Android设置里面默认存储器选项（default write disk）的实现
原生的Android设置里面没有默认存储器的选项，可是MTK偏偏加上了这个功能，可能MTK认为这个比較实用吧，所以，他们在原生的基础上面做了改动。加上了这个功能。可是高通平台没有这个功能。相对MTK来说。高通比較严谨一点，不会随随便便加上一些功能。可是MTK平台优化了非常多东西（有有点也有缺点），开发人员这可能是非常多山寨手机选择MTK平台的原因吧。
我给“默认存储器”做了一个简单的定义：一些内置应用的数据存放位置。当然。假设其它应用知道这个接口（不是标准接口。所以仅仅有开发人员本人知道，或者MTK的人），也能够使用该功能。
之前接到一个在高通平台上的手机里面加上默认存储器的选项，即假设选择本地内存，一些内置应用的数据将存储到本地内存里面，假设选择SD卡存储。则这些应用的数据将会存储到SD卡里面。借鉴MTK平台的实现方法。整理其思路是：通过SystemProperties接口往系统内存里面写入存储路径（set），然后在一些指定应用里面存储数据的时候推断当前默认存储器,使用get方法读取这个属性。为什么使用SystemProperties，由于其设置的值全局都能够使用，即不同应用都能够通过共享内存取出其值，攻克了进程间通信的问题。
1：我们先在framework层加上一些自己定义的接口文件。我加的位置是 ....../frameworks/base/core/java/android/os/storage/。加入的文件名称StorageManagerEx.java,内容例如以下：
package android.os.storage;
import android.util.Log;
import com.android.internal.R;
import android.os.SystemProperties;
import java.io.File;
import android.os.Environment;
public class StorageManagerEx {
» private static final String TAG ="StorageManagerEx";
» private static final String PROP_SD_DEFAULT_PATH = "persist.sys.sd.defaultpath";
»
» private static final String STORAGE_PATH_SD1 ="/storage/sdcard0";
» private static final String STORAGE_PATH_SD2 ="/storage/sdcard1";
» private static final String STORAGE_PATH_SD1_ICS = "/mnt/sdcard";
» private static final String STORAGE_PATH_SD2_ICS = "/mnt/sdcard2";
»
» private static final String STORAGE_PATH_SHARE_SD = "/storage/emulated/0";
»
» /**
» * Return default path for writing.
» * @return default path.
» * @hide
» * @internal
» */
public static String getDefaultPath(){
» String path = STORAGE_PATH_SD1;
» try {
» » path = SystemProperties.get(PROP_SD_DEFAULT_PATH);
» » Log.i(TAG,"default path = "+path);
» } catch (IllegalArgumentException e) {
» » Log.e(TAG,"IllegalArgumentException when get default path:"+e);
» }
» //Property will be empty when first boot should set to default
» if(path.equals("")){
» » Log.i(TAG,"getDefaultPath empty! set to default");
» » //Here may be some problems.refer to MTK:only share sd and no swap,internal path
is
» » //"/storage/emulated/0",i don't know "share" and "no swap",so i skip.
» » // if (FeatureOption.MTK_SHARED_SDCARD && !FeatureOption.MTK_2SDCARD_SW
AP) {» »
» » // setDefaultPath(STORAGE_PATH_SHARE_SD);
» » // path = STORAGE_PATH_SHARE_SD;
» » // } else {
» » // setDefaultPath(STORAGE_PATH_SD1);
» » // path = STORAGE_PATH_SD1;
» » // }
» » setDefaultPath(STORAGE_PATH_SD1);
» » path = STORAGE_PATH_SD1;
» }
»
» //Here we don't care multi user which will be used by google,ignore and go on.
»
» //MOTA upgrade from ICS to JB,update defaultPath to JB.
» if(path.equals(STORAGE_PATH_SD1_ICS)){
» » path = STORAGE_PATH_SD1;
» » setDefaultPath(path);
» }else if(path.equals(STORAGE_PATH_SD2_ICS)){
» » path = STORAGE_PATH_SD2;
» » setDefaultPath(path);
» }
»
» Log.i(TAG,"getDefaultPath path="+path);
» return path;
}
/**
* set default path for Appto storage data
* this only can used by settings.
*
* @param path
* @hide
* @internal
*/
public static void setDefaultPath(String path){
» Log.i(TAG,"setDefaultPath path = " + path);
» if (path == null) {
» » Log.e(TAG,"setDefaultPath error! path = null");
» » return;
» }
»
» try {
» » SystemProperties.set(PROP_SD_DEFAULT_PATH,path);
» } catch (IllegalArgumentException e) {
» » Log.e(TAG,"IllegalArgumentException when setDefaultPath:" + e);
» }
}
/**
* Returns external SD card path.» /sdcard2
* @hide
* @internal
*/
// public static String getExternalStoragePath(){» //method 1:
//» String sdCardDir = null;
// android.os.storage.StorageManager storageManager =
// (android.os.storage.StorageManager) context
// .getSystemService(Context.STORAGE_SERVICE);
// StorageVolume[] volumes = storageManager.getVolumeList();
// for (int i = 0; i < volumes.length; i++) {
// if (volumes[i].isRemovable() && volumes[i].allowMassStorage()) {
// sdCardDir = volumes[i].getPath();
// break;
// }
// }
// return sdCardDir;
// }
public static String getExternalStoragePath(){» //method 2:
String sdCardDir = null;
String state = Environment.getStorageState(new File(STORAGE_PATH_SD2));
if(state.equals(Environment.MEDIA_MOUNTED)){
» sdCardDir = STORAGE_PATH_SD2;
}else if(state.equals(Environment.MEDIA_UNMOUNTED)){
» sdCardDir = Environment.MEDIA_UNMOUNTED;
}else{
» sdCardDir = STORAGE_PATH_SD2;
}
return sdCardDir;
}
/**
* Returns internal storage path.
