Android下ContentProvider的实例

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一.前些日期研究了下Android下ContentProvider的使用，先将具体的使用方法记下来，方便以后的实际使用扩展。

1.新建工程TestContentProvider此工程是独立的ContentProvider类类似如系统内置的ContactProvider，新建包名com.test.content。

2.文件DataBaseOpen.java,代码如下，主要用于建立数据库，表，及进行数据库的操作等。

package com.test.content;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class DataBaseOpen extends SQLiteOpenHelper {

private final static String DB_NAME = "test.db";
public static final int DB_VERSION = 1;

public DataBaseOpen(Context context, String name, CursorFactory factory,
   int version) {
  super(context, name, factory, version);
  // TODO Auto-generated constructor stub
}
public DataBaseOpen(Context context) {
  super(context, DB_NAME, null, DB_VERSION);
  // TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase arg0) {
  // TODO Auto-generated method stub
  String sql = "CREATE TABLE IF NOT EXISTS student (id integer PRIMARY KEY autoincrement,stuId text NOT NULL unique,name text NOT NULL)";
  arg0.execSQL(sql);
  sql = "CREATE TABLE IF NOT EXISTS score (id integer PRIMARY KEY autoincrement,stuId text NOT NULL unique,name text NOT NULL)";

  arg0.execSQL(sql);
}

@Override
public void onUpgrade(SQLiteDatabase arg0, int arg1, int arg2) {
// TODO Auto-generated method stub
onCreate(arg0);
}

}

2.TestProvider.java继承ContentProvider定义外部访问的规则，具体如下

package com.test.content;

import org.apache.http.client.utils.URIUtils;

import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;

public class TestProvider extends ContentProvider {
//数据集的MIME类型字符串则应该以vnd.android.cursor.dir/开头
public static final String STUDENTS_TYPE = "vnd.android.cursor.dir/student";
//单一数据的MIME类型字符串应该以vnd.android.cursor.item/开头
public static final String STUDENTS_ITEM_TYPE = "vnd.android.cursor.item/student";

public static final String SCORES_TYPE = "vnd.android.cursor.dir/score";
//单一数据的MIME类型字符串应该以vnd.android.cursor.item/开头
public static final String SCORES_ITEM_TYPE = "vnd.android.cursor.item/score";

public static final String AUTHORITY = "com.android.provider.studentprovider";
/*自定义匹配码*/
public static final int STUDENTS = 1;
/*自定义匹配码*/
public static final int STUDENT = 2;

public static final int SCORES = 3;
/*自定义匹配码*/
public static final int SCORE = 4;
public static final Uri STUDENTS_URI = Uri.parse("content://" + AUTHORITY + "/student");
public static final Uri SCORES_URI = Uri.parse("content://" + AUTHORITY + "/score");
/*这里UriMatcher是用来匹配Uri的类，使用match()方法匹配路径时返回匹配码*/
private static final UriMatcher sMatcher;
protected SQLiteDatabase mDb;
static {
  sMatcher = new UriMatcher(UriMatcher.NO_MATCH);//常量UriMatcher.NO_MATCH表示不匹配任何路径的返回码
  //如果match()方法匹配content://cn.android.provider.personprovider/person路径，返回匹配码为PERSONS
  sMatcher.addURI(AUTHORITY, "student", STUDENTS);
  //如果match()方法匹配content://cn.android.provider.personprovider/person/230路径，返回匹配码为PERSON
  sMatcher.addURI(AUTHORITY, "student/#", STUDENT);
  sMatcher.addURI(AUTHORITY, "score", SCORES);
  sMatcher.addURI(AUTHORITY, "score/#", SCORE);
}
private DataBaseOpen databaseHelper;
@Override
public int delete(Uri arg0, String arg1, String[] arg2) {
  // TODO Auto-generated method stub
  return 0;
}

@Override
public String getType(Uri uri) {
  // TODO Auto-generated method stub
  switch (sMatcher.match(uri))
  {
   case STUDENTS:
   return STUDENTS_TYPE;
   case STUDENT:

   return STUDENTS_ITEM_TYPE;
   case SCORES:
    return SCORES_TYPE;
   case SCORE:
    return SCORES_ITEM_TYPE;
   default:
    return null;
  }
}

