Android 自定义ContentProvider简单实例

Android 自定义ContentProvider简单实例

Android允许我们定义自己的的ContentProvider对象来共享数据，练练手，简单来实现一下。

要使用ContentProvider来操作数据，必须要有保存数据的场所。可以使用文件或SQLite数据库的方式来保存数据，通常使用SQLite数据库。

1，创建一个数据库帮助类，归根结底都是它在操作数据库。代码如下：

package com.njue; 

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

public class DBManager extends SQLiteOpenHelper {
public static final String myProvider_table_name="myProvider_table_name";
String sql="create table myProvider_table_name(id integer,name text)";
  public DBManager(Context context) {
    super(context, "myPrivoder.db", null, 1);
    // TODO Auto-generated constructor stub
  } 

  @Override
  public void onCreate(SQLiteDatabase arg0) {
    // TODO Auto-generated method stub
   arg0.execSQL(sql);
  } 

  @Override
  public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    // TODO Auto-generated method stub 

  } 

}

2，创建一个myProvider类，该类继承ContentProvider，实现其抽象方法来操作数据库，该类引用DBManager类来获得数据库实例。

package com.njue; 

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

public class myProvider extends ContentProvider {
  DBManager dbHelper;
  @Override
  public int delete(Uri arg0, String arg1, String[] arg2) {
    // TODO Auto-generated method stub
    SQLiteDatabase db=dbHelper.getWritableDatabase();
    int id=db.delete(DBManager.myProvider_table_name, arg1, arg2);
    if(id!=0)return id;
    return 0;
  } 

  @Override
  public String getType(Uri uri) {
    // TODO Auto-generated method stub
    return null;
  } 

  @Override
  public Uri insert(Uri uri, ContentValues values) {
    // TODO Auto-generated method stub
    SQLiteDatabase db=dbHelper.getWritableDatabase();
    db.insert(DBManager.myProvider_table_name, "id", values);
    return null;
  } 

  @Override
  public boolean onCreate() {
    // TODO Auto-generated method stub
    dbHelper=new DBManager(getContext());
    return true;
  } 

  @Override
  public Cursor query(Uri uri, String[] projection, String selection,
      String[] selectionArgs, String sortOrder) {
    // TODO Auto-generated method stub
    SQLiteDatabase db=dbHelper.getWritableDatabase();
    Cursor c=db.query(DBManager.myProvider_table_name,projection, selection, selectionArgs, null, null, sortOrder);
    return c;
  } 

  @Override
  public int update(Uri uri, ContentValues values, String selection,
      String[] selectionArgs) {
    // TODO Auto-generated method stub
    SQLiteDatabase db=dbHelper.getWritableDatabase();
    int id=db.update(DBManager.myProvider_table_name, values, selection, selectionArgs);
    if(id!=0)return id;
    return 0;
  } 

}

3，ContextProvider必须声明才能使用，因此，需要在AndroidManifest.xml配置文件中声明。声明很简单，需要类名称和授权名称两个属性。

<provider android:name="myProvider"
    android:authorities="com.njue.myProvider" />

到这里，我们自定义的ContentProvider就完成了。我们可以在Eclipse中的File Explorer 窗口中看到自定义的ContentProvider

 4，简单测试

package com.njue; 

import android.app.Activity;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView; 

public class Content_providerActivity extends Activity {
  /** Called when the activity is first created. */
   Uri uri;
   String AUTHORITY="content://com.njue.myProvider/myProvider_table_name";
   ContentResolver cr;
   EditText input;
   Button insert;
   TextView show;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    input=(EditText)findViewById(R.id.input);
    insert=(Button)findViewById(R.id.insert);
    show=(TextView)findViewById(R.id.show);
    uri=uri.parse(AUTHORITY);
    cr=this.getContentResolver();
    insert.setOnClickListener(new Button.OnClickListener(){ 

      @Override
      public void onClick(View v) {
        // TODO Auto-generated method stub
         ContentValues values=new ContentValues();
          values.put("name", input.getText().toString());
          cr.insert(uri, values);
          Cursor c=cr.query(uri, null, null, null, null);
          show.setText("");
          c.moveToFirst();
          while(c.moveToNext()){
           show.append(c.getString(1)+"\r\n");
          }
          input.setText("");
      }}); 

  }
}

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