Android Api Demos登顶之路（十二）Presentation
分类：Android ApiDemos
这个demo主要演示presentation的用法，presentation是一种特殊的对话框，主要用于在另外一块屏幕上显示内容。值得注意的是在创建presentation前必须把presentation与它的目标屏幕相关联。所以在使用它之前必须为它选择一个Display。 选择display的方法主要有两种 一是利用MediaRouter 二是利用DisplayManager， 本例演示的是后一种方法 创建主布局文件：activity_main.xml 主要是一个用于控制显示所有屏幕的复选框和一个显示所有屏幕的列表框
=====”?android:attr/textAppearanceMedium”android:text=”Tish demostrates how to use a presentation and the DisplayManger to show content on other displaytry connecting a second display and watch what happenes selecting a display and will open a presentatio on it.”/>====>
编写MainActivity
public {private static final String PRESENTATION_KEY = “presentation”;private DisplayManager displayManager;private CheckBox show_all_displays;private DisplayListAdapter displayAdapter;private ListView listView;// 定义存储photo的数组private int[] photos = new int[] { R.drawable.guild1, R.drawable.guild2,R.drawable.guild3, R.drawable.ic_launcher, R.drawable.puzzle,R.drawable.test };// 记录下一张照片的Idprivate int nextPhotoNumber = 0;/** 利用SparseArray存储所有屏幕的prsentation上显示的内容（尤其是当屏幕不止一个时数组的作用更大）* SparseArray：稀疏数组，在存储数据不多的情况下可以大大地节省空间，此时可以代替hasmap使用*/SparseArray<PresentationContents> mSavedPresentationContents;// 根据displayId记录当前显示的presentationSparseArray<DemoPresentation> mActivePresentations = new SparseArray<DemoPresentation>();@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);// 首先检查是否存在需要恢复的状态信息if (savedInstanceState != null) {mSavedPresentationContents = savedInstanceState.getSparseParcelableArray(PRESENTATION_KEY);} else {mSavedPresentationContents = new SparseArray<PresentationContents>();}displayManager = (DisplayManager) getSystemService(Context.DISPLAY_SERVICE);show_all_displays = (CheckBox) findViewById(R.id.show_all_presentation);show_all_displays.setOnCheckedChangeListener(this);listView = (ListView) findViewById(R.id.listView);displayAdapter = new DisplayListAdapter(this);listView.setAdapter(displayAdapter);}/*** 定义listView的适配器，用于显示所有的屏幕信息** @author aaaa**/<Display> {private Context mContext;// 构造函数，布局文件为R.layout.list_itempublic DisplayListAdapter(Context context) {super(context, R.layout.list_item);mContext = context;}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {View v = null;if (convertView == null) {v = LayoutInflater.from(mContext).inflate(R.layout.list_item,null);} else {v = convertView;}// 找到各个组件CheckBox cb_display_presentation = (CheckBox) v.findViewById(R.id.cb_presentation);TextView tv_showId = (TextView) v.findViewById(R.id.tv_displayId);Button bt_info = (Button) v.findViewById(R.id.bt_info);Display display = getItem(position);String text = “Display#” + display.getDisplayId()+ display.getName();tv_showId.setText(text);// 将dispaly设置为复选框的标志位，将dispaly与复选框绑定在一起，找到复选框时就可以找到display了cb_display_presentation.setTag(display);// 如果当前presentation可见（存在于mActivePresentations中）或者mSavedPresentationContents中保存了// 当前presentation显示的内容，则复选框为选中状态，否则为非选中状态cb_display_presentation.setChecked(mActivePresentations.indexOfKey(display.getDisplayId()) >= 0|| mSavedPresentationContents.indexOfKey(display.getDisplayId()) >= 0);cb_display_presentation.setOnCheckedChangeListener(MainActivity.this);bt_info.setTag(display);bt_info.setOnClickListener(mInfoClickListener);return v;}/*** 更新listVIew的显示信息*/public void updateListView() {// 清空一下数据clear();String displayCategory = getDisplayCategory();if (displayCategory == null) {System.out.println(“displayCategory is null”);}Display[] displays = displayManager.getDisplays(displayCategory);// 将所有的屏幕添加到数组中addAll(displays);}/*** 当复选框处于选中状态时列出所有的屏幕信息 处于非选中状态时只列出presentation屏幕信息** @return*/private String getDisplayCategory() {System.out.println(show_all_displays.isChecked());return show_all_displays.isChecked() ? null: DisplayManager.DISPLAY_CATEGORY_PRESENTATION;}}private OnClickListener mInfoClickListener = new OnClickListener() {/*** 点击时创建一个对话框，用于显示dispaly的信息*/@Overridepublic void onClick(View v) {Context