Android构建音频播放器课程(二)

Android构建音频播放器教程(二)

6. 为PlayList（播放列表）写ListView  使用列表视图（ListView）来显示播放列表，在drawable文件夹下创建一个xml布局文件并叫做list_selector.xml，这个xml是用于对列表项渐变背景。list_selector.xml<?xmlversion="1.0"encoding="utf-8"?><selectorxmlns:android="http://schemas.android.com/apk/res/android"><!-- Selector style for listrow --><item android:state_selected="false"    android:state_pressed="false"    android:drawable="@drawable/gradient_bg"/><itemandroid:state_pressed="true"    android:drawable="@drawable/gradient_bg_hover"/><itemandroid:state_selected="true" android:state_pressed="false"    android:drawable="@drawable/gradient_bg_hover"/></selector>
在drawable文件夹下创建一个xml布局文件并叫做playlist.xml，这个xml文件是为了显示列表视图。
playlist.xml<?xmlversion="1.0"encoding="utf-8"?><LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:orientation="vertical">     <ListView        android:id="@android:id/list"        android:layout_width="fill_parent"        android:layout_height="fill_parent"        android:divider="#242424"        android:dividerHeight="1dp"        android:listSelector="@drawable/list_selector"/> </LinearLayout>
再在drawable文件夹下创建一个xml布局文件并叫做playlist_item.xml，这个xml文件是为单一列表项显示歌曲的标题。playlist_item.xml<?xmlversion="1.0"encoding="utf-8"?><LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    android:gravity="center"    android:background="@drawable/list_selector"    android:padding="5dp">    <TextView        android:id="@+id/songTitle"        android:layout_width="fill_parent"        android:layout_height="wrap_content"        android:textSize="16dp"        android:padding="10dp"        android:color="#f3f3f3"/></LinearLayout>
通过使用以上布局我们可以实现以下列表视图通过将数据加载到它。
                                                                                                 

7. 写从SDcard读取mp3文件的类  到目前为止,我们已经完成了player的静态布局，现在的实际代码开始。创建一个新的类文件,并将其命名为SongsManager.java。这个类将从设备上的sdcard阅读所有的文件并且过滤只留带.mp3后缀的文件。SongsManager.mp3packagecom.androidhive.musicplayer; importjava.io.File;importjava.io.FilenameFilter;importjava.util.ArrayList;importjava.util.HashMap; publicclassSongsManager {    // SDCard Path    finalString MEDIA_PATH = newString("/sdcard/");    privateArrayList<HashMap<String, String>> songsList = newArrayList<HashMap<String, String>>();     // Constructor    publicSongsManager(){     }     /**     * Function to read all mp3 files from sdcard     * and store the details in ArrayList     * */    publicArrayList<HashMap<String, String>> getPlayList(){        File home =newFile(MEDIA_PATH);         if(home.listFiles(newFileExtensionFilter()).length > 0) {            for(File file : home.listFiles(newFileExtensionFilter())) {                HashMap<String, String> song =newHashMap<String, String>();                song.put("songTitle", file.getName().substring(0, (file.getName().length() - 4)));                song.put("songPath", file.getPath());                 // Adding each song to SongList                songsList.add(song);            }        }        // return songs list array        returnsongsList;    }     /**     * Class to filter files which are having .mp3 extension     * */    classFileExtensionFilterimplementsFilenameFilter {        publicbooleanaccept(File dir, String name) {            return(name.endsWith(".mp3") || name.endsWith(".MP3"));        }    }}

8. 为PlayList写列表视图  为播放列表的列表视图创建一个新的活动类，叫做PlayListActivity.java ，PlayListActivity.java 这个类通过使用SongsManager.java类来显示歌曲列表。PlayListActivity.javapackagecom.androidhive.musicplayer; importjava.util.ArrayList;importjava.util.HashMap; importandroid.app.ListActivity;importandroid.content.Intent;importandroid.os.Bundle;importandroid.view.View;importandroid.widget.AdapterView;importandroid.widget.AdapterView.OnItemClickListener;importandroid.widget.ListAdapter;importandroid.widget.ListView;importandroid.widget.SimpleAdapter; publicclassPlayListActivityextendsListActivity {    // Songs list    publicArrayList<HashMap<String, String>> songsList = newArrayList<HashMap<String, String>>();     @Override    publicvoidonCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.playlist);         ArrayList<HashMap<String, String>> songsListData =newArrayList<HashMap<String, String>>();         SongsManager plm =newSongsManager();        // get all songs from sdcard        this.songsList = plm.getPlayList();         // looping through playlist        for(inti = 0; i < songsList.size(); i++) {            // creating new HashMap            HashMap<String, String> song = songsList.get(i);             // adding HashList to ArrayList            songsListData.add(song);        }         // Adding menuItems to ListView        ListAdapter adapter =newSimpleAdapter(this, songsListData,                R.layout.playlist_item,newString[] { "songTitle"},newint[] {                        R.id.songTitle });         setListAdapter(adapter);         // selecting single ListView item        ListView lv = getListView();        // listening to single listitem click        lv.setOnItemClickListener(newOnItemClickListener() {             @Override            publicvoidonItemClick(AdapterView<?> parent, View view,                    intposition,longid) {                // getting listitem index                intsongIndex = position;                 // Starting new intent                Intent in =newIntent(getApplicationContext(),                        AndroidBuildingMusicPlayerActivity.class);                // Sending songIndex to PlayerActivity                in.putExtra("songIndex", songIndex);                setResult(100, in);                // Closing PlayListView                finish();            }        });    }}

9. 辅助类的功能创建一个新类,叫作Utilities.java，用来处理额外的工作像转换时间进度百分比,反之亦然。此外，它具有功能将毫秒定时器转换为时间字符串显示在播放器的seekbar上。Utilities.javapackagecom.androidhive.musicplayer; publicclassUtilities {     /**     * Function to convert milliseconds time to     * Timer Format     * Hours:Minutes:Seconds     * */    publicString milliSecondsToTimer(longmilliseconds){        String finalTimerString ="";        String secondsString ="";         // Convert total duration into time           inthours = (int)( milliseconds / (1000*60*60));           intminutes = (int)(milliseconds % (1000*60*60)) / (1000*60);           intseconds = (int) ((milliseconds % (1000*60*60)) % (1000*60) / 1000);           // Add hours if there           if(hours > 0){               finalTimerString = hours +":";           }            // Prepending 0 to seconds if it is one digit           if(seconds < 10){               secondsString ="0"+ seconds;           }else{               secondsString =""+ seconds;}            finalTimerString = finalTimerString + minutes +":"+ secondsString;         // return timer string        returnfinalTimerString;    }     /**     * Function to get Progress percentage     * @param currentDuration     * @param totalDuration     * */    publicintgetProgressPercentage(longcurrentDuration,longtotalDuration){        Double percentage = (double)0;         longcurrentSeconds = (int) (currentDuration / 1000);        longtotalSeconds = (int) (totalDuration / 1000);         // calculating percentage        percentage =(((double)currentSeconds)/totalSeconds)*100;         // return percentage        returnpercentage.intValue();    }     /**     * Function to change progress to timer     * @param progress -     * @param totalDuration     * returns current duration in milliseconds     * */    publicintprogressToTimer(intprogress,inttotalDuration) {        intcurrentDuration = 0;        totalDuration = (int) (totalDuration / 1000);        currentDuration = (int) ((((double)progress) / 100) * totalDuration);         // return current duration in milliseconds        returncurrentDuration * 1000;    }}