本篇文章给大家谈谈AndroidStdiosqlite配置，同时本文还将给你拓展AndrioidSQLite操作与SQLiteStatement关系、androidEditTextandroid：te
本篇文章给大家谈谈Android Stdio sqlite配置，同时本文还将给你拓展Andrioid SQLite 操作与SQLiteStatement关系、android EditText android：textDirection、Android SQLite数据库：SQLiteDiskIOException：磁盘I / O错误(代码1802)、android stdio 编译项目报Error:Failed to find target with hash string ''android-24等相关知识，希望对各位有所帮助，不要忘了收藏本站喔。
本文目录一览：- Android Stdio sqlite配置
- Andrioid SQLite 操作与SQLiteStatement关系
- android EditText android：textDirection
- Android SQLite数据库：SQLiteDiskIOException：磁盘I / O错误(代码1802)
- android stdio 编译项目报Error:Failed to find target with hash string ''android-24
Android Stdio sqlite配置
1.打开Android Studio，找出自己AndroidSDK的安装路径
可以点击File->ProjectStructure快速找到
2.在SDK目录下点击platform-tools
3.点进去直接拉到最后面找到sqlite3.exe双击
4.将你的platform-tools文件路径添加到环境变量的系统变量的 path里面
选择环境变量
5.在命令行查看是否安装成功
出现上面的图片则配置成功
Andrioid SQLite 操作与SQLiteStatement关系
以插入数据为例，有三种方法：
1）直接拼接sql语句，执行execsql方法；
2）借用ContentValues进行插入；
3）使用compileStatement进行插入；
1）直接拼接sql语句，执行execsql方法
String sql = "create table msgTable(uid INTEGER NOT NULL,msg TEXT NOT NULL)"; db.execsql(sql);
缺点：存在sql注入危险；
源码分析：
execsql 调用关系如下：
public void execsql(String sql) throws sqlException {
executesql(sql,null);
}
public void execsql(String sql,Object[] bindArgs) throws sqlException {
if (bindArgs == null) {
throw new IllegalArgumentException("Empty bindArgs");
}
executesql(sql,bindArgs);
}
private int executesql(String sql,Object[] bindArgs) throws sqlException {
if (DatabaseUtils.getsqlStatementType(sql) == DatabaseUtils.STATEMENT_ATTACH) {
disableWriteAheadLogging();
mHasAttachedDbs = true;
}
sqliteStatement statement = new sqliteStatement(this,sql,bindArgs);
try {
return statement.executeUpdateDelete();
} catch (sqliteDatabaseCorruptException e) {
onCorruption();
throw e;
} finally {
statement.close();
}
}
从调用关系看：execsql调用的本质就是创建sqliteStatement对象，调用其executeUpdateDelete插入方法，
而executeUpdateDelete() 方法调用native c++方法，具体如下：
public int executeUpdateDelete() {
try {
savesqlAsLastsqlStatement();
acquireAndLock(WRITE);
int numChanges = 0;
if ((mStatementType & STATEMENT_DONT_PREPARE) > 0) {
// since the statement doesn't have to be prepared,// call the following native method which will not prepare
// the query plan
native_executesql(msql);
} else {
numChanges = native_execute();
}
return numChanges;
} finally {
releaseAndUnlock();
}
}
2）借用ContentValues进行插入
ContentValues values = new ContentValues();
values.put("uid",12);
values.put("msg","test");
long newRowId = db.insert("msgTable",null,values);
优点：解决了执行纯sql语句引入的sql注入漏洞。
源码分析：
public long insert(String table,String nullColumnHack,ContentValues values) {
try {
return insertWithOnConflict(table,nullColumnHack,values,CONFLICT_NONE);
} catch (sqlException e) {
Log.e(TAG,"Error inserting " + values,e);
return -1;
}
}
public long insertWithOnConflict(String table,ContentValues initialValues,int conflictAlgorithm) {
StringBuilder sql = new StringBuilder();
sql.append("INSERT");
sql.append(CONFLICT_VALUES[conflictAlgorithm]);
sql.append(" INTO ");
sql.append(table);
sql.append('(');
Object[] bindArgs = null;
int size = (initialValues != null && initialValues.size() > 0) ? initialValues.size() : 0;
if (size > 0) {
bindArgs = new Object[size];
int i = 0;
for (String colName : initialValues.keySet()) {
sql.append((i > 0) ? "," : "");
sql.append(colName);
bindArgs[i++] = initialValues.get(colName);
}
sql.append(')');
sql.append(" VALUES (");
for (i = 0; i < size; i++) {
sql.append((i > 0) ? ",?" : "?");
}
} else {
sql.append(nullColumnHack + ") VALUES (NULL");
}
sql.append(')');
sqliteStatement statement = new sqliteStatement(this,sql.toString(),bindArgs);
try {
return statement.executeInsert();
} catch (sqliteDatabaseCorruptException e) {
onCorruption();
throw e;
} finally {
statement.close();
}
}
使用ContentValues 最终是创建sqliteStatement对象，并调用executeInsert()方法。
3）使用compileStatement进行插入
sqliteStatement sqliteStatement = db.compileStatement("insert into msgTable(uid,msg) values(?,?)");
sqliteStatement.bindLong(1,12);
sqliteStatement.bindString(3,"text");
long newRowId = sqliteStatement.executeInsert();
源码分析：
public sqliteStatement compileStatement(String sql) throws sqlException {
verifyDbIsopen();
return new sqliteStatement(this,null);
} compileStatement 更加直接，之间是根据传入的参数，创建一个sqliteStatement对象。 小结： 对于执行纯sql，ContentValues和compileStatement最终都是new 一个sqliteStatement对象，并调用sqliteStatement对象的相应方法。
android EditText android：textDirection
我想在任何时候都将EditText设置为LTR,我该怎么做？
android：textDirection似乎确实是答案,我不能让该项目使用该指令进行编译
android：textDirection似乎确实是答案,我不能让该项目使用该指令进行编译
解决方法
使用gravity为editText
android:gravity="right"
Android SQLite数据库：SQLiteDiskIOException：磁盘I / O错误(代码1802)
我有一个使用sqlite数据库的应用程序.
