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Android-ContentProvider数据库操作

2013-11-01 23:05 344 查看
在实际的开发过程中,Android提供了5种方式存储数据:

1.文件存储数据
2.使用 Sharedpreferences 存储数据
3.SQLite数据库存储数据
4.使用ContentProvider存储数据
5.网络存储数据

首先我们先简单了解下文件、SharedPreferred如何进行数据存储

1.文件存储操作

文件存储一般存储在sdcard或者ROM,当文件存储在ROM上时,如果是存储在除自己私有空间外(data/data/包名/),在其他地方是需要system系统权限的(http://my.oschina.net/zhoulc/blog/119282)。

文件IO流创建比较简单,就不详述了,在进行文件存储的时候注意两个路径方法就行。
存储到ROM
Context mContext = XXXActivity.this;
mContext.getFilesDir().getAbsolutePath();
获取路径:/data/data/包名/files
存储到sdCard :
首先判断sdcard是否可用
Environment.getExternalStorageState()是否等于Environment.MEDIA_MOUNTED
Environment.getExternalStorageDirectory().getAbsolutePath()
对sdcard目录操作需要添加权限:
<!-- 添加对SDCARD的写权限 -->
< uses-permission android:name ="android.permission.WRITE_EXTERNAL_STORAGE" >
获取路径:/sdcard
拓展下 :支持u盘的移动设备,u盘一般都是挂载mnt/sda/sdal外设上面
顺带说下以前一直纠结的一个问题:
getApplicationContext() 生命周期是整个应用,应用摧毁它才摧毁
Activity.this的context属于activity ,activity 摧毁他就摧毁

2.通过Sharedpreferences进行数据存储

private final static String PERFS_NAME = "com.zlc.test";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//存放
//第一个参数是存储时的名称,第二个参数则是文件的打开方式(Context.
MODE_PRIVATE)
SharedPreferences userInfo = getSharedPreferences(PERFS_NAME,0);
SharedPreferences.Editor editor = userInfo.edit();
editor.putString("userName", "zhoulc");
editor.putString("passWord", "ds");
editor.commit();
//读取
System.out.println("##########################################");
SharedPreferences readInfo = getSharedPreferences(PERFS_NAME, 0);
String name = readInfo.getString("userName", "no_name");
String psword = readInfo.getString("passWord", "000000");
System.out.println("name = "+name+" password = "+psword);
}

使用过程中注意三个问题

1)getSharedPreferences有两个参数,第一个参数是存储时的名称, 第二个参数则是文件的打开方式(一般使用0或者Context.MODE_PRIVATE)

2)默认的模式为0或MODE_PRIVATE,如果访问其他应用中的Preference,前提条件是:该 preference创建时指定了Context.MODE_WORLD_READABLE或者Context.MODE_WORLD_WRITEABLE权限。

3)千万不要偷懒写成

userInfo.edit().putString("userName", "zhoulc");

userInfo.edit().putString("passWord", "ds");

userInfo.edit().commit();

edit()方法每次都要产生一个新的SharedPreferences.Edit类的对象,所以commit

之后数据没有存储成功。

3.其他几个就不详细介绍了,说下今天的重点ContentProvider

创建一个可对数据库进行操作的ContentProvider我们先要了解涉及到的知识点:
(1)Parcelable(实体类数据一般会用在进程之间通信) http://my.oschina.net/zhoulc/blog/172163 (2)BaseColumns,这个类只是提供了两个字段,一个是"_id"一个是"_count",便于调用数据库时导致拼写错误,你也可以扩展它,或者自定义这么个,然后直接调用它的常量名,防止写sql语句时把列名拼错。

package android.provider;

public interface BaseColumns
{
/**
* The unique ID for a row.
* <P>Type: INTEGER (long)</P>
*/
public static final String _ID = "_id";

/**
* The count of rows in a directory.
* <P>Type: INTEGER</P>
*/
public static final String _COUNT = "_count";
}

(3)SQLiteOpenHelper,包装了数据库的创建、打开、更新的抽象类,通过实现和使用SQLiteOpenHandle可以隐去数据库打开的之前判断数据库是否需要创建或更新的逻辑。

主要实现三个方法

创建数据库:public DatabaseHelper(Context context)

创建表:public void onCreate(SQLiteDatabase db)

更新表:public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)

(4)UriMatcher用来匹配URI。

主要实现两个接口:

添加需要匹配的URI:MATCHER.addURI(String authority, String path, int code) 进行匹配返回定义的value;MATCHER.match(Uri uri)

例:

MATCHER.addURI(Information.AUTHORITY, "informations", INFORMATIONS);

MATCHER.addURI(Information.AUTHORITY, "informations/#", INFORMATION);

