Android 下 ListView 的使用
[導(dǎo)讀]ListView 的使用比我想像中的要麻煩很多，所以有必要記錄下來(lái)。首先在界面拖放一個(gè) ListView 控件，生成的 XML 如下所示：ListView 每個(gè)子項(xiàng)顯示需要與 Adapter 配合，這
ListView 的使用比我想像中的要麻煩很多，所以有必要記錄下來(lái)。
首先在界面拖放一個(gè) ListView 控件，生成的 XML 如下所示：
ListView 每個(gè)子項(xiàng)顯示需要與 Adapter 配合，這對(duì)于我來(lái)說(shuō)不太好理解。
每個(gè) ListView 子項(xiàng)需要格式說(shuō)明，其 XML 如下(文件名是: my_mp3filelist.xml, 在后繼的代碼中要使用的)：
以上，ListView 的準(zhǔn)備就緒了。接下來(lái)就是準(zhǔn)備數(shù)據(jù)，此示例用于顯示音樂文件列表，音樂文件的信息來(lái)自于系統(tǒng)的類: MediaStore.Audio.Media。
將 MediaStore.Audio.Media 中程序需要的信息轉(zhuǎn)存在自定義的類中，自定義的類如下：
// 此類中成員的個(gè)數(shù)根據(jù)個(gè)人需要定義,沒有必要的成員可以刪除的
public?class?Mp3Info?{
private?String?id;
private?String?mp3Name;
private?String?mp3Size;
private?String?lrcName;
private?String?lrcSize;
private?String?mp3Artist;
private?long?mp3Duration;
private?String?mp3Url;
public?Mp3Info()?{
super();
}
public?Mp3Info(String?id,?String?mp3Name,?String?mp3Size,?String?lrcName,
String?lrcSize,?String?mp3Artist)?{
super();
this.id?=?id;
this.mp3Name?=?mp3Name;
this.mp3Size?=?mp3Size;
this.lrcName?=?lrcName;
this.lrcSize?=?lrcSize;
this.mp3Artist?=?mp3Artist;
}
@Override
public?String?toString()?{
return?"Mp3Info?[id="?+?id?+?",?mp3Name="?+?mp3Name?+?",?mp3Size="
+?mp3Size?+?",?lrcName="?+?lrcName?+?",?lrcSize="?+?lrcSize
+?",?duration="?+?mp3Duration?+?"]";
}
public?String?getId()?{
return?id;
}
public?void?setId(String?id)?{
this.id?=?id;
}
public?void?setId(long?id)?{
this.id?=?Long.toString(id);
}
public?String?getMp3Name()?{
return?mp3Name;
}
public?void?setTitle(String?strName){
this.mp3Name?=?strName;
}
public?void?setArtist(String?strArtist){
mp3Artist?=?strArtist;
}
public?String?GetArtist()?{
return?this.mp3Artist;
}
public?void?setDuration(long?duration){
mp3Duration?=??duration;
}
public?void?setMp3Name(String?mp3Name)?{
this.mp3Name?=?mp3Name;
}
public?String?getMp3Size()?{
return?mp3Size;
}
public?void?setMp3Size(String?mp3Size)?{
this.mp3Size?=?mp3Size;
}
public?void?setSize(long?strSize)?{
this.mp3Size?=?Long.toString(strSize);
}
public?String?getLrcName()?{
return?lrcName;
}
public?void?setLrcName(String?lrcName)?{
this.lrcName?=?lrcName;
}
public?String?getLrcSize()?{
return?lrcSize;
}
public?void?setLrcSize(String?lrcSize)?{
this.lrcSize?=?lrcSize;
}
public?void?setUrl(String?strUrl)?{
this.mp3Url?=?strUrl;
}
public?String?GetUrl()?{
return?this.mp3Url;
}
}
音樂信息的獲取與轉(zhuǎn)存代碼如下：
/**
*?用于從數(shù)據(jù)庫(kù)中查詢歌曲的信息，保存在List當(dāng)中
*?class?Mp3Info?有什么成員,?由?MediaStore.Audio.Media?和實(shí)際需要確定
*/
public?static?ListgetMp3Infos(Context?context)?{
Cursor?cursor?=?context.getContentResolver().query(
MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,?null,?null,?null,
MediaStore.Audio.Media.DEFAULT_SORT_ORDER);
Listmp3Infos?=?new?ArrayList();
for?(int?i?=?0;?i?<?cursor.getCount();?i++)?{
Mp3Info?mp3Info?=?new?Mp3Info();
cursor.moveToNext();
long?id?=?cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media._ID)); //?音樂id
String?title?=?cursor.getString((cursor.getColumnIndex(MediaStore.Audio.Media.TITLE))); //?音樂標(biāo)題
String?artist?=?cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST)); //?藝術(shù)家
long?duration?=?cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.DURATION)); //?時(shí)長(zhǎng)
long?size?=?cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.SIZE)); //?文件大小
String?url?=?cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA)); //?文件路徑
