android之读取SD卡状态

package xidian.dy.com.chujia;

import android.os.Build;
import android.os.Environment;
import android.os.StatFs;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.format.Formatter;
import android.widget.TextView;

import java.io.File;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            TextView tv1 = (TextView)findViewById(R.id.total);
            TextView tv2 = (TextView)findViewById(R.id.available);
            File f = Environment.getExternalStorageDirectory();
            StatFs stat = new StatFs(f.getPath());
            long blockSize,totalBlocks,availableBlocks;
            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();
            }
            if(tv1 != null)
                tv1.setText("总大小:"+formatSize(blockSize*totalBlocks));
            if(tv2 != null)
                tv2.setText("剩余容量:"+formatSize(blockSize*availableBlocks));
        }
    }

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

在查看SD卡容量的时候首先看SD卡是否挂载，如果已挂载则再检查系统的版本。根据不同的版本调用不同的系统API。计算SD卡容量的时候是根据每个区块的大小*总区块个数来计算的。FormatFileSize函数是将字节转换为MB/GB。