# 号为通配符

* 号为任意字符

(5)ContentUris一个工具类,主要是用来处理使用 "content" 约束的Uri对象,经常用到条件查询某个_ID的数据。

主要实现两个接口:

static long parseId(Uri contentUri) 将uri中的id解析出来,此方法返回的是一个long型的id。

static Uri withAppendedId(Uri contentUri, long id)在指定的uri后面添加一条id

为指定参数的记录。

(6)SQLiteDatabase,这个类是核心类,用于管理和操作SQLite数据库,几乎所有的数据库操作,最终都将由这个类完成。

(7)ContentProvider,提供数据库增删改查的接口。

主要实现接口:

public int delete(Uri uri, String selection, String[] selectionArgs)

public String getType(Uri uri)

public Uri insert(Uri uri, ContentValues values)

public boolean onCreate()

public Cursor query(Uri uri, String[] projection, String selection,String[] selectionArgs, String sortOrder)

public int update(Uri uri, ContentValues values, String selection,

String[] selectionArgs)

(8)ContentResolver接口和ContentProvider类似,两个区别一个是用户是通过ContentResolver调用ContentProvider提供的接口。

以上类都只是简单介绍,有兴趣的朋友可以去研究下源码和实现过程。这里主要讲使用过程和一些注意细节。

4.ContentProvider 在使用过程中需要注意两点

(1)在AndroidManifest.xml里面需要注册这个ContentProvider

<provider android:name=".MyProvider" android:authorities="com.zlc.provider.MyProvider" />

(2)当提供给其他进程调用(假如是其他应用),如果当前提供ContentProvider的应用在退出的时候把自己给kill掉了(这个时候ContentProvider也无法使用),则我们需要在AndroidManifest.xml里面再添加一条属性

android:process="com.zlc.provider.MyProvider"

为该组件指定一个不同的默认进程

5.下面贴一下具体实现代码

(1)ContentProvider提供者TestContentProvider.apk

实体类:Information.java

package com.zlc.provider;

import android.net.Uri;
import android.os.Parcel;
import android.os.Parcelable;
import android.provider.BaseColumns;

public class Information implements Parcelable,BaseColumns{
public final static String AUTHORITY = "com.zlc.provider.MyProvider";
public final static Uri CONTENT_URI = Uri.parse("content://"+AUTHORITY+"/informations");
//表字段
public final static String INFO_ID = "info_id";
public final static String INFO_NAME = "info_name";
public final static String INFO_AGE = "info_age";

private String info_id,info_name,info_age;

public Information(Parcel source){
info_id = source.readString();
info_name = source.readString();
info_age = source.readString();
}
public String getInfo_id() {
return info_id;
}

public void setInfo_id(String info_id) {
this.info_id = info_id;
}

public String getInfo_name() {
return info_name;
}

public void setInfo_name(String info_name) {
this.info_name = info_name;
}

public String getInfo_age() {
return info_age;
}

public void setInfo_age(String info_age) {
this.info_age = info_age;
}

@Override
public int describeContents() {
// TODO Auto-generated method stub
return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
// TODO Auto-generated method stub
dest.writeString(info_id);
dest.writeString(info_name);
dest.writeString(info_age);
}
public final static Parcelable.Creator<Information> CREATOR = new Parcelable.Creator<Information>() {

@Override
public Information createFromParcel(Parcel source) {
// TODO Auto-generated method stub
return new Information(source);
}

@Override
public Information[] newArray(int size) {
// TODO Auto-generated method stub
return new Information[size];
}
};
}

MyProvider.java

package com.zlc.provider;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Context;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.net.Uri;
import android.provider.BaseColumns;
import android.util.Log;

public class MyProvider extends ContentProvider {
private SQLiteDatabase sqDb;
private DatabaseHelper helper;
// 数据库名
private final static String DATABASE_NAME = "zhoulc.db";
// 版本
private static final int DATABASE_VERSION = 1;
// 表名
private static final String TABLE_NAME = "Information";
// 创建表的sql语句
private final static String CREATE_TABLE = "Create table " + TABLE_NAME
+ "( "+Information._ID+" integer primary key autoincrement," + Information.INFO_ID
+ " TEXT," + Information.INFO_NAME + " TEXT," + Information.INFO_AGE
+ " TEXT);";

// Declaration Datababsehelper
private static class DatabaseHelper extends SQLiteOpenHelper {

public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
db.execSQL(CREATE_TABLE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS" + TABLE_NAME);
onCreate(db);
}

}

// UriMatcher add URI
private static final UriMatcher MATCHER = new UriMatcher(
UriMatcher.NO_MATCH);
private final static int INFORMATIONS = 1;
private final static int INFORMATION = 2;
static {
MATCHER.addURI(Information.AUTHORITY, "informations", INFORMATIONS);
MATCHER.addURI(Information.AUTHORITY, "informations/#", INFORMATION);
}