我在应用程序启动时创建了数据库,调用了RSSDatabase的构造函数,工作正常.单击一个按钮后,我从RSS提要中获取数据并在AsyncTask中插入数据,但是当我调用db.insert(“posts”,“”,values)时会导致错误,这是logcat的错误消息：
02-04 21:43:22.050 19154-19357/com.example.aolreader E/sqliteLog﹕ (1802) os_unix.c:30026: (2) stat(/data/data/com.example.aolreader/databases/RSS_db) -
02-04 21:43:22.050 19154-19357/com.example.aolreader E/sqliteLog﹕ (1802) statement aborts at 13: [INSERT INTO posts(author,title,date,description,link) VALUES (?,?,?)]
02-04 21:43:22.050 19154-19357/com.example.aolreader E/sqliteDatabase﹕ Error inserting author=AP title=UK admits ‘limited’ role in Operation Blue Star date=Tue,4 Feb 2014 19:03:27 +0530 description=
The British government had recently ordered an urgent investigation into possible U.K. involvement in the raid.
link=http://www.thehindu.com/news/international/world/uk-admits-limited-role-in-operation-blue-star/article5653316.ece
android.database.sqlite.sqlitediskIOException: disk I/O error (code 1802)
at android.database.sqlite.sqliteConnection.nativeExecuteForLastInsertedRowId(Native Method)
at android.database.sqlite.sqliteConnection.executeForLastInsertedRowId(sqliteConnection.java:782)
at android.database.sqlite.sqliteSession.executeForLastInsertedRowId(sqliteSession.java:788)
at android.database.sqlite.sqliteStatement.executeInsert(sqliteStatement.java:86)
at android.database.sqlite.sqliteDatabase.insertWithOnConflict(sqliteDatabase.java:1469)
at android.database.sqlite.sqliteDatabase.insert(sqliteDatabase.java:1339)
at com.example.aolreader.RSSDatabase.insertPost(RSSDatabase.java:44)
at com.example.aolreader.XMLRSSActivity.parseNews(XMLRSSActivity.java:386)
at com.example.aolreader.XMLRSSActivity.access$000(XMLRSSActivity.java:33)
at com.example.aolreader.XMLRSSActivity$ParseTask.doInBackground(XMLRSSActivity.java:171)
at com.example.aolreader.XMLRSSActivity$ParseTask.doInBackground(XMLRSSActivity.java:134)
at android.os.AsyncTask$2.call(AsyncTask.java:288)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:841)
我搜索了这个错误,发现它可能是由同一时间访问数据库的不同线程引起的,但我查看了我的代码,发现没有多线程有竞争条件的情况.
这是我的数据库助手类：
class RSSDatabaseHelper extends sqliteOpenHelper {
private static final String createPostTablesql = "create table posts (" +
"_id integer primary key autoincrement," +
"title varchar," +
"author varchar," +
"link varchar," +
"description varchar," +
"date varchar)";
private Context context;
public RSSDatabaseHelper(Context c,String name,sqliteDatabase.CursorFactory factory,int version) {
super(c,name,factory,version);
context = c;
}
@Override
public void onCreate(sqliteDatabase db) {
db.execsql(createPostTablesql);
}
@Override
public void onUpgrade(sqliteDatabase db,int oldVersion,int newVersion) {
db.execsql("drop table if exists posts");
onCreate(db);
}
}
我的数据库类：
public class RSSDatabase {
private static RSSDatabase instance;
private sqliteDatabase db;
private RSSDatabaseHelper dbHelper;
private RSSDatabase(Context c) {
dbHelper = new RSSDatabaseHelper(c,"RSS_db",null,1);
db = dbHelper.getWritableDatabase();
}
public static synchronized RSSDatabase getDatabaseInstance(Context c) {
if (instance == null) {
instance = new RSSDatabase(c);
}
return instance;
}
public void insertPost(Post post) {
ContentValues values = new ContentValues();
values.put("title",post.title);
values.put("author",post.author);
values.put("link",post.link);
values.put("description",post.description);
values.put("date",post.date);
db.insert("posts","",values);
}
}
谁能解释一下这个问题呢？
提前致谢！
解决方法
当应用程序启动时,调用RSSDatabase的构造函数,UI Thread会锁定您的数据库
db = dbHelper.getWritableDatabase(); // In the constructor
现在从Async任务(不同的线程),您正在尝试在由UI线程锁定的数据库中插入数据.这将引发异常,因为第一次写入对db有锁定.
android stdio 编译项目报Error:Failed to find target with hash string ''android-24
android stdio 编译项目报Error:Failed to find target with hash string ''android-24
- 查看已有的SDK
- 设置项目的sdk为 25
android {
compileSdkVersion 25
buildToolsVersion "25.0.0"
defaultConfig {
applicationId "com.accessibility"
minSdkVersion 14
targetSdkVersion 25
versionCode 1
versionName "1.0"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile(''proguard-android.txt''), ''proguard-rules.pro''
}
}
}
编译之后一切OK
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