最近又折腾上安卓了，开发了两个APP，相比于iOS,android的开发还是感觉更容易一点。界面layout xml非常强大。
我整理一些网上比较难找到，或者自己琢磨出来的一些经验在这个文章里列出来，不定期更新（可能就不更新了。。。）

列出系统内所有歌曲

//返回歌曲id列表
public List<Integer> querySongs(Context context) {
    ArrayList<Integer> list = null;
    String[] columns = { MediaStore.Audio.AudioColumns._ID
            ,MediaStore.Audio.AudioColumns.IS_MUSIC};  
    
    Cursor c = context.getContentResolver().query(  
            MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, columns, null,  
            null, null);  
  
    list = new ArrayList<Integer>();
    while (c.moveToNext())  
    {  
        if(c.getInt(1) != 0) {
            list.add(c.getInt(0));  
        }
    }
    return list;
}

通过歌曲id查询歌曲详细信息

public Bundle querySong(Context context,int id) {
    Bundle bundle = null;
    Uri uri = Uri.withAppendedPath( MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
            Integer.toString(id) );
    ContentResolver resolver = context.getContentResolver();
    Cursor cursor = resolver.query(uri, new String[]{
            MediaStore.Audio.AudioColumns.ARTIST
            ,MediaStore.Audio.AudioColumns.TITLE}, null, null, null);
    if(cursor == null) {
        //权限不允许
        return null;
    }
    if (cursor.moveToFirst()) {
        bundle = new Bundle();
        bundle.putInt("id", id);//歌曲id
        bundle.putString("artist", cursor.getString(0));//作者
        bundle.putString("title", cursor.getString(1));//歌曲标题
    }
    cursor.close();
    return bundle;
}

显示歌曲专辑封面

//mediaId是歌曲id
Uri uri = Uri.parse("content://media/external/audio/media/" + mediaId + "/albumart");
imageView.setImageURI(uri);

通过电话号码查询联系人信息

public Bundle queryContact(Context context,String number) {
    Bundle bundle = null;
    Uri uri = Uri.parse(ContactsContract.PhoneLookup.CONTENT_FILTER_URI + "/" + number);
    ContentResolver resolver = context.getContentResolver();
    Cursor cursor = resolver.query(uri, new String[]{PhoneLookup._ID,PhoneLookup.DISPLAY_NAME}, null, null, null);
    if(cursor == null) {
        //权限不允许
        return null;
    }
    if (cursor.moveToFirst()) {
        long id = cursor.getLong(0);
        String name = cursor.getString(1);
        
        bundle = new Bundle();
        bundle.putLong("id", id);//id
        bundle.putString("name", name);//名字
        
        Uri uri1 = ContentUris.withAppendedId(  
                ContactsContract.Contacts.CONTENT_URI, id);  
        InputStream input = ContactsContract.Contacts  
                .openContactPhotoInputStream(context.getContentResolver(), uri1);  
        Bitmap bitmap = BitmapFactory.decodeStream(input); 

        bundle.putParcelable("avatar", bitmap);//头像
    }
    cursor.close();
    
    return bundle;
}

当天的时间戳

public static long getToday() {
    Calendar c = Calendar.getInstance();
    c.setTimeInMillis(System.currentTimeMillis());
    c.set(Calendar.HOUR_OF_DAY, 0);
    c.set(Calendar.MINUTE, 0);
    c.set(Calendar.SECOND, 0);
    c.set(Calendar.MILLISECOND, 0);
    return c.getTimeInMillis();
}

展开通知栏

void expandNotify(Context context) {
    int currentApiVersion = android.os.Build.VERSION.SDK_INT;
    try {
        Object service = context.getSystemService("statusbar");
        Class<?> statusbarManager = Class
                .forName("android.app.StatusBarManager");
        Method expand = null;
        if (service != null && statusbarManager != null) {
            if (currentApiVersion <= 16) {
                expand = statusbarManager.getMethod("expand");
                expand.setAccessible(true);
                expand.invoke(service);
            } else {
                expand = statusbarManager
                        .getMethod("expandNotificationsPanel");
            }
            expand.setAccessible(true);
            expand.invoke(service);
        }

    } catch (Exception e) {
    }
}

读取assets目录下的文件

String readFromAssets(Context context,String fileName){ 
    try { 
        InputStreamReader inputReader = new InputStreamReader(context.getResources().getAssets().open(fileName) ); 
        BufferedReader bufReader = new BufferedReader(inputReader);
        String line="";
        String Result="";
        while((line = bufReader.readLine()) != null)
            Result += line;
        return Result;
    } catch (Exception e) { 
        e.printStackTrace(); 
    }
    return null;
}

点亮屏幕

void brightScreen(Context context) {
    //获取电源管理器对象  
    PowerManager powerMgr = (PowerManager)context.getSystemService(Context.POWER_SERVICE);  
    //获取PowerManager.WakeLock对象,后面的参数|表示同时传入两个值,最后的是LogCat里用的Tag  
    PowerManager.WakeLock wl = powerMgr.newWakeLock(PowerManager.ACQUIRE_CAUSES_WAKEUP | PowerManager.SCREEN_DIM_WAKE_LOCK, "bright");  
    //点亮屏幕  
    wl.acquire();  
    wl.release();  
}