@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
sqDb = helper.getWritableDatabase();
int count = 0;
switch (MATCHER.match(uri)) {
case INFORMATIONS:
count = sqDb.delete(TABLE_NAME, selection, selectionArgs);
break;
default:
throw new IllegalArgumentException("Unkwon Uri:" + uri.toString());
}
return count;
}

@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
switch (MATCHER.match(uri)) {
case INFORMATIONS:
return "vnd.android.cursor.dir/Information";
case INFORMATION:
return "vnd.android.cursor.item/Information";
default:
throw new IllegalArgumentException("Unkwon Uri:" + uri.toString());
}
}

@Override
public Uri insert(Uri uri, ContentValues values) {
// TODO Auto-generated method stub
sqDb = helper.getWritableDatabase();
Uri insertUri = null;
long rowid = 0;
switch (MATCHER.match(uri)) {
case INFORMATIONS:
rowid = sqDb.insert(TABLE_NAME, Information.INFO_ID, values);
insertUri = ContentUris.withAppendedId(uri, rowid);
Log.i("zhoulc", "insert record...values:" + values.toString());
break;
default:
throw new IllegalArgumentException("Unkwon Uri:" + uri.toString());
}
return insertUri;
}

@Override
public boolean onCreate() {
// TODO Auto-generated method stub
helper = new DatabaseHelper(getContext());
return helper == null ? false : true;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
// TODO Auto-generated method stub
sqDb = helper.getWritableDatabase();
switch (MATCHER.match(uri)) {
case INFORMATIONS:
Cursor cursor = sqDb.query(TABLE_NAME, projection, selection,
selectionArgs, null, null, sortOrder);
return cursor;
case INFORMATION://条件查询,
long id = ContentUris.parseId(uri);
String where = Information._ID + "=" + id;
if (selection != null && !"".equals(selection))
{
where = where + " and " + selection;
}
return sqDb.query(TABLE_NAME, projection, where, selectionArgs, null,
null, sortOrder);
default:
throw new IllegalArgumentException("unknow uri" + uri.toString());
}
}

@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO Auto-generated method stub
sqDb = helper.getWritableDatabase();
int count = 0;
switch (MATCHER.match(uri)) {
case INFORMATIONS:
count = sqDb.update(TABLE_NAME, values, selection, selectionArgs);
return count;
default:
throw new IllegalArgumentException("unknow uri" + uri.toString());
}

}

}

在同一个应用本身里面(进程)测试插入数据:MainActivity.java

package com.zlc.provider;

import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.net.Uri;
import android.os.Bundle;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Context mContext = MainActivity.this;
Uri myUri = Information.CONTENT_URI;
ContentValues values = new ContentValues();
values.put(Information.INFO_NAME, "zhoulc");
values.put(Information.INFO_AGE, "99");
getContentResolver().insert(myUri, values);

}
}

运行结果:





其他应用里面测试(跨进程使用)

TestActivity.java

package com.zlc.database;

import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;

public class TestActivity extends Activity {
private ContentResolver resolver;
public final static String AUTHORITY = "com.zlc.provider.MyProvider";
private  final static Uri CONTENT_URIS = Uri.parse("content://"+AUTHORITY+"/informations");
private  final static Uri CONTENT_URI =  Uri.parse("content://"+AUTHORITY+"/informations/1");
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
resolver = getContentResolver();
//step 1 insert data
ContentValues values = new ContentValues();
values.put("info_name", "zhoulc");
values.put("info_age", "24");
insert(CONTENT_URIS,values);
//查询
Cursor cursor = query(CONTENT_URI,null,null,null,null);
if(cursor != null){
if(cursor.moveToFirst()){
int index[] = new int[]{
cursor.getColumnIndex("info_id"),
cursor.getColumnIndex("info_name"),
cursor.getColumnIndex("info_age")
};
do {
System.out.println(cursor.getString(index[1]));
System.out.println(cursor.getString(index[2]));
} while (cursor.moveToNext());
}
}
}
//  该方法用于往ContentProvider添加数据。
public Uri insert(Uri uri,ContentValues values){
Uri dst = resolver.insert(uri, values);
return dst;
}
//  该方法用于从ContentProvider删除数据。
public int delete(Uri uri,String where, String[] selectionArgs){
int colums = resolver.delete(CONTENT_URI, where, selectionArgs);
return colums;
}
//  该方法用于更新ContentProvider中的数据。
public int update(Uri uri,ContentValues values, String where, String[] selectionArgs){
int colums = resolver.update(CONTENT_URI, values, where, selectionArgs);
return colums;
}
//  该方法用于从ContentProvider中获取数据。
public Cursor query(Uri uri,String[] projection, String where, String[] selectionArgs, String sortOrder){
Cursor cursor = resolver.query(CONTENT_URI, projection, where, selectionArgs, sortOrder);
return cursor;
}

