallback mCallback;


//當前狀態(tài)下的母文件夾

File mCurrentFileParent;

//當前所有文件

List mCurrentFiles;

//選中的文件列表

List mSelectedFiles = new ArrayList<>();

private FileAdapter adapter;

    @Override

    protected void onCreate(@Nullable Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_file_explore);

        ButterKnife.bind(this);

        initView();

    }

    //回退

    @Override

    public void onBackPressed() {

        if(mFileStack.size() == 0){

            super.onBackPressed();

        }else {

            restoreTreeStack(mFileStack.pop());

        }

    }

    private void initView() {

        adapter = new FileAdapter(this,null);

        adapter.setOnClickListener(new ListAdapter.OnItemClickListener() {

            @Override

            public void onClick(View itemView, int position) {

                //獲取選中文件

                FileWraper item = adapter.getItem(position);

                if(item.file.isDirectory()){

                    //如果是在選擇狀態(tài)

                    if(isInModeAction()){

                        //選中或取消文件

                        updateSelectFiles(item,position);

                    }else {

                        //進入文件夾 首先堆棧

                        storeTreeStack();

                        //加載文件

                        loadFiles(item.file);

                        //刷新標題

                        updateTitle();

                    }

                }

            }

        });

        adapter.setOnItemLongClickListener(new ListAdapter.OnItemLongClickListener() {

            @Override

            public void onLongClick(View itemView, int position) {

                FileWraper item = adapter.getItem(position);

                //長按進入選則文件狀態(tài)

                if(item.file.isDirectory()){

                    if(mCallback == null || !mCallback.isShowing()){

                        startActionMode();

                    }

                    //選中或取消文件

                    updateSelectFiles(item,position);

                }

            }

        });

        recyclerView.setAdapter(adapter);

        //加載音樂

        loadFiles(rootFile);

    }

    private void startActionMode() {

        if(mCallback == null){

            mCallback = new ActionModeCallback(this, new ActionModeCallback.ActionListener() {

                @Override

                public void onFinishAction() {

                    //選中

                    Toast.makeText(FileExploreActivity.this, "選中所有", Toast.LENGTH_SHORT).show();

                    if(mSelectedFiles.size() > 0){

                        //操作

                    } else {

                        mCallback.dismiss();

                    }

                }

                @Override

                public void onDismissAction() {

                    //取消

                    Toast.makeText(FileExploreActivity.this, "取消續(xù)重", Toast.LENGTH_SHORT).show();

                    clearSelections();

                }

                @Override

                public void onDeleteAction() {

                    //刪除

                    Toast.makeText(FileExploreActivity.this, "刪除選中文件", Toast.LENGTH_SHORT).show();

                }

            });

        }

        startSupportActionMode(mCallback);//開啟ActionMode ActionBar被替代，進入選擇文件狀態(tài)

        mCallback.setShowing(true);

    }

    //清楚當前所有選中文件

    private void clearSelections() {

        boolean needClear = mSelectedFiles.size() > 0;

        mSelectedFiles.clear();

        if(needClear){

            adapter.clearSelections();

            adapter.notifyDataSetChanged();

        }

    }

    //更新選中或取消

    private void updateSelectFiles(FileWraper fileWraper,int position) {

        if(fileWraper.file.isFile()) return;

        //更新文件選中狀態(tài)

        fileWraper.isSelected = !fileWraper.isSelected;

        //添加或取消選中

        if(fileWraper.isSelected){

            mSelectedFiles.add(fileWraper.file);

        }else {

            if(mSelectedFiles.indexOf(fileWraper.file) != -1){

                mSelectedFiles.remove(fileWraper.file);

            }

        }

        //更新UI

        adapter.notifyItemChanged(position);

        //更新選中UI

        mCallback.updateTitleSelectItemCount(mSelectedFiles.size());

    }

    /**

    * 更新標題

    */

    private void updateTitle() {

        getSupportActionBar().setTitle(mCurrentFileParent.getName());

    }

    /**

    * 存儲節(jié)點

    */

    private void storeTreeStack() {

        //把當前節(jié)點加入樹棧中

        FileTreeStack.FileShotSnap shotSnap = new FileTreeStack.FileShotSnap();

        shotSnap.parent = mCurrentFileParent;

        shotSnap.files = mCurrentFiles;

        mFileStack.push(shotSnap);

    }

    /**

    * 取出節(jié)點

    * @param top

    */

    private void restoreTreeStack(FileTreeStack.FileShotSnap top) {

        mCurrentFileParent = top.parent;

        mCurrentFiles = top.files;

        int scrollOffsetY = top.ScrollY;

        adapter.setDate(mCurrentFiles);

        adapter.notifyDataSetChanged();

        recyclerView.scrollTo(0,scrollOffsetY);

    }

    /**

    * 判斷是否在選擇模式下

    * @return

    */

    private boolean isInModeAction() {

        //如果第一個條件不符合 就直接返回 不會看第二個

        return mCallback != null && mCallback.isShowing();

    }

    /**

    * 加載文件 并更新UI

    */

    private void loadFiles(File parent) {

        //rxAndroid 加載文件

        Subscription subscription = Observable.just(parent)

                .flatMap(new Func1>>() {

                    @Override

                    public Observable> call(File parent) {

                        List files = Arrays.asList(parent.listFiles(SystemFileFilter.DEFAULT_INSTANCE));

                        Collections.sort(files, new Comparator() {

                            @Override

                            public int compare(File f1, File f2) {

                                if (f1.isDirectory() && f2.isFile()) {

                                    return -1;

                                }

                                if (f2.isDirectory() && f1.isFile()) {

                                    return 1;

                                }

                                return f1.getName().compareToIgnoreCase(f2.getName());

                            }

                        });

                        // 創(chuàng)建文件列表

                        List fileWrappers = new ArrayList<>(files.size());

                        for (File file : files) {

                            fileWrappers.add(new FileWrapper(file));

                        }

                        return Observable.just(fileWrappers);

                    }

                })

                .subscribeOn(Schedulers.io())

                .observeOn(AndroidSchedulers.mainThread())

                .subscribe(new Subscriber>() {

                    @Override

                    public void onCompleted() {


}

                    @Override

                    public void onError(Throwable throwable) {

                        Log.e(TAG, "onError: ", throwable);

                    }

                    @Override

                    public void onNext(List files) {

                        mCurrentFiles = files;

                        onFileLoaded(parent);

                    }

                });

        addSubscription(subscription);

    }

    private void onFileLoaded(File parent) {

        mCurrentFileParent = parent;

        //刷新數(shù)據(jù)

        adapter.setDate(mCurrentFiles);

        adapter.notifyDataSetChanged();

        //進入文件夾的時候滑動到第一個位置就可以

        recyclerView.scrollTo(0,0);

    }

}
```

適配器及數(shù)據(jù)的綁定就省略了