查看源代码查找获取sd卡剩余容量的代码

 <string name="memory_available" msgid="418542433817289474">"可用空间"</string>

<Preference android:key="memory_sd_avail"
    style="?android:attr/preferenceInformationStyle"
    android:title="@string/memory_available"
    android:summary="00"/>

//这个字符串就是sd卡剩余容量
formatSize(availableBlocks * blockSize) + readOnly
//这两个参数相乘，得到sd卡以字节为单位的剩余容量
availableBlocks * blockSize

File path = Environment.getExternalStorageDirectory();
    StatFs stat = new StatFs(path.getPath());
    long blockSize;
    long totalBlocks;
    long availableBlocks;

    //获取当前系统版本的等级
    if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2){
         blockSize = stat.getBlockSizeLong();
         totalBlocks = stat.getBlockCountLong();
         availableBlocks = stat.getAvailableBlocksLong();
    }
    else{
        blockSize = stat.getBlockSize();
        totalBlocks = stat.getBlockCount();
        availableBlocks = stat.getAvailableBlocks();
    }

    TextView tv = (TextView) findViewById(R.id.tv);
    tv.setText(formatSize(availableBlocks * blockSize));
}

private String formatSize(long size) {
    return Formatter.formatFileSize(this, size);
}