Android-ContentProvider数据库操做

时间 2019-11-20

标签 android contentprovider 数据库栏目 Android 繁體版

原文原文链接

在实际的开发过程当中，Android提供了5种方式存储数据： java

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 android

首先咱们先简单了解下文件、SharedPreferred如何进行数据存储 sql

1.文件存储操做 shell

文件存储通常存储在sdcard或者ROM，当文件存储在ROM上时，若是是存储在除本身私有空间外(data/data/包名/)，在其余地方是须要system系统权限的（http://my.oschina.net/zhoulc/blog/119282）。

    文件IO流建立比较简单，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目录操做须要添加权限：

< 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盘通常都是挂载mnt/sda/sdal外设上面
    顺带说下之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
数据库

2.经过Sharedpreferences进行数据存储
网络

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); }

使用过程当中注意三个问题：

    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(通常使用0或者Context.MODE_PRIVATE)
    2）默认的模式为0或MODE_PRIVATE，若是访问其余应用中的Preference，前提条件是：该 preference建立时指定了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，因此commit
以后数据没有存储成功。

3.其余几个就不详细介绍了，说下今天的重点ContentProvider app

    建立一个可对数据库进行操做的ContentProvider咱们先要了解涉及到的知识点：
    （1）Parcelable（实体类数据通常会用在进程之间通讯）
      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"，便于调用数据库时致使拼写错误，你也能够扩展它，或者自定义这么个，而后直接调用它的常量名，防止写sql语句时把列名拼错。
ide

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，包装了数据库的建立、打开、更新的抽象类，经过实现和使用SQLiteOpenHandle能够隐去数据库打开的以前判断数据库是否须要建立或更新的逻辑。
          主要实现三个方法
          建立数据库：public DatabaseHelper(Context context)
       建立表：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：
             添加须要匹配的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，常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，用于管理和操做SQLite数据库，几乎全部的数据库操做，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相似，两个区别一个是用户是经过ContentResolver调用ContentProvider提供的接口。
    以上类都只是简单介绍，有兴趣的朋友能够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 在使用过程当中须要注意两点：

    （1）在AndroidManifest.xml里面须要注册这个ContentProvider
            <provider android:name=".MyProvider" android:authorities="com.zlc.provider.MyProvider" />
    （2）当提供给其余进程调用（假如是其余应用），若是当前提供ContentProvider的应用在退出的时候把本身给kill掉了（这个时候ContentProvider也没法使用），则咱们须要在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一样的默认进程

5.下面贴一下具体实现代码：工具

（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";
	// 建立表的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());
		}
		
	}

}

在同一个应用自己里面（进程）测试插入数据:MainActivity.java oop

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：

其余应用里面测试（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.运行过程当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