Settings指令分析

1, 概述

Settings指令也是和ContentProvider进行交互,对系统的数据库属性值进行查询、删除和修改。

2, Settings详细流程

  SettingsCmd的main方法如下,

public static void main(String[] args) {        if (args == null || args.length < 2) {            printUsage();            return;        }        mArgs = args;        try {            new SettingsCmd().run();        } catch (Exception e) {            System.err.println("Unable to run settings command");        }    } 

直接调用run方法,方法如下,

public void run() {        boolean valid = false;        String arg;        try {            while ((arg = nextArg()) != null) {                if ("--user".equals(arg)) {                    if (mUser != -1) {                        // --user specified more than once; invalid                        break;                    }                    mUser = Integer.parseInt(nextArg());                } else if (mVerb == CommandVerb.UNSPECIFIED) {                    if ("get".equalsIgnoreCase(arg)) {                        mVerb = CommandVerb.GET;                    } else if ("put".equalsIgnoreCase(arg)) {                        mVerb = CommandVerb.PUT;                    } else if ("delete".equalsIgnoreCase(arg)) {                        mVerb = CommandVerb.DELETE;                    } else if ("list".equalsIgnoreCase(arg)) {                        mVerb = CommandVerb.LIST;                    } else {                        // invalid                        System.err.println("Invalid command: " + arg);                        break;                    }                } else if (mTable == null) {                    if (!"system".equalsIgnoreCase(arg)                            && !"secure".equalsIgnoreCase(arg)                            && !"global".equalsIgnoreCase(arg)) {                        System.err.println("Invalid namespace '" + arg + "'");                        break;  // invalid                    }                    mTable = arg.toLowerCase();                    if (mVerb == CommandVerb.LIST) {                        valid = true;                        break;                    }                } else if (mVerb == CommandVerb.GET || mVerb == CommandVerb.DELETE) {                    mKey = arg;                    if (mNextArg >= mArgs.length) {                        valid = true;                    } else {                        System.err.println("Too many arguments");                    }                    break;                } else if (mKey == null) {                    mKey = arg;                    // keep going; there's another PUT arg                } else {    // PUT, final arg                    mValue = arg;                    if (mNextArg >= mArgs.length) {                        valid = true;                    } else {                        System.err.println("Too many arguments");                    }                    break;                }            }        } catch (Exception e) {            valid = false;        }        if (valid) {            if (mUser < 0) {                mUser = UserHandle.USER_OWNER;            }            try {                IActivityManager activityManager = ActivityManagerNative.getDefault();                IContentProvider provider = null;                IBinder token = new Binder();                try {                    ContentProviderHolder holder = activityManager.getContentProviderExternal(                            "settings", UserHandle.USER_OWNER, token);                    if (holder == null) {                        throw new IllegalStateException("Could not find settings provider");                    }                    provider = holder.provider;                    switch (mVerb) {                        case GET:                            System.out.println(getForUser(provider, mUser, mTable, mKey));                            break;                        case PUT:                            putForUser(provider, mUser, mTable, mKey, mValue);                            break;                        case DELETE:                            System.out.println("Deleted "                                    + deleteForUser(provider, mUser, mTable, mKey) + " rows");                            break;                        case LIST:                            for (String line : listForUser(provider, mUser, mTable)) {                                System.out.println(line);                            }                            break;                        default:                            System.err.println("Unspecified command");                            break;                    }                } finally {                    if (provider != null) {                        activityManager.removeContentProviderExternal("settings", token);                    }                }            } catch (Exception e) {                System.err.println("Error while accessing settings provider");                e.printStackTrace();            }        } else {            printUsage();        }    } 

如果是put指令，则会调用putForUser方法

void putForUser(IContentProvider provider, int userHandle,            final String table, final String key, final String value) {        final String callPutCommand;        if ("system".equals(table)) callPutCommand = Settings.CALL_METHOD_PUT_SYSTEM;        else if ("secure".equals(table)) callPutCommand = Settings.CALL_METHOD_PUT_SECURE;        else if ("global".equals(table)) callPutCommand = Settings.CALL_METHOD_PUT_GLOBAL;        else {            System.err.println("Invalid table; no put performed");            return;        }        try {            Bundle arg = new Bundle();            arg.putString(Settings.NameValueTable.VALUE, value);            arg.putInt(Settings.CALL_METHOD_USER_KEY, userHandle);            provider.call(resolveCallingPackage(), callPutCommand, key, arg);        } catch (RemoteException e) {            System.err.println("Can't set key " + key + " in " + table + " for user " + userHandle);        }    }  

如果是get指令,则会调用getForUser方法,

String getForUser(IContentProvider provider, int userHandle,            final String table, final String key) {        final String callGetCommand;        if ("system".equals(table)) callGetCommand = Settings.CALL_METHOD_GET_SYSTEM;        else if ("secure".equals(table)) callGetCommand = Settings.CALL_METHOD_GET_SECURE;        else if ("global".equals(table)) callGetCommand = Settings.CALL_METHOD_GET_GLOBAL;        else {            System.err.println("Invalid table; no put performed");            throw new IllegalArgumentException("Invalid table " + table);        }        String result = null;        try {            Bundle arg = new Bundle();            arg.putInt(Settings.CALL_METHOD_USER_KEY, userHandle);            Bundle b = provider.call(resolveCallingPackage(), callGetCommand, key, arg);            if (b != null) {                result = b.getPairValue();            }        } catch (RemoteException e) {            System.err.println("Can't read key " + key + " in " + table + " for user " + userHandle);        }        return result;    }

如果是delete指令，则会调用deleteForUser方法,

int deleteForUser(IContentProvider provider, int userHandle,            final String table, final String key) {        Uri targetUri;        if ("system".equals(table)) targetUri = Settings.System.getUriFor(key);        else if ("secure".equals(table)) targetUri = Settings.Secure.getUriFor(key);        else if ("global".equals(table)) targetUri = Settings.Global.getUriFor(key);        else {            System.err.println("Invalid table; no delete performed");            throw new IllegalArgumentException("Invalid table " + table);        }        int num = 0;        try {            num = provider.delete(resolveCallingPackage(), targetUri, null, null);        } catch (RemoteException e) {            System.err.println("Can't clear key " + key + " in " + table + " for user "                    + userHandle);        }        return num;    }

如果是list指令,则会调用listForUser方法

private List<String> listForUser(IContentProvider provider, int userHandle, String table) {        final Uri uri = "system".equals(table) ? Settings.System.CONTENT_URI                : "secure".equals(table) ? Settings.Secure.CONTENT_URI                : "global".equals(table) ? Settings.Global.CONTENT_URI                : null;        final ArrayList<String> lines = new ArrayList<String>();        if (uri == null) {            return lines;        }        try {            final Cursor cursor = provider.query(resolveCallingPackage(), uri, null, null, null,                    null, null);            try {                while (cursor != null && cursor.moveToNext()) {                    lines.add(cursor.getString(1) + "=" + cursor.getString(2));                }            } finally {                if (cursor != null) {                    cursor.close();                }            }            Collections.sort(lines);        } catch (RemoteException e) {            System.err.println("List failed in " + table + " for user " + userHandle);        }        return lines;    }