* @return
* @hide
* @internal
*/
public static String getInternalStoragePath(){
» String sdCardDir = null;
» String state = Environment.getStorageState(new File(STORAGE_PATH_SHARE_SD));
»
» if(state.equals(Environment.MEDIA_MOUNTED)){
» » sdCardDir = STORAGE_PATH_SD1;
» }else if(state.equals(Environment.MEDIA_UNMOUNTED)){
» » sdCardDir = Environment.MEDIA_UNMOUNTED;
» }else{
» » sdCardDir = STORAGE_PATH_SD1;
» }
» return sdCardDir;
} 1
}
定义的主要作用是往系统内存的属性里面加入属性presist.sys.sd.default.我们能够进入adb里面查看和改动一些属性1：adb shell 2：getprop + 键（或不加） tip:我们也能够setprop + 键 +值
2：在设置里面加入默认存储器的选项：
在Settings的project里面的.....res/xml/device_info_memory.xml的文件中面加入
然后在PreferenceCategory里面加入RadioButtonPreference （此处省略）在Memroy.java文件中面加入
private void initDefaultWriteDisk(){ » mDefaultWriteCategory = (PreferenceCategory)findPreference(DEFAULT_WRITE_CATEGORY_KEY); List<RadioButtonPreference> defaultWritePreference = new ArrayList<RadioButtonPreference>(); StorageVolume[] volumes = mStorageManager.getVolumeList(); List<StorageVolume> storageVolumesEx = initVolumeList(volumes); for (int i = 0; i < storageVolumesEx.size(); i++) { » StorageVolume volumn = storageVolumesEx.get(i); » RadioButtonPreference avalibileDisk = new RadioButtonPreference(getActivity()); » String path = volumn.getPath();» //volumn path » android.util.Log.i("haiyong.liu","volumn.path="+path); » String state = Environment.getStorageState(new File(path)); » » avalibileDisk.setKey(path); » avalibileDisk.setTitle(volumn.getDescription(getActivity())); » avalibileDisk.setPath(path); » avalibileDisk.setOnPreferenceChangeListener(this); » defaultWritePreference.add(avalibileDisk); » android.util.Log.e("haiyong.liu","Environment="+state); » if(state.equals(Environment.MEDIA_UNMOUNTED)||state.equals(Environment.MEDIA_REMOVED )){ » » » }else { » » mDefaultWriteCategory.addPreference(avalibileDisk); » » if(path.equals(StorageManagerEx.getDefaultPath())){ » » » avalibileDisk.setChecked(true); » » » mDeafultWritePathPref = avalibileDisk; » » }else{ » » » avalibileDisk.setChecked(false); » » } » } » » } } private List<StorageVolume> initVolumeList(StorageVolume[] volumes){ » List<StorageVolume> storageVolumes = new ArrayList<StorageVolume>(); » /*if(UserManager.supportsMultipleUsers()){» //return the current user's volumn lis t if supported,otherwise ignore. » » StorageVolume[] sv = mStorageManager.getVolumeListAsUser(); » » for (int i = 0; i < sv.length; i++) { if (!"not_present".equals(mStorageManager.getVolumeState(volumes[i].getPath()))) { storageVolumes.add(volumes[i]); } } » » return storageVolumes; » }*/ » for (int i = 0; i < volumes.length; i++) { if (!"not_present".equals(mStorageManager.getVolumeState(volumes[i].getPath()))) { storageVolumes.add(volumes[i]); } } return storageVolumes; } @Override public boolean onPreferenceChange(Preference preference, Object newValue) { if (preference != null && preference instanceof RadioButtonPreference) { if (mDeafultWritePathPref != null) { mDeafultWritePathPref.setChecked(false); } StorageManagerEx.setDefaultPath(preference.getKey()); mDeafultWritePathPref = (RadioButtonPreference) preference; return true; } return false; }
然后在oncreate方法里面调用initDefaultWriteDisk（）这种方法，这种方法放在Memory.java的onCreate(...)方法里面，另外，StorageManagerEx.setDefaultPath(),这种方法仅仅能够在settings这个apk里面使用，即仅仅有settings这个apk能够写入。3：找到相应须要加入该功能的project，我们须要加入的是Camrea2。蓝牙，下载器，录音这几个Apk。找到这几个源代码存储数据的地方，将存储位置改为StorageManagerEx.getDefaultPath()
tip:SystemProperties写入数据时候须要权限。在Manifests.xml文件加上android:sharedUserId="android.uid.system"，在Android.mk中。將LOCAL_CERTIFICATE := XXX改动成LOCAL_CERTIFICATE :=platform。