context = v.getContext();AlertDialog.Builder builder = new Builder(context);Display display = (Display) v.getTag();String title = “Dispaly #” + display.getDisplayId() + “Info”;builder.setTitle(title).setMessage(display.toString()).setNeutralButton(“OK”, new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {dialog.dismiss();}});builder.show();}};/*** 同时为两个复选框提供监听服务*/@Overridepublic void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {if (buttonView == show_all_displays) {// 更新列表框displayAdapter.updateListView();} else {// 从复选框中取出DisplayDisplay display = (Display) buttonView.getTag();if (isChecked) {// 显示下一张图片PresentationContents contents = new PresentationContents(getNextPhoto());showPresentation(display, contents);} else {hidePresentation(display);}}}private int getNextPhoto() {int nextPhoto = photos[nextPhotoNumber];nextPhotoNumber = (nextPhotoNumber + 1) % photos.length;return nextPhoto;}private void showPresentation(Display display, PresentationContents contents) {int dispalyId = display.getDisplayId();// 如果当前resentation已经是显示状态则直接返回if (mActivePresentations.get(dispalyId) != null) {return;}// 否则则新建一个presentation，并存储到mActivePresentations当中DemoPresentation presentation = new DemoPresentation(this, display,contents);presentation.show();// 设置prsentation的解除监听presentation.setOnDismissListener(mPresentationDismissListener);mActivePresentations.put(dispalyId, presentation);}private void hidePresentation(Display display) {int dispalyId = display.getDisplayId();DemoPresentation presentation = mActivePresentations.get(dispalyId);if (presentation != null) {presentation.dismiss();mActivePresentations.remove(dispalyId);}}private OnDismissListener mPresentationDismissListener = new OnDismissListener() {@Overridepublic void onDismiss(DialogInterface dialog) {DemoPresentation prsentation = (DemoPresentation) dialog;int displayId = prsentation.getDisplay().getDisplayId();// 从presentation数组当中将当前presentation删除mActivePresentations.delete(displayId);// 更新listViewdisplayAdapter.notifyDataSetChanged();}};/*** 当activity恢复时，首先从之前在pause状态中保存的presentation中显示的内容恢复过来*/@Overrideprotected void onResume() {super.onResume();// 更新listViewdisplayAdapter.updateListView();// 恢复保存的presentationContentif (mSavedPresentationContents.size() > 0) {for (int i = 0; i < displayAdapter.getCount(); i++) {Display display = displayAdapter.getItem(i);PresentationContents content = mSavedPresentationContents.get(display.getDisplayId());if (content != null) {showPresentation(display, content);}}// 恢复完成后清空mSavedPresentationContents中的内容mSavedPresentationContents.clear();}// 注册屏幕的监听事件displayManager.registerDisplayListener(mDisplayListener, null);}/*** 当activity不可见时保存presentation中显示的内容 将所有屏幕的presentation解除*/@Overrideprotected void onPause() {super.onPause();// 注销掉对屏幕的监听displayManager.unregisterDisplayListener(mDisplayListener);// 遍历当前所有可见的presentationfor (int i = 0; i < mActivePresentations.size(); i++) {// 如果当前的presentation是可见的则将共内容保存DemoPresentation presentation = mActivePresentations.valueAt(i);int displayId = mActivePresentations.keyAt(i);if (presentation != null) {// 将所有display的显示内容保存mSavedPresentationContents.put(displayId,presentation.getmContents());presentation.dismiss();}// 清空所mActivePresentations数组（所有presentation都不可见了）mActivePresentations.clear();}}/*** 保存presentation的状态信息，用于当activity被非正常杀死时再次调用oncreate方法重建activity时 恢复状态*/@Overrideprotected void onSaveInstanceState(Bundle outState) {super.onSaveInstanceState(outState);outState.putSparseParcelableArray(PRESENTATION_KEY,mSavedPresentationContents);}private DisplayManager.DisplayListener mDisplayListener = new DisplayManager.DisplayListener() {@Overridepublic void onDisplayRemoved(int displayId) {displayAdapter.updateListView();}@Overridepublic void onDisplayChanged(int displayId) {displayAdapter.updateListView();}@Overridepublic void onDisplayAdded(int displayId) {displayAdapter.updateListView();}};}我们大都接受的是正面的教育，