int?isMusic?=?cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media.IS_MUSIC)); //?是否為音樂
?? if?(isMusic?!=?0)?{ //?只把音樂添加到集合當(dāng)中
?? mp3Info.setId(id);
?? mp3Info.setTitle(title);
?? mp3Info.setArtist(artist);
?? mp3Info.setDuration(duration);
?? mp3Info.setSize(size);
?? mp3Info.setUrl(url);
?? mp3Infos.add(mp3Info);
?? }
??}
return?mp3Infos;
}
將保存后的音樂信息顯示在 ListView 中：
(1) 定義相應(yīng)變量及初始化
private?ListView?lvMp3File; Listmp3Infos; lvMp3File?=?(ListView)findViewById(R.id.listView1);
(2) 數(shù)據(jù)顯示
//?測(cè)試音樂文件遍歷?-?需改為線程(考慮若數(shù)據(jù)量大時(shí)是否會(huì)影響?UI?顯示的時(shí)長(zhǎng))
//?生成動(dòng)態(tài)數(shù)組，并且加載數(shù)據(jù)
ArrayList<HashMap>?mylist?=?new?ArrayList<HashMap>();
mp3Infos?=?getMp3Infos(getApplicationContext());
for?(Iteratoriterator?=?mp3Infos.iterator();?iterator.hasNext();)?{
Mp3Info?mp3Info?=?(Mp3Info)?iterator.next();??
Log.v("Leo?-?MP3?Name:?",?mp3Info.getMp3Name());
HashMapmap?=?new?HashMap();
???? map.put("ItemTitle",?mp3Info.getMp3Name());
???? map.put("ItemText",?mp3Info.GetArtist());
???? //?map.put("url",?mp3Info.GetUrl());
???? mylist.add(map);
????
????//?生成?Apapter(適配器),?數(shù)組?->?ListItem
????SimpleAdapter?mSchedule?=?new?SimpleAdapter(this,
???? //?數(shù)據(jù)來(lái)源
???? mylist,
???? //?ListItem?的?XML?實(shí)現(xiàn)
???? R.layout.my_mp3filelist,
???? //?動(dòng)態(tài)數(shù)組與?ListItem?對(duì)應(yīng)的子項(xiàng)
???? new?String[]?{"ItemTitle",?"ItemText"},
???? //?ListItem?的?XML?文件里面的兩個(gè)?TextView?ID
???? new?int[]?{R.id.ItemTitle,R.id.ItemText});
lvMp3File.setAdapter(mSchedule);
}
此段代碼在示例中，是放在主窗體的 protected void onCreate(Bundle savedInstanceState) 過(guò)程中。
ListView 還需要響應(yīng)用戶的點(diǎn)擊操作，需要如下的聲明：
lvMp3File.setOnItemClickListener(new?MusicListItemClickListener());
MusicListItemClickListener 的實(shí)現(xiàn)如下：
private?class?MusicListItemClickListener?implements?OnItemClickListener
{
????@Override
????public?void?onItemClick(AdapterView?parent,?View?view,?int?position,long?id)
????{
????????if(mp3Infos?!=?null)
????????{
???????? //?Leo?界面切換:?切換到播放界面
???????? //?Intent?goPlaying?=?new?Intent(MainActivity.this,?PlayingActivity.class);
???????? //?startActivity(goPlaying);
????????????Intent?goPlayingIntent?=?new?Intent();
????????????goPlayingIntent.setClass(MainActivity.this,?PlayingActivity.class);
????????????startActivity(goPlayingIntent);
????????????
????????????//?啟動(dòng)音樂后臺(tái)播放服務(wù)
????????????/*?若不做延時(shí)直接調(diào)用?run?中的代碼,歌曲信息無(wú)法正確獲取到?*/
????????????positionSelected?=?position;
????????????Timer?timer?=?new?Timer();
????????????TimerTask?task?=?new?TimerTask(){
????????????????public?void?run(){
???? ????????????Mp3Info?mp3Info?=?mp3Infos.get(positionSelected);
???? ????????????Log.d("mp3Info-->",?mp3Info.toString());
???? ????????????Intent?intent?=?new?Intent();
???? ????????????intent.putExtra("url",?mp3Info.GetUrl());
???? ????????????intent.putExtra("listPosition",?positionSelected/*getPlayingIndex(mp3Info.GetUrl())*/);
???? ????????????intent.putExtra("MSG",?AppConstant.PlayerMsg.PLAY_MSG.ordinal());
???? ????????????intent.setClass(MainActivity.this,?PlayerService.class);
???? ????????????startService(intent);???????//?啟動(dòng)服務(wù)
?????????????????}
????????????};
????????????timer.schedule(task,?300);?//?0.3?秒后執(zhí)行?run?中的代碼段
????}
}
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