Android中通过反射的方式判断U盘是否真正挂载

本文主要是介绍Android中通过反射的方式判断U盘是否真正挂载，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

由于StorageManager.java类中的getVolumeList()和getVolumeState(String mountPoint)方法是hide（隐藏）的，所以需要通过反射的方式获取对应的存储信息。源码./frameworks/base/core/java/android/os/storage/StorageManager.java类中的getVolumeList()跟getVolumeState(String mountPoint)方法如下：

/*** Returns list of all mountable volumes.* @hide*/public StorageVolume[] getVolumeList() {if (mMountService == null) return new StorageVolume[0];try {Parcelable[] list = mMountService.getVolumeList();if (list == null) return new StorageVolume[0];int length = list.length;StorageVolume[] result = new StorageVolume[length];for (int i = 0; i < length; i++) {result[i] = (StorageVolume)list[i];}return result;} catch (RemoteException e) {Log.e(TAG, "Failed to get volume list", e);return null;}}/*** Gets the state of a volume via its mountpoint.* @hide*/public String getVolumeState(String mountPoint) {if (mMountService == null) return Environment.MEDIA_REMOVED;try {return mMountService.getVolumeState(mountPoint);} catch (RemoteException e) {Log.e(TAG, "Failed to get volume state", e);return null;}}

可以通过反射的方式获取 getVolumeList()跟getVolumeState(String mountPoint)的方法，实现如下：

    /*** Returns list of all mountable volumes.*/public static StorageVolume[] getVolumeList(StorageManager storageManager){try {Class clz = StorageManager.class;Method getVolumeList = clz.getMethod("getVolumeList", null);StorageVolume[] result = (StorageVolume[]) getVolumeList.invoke(storageManager, null);return result;} catch (Exception e) {e.printStackTrace();}return null;}/*** Gets the state of a volume via its mountpoint.*/public static String getVolumeState(StorageManager storageManager, String path){String result = "";if(null == storageManager || TextUtils.isEmpty(path)){return result;}try {Class clz = StorageManager.class;Method getVolumeList = clz.getMethod("getVolumeState", String.class);result = (String) getVolumeList.invoke(storageManager, path);} catch (Exception e) {e.printStackTrace();}return result;}

为了方便使用，把这两个方法封装到了USBUtil.java类中，具体实现如下：

package com.example.helloworld.util;import java.lang.reflect.Method;import android.os.storage.StorageManager;
import android.os.storage.StorageVolume;
import android.text.TextUtils;/*** Created by ryan on 01/03/2018.*/public class USBUtil {private static final USBUtil mUtil = new USBUtil();public static USBUtil getInstance() {return mUtil;}/*** Returns list of all mountable volumes.*/public static StorageVolume[] getVolumeList(StorageManager storageManager){try {Class clz = StorageManager.class;Method getVolumeList = clz.getMethod("getVolumeList", null);StorageVolume[] result = (StorageVolume[]) getVolumeList.invoke(storageManager, null);return result;} catch (Exception e) {e.printStackTrace();}return null;}/*** Gets the state of a volume via its mountpoint.*/public static String getVolumeState(StorageManager storageManager, String path){String result = "";if(null == storageManager || TextUtils.isEmpty(path)){return result;}try {Class clz = StorageManager.class;Method getVolumeList = clz.getMethod("getVolumeState", String.class);result = (String) getVolumeList.invoke(storageManager, path);} catch (Exception e) {e.printStackTrace();}return result;}}

接下来是方法的使用，通过UsbTest.java类来进行界面测试，具体实现如下：

package com.example.helloworld;import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.os.storage.StorageManager;
import android.os.storage.StorageVolume;
import android.view.View;
import android.widget.TextView;import com.example.helloworld.util.Logger;
import com.example.helloworld.util.USBUtil;public class UsbTest extends Activity{private StorageManager storageManager;Context context;TextView mTextView;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.usb);context = UsbTest.this;storageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE); //存储服务初始化mTextView = (TextView) findViewById(R.id.show_tv);}public void startVoice(View view){Logger.d();if (USBExist(context)){mTextView.setText("USB is exist!");}else {mTextView.setText("USB isn't exist!");}}public void finishVoice(View view){Logger.d();finish();}//判断/storage/udisk是否为挂载的路径private boolean USBExist(Context context){if (null == storageManager){Logger.d("Invalid reference to StorageManager received.");return false;}String usbPath = getUSBPath(context);if (USBUtil.getVolumeState(storageManager, usbPath).equals(android.os.Environment.MEDIA_MOUNTED)){return true;}return false;}//判断USB路径（/storage/udisk）是否存在private String getUSBPath(Context context){Logger.d();String usb = null;StorageVolume[] volumes = USBUtil.getVolumeList(storageManager);for (int i = 0; i < volumes.length; i++){if (volumes[i].isRemovable() && volumes[i].getDescription(context).contains("USB")){usb = volumes[i].getPath();Logger.d("usb = " + usb);if (usb.equals("/storage/udisk")){break;}}}return usb;}}

usb.xml布局如下：

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="vertical" ><TextViewandroid:id="@+id/show_tv"android:layout_width="match_parent"android:layout_height="wrap_content"android:textSize="18sp"/><Button android:layout_width="wrap_content"android:layout_height="wrap_content"android:onClick="startVoice"android:text="@string/usb_check"/><Button android:layout_width="wrap_content"android:layout_height="wrap_content"android:onClick="finishVoice"android:text="@string/version_quit"/></LinearLayout>

测试结果如下：

a.未插U盘