您的位置:首页 > 移动开发 > Android开发

记录使用SeekBar遇到的一些错误

2016-03-07 19:03 791 查看
最近初学Android写一个音乐播放器,用到SeekBar显示歌曲进度遇到的一个坑,记录之。

程序比较简单,用ListView显示歌曲列表,底部用一个SeekBar显示播放进度,两个TextView,一个显示歌曲当前播放位置,一个显示歌曲总时长。

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.androidbasis3_10_4.MainActivity" >

<ListView
android:id="@+id/main_lv_musiclist"
android:layout_width="match_parent"
android:layout_height="match_parent" />

<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_alignParentBottom="true"
android:gravity="center_horizontal">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/main_ll_tv_currentTime"
android:textSize="18sp"
android:text="00:00"/>
<SeekBar
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_weight="1"
android:progress="0"
android:max="100"
android:id="@+id/main_ll_sb_playProcess"
style="@android:style/Widget.DeviceDefault.SeekBar"/>
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/main_ll_tv_totalTime"
android:textSize="18sp"
android:text="00:00"/>
</LinearLayout>

</RelativeLayout>


点击列表中的歌曲开始播放歌曲开始播放,拖动SeekBar改变播放进度。运行没什么问题,歌曲也能播放,但是播放一卡一卡的。代码如下:

public class MainActivity extends Activity implements OnItemClickListener, OnSeekBarChangeListener {

private TextView currentTime,totalTime;
private SeekBar playProcess;
private ListView musicList;
private Cursor cursor;
private SimpleCursorAdapter adapter;
private MediaPlayer player;
private boolean flag = true;
private Thread thread = null;
private Handler mhandler = new Handler(){
public void handleMessage(android.os.Message msg) {
if (msg.what == 0x01) {
if (flag) {
long duration = player.getDuration();
long currentPosition = player.getCurrentPosition();
long position = 100*currentPosition/duration;
playProcess.setProgress((int) position);
currentTime.setText(parseTime(currentPosition));
}
}
};
};

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initViews();
initDatas();
initViewOpr();
}

private void initViewOpr() {
adapter = new SimpleCursorAdapter(MainActivity.this, R.layout.item_list_main, cursor, new String[]{Media.TITLE}, new int[]{R.id.item_list_musicName});
musicList.setAdapter(adapter);
musicList.setOnItemClickListener(this);
playProcess.setOnSeekBarChangeListener(this);
}

private void initDatas() {
ContentResolver resolver = getContentResolver();
cursor = resolver.query(Media.EXTERNAL_CONTENT_URI, new String[]{Media._ID,Media.TITLE,Media.DURATION,Media.DATA}, null, null, null);
}

private void initViews() {
currentTime = (TextView) findViewById(R.id.main_ll_tv_currentTime);
totalTime = (TextView) findViewById(R.id.main_ll_tv_totalTime);
playProcess = (SeekBar) findViewById(R.id.main_ll_sb_playProcess);
musicList = (ListView) findViewById(R.id.main_lv_musiclist);
player = new MediaPlayer();
}

@Override
protected void onDestroy() {
super.onDestroy();
flag = false;
player.release();
}

@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
cursor.moveToPosition(position);
long musicTime = cursor.getLong(2);
String musicLength = parseTime(musicTime);
totalTime.setText(musicLength);
player.stop();
player.reset();
try {
player.setDataSource(cursor.getString(3));
player.prepare();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
player.start();
if (thread == null) {
thread = new Thread(){
@Override
public void run() {
while (flag) {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
mhandler.sendEmptyMessage(0x01);
super.run();
}
}
};
thread.start();
}
}

private String parseTime(long musicTime) {
long min = musicTime/1000/60;
long sec = (musicTime/1000)%60;
String minStr = ""+min;
String secStr = ""+sec;
if (min < 10) {
minStr = "0" + min;
}
if (sec < 10) {
secStr = "0" + sec;
}
return minStr+":"+secStr;
}

/*
*通知进度被更改
*参数:
*seekBar:当前被修改进度的SeekBar
*process:当前进度值。
*fromUser:如果是用户触发的则返回true
*/
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
if (fromUser) {
long position = player.getDuration()*progress/100;
player.seekTo((int)position);
}
}

@Override
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

}

@Override
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub

}

}
找了半天没发现哪里问题,后来仔细查了onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) 这个方法,终于发现了问题的所在,第三个参数fromUser表示如果是用户拖动色SeekBar触发的进度改变的话返回true,之前没有判断fromUser就直接调用player.seekTo()方法了,由于前面在Handler的handleMessage方法中有每隔一秒调用seekbar的setProgress()方法设置进度,也会触发onProgressChanged()方法,形成了一种“递归”的效果,不断的调用player.seekTo()方法,造成了这种一卡一卡的效果。


                                            
内容来自用户分享和网络整理,不保证内容的准确性,如有侵权内容,可联系管理员处理 点击这里给我发消息
标签:  java Android