}




6.运行过程中遇到的一些问题以及如何解决

(1)Open quote is expected for attribute "{1}" associated with an element type "
android:authorities".
android:authorities="com.zlc.provider.MyProvider" /

解决:不能使用中文的引号

(2)E/AndroidRuntime( 4509): FATAL EXCEPTION: main
E/AndroidRuntime( 4509): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.zlc.provider/com.zlc.provider.MainActivity}: java.lang.IllegalArgumentException: Unknown URL content://com.zlc.provider.MyProviderinformations
E/AndroidRuntime( 4509):        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
E/AndroidRuntime( 4509):        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
E/AndroidRuntime( 4509):        at android.app.ActivityThread.access$600(ActivityThread.java:141)
E/AndroidRuntime( 4509):        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
E/AndroidRuntime( 4509):        at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime( 4509):        at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime( 4509):        at android.app.ActivityThread.main(ActivityThread.java:5041)
E/AndroidRuntime( 4509):        at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 4509):        at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime( 4509):        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
E/AndroidRuntime( 4509):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
E/AndroidRuntime( 4509):        at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime( 4509): Caused by: java.lang.IllegalArgumentException: Unknown URL content://com.zlc.provider.MyProviderinformations
E/AndroidRuntime( 4509):        at android.content.ContentResolver.insert(ContentResolver.java:862)
E/AndroidRuntime( 4509):        at com.zlc.provider.MainActivity.onCreate(MainActivity.java:17)
E/AndroidRuntime( 4509):        at android.app.Activity.performCreate(Activity.java:5104)
E/AndroidRuntime( 4509):        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
E/AndroidRuntime( 4509):        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
E/AndroidRuntime( 4509):        ... 11 more
W/ActivityManager( 2138):   Force finishing activity com.zlc.provider/.MainActivity
D/dalvikvm( 2138): GC_FOR_ALLOC freed 596K, 13% free 7327K/8412K, paused 63ms, total 63ms

声明的时候掉了一个public final static Uri CONTENT_URI = Uri.parse("content://"+AUTHORITY+"/informations");

(3)E/AndroidRuntime( 5411): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.zlc.provider/com.zlc.provider.MainActivity}: android.database.sqlite.SQLiteException: near "tableInformation": syntax error (code 1): , while compiling: Create tableInformation(_id integer primary key autoincrement,info_idTEXT,info_nameTEXT,info_ageTEXT);
E/AndroidRuntime( 5411):        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
E/AndroidRuntime( 5411):        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
E/AndroidRuntime( 5411):        at android.app.ActivityThread.access$600(ActivityThread.java:141)
E/AndroidRuntime( 5411):        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
E/AndroidRuntime( 5411):        at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime( 5411):        at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime( 5411):        at android.app.ActivityThread.main(ActivityThread.java:5041)
E/AndroidRuntime( 5411):        at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime( 5411):        at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime( 5411):        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
E/AndroidRuntime( 5411):        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
E/AndroidRuntime( 5411):        at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime( 5411): Caused by: android.database.sqlite.SQLiteException: near "tableInformation": syntax error (code 1): , while compiling: Create tableInformation(_id integer primary key autoincrement,info_idTEXT,info_nameTEXT,info_ageTEXT);
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteStatement.<init>(SQLiteStatement.java:31)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteDatabase.executeSql(SQLiteDatabase.java:1663)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteDatabase.execSQL(SQLiteDatabase.java:1594)
E/AndroidRuntime( 5411):        at com.zlc.provider.MyProvider$DatabaseHelper.onCreate(MyProvider.java:39)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteOpenHelper.getDatabaseLocked(SQLiteOpenHelper.java:252)
E/AndroidRuntime( 5411):        at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:164)
E/AndroidRuntime( 5411):        at com.zlc.provider.MyProvider.insert(MyProvider.java:92)
E/AndroidRuntime( 5411):        at android.content.ContentProvider$Transport.insert(ContentProvider.java:201)
E/AndroidRuntime( 5411):        at android.content.ContentResolver.insert(ContentResolver.java:866)
E/AndroidRuntime( 5411):        at com.zlc.provider.MainActivity.onCreate(MainActivity.java:17)
E/AndroidRuntime( 5411):        at android.app.Activity.performCreate(Activity.java:5104)
E/AndroidRuntime( 5411):        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
E/AndroidRuntime( 5411):        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
E/AndroidRuntime( 5411):        ... 11 more
W/ActivityManager( 2138):   Force finishing activity com.zlc.provider/.MainActivity

private final static String CREATE_TABLE = "Create table " + TABLE_NAME

+ "( _id integer primary key autoincrement," + Information.INFO_ID

+ " TEXT," + Information.INFO_NAME + " TEXT," + Information.INFO_AGE+ " TEXT);";

注意空格

代码下载
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