@Override
public Uri insert(Uri uri, ContentValues values) {
  // TODO Auto-generated method stub
  switch (sMatcher.match(uri))
  {
   case STUDENTS:
    mDb = databaseHelper.getWritableDatabase();
    long rowId = 0;
    try
    {
     rowId = mDb.insertOrThrow("student", "stuId", values);
    }
    catch(Exception e)
    {
     e.printStackTrace();
    }
      return ContentUris.withAppendedId(STUDENTS_URI, rowId);
   case STUDENT:

      return null;
   case SCORES:
    mDb = databaseHelper.getWritableDatabase();
    long Id = 0;
    try
    {
     Id = mDb.insertOrThrow("score", "stuId", values);
    }
    catch(Exception e)
    {
     e.printStackTrace();
    }
      return ContentUris.withAppendedId(SCORES_URI, Id);

   case SCORE:
    return null;
   default:
    return null;
  }
}

@Override
public boolean onCreate() {
  // TODO Auto-generated method stub
  databaseHelper = new DataBaseOpen(this.getContext());
  return false;
}

@Override
public Cursor query(Uri uri, String[] projection, String selection,
   String[] selectionArgs, String sortOrder) {
  // TODO Auto-generated method stub
  return null;
}

@Override
public int update(Uri uri, ContentValues values, String selection,
   String[] selectionArgs) {
  // TODO Auto-generated method stub
  return 0;
}

}

3.AndroidManifest.xml 配置自定义的ContentProvider如下

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.test.content"
    android:versionCode="1"
    android:versionName="1.0" >

<uses-sdk android:minSdkVersion="8" />

</manifest>

二.编写测试范文自定义的ContentProvider

1.新建工程TestProviderClient。包名com.test.client

其中一个测试入口的Activiy TestProviderClientActivity.java代码如下

package com.test.client;

import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class TestProviderClientActivity extends Activity {
    /** Called when the activity is first created. */
private Button mStu;
private Button mSco;
private EditText mMsg;
private EditText mNum;
TextView mRet;
private Context mConText;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mMsg = (EditText)this.findViewById(R.id.msgId);
        mNum = (EditText)this.findViewById(R.id.num);
        mStu = (Button)this.findViewById(R.id.btnStu);
        mSco = (Button)this.findViewById(R.id.btnSco);
        mRet = (TextView)this.findViewById(R.id.ret);
        mConText = this.getBaseContext();
        View.OnClickListener l = new View.OnClickListener() {

   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    int id = v.getId();
    String msg = mMsg.getText().toString();
    String num = mNum.getText().toString();
    if(null == msg || null == num)return;
    ContentValues value = new ContentValues();
    ContentResolver cr = mConText.getContentResolver();
    value.clear();
    value.put("stuId", msg);
    value.put("name", num);
    Uri uri = null;

    try {
     if(id == R.id.btnStu)
     {

      uri = cr.insert(Uri.parse("content://com.android.provider.studentprovider/student"), value);

     }
     else if(id == R.id.btnSco)
     {
      uri = cr.insert(Uri.parse("content://com.android.provider.studentprovider/score"), value);
     }
     mRet.setText(uri.toString());
    } catch (Exception e) {
     // TODO Auto-generated catch block
     e.printStackTrace();
    }

   }
  };
  mStu.setOnClickListener(l);
  mSco.setOnClickListener(l);
    }

}

2.布局文件如下main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

3.工程的AndroidManifest.xml文件如下

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.test.client"
    android:versionCode="1"
    android:versionName="1.0" >

<uses-sdk android:minSdkVersion="8" />

</manifest>

三1.总结一下，本实例不够完整，只是测试了下调用ContenProvider的插入数据的操作，且系统没有该自定义ContentProvider会报错（可以检查系统是否已经有了自定义的ContentProvider的安装包如存在则进行后续的操作，无可以提示安装）。

2.ContenProvider可以随运用一起发布，方便其他运用访问数据，对数据库的操作可以采用事务处理。