Android--SDcard permission权限，mounted挂载，Available space可用空间，TotalSpace总空间

一、在Manifest.xml文件中，写外部设备写权限：

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

如果是用得模拟器，要确保创建AVD时，已经为SDcard分配了空间。

二、判断SDcard有没有挂载，若没有挂载，则弹提示：

if(!Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())){
    Toast.makeText(this, "External SD card not mounted没有挂载", Toast.LENGTH_LONG).show();
}

三、SDcard总空间，可用空间：

package com.jiangge.sdcardsize;

import java.io.File;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.os.StatFs;
import android.text.format.Formatter;
import android.widget.TextView;

public class MainActivity extends Activity {

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		TextView textView = (TextView) findViewById(R.id.tv_show);
		
		File path = Environment.getExternalStorageDirectory();
		StatFs stat = new StatFs(path.getPath());
		long blockSize = stat.getBlockSize();
		long totalBlockCounts = stat.getBlockCount();
		long availableBlocks = stat.getAvailableBlocks();
		
		long totalSize = blockSize * totalBlockCounts;
		long avaliableSize = availableBlocks * blockSize;
		
		String totalSizeStr = Formatter.formatFileSize(this, totalSize);
		String avaliableSizeStr = Formatter.formatFileSize(this, avaliableSize);
		textView.setText("总内存：" + totalSizeStr + "\n" + "可用内存：" + avaliableSizeStr);
	}


}

小米手机真机调试结果：（可以在手机中，Menu->Settings->SD card and phone storage's number）

StackOverFlow 上一个问答：

点击打开链接

StatFs stat = new StatFs(Environment.getExternalStorageDirectory().getPath());
double sdAvailSize = (double)stat.getAvailableBlocks()
                   * (double)stat.getBlockSize();
//One binary gigabyte equals 1,073,741,824 bytes.
double gigaAvailable = sdAvailSize / 1073741824;

getAvailableBlocks() and getBlockSize() are bothdeprecated in API 18 so I would do some kind of check on your build version to make sure you are applying the correct methods:

		if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR2) {
			@SuppressWarnings("deprecation")
			long sdAvailSize = (long) stat.getAvailableBlocksLong() * (long) stat.getBlockSizeLong();
		} else {
			@SuppressWarnings("deprecation")
			double sdAvailSize = (double) stat.getAvailableBlocks() * (double) stat.getBlockSize();
		}